Emeline Verna
email: verna.emeline@yahoo.fr

Sébastien Villotte
email: s.villotte@pacea.u-bordeaux1.fr

Several infra-cranial non-metric variations in a single Neolithic individual: A common genetic underlying predisposition?

Keywords: Non-metric variation, genetic etiology, mechanical stress, Neolithic Non-metric variation, genetic etiology, mechanical stress, Neolithic

Non-metric variations have been the subject of anatomical and anthropological studies for more than a century. In this study, we present an individual from Sion (Canton of Valais, Southern Switzerland) dated from the Middle Neolithic who shows evidence for four nonmetric variations. This young adult male presents an os acromiale, spondylolysis, a bipartite

INTRODUCTION

Non-metric variations, also called discrete traits, have been the subject of anatomical and anthropological studies for more than a century. These minor non-pathological skeletal variants can be found throughout the human skeleton [START_REF] Pfister | Création d'une collection anthropologique de référence et application des caractères discrets dans le cas de généalogies connues[END_REF].

Non-metric variations are commonly used as a measure of biological or genetic distance and variation in archaeological human skeletal samples (e.g. [START_REF] Berry | The Use of Non-metrical Variations of the Cranium in the Study of Scandinavian Population Movements[END_REF][START_REF] Crubézy | Microévolution d'une population historique: Etude des caractères discrets d'une population Missiminia (Soudan, III-IVe siècle)[END_REF], although some of them are also considered as activy-related skeletal morphologies (e.g. [START_REF] Stirland | A possible correlation between os acromiale and occupation in the burials from the Mary Rose[END_REF][START_REF] Villotte | External auditory exostoses and aquatic activities during the Mesolithic and the Neolithic in Europe: Results from a large prehistoric sample[END_REF]. The developmental genetic bases for most of these discrete morphological variants are not well known [START_REF] Hauser | Epigenetic variants of the human skull[END_REF]. A few traits have been studied in humans (Saunders and Popovich, 1978), but most of what is known comes from studies of other primates (for a review see: [START_REF] Wilmore | Developmental Origins of and Covariation Between Metric and Nonmetric Cranial Traits[END_REF] or mice [START_REF] Grüneberg | Genetical studies on the skeleton of the mouse. IV. Quasi-continuous variations[END_REF]. Genetic, epigenetic (cellular and physiological traits inherited by daughter cells and not caused by changes in the DNA sequence), and environmental factors are probably involved in the appearance of non-metric variations, so a polyfactorial origin could be posited for the appearance of most non-metric variations [START_REF] Konigsberg | Cranial Deformation and Nonmetric Trait Variation[END_REF].

In this study, we present a single individual in whom four infra-cranial non-metric variations were observed.

MATERIAL AND METHOD

The individual presented here come from a necropolis of 25 burials (24 single inhumations and one double burial), discovered in 1988 and excavated by Brunier in Sion, at the so-called chemin des Collines (Canton of Valais, Southern Switzerland) [START_REF] Moinat | Les sites de l'avenue Ritz et du chemin des Collines: deux exemples de nécropoles en ville de Sion (Valais, Suisse)[END_REF].

Radiocarbon determinations indicate a date for the necropolis of between 4550 and 4100 BC, which corresponds to the Middle Neolithic [START_REF] Moinat | Les sites de l'avenue Ritz et du chemin des Collines: deux exemples de nécropoles en ville de Sion (Valais, Suisse)[END_REF].

The non-metric variations were observed and scored as present/absent. The sex of this individual was determined using two methods applied to the ossa coxae [START_REF] Bruzek | A method for visual determination of sex, using the human hip bone[END_REF][START_REF] Murail | DSP: A tool for probabilistic sex diagnosis using worldwide variability in hip-bone measurements[END_REF]. Age at death was estimated using the stage of epiphyseal fusion of the bones [START_REF] Scheuer | Developmental Juvenile Osteology[END_REF].

RESULTS

The individual is an adult male, around 16-21 years old. The skeleton is in a moderately wellpreserved state. The cranium and mandible and most of the infra-cranial bones are incomplete or fragmentary. Some of the long bones and the left os coxae are complete.

Lumbar vertebrae are poorly preserved but L4 and L5 were identified. L5 presents a spondylolysis (a separation at the pars interarticularis of the neural arch) on the right side (figures 1a, b). The left side is absent. The surface at the separation is smooth and looks like a fibrocartilagineous enthesis (see [START_REF] Boszczyk | An immunohistochemical study of the tissue bridging adult spondylolytic defects -the presence and significance of fibrocartilaginous entheses[END_REF]. L4 does not present any trace of spondylolysis on the right side and the left side is missing. We also observed two inferior articular processes, one right and one left, which presented spondylolysis. The right process corresponds with the body of L5 but it was impossible to associate the left one to the body and the two processes have very different shapes. Thus, this individual presents either: a case of bilateral spondylolysis of L5 with asymmetry of articular processes, unilateral cases of spondylolysis of L4 and L5, or a bilateral spondylolysis of L5 and unilateral spondylolysis of L4.

The individual has an os acromiale on the right scapula (figures 1c, d). Considering the age of the individual it is possible to confuse os acromiale with a normal, unfused acromial epiphysis. However, according to the classifications of [START_REF] Sammarco | Os acromiale: Frequency, anatomy, and clinical implications[END_REF] and [START_REF] Case | Os acromiale: Population differences and their etiological significance[END_REF], it looks clearly to be an os acromiale with a free, separate fragment and a welldefined articulation: it does not have the appearance of an epiphysis, there is pitting present, and the joint is linear and horizontal to the axis of the acromion. The left scapula is absent.

The individual shows a bipartite right patella (figures 2a, b), the left bone being absent. Only the body of the right patella is present, the bipartite fragment is missing. There is an oblique rupture at the junction between the medial part and the lateral part of the body.

A calcaneus secundarius (a small accessory bone located on the anterior facet of the calcaneus) is present on both calcanei (figures 2c, d), and it is identified via the presence of a notch on the anterior facet.

The four infra-cranial non-metric variations seen in this individual are seen in low frequencies in most contemporary and archaeological populations (table 1). Such a case with several nonmetric variations, each presenting a low frequency is very rare [START_REF] Saunders | The development and distribution of discontinuous morphological variation of the human infracranial skeleton[END_REF]. A study of two French collections shows very few cases and the association of those four traits was not found in any of 295 adult skeletons analysed (table 2) [START_REF] Verna | Les variations osseuses asymptomatiques du squelette postcrânien: leur contribution à l'identification en anthropologie[END_REF]. Frequencies for three of these non-metric variations 1 are provided in the table 3 for the Middle Neolithic from Southern Switzerland. None of these variations is especially frequent in this prehistoric sample, and a combination of all of them was not seen apart from the individual presented here.

Apart from these non-metric variations, the skeleton displays only a few other notable features: a metopic suture, shovelling of the upper central incisors, diminutive upper lateral incisors, lateral squatting facets on both tibiae, and a new bone formation on the posterior surface of the left tibia, in the area of the M. soleus attachment site.

DISCUSSION AND CONCLUSIONS

Mann (1990) examined 1,367 calcanei from several populations. According to him, the origin of calcaneus secundarius is congenital or the result of traumatic injury of the immature calcaneus (i.e. at a cartilaginous stage) resulting in a "pinched off" island of cartilage and an accessory center of ossification. [START_REF] Anderson | Calcaneus Secundarius: An Osteo-Archaeological Note[END_REF] suggested that calcaneus secundarius was the consequence of a congenital defect of ossification with mechanical factors causing the separation of the ossicle. An association of calcaneus secundarius, os tibiale externum, and os vesalium, has been reported in one individual in a clinical and radiographic study [START_REF] Heikel | Coalitio calcaneo-navicularis and calcaneus secundarius. A clinical and radiographic study of twenty-three patients[END_REF].

Genetic predisposition has been reported by several authors for the appearance of spondylolysis [START_REF] Haukipuro | Familial occurrence of lumbar spondylolysis and spondylolisthesis[END_REF][START_REF] Wynnedavies | Inheritance and spondylolisthesis -radiographic family survey[END_REF]), but at the same time the prevalence of spondylolysis seems to be higher in the young athletic population (adolescent and young adult) than in the general population, 15% for gymnasts for example [START_REF] Jackson | Spondylolysis in female gymnast[END_REF][START_REF] Goldstein | Spine injuries in gymnasts and swimmers -an epidemiologic investigation[END_REF][START_REF] Soler | The prevalence of spondylolysis in the Spanish elite athlete[END_REF]. Moreover [START_REF] Boszczyk | An immunohistochemical study of the tissue bridging adult spondylolytic defects -the presence and significance of fibrocartilaginous entheses[END_REF] found that the lysis-zone tissue had an ordered collagenous structure with distinct fibrocartilaginous entheses at both ends, suggesting that compressive and shear forces act at this area. [START_REF] Stirland | A possible correlation between os acromiale and occupation in the burials from the Mary Rose[END_REF] supports a mechanical origin by which the os acromiale results from mechanical strain on the developing acromion, whereas the genetic origin is supported by others [START_REF] Angel | Life stresses of the free blackcommunity as represented by the 1st-african-baptist-church, philadelphia, 1823-1841[END_REF][START_REF] Sammarco | Os acromiale: Frequency, anatomy, and clinical implications[END_REF][START_REF] Hunt | The frequency of os acromiale in the Robert J. Terry collection[END_REF]. According to [START_REF] Case | Os acromiale: Population differences and their etiological significance[END_REF] the most likely explanation is a combination of genetic predisposition and high mechanical stresses.

While the cause of a painful bipartite patella is relatively well understood (e.g. [START_REF] Gaheer | Contemporary Management of Symptomatic Bipartite Patella[END_REF][START_REF] Oohashi | Developmental anomaly of ossification type patella partita[END_REF], the origin of this variation is not. The patella ossifies from one center in most children, but in ca. 25% of the population two or three centers are present (Gaheer et , 2009). While this is considered as a normal variant by many authors, some others consider the accessory ossification centre(s) as the result of a disorder of ossification in the primarily cartilaginous formation of the patella due to abnormal stresses produced by excessive action of the inserting musculature during growth [START_REF] Soren | Patella partita[END_REF]. The ossicle may fuse to the main patellar body (see for instance [START_REF] Anderson | A bipartite patella in a juvenile from a medieval context[END_REF] for an archeological case) or stays unfused. Why the fusion occurs or does not is still not understood (e.g. [START_REF] Soren | Patella partita[END_REF][START_REF] Anderson | A bipartite patella in a juvenile from a medieval context[END_REF], but it is likely that genetic predisposition plays a role in some cases [START_REF] Aloisio | Rotula partita congenita. Considerazioni su tre casi familiari[END_REF]. It is also noteworthy that a case of bipartite patella has been described in association with an autosomal dominant disorder called nail-patella syndrome [START_REF] Kumar | Separation of bipartite patella in nail-patella syndrome: a case report[END_REF].

Thus, for all these infra-cranial non-metric variations, high mechanical stresses during growth, a genetic predisposition, or a combination of both are evoked to explain their origin. For all of these anatomical areas, authors indicate that fractures due to acute trauma can occur during adulthood, but: 1) they are very uncommon, and 2) usually they can be easily distinguished from the non-union form (e.g. [START_REF] Heikel | Coalitio calcaneo-navicularis and calcaneus secundarius. A clinical and radiographic study of twenty-three patients[END_REF][START_REF] Merbs | Spondylolysis and spondylolisthesis: A cost of being an erect biped or a clever adaptation?[END_REF][START_REF] Anderson | A bipartite patella in a juvenile from a medieval context[END_REF][START_REF] Case | Os acromiale: Population differences and their etiological significance[END_REF]. The changes seen in the individual studied here present the "classical" aspect of a non-union, and so do not seem related to acute trauma.

It is possible that this individual performed a range of strenuous physical activities during childhood or adolescence leading to the changes described here. However, even in that case, considering the fact that the four non-metric traits are very similar in their expression (an unattached piece of bone), it seems very likely that this individual was genetically predisposed. Our first conclusion is that in some cases at least, the presence of one of these traits in a single individual or in a sample may be more related to genetic conditions than to mechanical stresses, and thus authors must be cautious before considering these traits in studies of activity-related skeletal morphology. Our second conclusion concerns the relationship between these traits. Indeed, the unique combination of these four non-metric variations, being rare and very similar in their expression, may indicate that a common DNA coding area is involved in their presence.

The systematic research for combinations of these infra-cranial non-metric variations, along with descriptions of other non-metric characteristics that can be associated with a "syndrome" (in the present case possibly the metopic suture, and the diminutive upper lateral incisors) may lead to a better understanding of the underlying genetic control of the expression of these morphological changes in the skeleton. [START_REF] Saunders | The development and distribution of discontinuous morphological variation of the human infracranial skeleton[END_REF][START_REF] Sammarco | Os acromiale: Frequency, anatomy, and clinical implications[END_REF]Case et al., 2005;[START_REF] Hunt | The frequency of os acromiale in the Robert J. Terry collection[END_REF][START_REF] Kumar | The prevalence of os acromiale in Korean patients visiting shoulder clinic[END_REF]Verna, 2014 S 3.2 -33 M > F B>U [START_REF] Stewart | The age incidence of neural-arch defects in alaskan natives, considered from the standpoint of etiology[END_REF][START_REF] Saunders | The development and distribution of discontinuous morphological variation of the human infracranial skeleton[END_REF][START_REF] Merbs | Spondylolysis: its nature and anthropological significance[END_REF][START_REF] Merbs | Spondylolysis and spondylolisthesis: A cost of being an erect biped or a clever adaptation?[END_REF][START_REF] Masnicova | Developmental anomalies in skeletal remains from the Great Moravia and Middle Ages cemeteries at Devin (Slovakia)[END_REF]Verna, 2014 BP 1.4 -8.5 M > F - [START_REF] Saunders | The development and distribution of discontinuous morphological variation of the human infracranial skeleton[END_REF][START_REF] Lawson | Clinically significant radiologic anatomic variants of the skeleton[END_REF][START_REF] Anderson | A bipartite patella in a juvenile from a medieval context[END_REF]Verna, 2014 CS 1.4 -14.3 M > F, European U>B Anderson, 1988;[START_REF] Mann | Calcaneus Secundarius: Description and Frequency in Six Skeletal Samples[END_REF]

Figure 1 :

 1 Figure 1: A. Spondylolysis of the fifth lumbar vertebra. B. Articular process of lumbar verterba with spondylolysis. C. Os acromiale on the right scapula. Acromion from the postero-superior view. D. Part of the acromion process with the line indicative of non-fusion.

Figure 2 :

 2 Figure 2: A. Bipartite right patella. Anterior view. B. Bipartite right patella. Posterior view. C. Calcaneus secundarius on the right calcaneus. Dorsal view. D. Calcaneus secundarius on the right calcaneus. Plantar view.

  ; Verna, 2014 OA = os acromiale, S = spondylolysis, BP = bipartite patella, CS = calcaneus secundarius. M = male, F = female, U = unilaterally, B = bilaterally, L = left, R = right.

  of the fifth lumbar vertebra. B. Articular process of lumbar verterba with spondylolysis. C. Os acromiale on the right scapula. Acromion from the postero-superior view. D. Part of the acromion process with the line indicative of non-fusion. 119x80mm (300 x 300 DPI) right patella. Anterior view. B. Bipartite right patella. Posterior view. C. Calcaneus secundarius on the right calcaneus. Dorsal view. D. Calcaneus secundarius on the right calcaneus. Plantar view. 80x99mm (300 x 300 DPI)

Table 1 :

 1 Frequencies of the four non-metric variations in various current and archaeological populations

	Non-metric variations	%	Liaison with sex	Liaison laterality with	References
			M > F,
	OA	0.7 -20	North	U>B, L>R
			American

Table 2 :

 2 Frequencies and association of the four non-metric variations in two French collections (one contemporary and one from Middle Ages)

	Non-metric variations	n/N	Olivier	%	Saint Jean de Todon n/N %
	OA	5/91		5.5	15/136	11.0
	S	5/85		5.9	8/167	4.8
	BP	7/82		8.5	1/129	0.8
	CS	6/63		9.5	16/121	13.2
	OA + S	0/63		0	1/121	0.8
	S + BP	0/63		0	0/121	0
	BP + CS	1/63		1.6	0/121	0
	S + CS	0/63		0	1/121	0.8
	OA + CS	0/63		0	3/121	2.5
	OA + BP	0/63		0	0/121	0
	OA + S + BP	0/63		0	0/121	0
	S + BP + CS	0/63		0	0/121	0
	OA + BP + CS	0/63		0	0/121	0
	CS + S + OA	0/63		0	0/121	0
	OA + S + BP + CS	0/63		0	0/121	0

n: number of cases, N: number of individuals for which the present or absence of a trait or of an association can be scored. OA = os acromiale, S = spondylolysis, BP = bipartite patella, CS = calcaneus secundarius

Table 3 :

 3 Frequencies of non-metric variations and associations in the Middle Neolithic sample for Switzerland (73 individuals from Barmaz I, Barmaz II, Chamblandes, Sion Collines, Sion Ritz, Sion St Guerin, St Leonard 4, Corseaux). : number of cases, N: number of individuals for which the present or absence of a trait or of an association can be scored. OA = os acromiale, S = spondylolysis, BP = bipartite patella.

	Non-metric variations	n/N	%
	OA	2/44	4.5
	S	4/51	7.8
	BP	2/54	3.7
	OA + BP	1/32	3.1
	OA + S	1/34	2.9
	S +BP	1/38	2.6
	OA + BP + S	1/28	3.6

n

http://mc.manuscriptcentral.com/oa International Journal of Osteoarchaeology

Acknowledgements

We thank Dr. Jocelyne Desideri, anthropologist at the Laboratory of Prehistoric Archaeology and Anthropology at the University of Geneva, who allowed access to the remains; and Christopher Knüsel and Sacha Kacki (PACEA) for their useful comments on the manuscript.

The authors declare no conflict of interest.

Footnotes

Presence or absence of calcaneus secundarius was not recorded systematically at the time of the original study on activity-related skeletal morphological changes. So, even if no other case was apparently present, frequencies cannot be calculated.


Vincent Escande

Cyril Poullain

Guillaume Clavé

Eddy Petit

Nathalie Masquelez

Peter Hesemann

Claude Grison
email: claude.grison@cnrs.fr

Bio-based and environmental input for transfer hydrogenation using EcoNi(0) catalyst in isopropanol

Keywords:

Introduction

Mining and metallurgical operations are in the top for the metal waste production. They are problematic, because they are not biodegradable and persistent in organisms and ecosystems. These environmental issues can be addressed by an ecological solution, called phytoextraction [START_REF] Raskin | Phytoremediation of Toxic Metals: Using Plants to Clean up the Environment[END_REF][START_REF] Garbisu | Phytoextraction: a cost-effective plant-based technology for the removal of metals from the environment[END_REF][START_REF] Andrew | Phytoextraction as a tool for green chemistry[END_REF]. Phytoextraction has emerged as a novel approach to clean up metal-polluted soils in which plants are used to transfer metal trace elements (TE) from soils to shoots. This phytotechnology leads to the development of a vegetative cover, which forms a protection against wind and water erosion of TE. It is among the less costly technologies of soils remediation and has a good public acceptance [START_REF] Bhargava | Approaches for enhanced phytoextraction of heavy metals[END_REF]. However, TE concentration in plant leaves is high enough to generate new contaminated wastes.

Our group has shown that these plant wastes produced could be recovered using an innovative concept of sustainable chemistry. Taking advantage of the remarkable adaptive capacity of some plants to hyperaccumulate metals, ecocatalysis is based on the original use of metal species of plant origin as catalysts in fine organic chemical reactions. This allows the preparation of biomolecules using an eco-responsible and bio-inspired approach [START_REF] Grison | Ecocatalysis: a new approach toward bioeconomy[END_REF]. The obtained results demonstrate that these new polymetallic catalysts present a unique chemical structure [START_REF] Grison | Psychotria douarrei and Geissois pruinosa, novel resources for the plant-based catalytic chemistry[END_REF][START_REF] Garel | CC bond formation strategy through ecocatalysis: insights from structural studies and synthetic potential[END_REF][START_REF] Escande | Phytoextracted mining wastes for ecocatalysis: eco-Mn, an efficient and eco-friendly plant-based catalyst for reductive amination of ketones[END_REF]. They offer new opportunities for cooperative catalysis within the synergy between metals [START_REF] Escande | Lewis acid catalysis and Green oxidations: sequential tandem oxidation processes induced by Mn-hyperaccumulating plants[END_REF][START_REF] Grison | Metallophytes for organic synthesis: towards new bio-based selective protection/deprotection procedures[END_REF][START_REF] Grison | The leguminous species Anthyllis vulneraria as a Zn-hyperaccumulator and eco-Zn catalyst resources[END_REF], and present huge potential for the future [12]. Their activities, chemoselectivity and recyclability are higher than traditional catalysts in many reactions [START_REF] Escande | Biosourced polymetallic catalysts: an efficient means to synthesize underexploited platform molecules from carbohydrates[END_REF][START_REF] Escande | Switchable alkene epoxidation/oxidative cleavage with H2O2/NaHCO3: efficient heterogeneous catalysis derived from biosourced eco-Mn[END_REF][START_REF] Clave | Ullmann reaction through ecocatalysis: insights from bioresource and synthetic potential[END_REF]. Ecocatalysts constitute an entirely new generation of efficient green oxidative catalysts [START_REF] Grison | Use of Certain Manganese-accumulating Plants for Carrying Out Organic Chemistry Reactions[END_REF], Lewis acid catalysts [START_REF] Grison | Use of Certain Metal-Accumulating Plants for the Performance of Organic Chemistry Reactions[END_REF], and sustainable C C formation agents [START_REF] Grison | Use of Certain Organic Materials, Containing Alkali or Alkaline-earth Metals, for Implementing Organic Chemical Reactions[END_REF]. They can be used as alternative reagents to replace those prohibited by European REACH regulations [START_REF] Escande | Switchable alkene epoxidation/oxidative cleavage with H2O2/NaHCO3: efficient heterogeneous catalysis derived from biosourced eco-Mn[END_REF][START_REF] Escande | EcoMnOx, a biosourced catalyst for selective aerobic oxidative cleavage of activated 1,2-Diols[END_REF].

Ecocatalysis brings a change in paradigm: biomass from phytoextraction is no longer considered as contaminated waste, but rather as a natural restoration system with high added value [START_REF] Losfeld | The chemical exploitation of nickel phytoextraction: an environmental, ecologic and economic opportunity for New Caledonia[END_REF]. This biomass is a natural reservoir of transition metals, precious in organic synthesis. In other words, waste becomes a useful and innovative chemical tool.

However, the use of ecocatalysts as potential green reducing agents has never been studied. The interest of EcoNi in the area of reduction is thus promising for ecological and chemical reasons.

We have recently reported that biosourced polymetallic ecocatalysts EcoNi(II) prepared from biomass derived from Ni hyperaccumulating plants, could efficiently and selectively mediate different addition reactions on alkenes and aromatic compounds [START_REF] Losfeld | The chemical exploitation of nickel phytoextraction: an environmental, ecologic and economic opportunity for New Caledonia[END_REF][START_REF] Losfeld | Design and performance of supported Lewis acid catalysts derived from metal contaminated biomass for Friedel-Crafts alkylation and acylation[END_REF][START_REF] Escande | From biodiversity to catalytic diversity: how to control the reaction mechanism by the nature of metallophytes[END_REF]. The synthetic protocols based on the use of EcoNi(II) catalysts combined several advantages: low catalyst loading, high yields of reaction products, short reaction times, ecofriendly reaction conditions, high selectivity and the possibility of the catalyst recovery and reuse. Therefore, we envisaged the possibility of applying these EcoNi(II) materials as new bio-based feedstock to synthetize novel EcoNi(0) catalysts and to study their catalytic activity in the transfer hydrogenation of carbonyl compounds. In this communication, we show that greener reductions of ketones and aldehydes can be performed with high yield and selectivity, with a biosourced EcoNi(0) catalyst.

The reduction of the carbonyl group of aldehydes and ketones to the corresponding alcohols is among the most common transformations in organic synthesis. Since early reports of reduction by diborane, metal hydrides are some of the most important reagents for performing this synthetic transformation at the laboratory scale. Alkali and alkaline earth metal hydrides, boranes and derivatives, alanes and derivatives, metal borohydrides, metal aluminohydrides, silanes, stannanes and transition metal hydrides have been largely described [START_REF]Comprehensive organic synthesis II Reduction[END_REF]. The synthetic utility of these reagents is beyond question. However, in the context of Green Chemistry, the operating conditions and safety of the reagents/solvent/process are obvious drawbacks of this methodology. Workup procedures are hazardous to handle and generate a large amount of wastes as by-products. The reduction step is often carried out with a stoichiometric amount of metal hydride. The reduction of carbonyl compounds to alcohols by catalytic hydrogenation represents the main industrial alternative to the use of hazardous metal hydrides [START_REF] Sanfilippo | Ullmann's Encyclopedia of Industrial Chemistry[END_REF]. Currently, the preferred transition metals for hydrogenation of carbonyl compounds are Ru, Pt, Pd, Rh and Ni. However, these catalytic processes often require high temperatures and pressures, which can be an industrial risk. Another challenge associated with the catalytic hydrogenation of carbonyl group into alcohol is the cost of the metal catalyst. A major concern regarding the future availability of these metal elements is their resource depletion and the difficultly of access to metal deposits [START_REF] Hunt | Elemental Sustainability and the Importance of Scarce Element Recovery, Element Recovery and Sustainability[END_REF].

Transfer hydrogenation (hydrogen transfer, H-transfer) is an interesting alternative methodology for the reduction of carbonyl compounds. The first advantage of this process over catalytic hydrogenation is the elimination of safety restrictions associated with the use of high pressure and temperature. The first examples of H-transfer reduction of ketones were reported with aluminium alkoxides (Meerwein-Ponndorf-Verley (MPV) reduction). The main drawback of this method is the reversibility of the reaction, the necessity of using a stoichiometric amount of catalyst and the hazardousness of Al(OiPr) 3 . A milestone was the discovery that metal complexes were able to catalyze the H-transfer reduction of ketones [START_REF] Wu | Reduction of CO to CHOH by metal-catalyzed hydrogenation and transfer hydrogenation[END_REF]. While a number of catalysts still rely on homogeneous complexes of expensive metals, such as Ru, Rh or Ir, several greener alternative catalysts have been proposed, including the use of heterogeneous catalysts. These materials comprise zeolites, hydrotalcite and various metal oxides, which are easily available and cheap [START_REF] Chuah | Meerwein-Ponndorf-Verley reduction over heterogeneous catalysts[END_REF][START_REF] Ruiz | Heterogeneous catalysis in the Meerwein-Ponndorf-Verley reduction of carbonyl compounds[END_REF]. However, their synthetic potential is often limited to small substrates and their use frequently requires high temperatures.

Dehydrated alumina supported KOH can also be used as an effective catalyst in the presence of isopropanol as a source of active hydride and solvent, under microwave irradiation [START_REF] Kazemi | Reduction of carbonyl compounds to the corresponding alcohols with isopropanol on dehydrated alumina under microwave irradiation[END_REF].

A recent alternative is the description of H-transfer reduction of carbonyl compounds promoted by Ni(0) nanoparticles [START_REF] Alonso | Nickel Nanoparticles in the Transfer Hydrogenation of Functional Groups, Metal Nanoparticles for Catalysis: Advances and Applications[END_REF][START_REF] Alonso | Nickel nanoparticles in hydrogen transfer reactions[END_REF]. Good to high yields of the corresponding alcohols were obtained depending on the nature of the substrate. The Ni nanoparticles were reused several times, maintaining a high catalytic activity. In terms of Green Chemistry, this methodology raises however several issues: the mixture of THF/i-PrOH as solvent is less advantageous than the eco-friendly isopropanol solvent alone. The preparation of Ni(0) nanoparticles by reduction of Ni(II) with lithium powder and a catalytic amount of DTBB (4,4 -di-tert-butylbiphenyl) in THF, was hazardous and exhibited a high environmental impact.

Improvements were thus required in order to meet the standards of current eco-friendly chemistry.

Experimental section

Reagents and methods

All reagents and solvents were purchased from Sigma-Aldrich and were used without further purification. Leaves of Psychotria gabriellae were harvested in New Caledonia, in the Mont Koghi locality. GC-MS analyses were performed using a Shimadzu QP2010SE, equipped with a 30 m × 0.25 mm × 0.25 m ZB-5MSi Guardian column (Phenomenex ® ) with hydrogen as carrier gas.

Inductively coupled plasma mass spectrometry (ICP-MS) analyses were performed using the metal analysis of total dissolved solutes in water. The samples were acidified with nitric acid 2.5% and stirred for 30 min. The digestates were diluted to 0.005 gL -1 . Three blanks were recorded for each step of the digestion and dilution procedure on a HR-ICP-MS Thermo Scientific Element XR. Three analyses were performed for each sample in order to determine the standard deviation of the measurement. X-ray diffraction (XRD) data measurements on the samples dried at 110 • C for 2 h were performed by using a BRUKER diffractometer (D8 advance, with a CuK␣ radiation =1.54086 • A) equipped with a LynxEye detector. TGA was performed with a TA Instruments Q500, under a flow of N 2 , on 14 mg of material. Nitrogen sorption experiments were performed using a Micromeritics Tristar apparatus.

The specific surface area S BET was calculated by the Brunauer-Emmett-Teller method (BET). Pore volume and average pore size were estimated using the Barrett-Joyner-Halenda method with the Kruk-Jaroniec-Sayari equation (BJH/KJS). All calculations were performed on the adsorption branch of the isotherm. Prior to analyses, the sample was outgassed overnight at 110 • C. XPS analyses were performed with an ESCALAB 250 spectrometer (Thermo Electron Corporation), using a monochromatized focused Al K X-ray source (1486.6 eV). The calibration of the spectrometer was done with Cu 2p3/2(932.8 eV), Au 4f7/2(84.0 eV) and Ag 3d5/2(368.6 eV). TEM images were taken using a Jeol 1200-EX2 Transmission Electron Microscope at accelerating voltage of 100 kV. EDS analysis with energy resolution 133 eV in scanning mode was performed using a Jeol JEM-2200FS Field Emission Electron Microscope at accelerating voltage of 200 kV. SEM images were obtained at the 'Institut Européen des Membranes', Montpellier, France, using a Hitachi S-4800 Field Emission Scanning Electron Microscope.

Preparation of EcoNi(II) formate

Leaves of Psychotria gabriellae were air-dried and crushed, then heated to 400 • C under air for 5 h. The resulting powder (20 g) was heated in formic acid (400 mL) under stirring, to 90 • C for 18 h. The resulting blue-green suspension was cooled to room temperature, then filtrated through a pad of Celite ® , rinsed with 100 mL of formic acid. The acid solution was discarded, then the resulting solid (mixture of insoluble formates and Celite ® ) was rinsed with 3 × 100 mL of boiling water. The resulting bright green solution was collected by filtration, then concentrated under reduced pressure, affording EcoNi(II) formate as a light green solid (14.9 g).

Preparation of EcoNi(0)

The EcoNi(0) was obtained by thermolysis of EcoNi(II) formate. For this purpose, 180.7 mg of EcoNi(II) formate were placed in a tubular oven by the aid of a porcelain crucible. The sample was first heated to 250 • C for 2 h in a nitrogen stream in order to eliminate volatile species. After this time, the nitrogen flux was stopped and the temperature was raised to 380 • C during 3 h. After cooling to room temperature, the EcoNi(0) was recovered as a black powder. Yield: 70.8 mg.

Representative procedure for ecoNi(0)-catalyzed H-transfer reduction

EcoNi(0) (1 mol%) and Al 2 O 3 basic Brockmann I (1 g, activated by heating to 400 • C for 15 min) were added to a 25 mL flask containing i-PrOH (5 mL) and the carbonyl compound (1 mmol). The resulting mixture was magnetically stirred to 80 • C. The reaction progress was monitored by GC-MS analysis, with the following temperature programme: 4 min isothermal at 40 • C, then increasing from 40 • C to 270 • C at 20 • C.min -1 . GC-MS calibration was performed by analysis of known quantities of pure products and dodecane as an internal standard.

Results and discussion

We demonstrate here that EcoNi(0) prepared by thermal reduction of EcoNi(II) formate has high potential in green reduction of carbonyl compounds, and that this ecocatalyst is well adapted for the selective reduction of multifunctionalized compounds, including conjugated aldehydes. We focused on the formation of a Ni(0) catalyst for H-transfer hydrogenation starting from biomass of a Ni-hyperaccumulating plant. Leaves were harvested from Psychotria gabriellae (Rubiaceae), a native Ni-hyperaccumulating plant of the subtropical Pacific island New Caledonia. They were collected from plants growing in the Southern Province of New Caledonia. By following a procedure described in previous reports [START_REF] Grison | Psychotria douarrei and Geissois pruinosa, novel resources for the plant-based catalytic chemistry[END_REF][START_REF] Escande | From biodiversity to catalytic diversity: how to control the reaction mechanism by the nature of metallophytes[END_REF], thermal treatment of this biomass under air afforded a powder consisting of oxides of the metal elements present in the plant. Among these oxides, nickel was present as NiO, so that a reduction to Ni(0) was required. Production of Ni(0) nanoparticles used as catalyst for H-transfer hydrogenation has been previously performed by reduction of Ni(II) salts with several reducing agents, such as metal lithium [START_REF] Alonso | Nickel nanoparticles in hydrogen transfer reactions[END_REF][START_REF] Alonso | Hydrogen-transfer reduction of carbonyl compounds catalysed by nickel nanoparticles[END_REF][START_REF] Alonso | Hydrogen-transfer reduction of carbonyl compounds promoted by nickel nanoparticles[END_REF][START_REF] Alonso | Preparation of nickel(0) nanoparticles by arene-catalysed reduction of different nickel chloride-containing systems[END_REF][START_REF] Alonso | A new straightforward and mild preparation of nickel(0) nanoparticles[END_REF], hydrazine [START_REF] Dhakshinamoorthy | Clay entrapped nickel nanoparticles as efficient and recyclable catalysts for hydrogenation of olefins[END_REF][START_REF] Neelakandeswari | Preparation and characterization of nickel aluminosilicate nanocomposites for transfer hydrogenation of carbonyl compounds[END_REF][START_REF] Chen | Synthesis of nickel nanoparticles in water-in-Oil microemulsions[END_REF][START_REF] Chen | Synthesis of nickel nanoparticles in aqueous cationic surfactant solutions[END_REF][START_REF] Wu | Synthesis and characterization of nickel nanoparticles by hydrazine reduction in ethylene glycol[END_REF], NaBH 4 [START_REF] Polshettiwar | Nanoparticle-supported and magnetically recoverable nickel catalyst: a robust and economic hydrogenation and transfer hydrogenation protocol[END_REF][START_REF] Kidwai | Ni-nanoparticles: an efficient green catalyst for chemoselective reduction of aldehydes[END_REF][START_REF] Kidwai | Ni-nanoparticles usage for the reduction of ketones[END_REF], ethylene glycol [START_REF] Dutta | Synthesis and catalytic activity of Ni • -acid activated montmorillonite nanoparticles[END_REF][START_REF] Wada | Preparation of nano-sized nickel metal particles by microwave irradiation[END_REF][START_REF] Tsuji | Fast preparation of nano-sized nickel particles under microwave irradiation without using catalyst for nucleation[END_REF], oleylamine/trioctylphosphine [START_REF] Park | Chemical transformation and morphology change of nickel-silica hybrid nanostructuresvia nickel phyllosilicates[END_REF] or by thermal decomposition of nickel isopropoxide, prepared with an excess of Li, Na or K metal [START_REF] Boldrini | A new route to an active form of nickel. Transfer hydrogenation of alkenes and carbonyl compounds with 2-propanol[END_REF]. In spite of their efficiency, these reducing agents are toxic or hazardous to manipulate. The use of alkali metals in excess also raises sustainability issues, due to the high environmental footprint associated with their production. Formation of Ni(0) by reduction of bioaccumulated Ni(II) has been described in a previous report, by pyrolysis of wood of another Ni hyperaccumulating plant (tree Sebertia acuminata Pierre ex. Baillon), leading to Ni(0) supported on charcoal (Ni 5-7 wt%) [START_REF] Lerch | Carbon-supported nickel nanoparticles from a wood sample of the tree sebertia acuminata pierre ex. Baillon[END_REF]. However, the hyperaccumulating plant used was a rare, endangered species [START_REF] Dias | Metal and metalloid containing natural products and a brief overview of their applications in biology, biotechnology and biomedicine[END_REF], and no catalytic activity of the material was reported. In order to produce Ni(0) in a sustainable way from bioaccumulated Ni(II), we selected the thermal reductive decomposition of Ni(II) formate. This procedure allows the formation of Ni(0) without the use of additional reducing agents. This particular behavior is related to the reducing character of formates/formic acid, which is able to reduce Ni(II) 'in situ' [START_REF] Nishimura | Nickel from nickel formate[END_REF][START_REF] Xia | Preparation of nickel powders by spray pyrolysis of nickel formate[END_REF]. EcoNi(II) formate was firstly obtained by formic acid treatment of the mixture of oxides, resulting of the calcination of P. gabriellae leaves. As Ni(II) formate is not soluble in pure formic acid, EcoNi(II) formate was recovered by filtration as a solid containing 22.8 wt% Ni (Table 1). This value is slightly lower compared to the theoretically expected value, based on the chemical composition of nickel formate dihydrate (H 6 C 4 O 6 Ni). The result is due to the presence of other metallic species of plant origin (Ca, Mg, Na, K, Fe). This intermediate nickel salt was used to access EcoNi(0) via a simple thermolytic step. In addition of avoiding costly and hazardous reducing agents, the use of formic acid is another sustainable asset, because this molecule can be produced from biomass feedstocks [START_REF] Wang | Catalytic conversion of biomass-derived carbohydrates to formic acid using molecular oxygen[END_REF][START_REF] Müller | Selective production of formic acid by wet oxidation of aqueous-phase bio-oil[END_REF]. Here, we used this approach for the formation of biosourced Ni(0) catalysts, with high content in Ni, thanks to the elimination of carbon as CO and CO 2 (Scheme 1) [START_REF] Hofmann | Bildung von Formal-dehyd und anderen organischen Stoffen aus Ameisensäure. I. Mitteilung;1; Selbstreduktion der Formiate[END_REF][START_REF] Wheeler | Decomposition reactions of nickel formate, nickel malonate, nickel maleate and nickel fumarate in oxygen[END_REF][START_REF] Galwey | The thermal decomposition of metal salts of organic acids -Nickel formate[END_REF].

For this reason, we then studied the thermal behavior of our EcoNi(II) formate via thermogravimetric analysis (TGA). The TGA plot of the material in the range of 50-1000 • C is given in Fig. S1. It clearly appears that the material shows three distinct weight loss steps. The first step, occurring at temperatures below 250 • C, is related to the elimination of physisorbed water and formic acid. The decomposition of the EcoNi(II) formate and the formation of EcoNi(0) occurs at temperatures 300 • C < T < 350 • C. This behavior is very similar to previously reported results obtained with pure Ni(II) formate, also showing a sharp mass loss at approx. 300 • C [START_REF] Xia | Preparation of nickel powders by spray pyrolysis of nickel formate[END_REF]. Finally, a last mass decrease can be observed at higher temperatures (T > 800 • C). This mass loss is due to further dehydration steps of metallic hydroxides and/or sublimation of various metallic species. In this context, it has to be pointed out that despite the fact that the material is mainly constituted of Ni species, a multitude of other metals (Na, Mg, Ca) is present (see Table 1).

In order to synthesize sufficient biosourced EcoNi(0) and to study its catalytic properties, we exploited this thermal reduction of Ni(II) formate into Ni(0) to access to on a larger scale (Fig. 1). We first heated EcoNi(II) formate to 250 • C for 2 h in a nitrogen stream in order to eliminate volatile species such as physisorbed water and formic acid. After this time, the N 2 stream was stopped in order to form a reducing atmosphere due to the decomposition of formate and the formation of carbon monoxide in the reactor. The material was further heated to 380 • C during 3 h in order to form the EcoNi(0). This method can be advantageously compared to conventional processes, which required hazardous metallurgical preparation of Scheme 1. Mechanism of formation of EcoNi(0) derived from nickel hyperaccumulating plant. Ni precursors [START_REF] Johnson | Manufacture of nickel formate[END_REF]. EcoNi(0) was characterized via ICP-MS, nitrogen sorption, scanning electron microscopy and X-ray diffraction in order to determine the chemical composition, surface properties and crystallinity of the material.

ICP MS analysis

As shown by ICP-MS study (Table 1), EcoNi(0) obtained as a black powder, is a polymetallic solid with Ni as the major transition metal (40.7 wt%). The reproducibility of composition of similar EcoNi(0) was studied, and showed that the levels of transition elements are only slightly variable between samples derived from different plants of the same species. In particular, results show the necessity of considering leaves age in the design of sample collection to obtain a constant TE content in batches of EcoNi(0) [START_REF] Losfeld | Leaf-age and soil-plant relationships: key factors for reporting trace-elements hyperaccumulation by plants and design applications[END_REF]. EcoNi(0) was prepared from several batches of P. gabriellae in order to homogenize the content and minimize possible variations in the composition. Updated data on Ni-hyperaccumulating and accumulating plants from New Caledonia have been presented in some recent papers of our group, aimed at producing EcoNi catalysts on industrial scale in view of their commercialization [START_REF] Losfeld | Phytoextraction from mine spoils: insights from New Caledonia[END_REF][START_REF] Losfeld | Mining in New Caledonia: environmental stakes and restoration opportunities[END_REF].

XRD characterization of EcoNi(0)

In order to confirm the chemical composition of EcoNi(0), we performed X-ray diffraction measurements with this material. Fig. 2 shows the X-ray powder diffractogram of EcoNi(0), obtained by thermolysis of EcoNi(II) formate. The diffractogram shows the characteristic diffractions rays of Ni(0), along with the unexpected FeNi 3 , whose formation can be explained by reduction of iron formate, present in small amount in EcoNi(II) formate (according to Fe wt% detected in ICP-MS, see above). Besides Ni(0) and FeNi 3 , sharp diffraction rays at 14.7, 25.6, 29.7, 31.8 and 49.3 • indicate the presence of calcium sulfate. Furthermore, the diffraction ray of low intensity at 62.9 • suggests the presence of nickel oxide, probably formed during the sample preparation. Broadening of the corresponding peaks suggests the formation of small nickel particles, according to the Scherrer equation [START_REF] Dinnebier | Powder Diffraction: Theory and Practice[END_REF]. Subsequent characterization of EcoNi(0) morphology was thus conducted to determine the porosity and the particles size.

XPS analysis

X-ray photoelectron spectroscopy (XPS) with EcoNi(0) was performed in order to confirm the oxidation state of nickel in the EcoNi(0) material, after thermal decomposition of EcoNi(HCOO) 2 . The Ni 2p core level XPS spectrum (Fig. 3) shows three peaks centered around 856, 861 and 873 eV, which can readily be assigned to Ni(0) 3p3/2, Ni(II) 2p3/2and Ni(0)2p1/2, respectively. The peaks observed for Ni(II) 2p3/2 s could be assigned to the presence of NiO, that may originate from the surface oxidation of Ni(0) nanoparticles during the XPS sampling procedure. Ni(II) may be overestimated as XPS is a surface sensitive method which only takes into account the surface of the material. These observations are in agreement with the recently reported results of Zahmakiran et al. [START_REF] Karakas | Nickel nanoparticles decorated on electrospun polycaprolactone/chitosan nanofibers as flexible, highly active and reusable nanocatalyst in the reduction of nitrophenols under mild conditions[END_REF]

Characterization by nitrogen sorption and SEM

We studied the textural properties of the material via nitrogen sorption. The nitrogen sorption isotherm is given in Fig. 4. The isotherm shows that the EcoNi(0) is a moderately porous material with a specific surface area of 109 m 2 /g and a mesopore volume of 0.20 cm 3 /g. The progressive nitrogen uptake over a quite large P/P 0 range indicates rather broad pore size distribution. Finally, the strong nitrogen uptake at high partial pressures indicates intergrain porosity and suggests that the material is constituted of agglomerated primary nanoparticles.

These results are confirmed via scanning electron microscopy (SEM). SEM images of the material clearly confirm the granular morphology of the material; with consists of agglomerated particles displaying a particle size in the range of 15-50 nm (Fig. 5b).

TEM analysis

The characterization of EcoNi(0) via Transmission Electron Microscopy (TEM) affords valuable information about the texture and homogeneity of the material. Two representative TEM images are given in Fig. 6. The material is constituted of particles of a diam- eter of several hundreds of nanometers. It clearly appears that these particles are heterogeneous and consist of at least two phases. Ni(0) nanoparticles of variable size can clearly be seen. The diameter of these particles is in the range of 2-20 nm. The Ni(0) particles are embedded within a matrix of a support material, probably calcium sulfate, as indicated by XRD and ICP-MS analysis.

EDS analysis

Finally, we performed Energy-dispersive X-ray spectroscopy (EDS) analysis in order to confirm the morphological features of the material and its chemical composition. EDS analysis with EcoNi(0) (see Supporting information) clearly shows that this material displays a heterogeneous morphology. Elemental mapping allows differentiating nickel rich domains with Ni contents up to 70 wt-% on the one side, and nickel poor domains with nickel content lower 10 wt-% and containing mainly calcium, sulfur and oxygen. This result therefore confirms the XRD analysis which indicated the presence of a significant amount of calcium sulfate in the material. EDS analysis also indicates the presence of small amounts of magnesium and manganese in the material, therefore confirming the results obtained by ICP-MS analysis.

In conclusion, TEM, SEM, XPS and EDS analysis give concordant results regarding the elemental composition and the morphology of the EcoNi(0) material. In fact, EcoNi(0) is constituted of Ni(0) nanoparticles which are embedded in a calcium sulfate matrix. Nickel poor and nickel rich domains are present in the same particles. 3.2. Reduction of carbonyl compounds catalyzed by EcoNi(0)

Conditions of reduction

The catalytic properties of EcoNi(0) were assessed in the MPV reduction of carbonyl compounds. A preliminary study was conducted with cyclohexanone and 2-dodecanone, as model substrates (Table 2). Using EcoNi(0) alone, only a low yield of reduction product was observed for cyclohexanone (29%, entry 1), even with a stoichiometric amount of EcoNi(0), and after prolonged heating. However, addition of a catalytic amount of NaOH (20 mol%) allowed to lower the catalytic loading of EcoNi(0), while leading to a marked increase of reaction yield (56%, entry 2). The amount of EcoNi(0) could thus be reduced up to 1 mol%, by using 30 mol% NaOH, affording a quantitative reduction of cyclohexanone (entry 4). In spite of its efficiency, NaOH is a strong base, used in homogeneous phase in the reaction. We thus turned to alumina, a greener heterogeneous base. By using a ratio of one gram per mmol of ketone, alumina substituted for NaOH with the same efficiency, when associated to 1 mol% of EcoNi(0) (entry 5). Previous studies have reported the catalytic activity of alumina in MPV reduction of ketones, either at elevated temperatures (300 • C) [START_REF] Ramana | Hydrogen transfer reactions. I. Reduction of carbonyl compounds by alcohols catalyzed by alumina[END_REF], or with large amounts of solid (ca 5 g per mmol of substrate) [START_REF] Posner | Organic reactions at alumina surfaces. 6. Isopropyl alcohol and diisopropylcarbinol on dehydrated alumina as reagents for very selective carbonyl reductions[END_REF], or in drastic conditions to avoid any trace of moisture [START_REF] Wismeijer | Conditioning of ␥-Al2O3 catalyst in the transfer hydrogenation of 4-tert-butyl-cyclohexanone by 2-propanol[END_REF]. In this context, we evaluated the activity of alumina in our experimental conditions, without EcoNi(0): whereas reduction of 2-dodecanone occurred with 93% yield by combining alumina and 1 mol% EcoNi(0), only 11% yield was observed with alumina alone, in the same conditions (entries 6-7). The example of acetophenone (entry 8) confirmed the very low reactivity of sole alumina in isopropanol. These results thus showed that alumina was almost not active in our conditions without EcoNi(0), and that ketone reduction occurred with high yield only when both species were associated. This observation is consistent with a number of previous reports, both in homogeneous [START_REF] Wu | Reduction of CO to CHOH by metal-catalyzed hydrogenation and transfer hydrogenation[END_REF][START_REF] Zassinovich | Asymmetric hydrogen transfer reactions promoted by homogeneous transition metal catalysts[END_REF] and heterogeneous catalysis [START_REF] Chuah | Meerwein-Ponndorf-Verley reduction over heterogeneous catalysts[END_REF][START_REF] Ruiz | Heterogeneous catalysis in the Meerwein-Ponndorf-Verley reduction of carbonyl compounds[END_REF], where mechanistic studies have shown that addition of a base often promoted the interaction between isopropanol and the active metal species. It should be noted, that the amount of alumina could be reduced, but the reaction is slowed.

Although any attempt to directly reuse the EcoNi(0) failed, this methodology can be considered advantageous, because the addition of formic acid followed by the described thermic treatment (see part 3.1.1) allowed the regeneration and reuse of ecocatalyst. The properties of EcoNi(0) are preserved after regeneration.

Scope of the methodology

The conditions developed with EcoNi(0)/Al 2 O 3 were applied to a range of carbonyl compounds, to assess the scope of the method (Table 3). The previous result of cyclohexanone reduction was further optimized with reduction of reaction time to 2 h (entry 1). These conditions were extended to the reduction of other ketones (entries 2-3 and 5-6), but long reaction time (24 h) remained necessary for complete reduction of acetophenone (entry 3). Aldehydes are challenging substrates for H-transfer reduction, especially in basic conditions, as they can easily undergo unwanted aldol condensation. For this reason, whereas H-transfer reduction of ketones has been described with a large number of catalysts, only a few have been reported for aldehydes [START_REF] Wu | Reduction of CO to CHOH by metal-catalyzed hydrogenation and transfer hydrogenation[END_REF]. In our case, reaction of 1-heptanal afforded 78% yield of 1-heptanol (entry 4), demonstrating that the catalytic system EcoNi(0)/Al 2 O 3 was efficient for aldehyde reduction, with a minimal amount of side products. Interestingly, the conversion of benzaldehyde (entry 7, 99%) can be advantageously compared to literature (42 and 93%). [START_REF] Alonso | Nickel nanoparticles in hydrogen transfer reactions[END_REF][START_REF] Alonso | Hydrogen-transfer reduction of carbonyl compounds catalysed by nickel nanoparticles[END_REF][START_REF] Alonso | Hydrogen-transfer reduction of carbonyl compounds promoted by nickel nanoparticles[END_REF][START_REF] Kidwai | Ni-nanoparticles usage for the reduction of ketones[END_REF]The catalytic system showed a high selectivity toward carbonyl compounds, as illustrated by the reduction of the aldehyde group of 3-nitrobenzaldehyde, without any reduction of the nitro group, even after a prolonged reaction time (entry 9). Similarly, the reduction of the aldehyde group of 4cyanobenzaldehyde is chemoselective (entry 8). Contrary to Ni(0) nanoparticles described by Yus et al., our methodology is compatible with an alkyne moiety (entry 10) [START_REF] Alonso | Highly selective hydrogenation of multiple carbon-carbon bonds promoted by nickel(0) nanoparticles[END_REF]. Finally, the catalytic system EcoNi(0)/Al 2 O 3 revealed a high selectivity during the H-transfer reduction of ␣,␤-unsaturated aldehydes, like citral (entry 12). Reduction of citral can lead to a plethora of products, due to the combination of the three reducible groups. Whereas selective reduction of the carbonyl group is usually performed with catalysts based on precious metals like Pt, Au or Ir [START_REF] Stolle | Hydrogenation of citral: a wide-spread model reaction for selective reduction of alpha beta-unsaturated aldehydes[END_REF], EcoNi(0)/Al 2 O 3 catalyzed citral reduction into geraniol in 97% yield. Moreover, no modification of the cis/trans ratio of substrate occurred during reaction, conferring strong advantages to the EcoNi(0)/Al 2 O 3 system as an alternative to expansive catalysts. Interestingly, the hydrogenation of citronellal with Ni/Al 2 O 3 delivers citronellol, another compound used as fragrance ingredient (entry 11) [START_REF] Stolle | Hydrogenation of citral: a wide-spread model reaction for selective reduction of alpha beta-unsaturated aldehydes[END_REF]. We can conclude that Ni(0) and other elements present in EcoNi(0) demonstrate the interest of the original polymetallic complexes of the plant-based catalyst.

Conclusion

In conclusion, we exploited the thermal reductive decomposition of biosourced Ni(II) formate made from the Ni hyperaccumulating plant Psychotria gabriellae, as an green alternative method for preparation of Ni(0), without hazardous and toxic reducing agents. Characterization of the resulting material EcoNi(0) confirmed that the material consists of agglomerated primary Ni(0) nanoparticles. Combined to alumina as a mild heterogeneous base, EcoNi(0) catalyzed the transfer hydrogenation of a range of carbonyl compounds, with isopropanol as an eco-friendly reagent and solvent. With only 1 mol% of EcoNi(0), ketones and aldehydes were reduced into alcohols, with high yield and selectivity. In particular, reduction of citral into geraniol, a molecule of commercial importance in the fragrance industry, highlighted the performances of the catalytic system as a valuable alternative to classical catalysts based on precious metals. The alternative we propose, using nickel hyperaccumulating plants to produce bio-based reducing agents could bring extra added value to the phytoextraction and the programs of ecological restoration.

3. 1 .

 1 EcoNi(0) preparation and characterization 3.1.1. TGA analysis and reduction of EcoNi(II) formate: formation of EcoNi(0)

Fig. 1 .

 1 Fig. 1. Preparation of EcoNi(0) from Ni hyperaccumulator Psychotria gabriellae.

Fig. 2 .

 2 Fig.2. X-ray diffractogramm of EcoNi(0) and detected species.

2 Fig. 3 .

 23 Fig. 3. XPS spectrum of EcoNi(0).

Fig. 4 .

 4 Fig. 4. Nitrogen sorption isotherm of EcoNi(0).

Fig. 5 .

 5 Fig. 5. SEM images of EcoNi(0).

Fig. 6 .

 6 Fig. 6. TEM images of EcoNi(0).

  Reaction conditions: ketone (1 mmol), i-PrOH (5 mL), EcoNi(0) (amount based on Ni), base, 80 • C. a Yield of the corresponding alcohol determined by GC-MS analysis. b Al2O3 basic Brockmann I activated, 1 g/1 mmol ketone.

  Reaction conditions: substrate (1 mmol), i-PrOH (5 mL), EcoNi(0) (1 mol%), Al2O3 basic Brockmann I activated (1 g), 80 • C. a Yield determined by GC-MS analysis. b Side products resulting of aldol condensation were formed in 18% yield. c Same cis/trans ratio for substrate and product: 24/76.

Table 1

 1 ICP-MS analysis of EcoNi(II) formate and EcoNi(0).

		wt% (±sd a )
		EcoNi(II) formate	EcoNi(0)
	Na	4.7 (±0.2)	17.0 (±1.3)
	Mg	2.5 (±0.1)	4.1 (±0.3)
	Ca	3.0 (±0.2)	10.2 (±0.5)
	Ni	22.8 (±0.5)	40.7 (±2.9)
	Mn	0.3 (±0.006)	0.7 (±0.05)
	Fe	0.6 (±0.04)	0.9 (±0.06)

a Standard deviation.

Table 2

 2 Optimization of the reaction conditions.

	Entry	EcoNi(0) (mol%)	Base	Time (h)	Substrate	Yield (%) a
	1	100	-	25	Cyclohexanone	29
	2	10	NaOH 20 mol%	18	Cyclohexanone	56
	3	10	NaOH 30 mol%	18	Cyclohexanone	100
	4	1	NaOH 30 mol%	24	Cyclohexanone	100
	5	1	Al2O3 b	24	Cyclohexanone	100
	6	-	Al2O3 b	6	2-Dodecanone	11
	7	1	Al2O3 b	6	2-Dodecanone	93
	8	-	Al2O3 b	24	Acetophenone	9

Table 3

 3 Scope of the EcoNi(0)-catalyzed H-transfer reduction.

	Entry	Substrate	Time (h)	Product	Yield (%) a
	1		2		>99
	2		2		>99
	3		24		>99
	4		3		78 b
	5		20		>99
	6		6		93
	7		2		99
	8		18		83
	9		18		85
	10		24		75
	11		4		>99
	12		6		97 c

Acknowledgements

This work was supported by the Agence Nationale de la Recherche (ANR, programme 11ECOT01101), the Agence de l'Environnement et de la Maîtrise de l'Energie (ADEME) and the Centre National de la Recherche Scientifique (CNRS). The authors are grateful to Société Le Nickel (SLN) and the South Province of New Caledonia for the facilities and financial support on mining sites.