1. A process for the reduction of an organic compound, comprising the following steps:a) preparing a metal catalyst comprising less than 2% by weight of carbon, and nickel in the form Ni(0), Ni(II) or a mixture of Ni(0) and Ni(II); said step a) comprising:
i) calcinating a plant or part of a plant that has accumulated nickel, comprising Ni(II) in a quantity at least equal to 100 ppm of dehydrated plant, said plant being selected from the group consisting of Adiantum, Agatea, Alyssum, Arenaria, Argophyllum, Baloghia, Berkheya, Blepharis, Bornmuellera, Brackenridgea, Buxus, Campanula, Cardamine, Casearia, Chromolaena, Chrysanthemum, Cleidion, Cnidoscolus, Cochlearia, Dicoma, Dichapetalum, Esterhazya, Euphorbia, Geissois, Glochidion, Heliotropium, Homalium, Hybanthus, Indigofera, Juncus, Justicia, Knema, Lasiochlamys, Leucanthemopsis, Leucocroton, Linaria, Lophostachys, Luzula, Merremia, Minuartia, Mitracarpus, Myristica, Noccaea, Oncotheca, Pancheria, Pearsonia, Peltaria, Phyllanthus, Planchonella, Psychotria, Pcynandra, Rhus, Rinorea, Ruellia, Saxifraga, Sebertia, Senecio, Shorea, Solidago, Stachys, Stackhousia, Streptanthus, Thlaspi, Trichospermum, Trifolium, Trisetum, Turnera, Vellozia, Walsura, Xylosma, Garcinia, Mosiera, Ouratea, Psidium, Senecio, Rondeletia, Ariadne and Phyllomelia, and obtaining ashes from the calcination;
ii) treating the ashes obtained at the end of step ii) with an organic acid selected from the group consisting of formic acid, oxalic acid and phosphinic acid, and obtaining a product from the acid treatment;
iii) heating treating the product obtained at the end of step ii) and obtaining a metal catalyst comprising Ni(0), the Ni metal of which originating only from said plant or part of plant listed in step i); and
b) reducing an organic compound in the presence of a hydrogen donor, and in the presence of the metal catalyst obtained from step a),
wherein the organic compound comprises one or more functions selected from the group consisting of aldehyde, ketone, imine functions and conjugated carbon-carbon bonds; and
wherein the hydrogen donor is selected from the group consisting of an alcohol, a carbohydrate reducing agent, formic acid or a formic acid salt, a cycloalkene, an unsaturated heterocycle, phosphinic acid and a saline hydrophosphite.