Abstract: The invention relates to an organometallic complex obtainable by reaction:of a cation of a metal (M) in an oxidation state at least equal to 2 useful as a biocatalyst in living metabolism,of a mixture of sitosterol and sitostanol, or of pure sitostanol or of a plant extract containing same,of the diglyceride of formula (I): ##STR1## in which: R.sub.1 is an acyl residue of oleic acid (C.sub.18 :1),R2 in an acyl residue of a linear or branched, saturated or unsaturated fatty acid having between 2 and 18 carbon atoms. More particularly, the invention relates to complexes in which R.sub.2 is an oleoyl or acetyl group. The invention also relates to pharmaceutical compositions containing this complex, particularly those wherein the metal is vanadium, and to their use in the treatment and/or the prevention of hypercholesterolaemia and/or of hypertriglyceridaemia, of insulin-dependent or non insulin-dependent diabetes, of insulin resistance and associated pathologies.