The present invention relates to compounds comprising the general formula (I), in which R1 and R2, which may be identical or different, are selected from the group comprising —H or a linear or branched alkyl group having from 1 to 6 carbon atoms or together form an aromatic or aliphatic ring with 5 or 6 atoms； Y and Z, which may be identical or different, are selected from the group comprising —H, —OH, —COOH, —OR3, —CH(OR3)COOH, in which R3 is selected from H, phenyl, benzyl, —CF3 or —CF2CF3, vinyl, allyl and a linear or branched alkyl group having from 1 to 6 carbon atoms.
