r unsaturated, linear or branched C1-C10 alkyl radical; a saturated or unsaturated, linear or branched C1-C10 alkoxy radical or an HSO3 group; [0088] R10 is a hydrogen or HSO3; [0089] R8 is an OH group; a group OR11 in which R11 is a saturated or unsaturated, linear or branched C1-C10 alkyl radical; or a group having the following structure: [0090] in which R12 is hydrogen or HSO3; or a group havi