A compound of general formula (I): ** (See formula) ** in which 1 ** (See symbol) ** 2, 2 ** (See symbol) ** 3, 3 ** (See symbol) * * 4 are each independently a single or double bond； Ra is selected from a linear or branched C1-C5 alkyl, linear or branched C2-C5 alkenyl, linear or branched C2-C5 alkynyl and -C (>； = O) Rd, each optionally substituted with at least one group selected from - OH, -COOH, -NH2, C1-C5 amine, halogen, phenyl, heteroaryl； wherein Rd is selected from the group consisting of -H, -OH, linear or branched C1-C5 alkyl, linear or branched C2-C5 alkenyl, linear or branched C2-C5 alkynyl, linear or branched C1-C5 alkoxy, -NReRf； Re and Rf are each independently selected from H and linear or branched C1-C5 alkyl； and Rb and Rc are each independently selected from -H, -OH,>； = O,>； = CRgRh,>； = NRi>； = S, and a group of formula (II '): ** (See formula) ** in where Rj, Rk and Rmm are each independently selected from H and -ORn, where Rn is selected from H, -COORt, a linear or branched C1-C5 alkyl optionally substituted with at least one group selected from -COOH, -NH2, provided that at least one of Rj and Rk is different from H； Rm is selected from an optionally substituted linear or branched C3-C12 alkyl, an optionally substituted linear or branched C5-C9 alkoxy, an optionally substituted linear or branched C1-C7 ether； and Rt is selected from H, and C1-C5 alkyl； and wherein Rg, Rh, and Rj are each independently selected from H, linear or branched C1-C5 alkyl, linear or branched C1-C5 alkoxy and -NH2； and wherein at least one of Rb and Rc is a group of formula (II ').Un compuesto de fórmula general (I): **(Ver fórmula)** en la que 1 **(Ver simbolo)** 2, 2 **(Ver simbolo)** 3, 3 **(Ver simbolo)** 4 son cada uno independientemente un enlace simple o doble； Ra se selecciona entre un alquilo C1-C5 lineal o ramificado, alquenilo C2-C5 lineal o ramificado, alquinilo C2-C5 lineal o ramificado y -C(>；=O)Rd, cada uno opcionalmente sustituido con al
