Enzymatic preparation of acylated derivatives of silybin in organic and ionic liquid media and evaluation of their antitumor proliferative activity

Biocatalytic preparation of acylated derivatives of silybin using several acyl donors (free fatty acids or their esters), catalyzed by immobilized Candida antarctica lipase B, was performed in various organic solvents as well as in imidazolium-based ionic liquids containing either BF4- or PF6- anions. Total conversion of silybin was achieved in acetone using short-chain acyl donors (vinyl butanoate) at a 10: 1 molar ratio of acyl donor to silybin. The enzymatic process in ionic liquids depended strongly on the alkyl chain length of the cation as well the anion used. Higher conversion yields (up to 75.8%) and reaction rates (up to 0.31 mmol h(-1) g(-1) biocatalyst) were obtained in the BF4- as compared with PF6- containing ionic liquids. The amounts of silybin ester formed in a one-step biocatalytic process were high (>40 g L-1) in both reaction media. The antiproliferative effect of acylated silybin derivatives on the growth of K562 human leukemia cells was estimated and compared with that of silybin.