Lipase-catalysed synthesis of esters of ferulic acid with natural compounds and evaluation of their antioxidant properties

Lipases from Candida antarctica (Novozyme 435^®), Candida rugosa, Chromobacterium viscosum and Pseudomonas sp. were used to perform transesterifications of vinyl ferulate with hydroxyl-steroids and p-arbutin. The antioxidant activity of the products was evaluated using the free radical 2,2′-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) free radical quenching antioxidant assays, and inhibition of the oxidation of low-density lipoprotein, LDL. Arbutin ferulate was found to possess a 19% higher antiradical activity against the ABTS free radical than its precursor ferulic acid, and it also inhibited the oxidation of LDL more efficiently (by 10%) than its precursors. All of the biocatalytically synthesised products exhibited higher antioxidant activity than Trolox, the well known commercial benchmark antioxidant, and their precursor, ferulic acid.