Antioxidative Activity of 3-O-Octanoyl-(+)-Catechin, a Newly Synthesized Catechin, in Vitro

The antioxidative activities of 3-O-octanoyl-(+)-catechin were studied in vitro. Free radical scavenging activities were tested by spectrophotometrically measuring 2,2′-azinobis(3-ethylbenzothiazoline-6-sulphonate) (ABTS) radical cations, as well as by measuring luminol chemiluminescence induced by peroxyl radicals generated from 2,2′-azinobis(2-amidinopropane) dihydrochloride (AAPH). The radical scavenging activities of the 3-O-octanoyl-(+)-catechin for ABTS radical cations and peroxyl radicals were less effective than the original (+)-catechin, but stronger than 6-hydroxy-2,5,7,8-tetramethyl-chroman-2-carboxylic acid (Trolox). Furthermore, 3-O-octanoyl-(+)-catechin unlike (+)-catechin did not effectively antagonize the decrease in the intrinsic fluorescence intensity of allophycocyanin induced by AAPH, which was measured as an index of protein damage. Conversely, 3-O-octanoyl-(+)-catechin demonstrated more potent antioxidative activity for the linoleic acid peroxidation induced by AAPH than (+)-catechin and Trolox. These findings suggest that the introduction of an octanoyl group at the 3-OH position in a (+)-catechin effectively quench the secondary products of lipid peroxidation without much loss of free radical scavenging activity.