ANTIOXIDATIVE PROPERTIES OF PROANTHOCYANIDINS .2. RADICAL SCAVENGING ACTION AND ITS MODE IN PROCYANIDIN-B-1 AND PROCYANIDIN-B-3 FROM AZUKI-BEANS TO PEROXYL RADICALS

Procyanidins B-1 and B-3 from azuki beans showed remarkable scavenging activities, especially to hydrophilic radicals. The inhibition rate constants for the scavenging of hydrophilic peroxyl radicals generated from 2,2’-azobis(2-amidinopropane)hydrochloride in aqueous media were calculated at 37°C to be kinh=6.0×104 M−1S−1,5.9×104M−1S−1, 2.7×104 M−1S−1,5.0×104M−1S−1and 1.1×105M−1S−1, and the stoichiometric factors as n = 8.4,8.0,3.7,1.2 and 1.7 for procyanidin B-1, procyanidin B-3, (+)-catechin, ascorbic acid and α-tocopherol, respectively. Thus, the dimeric procyanidin molecule could trap eight radicals. The production and structures of procyanidin B-3 radicals are discussed on the basis of the ESR spectra observed by autoxidation of procyanidin B-3 in an aqueous alkaline methanol solution. © 1990 by the Japan Society for Bioscience, Biotechnology, and Agrochemistry.