Studies of the Antioxidative Activities of Humic Substances in Peat (1)

Abstract

Humic acid (HA) and fulvic acid (FA) were prepared from peat and they had high total polyphenol contents (HA: 421 mg/g and FA: 299 mg/g). Antioxidative activity assays were carried out as following; (1) scavenging activities for 1,1-Diphenyl-2- picrylhydrazyl (DPPH) radical, (2) inhibitory effect on oxidation of linoleic acid, (3) inhibitory effect on 2,2’-azobis (2-amidinopropane) dihydrochloride (AAPH)-induced hemolysis of rabbit erythrocytes in vitro, and (4) effect on Cu²⁺-mediated conjugated dienes formation in human low density lipoprotein (LDL). Both of HA and FA showed relative activities against (1)-(3). That is, (1) HA and FA showed about 90 % of scavenging activities for DPPH radical at the concentration of 250 μg/ml, (2) at the concentration of 81 μg/ml, HA and FA showed inhibitory effect on oxidation of linoleic acid 57 % and 27 %, respectively, (3) HA as well as ascorbic acid (AA) showed about 90 % of inhibitory effect on AAPH-induced hemolysis of rabbit erythrocytes (at the concentration of 67 μg/ml), and (4) HA inhibited Cu²⁺-mediated conjugated dienes formation in human LDL with the dose dependently. The inhibition mechanism by HA was suggested to be different from that of AA.