Studies of the Antioxidative Activities of Humic Substances in Peat (2)

Abstract

Humic substances (HS) have physical, chemical and biological activities. One of the main elements of HS is humic acid (HA) which is constituted of the mixture of heterogeneous large molecule electrolytes. In order to reuse HA effectively, the antioxidative activities of partially decomposed HAs were evaluated since HA had reported to show some antioxidative activities. Native HA (HA-a) from peat was treated with high temperature (132°C) and high pressure (190 kPa) for 20 min (HA-b), 60 min (HA-c) and 120 min (HA-d). The peak top time of HA-a-d by high-performance size exclusion chromatography were 15.4, 15.8, 16.0 and 16.0 min, respectively. All of HA-b-d showed the antioxidative activities, such as scavenging activities for 1,1-diphenyl-2-picrylhydrazyl radical and inhibitory effect on 2,2ʼ-azobis (2-amidinopropane) dihydro chloride-induced hemolysis of rabbit erythrocytes in vitro as much as HA-a. HA-a and HA-c were tested on the inhibitory effect of the damages by UVA irradiation (100 mJ/cm²) using human skin fibroblast cells. Both of them showed the inhibitory effect with significant differences.