Effect of fermentation time on antioxidative activities of Ganoderma lucidum broth using leguminous plants as part of the liquid fermentation medium

Oxidative damage plays an important role in the pathology of human diseases. Ganoderma lucidum, a medicinal fungus, has been used for thousands of years in traditional Oriental medicine. It is reported to have antioxidant functions such as inhibition of lipid peroxidation. The objective of the present study was to investigate the effect of fermentation time on the antioxidative activities of G. lucidum broth filtrate using leguminous plants as part of the liquid fermentation medium. Inhibition of Cu²⁺-induced oxidation of human low-density lipoprotein (LDL), DPPH radical-scavenging activity, total phenolic compounds, isoflavones and protocatechuic acid were measured to evaluate the antioxidant activity of G. lucidum fermentation broth filtrate. Our results showed that black soybean and Astragalus membranaceus improved the antioxidant activity of the G. lucidum fermentation broth filtrate. Protocatechuic acid was identified by LC-MS as the antioxidant compounds whose relative potency of inhibiting LDL oxidation to Trolox is 1.55. Protocatechuic acid showed positive correlation with the antioxidant activity of the fermentation broth filtrate while isoflavones did not contribute to antioxidant activity.