Phellinsin A from Phellinus sp. PL3 exhibits antioxidant activities

Phellinsin A, which was isolated from the culture broth of Phellinus sp. PL3, exhibited significant low-density lipoproteins (LDL)-antioxidant activity. It inhibited the Cu2+-mediated oxidation of LDL (IC50: 5.3 microM) and 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AAPH)-mediated oxidation of LDL (IC50: 2.8 microM) in the thiobarbituric acid-reactive substances (TBARS) assay as well as the macrophage-mediated LDL oxidation (73% inhibition at 5 microM). In addition, it delayed LDL oxidation with a prolonged lag time (192 min at 2 microM, control: 44 min). This compound also showed a 10-fold more potent 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity (IC50: 1.7 microM) than trolox (IC50: 18.6 microM), a known DPPH inhibitor. In addition, phellinsin A inhibited xanthine oxidase activity with an IC50 value of 31.0 microM, whereas allopurinol, a xanthine oxidase inhibitor, showed an IC50 value of 40.7 microM.