Antioxidant and free radical scavenging activities of Phellinus merrillii extracts

This study aimed to investigate possible antioxidant activity of various extracts of Phellinus merrillii (PM). The explored items include: ABTS free radical scavenging assay, determination of total phenolics contents (TPC), ferric reducing antioxidant power assay (FRAP), rapid screening of antioxidant by dot-blot DPPH (1, 1 -diphenyl-2-picrylhydrazyl) staining, DPPH radical-scavenging activities and reducing power measurement. In the ABTS free radical scavenging assay, the n-BuOH fraction displayed the highest total antioxidant activity (17.13 +/- 0.04 mM). In the determination of total phenolics contents (TPC) and ferric reducing antioxidant power assay (FRAP), the EtOAc fraction had the highest phenolics contents (46.21 +/- 0.02 mM) and reducing antioxidant power (19.09 +/- 0.03 mM). In the rapid screening of antioxidant by dot-blot DPPH staining, the n-BuOH fraction showed the highest strong dot-blot staining. In the reducing power measurement, the crude extract had the highest reducing power at 2 mg/ml concentration. In the DPPH radical-scavenging activities, the EtOAc fraction had the highest antioxidant activity (IC50 = 0.66 +/- 0.01 mg/ ml). As regard the correlation coefficients among ABTS assay, FRAP assay, and total phenolics contents, it can be seen that correlation coefficients in each case were significant. Among all extracts, the highest amount of total phenolics contents were found in the EtOAc fractiont. It is suggested that the PM might contribute its antioxidant activities on EtOAc and n-BuOH fraction. In high-performance liquid chromatography tandem mass (LC/MS/MS) analysis for hispolon, the daughter ion scanned chromatograms of PM was established. Both hispolon and PM showed similar daughter ion spectrum at the retention time of 4.7 min and had more lobes in m/z 219 and m/z 135. This indicated that PM did contain the active ingredient hispolon. Both the IC50 of DPPH radical scavenging activity for hispolon and BHT were 42.4 +/- 12.9 and 81.2 +/- 13.2 mu M, respectively. These findings mean that hispolon was most important in antiradical activities. It was suggested that hispolon might contribute to its antioxidant activities in PM.