Abstract: Laoshan mushroom was extracted with methanol:chloroform(1:1), and the extraction was then partitioned with petroleum ether, CHCl3, EtOAc and BuOH successively. Antioxidant activity (AA) of the extractions was evaluated in three different assays, namely, the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay, the deoxyribose assay and the potassium ferricyanide reduction methods, and compared with that of butylated hydroxytoluene (BHT), gallic acid (GA), propyl gallate(PG) and ascorbic acid (AscA). The results showed that the ethyl acetate-soluble fraction exhibited the highest AA at all of four concentration levels tested (from 0.4 to 50μg /ml), and was further fractionated into six subfractions EAF1–EAF6 by silica gel vacuum liquid chromatography. EAF4 was found to be the most effective subfraction in three assays, which was greater AA than BHT,PG and GA and similar to AscA in the DPPH assay at the concentration of 50μg /ml, while, in the deoxyribose assay, the EAF4 exhibited higher AA than four kinds of synthetic antioxidants at all of four concentration levels tested and in the potassium ferricyanide reduction methods exhibited higher AA than PG at the concentration of 10μg /ml and similar to PG at the concentration of 50μg /ml. The total phenolic content was determined using the Folin–Ciocalteu. Statistical analysis indicated a significant association between the antioxidant potency and total phenolic content.

Key words: natural antioxidant, Laoshan mushroom, DPPH, hydroxyl radical, reducing power, total phenolic content