This study is reporting the in vitro antioxidant activity of the fruiting body of the edible mushroom Pleurotus pulmonarius (Fr.) Quel. . The fruiting body of the edible mushroom was defatted with n-hexane and further extracted by successive maceration in dichloromethane (DCM) and 80% aqueous ethanol to obtain the DCM and AQE extracts respectively. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and iron chelating assays were used for antioxidant evaluation in vitro with ascorbic acid as reference standard for comparison. Isolation and structural elucidation of the steroid was done using chromatographic and spectroscopic techniques respectively. The trend for the DPPH radical scavenging activity: ascorbic acid (IC50 = 0.012 mg/mL) > AQE (IC50 =0.525 mg/mL) > DCM (IC50 = 1.820 mg/mL) and for the iron chelating activity: ascorbic acid (IC50 = 0.214 mg/mL) > AQE (IC50 = 1.318 mg/mL) > DCM (IC50 = 7.586 mg/mL) were observed. From the DCM was isolated a pure compound 1 elucidated to be the known steroidal isoprenoid: ergosta-5, 7, 22-trien-3â-ol. This study aside reporting the isolation of the known compound 1 from this species of Pleurotus has also shown that compound 1has a significant iron chelating activity at 0.001mg/ml, of 77.06% compared to 4.56 % at same concentration for DPPH scavenging activity.
Key words: Pleurotus pulmonarius, antioxidants, mushrooms, steroidal isoprenoid, amino acids, carbohydrates
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