Amino acids and antioxidant properties of the oyster mushrooms, Pleurotus ostreatus and Pleurotus sajor-caju

The objective of this study was to investigate the amino acid composition and antioxidant properties of two oyster mushroom species, Pleurotus ostreatus and Pleurotus sajor-caju, commercially cultivated in NE Thailand. Proximate composition and dietary fibre of dried mushrooms were determined. Amino acid composition of fresh mushrooms was analysed by HPLC. Water and ethanol extracts were obtained from dried mushrooms and determined for total phenolic contents (TPC) by the Folin-Ciocalteu method, free radical scavenging efficacy by the DPPH method, and reducing power by the ferric reducing-antioxidant power method. Except for protein, proximate compositions of dried mushrooms were significantly different. Similar amino acid profiles in both mushrooms were obtained, with glutamic acid, aspartic acid, and arginine being the three most abundant. Water extracts contained higher TPC and possessed better antioxidant activities than did ethanol extracts for both mushrooms. Overall, P ostreatus possessed more antioxidant than R sajor-caju. The EC50 Of P. ostreatus and P. sajor-caju water extracts were 11.56 and 13.38 mg/ml, respectively, while those of the ethanol extracts were 31.75 and 58.44 mg/ml, respectively.