Effects of substrates and drying methods on antioxidant compound and antioxidant activity of fruiting body extracts of two oyster mushrooms (Pleurotus ostreatus and Pleurotus cystidiosus)

The study was conducted to compare the effect of different substrate formulas and different fruiting body drying methods on the total phenolic contents (TPC) and total flavonoid contents (TFC), as well as the antioxidant activity of oyster mushroom Pleurotus ostreatus (PO) and Pleurotus cystidiosus (PC). Seven substrate formulas were used: 100% sawdust (SD), 100% sugarcane bagasse (SB), 50% SD+50% SB, 80% SD+20% SB, 100% corncob (CC), 50% SD+50% CC, 80% SD+20% CC. Oven-drying and freeze-drying methods were investigated. The antioxidant potential was determined using 1,1- diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, reducing power and chelating ability. The results indicated that the increasing SD ratio in substrate formulas reduced TPC and TFC which in turn decreased antioxidant activity of mushroom PO and PC extracts. In substrates containing higher contents of CC and SB (100% CC, 50% CC, 100% SB, and 50% SB), higher values of TPC, TFC, as well as high efficiency of DPPH radical scavenging ability, reducing power and chelating ability were obtained. These results suggest that CC and SB can be used to partially or entirely replace SD in substrate formulation for oyster mushroom cultivation which will improved its antioxidative capacity. With freeze-drying method, PO and PC showed better efficiency in TPC as well as antioxidant activities in comparison with oven-drying method. PO and PC might be used as potential source of natural antioxidants for food supplements as well as in the development of nutraceuticals