Phytochemical and Mineral Analysis of 12 Cultivated Oyster Mushrooms (Pleurotus Species)

Abstract

Phytochemical analysis was conducted on methanolic extracts of 4 oyster mushrooms species (Pleurotus pulmonarius, P. ostreatus, P. sapidus and P. citrinopileatus) made up of 12 different strains. The study was carried out to determine the contents of total phenol and flavonoids, beta carotene and lycopene, antioxidant properties and concentrations of mineral elements and heavy metals in the macrofungi methanolic extracts. Total phenolic contents ranged from 1.48 µg GAE/g to 3.58 µg of GAE/g with a mean of 2.5 µg of GAE/g and 0.36 coefficient of variation. The 12 strains were statistically different from each other. Total flavonoid content varied from 0.20 µg of RE/g to 2.03 µg of RE/g of dry weight of extracts with a grand mean of 0.85 µg of RE/g and 9.89 coefficient of variation. There was significant difference among the 12 mushroom strains (P<0.001). Beta carotene content varied from 0.60 to 11.46 µg/g and that of lycopene varied from 0.04 to 4.28 µg/g. The IC₅₀ values ranged between 43.21 µg/ml and 52.03 µg/ml, the inhibition of DPPH radical by P. sapidus strain PSC-1 and P. ostreatus strain POA-5 exhibited the highest activity. Significant difference was observed among the strains. Mg content varied from 660.0 mg/kg to 1993.7 mg/kg, Fe content ranged from 349.0 mg/kg to 1374.0 mg/kg and could not be detected in P. ostreatus strain POA-7.  Ca content ranged from 22.0 mg/kg to 415.3 mg/kg, Mn content varied from 10.7 mg/ kg to 48.3 mg/kg and was below detection in the six strains of P. pulmonarius strain PPA-2, P. ostreatus strain POA-5, P. ostreatus strain POA-6, P. ostreatus strain POA-7, P. ostreatus strain POA-10 and P. ostreatus strain POA-13. Cu content ranged from 15.3 mg/kg to 23.7 mg/kg but below detection in two strains P. ostreatus strain POA-6 and P. ostreatus strain POA-10. Zn content varied from 189.7 mg/kg to 411.3 mg/kg. Ni content varied from 175 mg/kg to 296.7 mg/kg, Cd content ranged between 57.7 mg/kg and 106.3 mg/kg, Pb content varied from 13.0 mg/kg to 230.7 mg/kg. Cr content ranged between 17.7 mg/kg and 124 mg/kg. All the Pleurotus strains showed appreciable levels of antioxidant activities and can be promoted as natural antioxidant preference in food and pharmaceutical

Keywords: 1,1-diphenyl-1-picrylhydrazyl (DPPH) assay, total flavonoids content, total phenolics content, beta carotene content, lycopene content, mineral elements, heavy metals