Phytochemical Screening, Proximate Composition and Antibacterial Activity of Oyster Mushroom, Pleurotus ostreatus Collected from Etim Ekpo in Akwa Ibom State, Nigeria

Abstract

Aim: This study determined the phytochemical, elemental and proximate nutritional compositions of P. ostreatus as well as the antibacterial potentials of the macro fungus collected during the tropical rainy season on selected bacteria. Methodology: The disease-free oyster mushroom fruiting body was collected from the wild bush at Etim Ekpo, in Akwa Ibom State, Nigeria. Preparation of the oyster mushroom material, ethanolic and aqueous extracts; bacterial culture, isolation and identification, screenings for phytochemical and nutritional constituents were done according to standard methods, while antimicrobial screening was carried out by agar well diffusion technique. Results: The preliminary phytochemical analysis of the extracts showed the occurrence of active polar compounds at varying amounts such as glycosides, alkaloids, saponins, flavonoids, reducing compounds, polyphenol, tannins, steroids/triterpenoids, proteins and amino acids. The wild edible oyster mushroom displayed varying degrees of inhibition on the test organisms. Ethanol extract had good antibacterial activity against all the test isolates compared to aqueous extract as indicated by the mean diameter of inhibition zones in the order of 27.50±0.02 mm > 25.30±0.01 mm > 24.40±0.01 mm for Staphylococcus aureus, Proteus species and Escherichia coli respectively.  E. coli was the most sensitive organism in aqueous extract (20.60±0.01 mm). The only resistant organism was S. aureus (15.80±0.02 mm) in aqueous extract. Proximate analysis revealed high levels of moisture (78.28±0.02 mg/100 g), carbohydrate (52.74±0.02 mg/100 g) and .crude protein (28.40±0.1 mg/100 g). Ethanol extract showed good nutritional potentials, with Vitamin A (295.72±0.02), proteins (28.40±0.1) and carbohydrates (52.74±0.02) present in a higher amounts. Elemental nutrients such as Fe=167.42 mg/100 g dry weight and Ca=32.08 mg/100 g dry weight were also detected. Conclusion: The results obtained in this study have shown the potential of oyster mushroom extract as a good therapeutic agent and food supplement. It could find applications as dietary supplements and possibly as alternative antibacterial agents.