Phytochemical Content and Antibacterial Effect of Ethanolic and Methanolic Extracts of Pleurotus ostreatus Mushroom

Aims: Microbial resistance is a threat to the successful treatment of microbial infections. Mushrooms are known to possess antimicrobial and antioxidant potential which could be inhibitory to some pathogenic organisms. The aim was to assess the phytochemicals and antimicrobial potential of Pleurotus ostreatus extracts on some pathogenic organisms. 
Methodology: The study was conducted at the Bells University of Technology, Nigeria, between December 2019 and August 2020. A 10% dried powder of Pleurotus ostreatus was extracted in absolute ethanol and methanol and evaporated in a water bath at 50 oC. Extracts were reconstituted in dimethyl Sulfoxide (DMSO) at 12.5, 25, 50, and 100% respectively. Antibiotic effects of extracts were tested on Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Staphylococcus saprophyticus by agar well diffusion method and compared with standard antibiotic discs. DMSO and the solvents served as positive and negative controls. Ethanolic extract was subjected to Gas Chromatography-Mass Spectrometer. 
Results: The extracts exhibited varying inhibitory effects on the organisms except on E coli at 12.5% ethanolic extract. The inhibition zones increased with extract concentration from 2-12 mm and 4-14 mm in ethanolic and methanolic extracts respectively. The inhibitory effect of standard antibiotics was higher 17-25 mm except for erythromycin (13-14 mm). Test organisms were resistant to Beta Lactams (augmentin, cefuroxime, and ceftazidime) and sensitive to Aminoglycoside (gentamicin), Fluoroquinolones (ofloxacin), Ciprofloxacin, and erythromycin. GC/MS revealed the presence of 30 organic compounds, amongst them were sugar, sugar alcohols, alkaloids, amines, fatty acids, esters, aldehydes, and alcohols. The most abundant were oleic acid (33.75%) and 9-octadecenoic acid (Z)-2-hydroxy-1- (21.21%). Phytochemicals are heterocyclic compounds found in natural products. 
Conclusion: P. ostreatus has been revealed to possess phytochemicals of medical relevance with potential for pharmacological application. The implication is that Pleurotus ostreatus extracts could serve as a lead to novel drug discoveries which could enhance health and nutritional well-being.