Mycochemical screening reveals exopolysaccharide secretion, antioxidant and larvicidal activities of three oyster mushrooms.

Background: Higher fungi such as oyster mushrooms have been well reported to have vast therapeutic and nutritive importance due to their bioactive constituents. Today, many interesting facts are also emerging regarding their importance in pest control. In this study, Pleurotus floridanus, P. ostreatus and P. sajor-caju were studied for exopolysacharide (EPS) and antioxidant production under different carbon sources, and assayed for larvicidal properties.

Results: We observed a positive response of these mushrooms to carbon sources. The highest EPS was produced by P. sajor-caju under sucrose carbon source, whereas P. ostreatus and P. floridanus preferred glucose. The antioxidant activity of their EPS was confirmed using radical scavenging of 1,1-diphenyl-2-picrylhydrazyl and potassium ferricyanide reduction methods. We also established the inhibition of lipid peroxidation by the EPS produced by these mushrooms, although this was concentration dependent, while P. floridanus EPS had the highest antioxidant properties. An EPS concentration of 100 mg L from all the mushrooms was sufficient for inhibition of lipid peroxidation; this also showed a significant difference from the scavenging effect of butylated hydroxytoluene. All the mushroom extracts in this study had positive inhibitory effects on the late third and early fourth stages of Anopheles gambiae. However, they were significantly different from each other as P. floridanus recorded a lethal concentration (LC ) of 0.0.563, P. ostreatus had an LC of 0.352, while P. sajor-caju had an LC of 0.715.

Conclusion: This study affirms the influence of carbon source on EPS production by selected oyster mushrooms, and reveals their antioxidant properties and potential applications in pest control. © 2021 Society of Chemical Industry.