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-1 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 (LC50 ) of 0.0.563, P. ostreatus had an LC50 of 0.352, while P. sajor-caju had an LC50 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.

Antimicrobial Activities of Laetiporus conifericola (Agaricomycetes) from the United States.

In this study, samples of polypore mushroom Laetiporus conifericola were collected from Pennsylvania, USA. The antimicrobial activity (AMA) of ethanolic, methanolic, and water extracts of this fungus were tested in vitro by the agar diffusion test against some selected clinically important microorganisms. These microorganisms included three Gram-positive bacteria (Staphylococcus aureus 5W1941, S. epidermidis 85W1940, and Bacillus cereus 85W1815), three Gram-negative bacteria (Escherichia coli 85W1860, Salmonella typhimurium 85W1956, and Pseudomonas aeruginosa 85W1903), and one fungus (Candida albicans). These extracts demonstrated varying degrees of inhibition against all of the test pathogenic microorganisms except C. albicans. Methanolic and ethanolic extracts of L. conifericola were very effective against S. aureus, while the aqueous extract was the least effective. All tested extracts were effective against S. epidermidis, methanolic extract produced the best zone of inhibition followed by the aqueous extract while ethanolic extract had the least zone of inhibition. B. cereus and P. aeruginosa were highly susceptible to ethanol extract. In addition, the growth of E. coli was best inhibited by the aqueous extract, followed by the methanolic and ethanolic extracts, respectively. The aqueous and methanolic extracts were most effective against S. typhimurium; however, this bacterium was not susceptible to ethanolic extract. The significance of these findings is discussed.