Phytochemical constituents and antimicrobial evaluation of ethanolic extracts from Pleurotus spp. cultivated on substrate fortified with selenium

Edible mushrooms have the ability to bio-accumulate minerals from the growth medium into the fruiting body. Selenium (Se) is an example of minerals that can be easily absorbed by mushroom. This study investigated the phytochemical constituents and antimicrobial properties of Pleurotus spp. fortified with selenium. Pleurotus spp. (fortified with selenium and nonfortified with selenium) were cultivated on corn cobs using standard procedures. The yield, biological efficiency, selenium absorption level, phytochemical constituents and antimicrobial properties were determined using standard methods. Non-fortified Pleurotus pulmonarius recorded the highest yield and biological efficiency, while fortified Pleurotus ostreatus had the lowest yields and biological efficiency. There was no significant difference (P<0.05) in the selenium concentration absorbed in Pleurotus ostreatus (51.79μg/g) and Pleurotus pulmonarius (59.29 μg/g) but no selenium was detected in the non-fortified samples. The presence of 5 phytochemicals viz; saponins, alkaloids, phenols, tannins and flavonoids were detected in cultivated mushrooms. Saponin was highest (7.08 mg/g) in non-fortified Pleurotus pulmonarius while tannin was the least with the value of 0.02 mg/g in fortified Pleurotus ostreatus. The ethanolic extracts of Pleurotus spp. inhibited the growth of Gram positive and negative bacteria with Pseudomonas aeruginosabeen the most susceptible (25.00 mm). The ethanolic extracts of fortified Pleurotus spp. inhibited Aspergillus flavus, Candida albicans and Candida parapsilosis. The non-fortified extracts however, had no inhibitory effects on the tested fungi. Based on the findings of this study, it can be concluded that Se-fortification increased the antibacterial activities of Pleurotus spp. These results therefore, suggest that Se-enriched mushrooms can be used as potential source of dietary supplements and nutraceuticals. Fortification of Pleurotus spp. with essential metals should be encouraged as this can improve its health promoting property.