LIPID PROFILES, PHYTOCHEMICAL CONSTITUENTS AND ANTIOXIDANT ACTIVITY OF SELECTED WILD EDIBLE NIGERIAN MUSHROOMS

Abstract

Phytochemical compounds have been demonstrated to exhibit antioxidant properties whileplants lipids are known to elicit both therapeutic and deleterious effects in the body system. Interest in lipids, especially in its fatty acids composition is currently expanding. Nutritionally, saturated fatty acids are essential for basal metabolisms in humans while long chain polyunsaturated fatty acids have many beneficial effects on human health. In this respect, considering the interest of the people around this locality inthe consumption of these four wild edible mushroom species and the lack of data with regard to fatty acids present in them, knowledge of phytochemical constituents, proximate composition,lipid and fatty acid profiles as well as the antioxidant properties ofPleurotuseryngii, Termitomycesrobustus, Picnoporuscinnabarinus, and Pleurotus ostreatusare of interest. The phytochemical screening was done using simple standard chemical methods. The proximate analyses were determined according to the established protocols of Official Methods of the Association of Official Analytical Chemists (AOAC, 1995). Lipid analysis was done using silica gel coated plates, separation was achieved using petroleum ether, diethyl ether, and acetic acid (80:20:1;v/v/v)for neutral lipids and chloroform, methanol, water (65:25:4;v/v/v) for phospholipids. Gas chromatography and mass spectrophotometer automated machine was used to characterise the fatty acid component of the lipids and their antioxidant activity determined using various standard antioxidant assays. All the experiments were done in triplicates and the data collected were analysed using ANOVA. The differences between means were reported as statistically significant (p< 0.05). Phytochemical screeningrevealed the presence of of alkaloids, flavonoids, saponins, tannins with the absence of anthraquinones and steroids. The results of the proximate analysis showed high level of proteins (13.50- 31.00 %), low crude fibre(3.40 – 7.20 %), ash (2.70 – 11.80 %) and fat(0.80-2.60 %)in all the species. The data of the lipid analysisshowed thatthe mushrooms contained free fatty acid and triacylglycerol (Natural lipids).Phosphatidic acid and phosphatidyl glycerol were present in all the four mushrooms.Pleurotus species andTermitomycesrobustuscontained phosphatidyl ethanolamine and sphingomyelinwhile, phophatidyl choline is the Phospholipid found inPicnoporuscinnabarinus and Pleurotus ostreatus. A total of eight different fatty acids were characterized in the respective edible mushrooms lipid with varying percentage relative abundance of oleic and stearic acidsbetween 32.53-48.74% and 6.12-23.06% respectively in all the four species. Palmitic acid 6.89-23.06% in Pleurotusspecies and Picnoporuscinnabarinus.Capricacid 7.28-22.01% in Termitomyces robustus and Pleurotusostreatus. Behenic acid33.07 %inTermitomyces robustus.Arachidic acid 34.18 % and Elaidic acid 11.13 % in pleurotusostreatus. Also, the results obtained from the antioxidant activity test revealed that they all possess high reductive potential; metal chelation, hydroxyl radical scavenging activities with high total phenol (103.34-188.65 mg/g) and total flavonoids (45.94-66.24 mg/g) etc. The findings obtained from this study not only make these wild edible mushrooms popular to consume as good food sources, but as well suggest that they may also be valuable in drug development. The bioactive compounds contained in the mushroom species as well as their high antioxidant activity properties and nutrient contents may be responsible for their nutritional and therapeutic uses.