Pleurotus ostreatus and Pleurotus eryngii as a source of phenolic compounds

The intake of phenolic compounds from food products and supplements has been associated to prevention of degenerative diseases, mainly due to their antioxidant activity. The phenolic compounds can be found in plant foods and mushrooms. The main goal of this study was to quantify the total phenolic compounds of aqueous extracts from two mushrooms species, Pleurotus ostreatus and Pleurotus eryngii, and evaluate their antioxidant activity. The aqueous extracts from P. ostreatus and P. eryngii were obtained through two extraction methods (M1 and M2). In M1, a hot extraction was performed (extract M1) (90 ºC, 500 rpm, 1 h). In M2, a room temperature extraction (extract M2A), followed by a hot extraction (extract M2B) (90 ºC, 500 rpm, 1 h) of extract M2A residue, was done. Extracts M1, M2A, and M2B obtained from each mushroom species were lyophilized, and the extraction yields were determined. Total phenolics content was quantified through Folin Ciocalteu method. The results were expressed as gallic acid equivalents (GAEs). In its turn, the antioxidant activity was determined through ABTS and ORAC methods. The results of the two methods were expressed as ascorbic acid equivalents (AAEs) and trolox equivalents (TEs), respectively. The cytotoxicity (PrestoBlue) and mutagenicity (Ames) of all extracts also were evaluated. The extraction yield of extracts M1, M2A and M2B from P. ostreatus were 41.33% ± 4.29, 33.60% ± 0.39 and 15.18% ± 0.70, respectively. In its turn, the extraction yield of extracts M1, M2A, and M2B from P. eryngii were 46.03 ± 2.18, 44.46 ± 3.96, 12.58 ± 0.94. All extracts from both mushroom species were good sources of phenolic compounds. The extracts M1, M2A and M2B from P. ostreatus had 15.80 ± 1.54, 16.57 ± 0.26 and 16.65 ± 1.01 mg GAEs / g dry extract, while extracts M1, M2A and M2B from P. eryngii had 9.06 ± 0.63, 7.90 ± 0.46, 9.25 ± 0.28 mg GAEs / g dry extract. Antioxidant activity was observed in all extracts. The antioxidant activity of extracts from P. ostreatus (M1: 5.78 ± 0.31; M2A: 6.33 ± 0.83; M2B: 4.39 ± 1.12 mg AAEs / g dry extract) was higher than antioxidant activity of extracts from P. eryngii (M1: 5.48 ± 0.03; M2A: 2.23 ± 0.15; M2B: 3.87 ± 0.39 mg AAEs / g dry extract). No extract showed any genotoxic or cytotoxic effect. The results of this study indicate that aqueous extracts from P. ostreatus and P. eryngii are a source of phenolic compounds. Possibly, these extracts have the potential to be used in the development of food products and nutraceuticals enriched in phenolic compounds associated to other relevant properties ascribed to these mushrooms.