Phenolics content and antioxidant activity of aqueous extracts from bio-residues of agrocybe cylindracea

Mushrooms are known as a rich source of functional and bioactive compounds. Among these, phenolic compounds as important antioxidants are included. In the present work, the antioxidant potential and total phenolic compounds from bio-residues obtained from edible mushroom production were evaluated in order to develop a circular bioeconomy approach. The studied species was Agrocybe cylindraceae. The extraction was performed using water as the only solvent, in order to obtain a process as green as possible and with minimal costs and it can be easily scaled up at industrial level. The aqueous extracts were obtained according to two different methods (1 and 2). In method 1, a hot extraction was performed (90°C; 1h; 500 rpms; extract 1A). In method 2, a temperature room extraction was done (extract 2A) and the resulting residue was subsequently extracted with hot water (90 °C; 1 h; 500 rpms; extract 2B). Extracts were freeze-dried and the extraction yields were determined. The content of total phenolic compounds was determined using Folin-Ciocalteu method. The antioxidant activity was also evaluated by ABTS, DPPH and ORAC assays. The extraction yields relative to aqueous extracts 1A, 2A and 2B from A. cylindraceae were 39.5 ± 1.5 %, 34.4 ± 1.2 % and 11.4± 0.8 %. The total phenolic contents obtained was 13.4 ± 0.3, 12,28 ± 0.01 and 12.3 ± 0.3 mg gallic acid equivalents per g dry extract for extracts 1A, 2A and 2B, respectively, which values are again lower than values reported in literature for ethanolic extracts, as expected. Regarding the antioxidant activity the results showed that the extracts of A. cylindraceae are a possible source of natural antioxidants. According to ABTS assay, the results were: 10 ± 1 (1A); 8.4 ± 0.1 (2A); 8.3 ± 0.9 (2B) mg ascorbic acid equivalent per g dry extract. According to the results, these extracts could still be considered as a natural source of antioxidants. Thus, the valorisation of these bio-residues through the development of value- added“green” products is an opportunity to increase the sustainability of the mushroom production chain.