Effect of Extraction Solvents on the Phenolic Content and Antioxidant Capacity in Xylaria Polymorpha and Xylaria Longipes Strains

Abstract

Background. Fungi of the genus Xylaria are known for their wide range of secondary metabolites, including antioxidant polyphenolic compounds. Due to their critical role as chain-breaking antioxidants, phenolic compounds have been studied extensively in plants and fungi. The objective of this study was to assess and compare the total phenolic content and antioxidant capacities of the biomass of different strains of two common representatives of this genus in Ukraine – Xylaria polymorpha and Xylaria longipes – by applying various solvents for extraction. Methods. A vegetative mycelium was cultivated in submerged conditions and extracted with ethanol, methanol, and ethyl acetate. Total phenolic content in extracts was determined using the Folin–Ciocalteu method with gallic acid as the standard. Antioxidant activity was assessed by determining the DPPH (2,2-Diphenyl-1-picrylhydrazyl) free radical scavenging spectrophotometric assay. The correlation between the total phenolic content and antioxidant capacity of the extracts was assessed using the Pearson correlation coefficient for each organic solvent. Results. Methanol was the most effective solvent in yielding the highest quantities of phenolic compounds. Among all the strains studied, X. polymorpha IBK 2736 exhibited the maximum yield of phenolic compounds at 21,64 ± 0,03 mg GAE/g. Conversely, when ethyl acetate was used as the solvent, the phenolic yield from the biomass of the same strain was significantly lower at 0,68 ± 0,14 mg GAE/g, as well as for other strains in our investigation. Furthermore, the methanol extract of X. longipes IBK 2726 demonstrated the highest antioxidant activity, reaching 88,99 ± 0,07 %, while the ethyl acetate extract of X. longipes IBK 2718 exhibited the lowest antioxidant activity with a value of 41,28 ± 0,33 %. Conclusіons. The results indicated that the amount of extracted phenolic compounds was greatly influenced by the choice of solvent. Methanol was found to be the most effective solvent for extracting these compounds from studied strains, outperforming ethanol and ethyl acetate. Moreover, methanol extracts displayed a strong antioxidant capacity, and the correlation analysis confirmed the relationship between it and the phenolic content present in them. Overall, all the strains investigated showed significant antioxidant potential, highlighting the importance of further studies of the chemical properties of their antioxidant components.