ABSTRACTObjective: Antioxidants neutralize free radicals generated in the human body and prevent them from causing damage. The present study is aimed toevaluate and optimize the antioxidant activity of Xylaria feejeensis HMJAU22039 an endophyte isolated from Tectona grandis.Methods: The antioxidant potential was measured by 1-1diphenyl-2-picryl-hydrazil (DPPH) radical scavenging assay and nitric oxide (NO) scavengingassay. Total phenolic content (TPC) of the samples was measured by Folin–Ciocalteu reagent based assay, and the values were obtained from theregression equation: y = 0.006141x + 0.157733.Results: Potato dextrose yeast extract broth medium was selected as the basal medium as it reported a high antioxidant activity. The basal mediumwas optimized with 2% dextrose, 0.2% yeast extract, and 200 g/L potato infusion. Dextrose and yeast extract were selected as carbon and nitrogensources, respectively, as they reported high antioxidant activity. The antioxidant activity and phenolic content are highest at static condition(18.14 mg/g). Incubation temperature of 30°C and pH of the initial medium at 6 were found to be optimum conditions for high antioxidant activity. Anincubation period of 20 days reported the highest antioxidant activity and phenolic content. Methanol extract recorded high antioxidant activity witha DPPH (73.86%) followed by ethyl acetate and chloroform fractions.Conclusion: The study highlights the importance of different physiochemical parameters in the production of secondary metabolites havingantioxidant properties. The results reveal a significant positive correlation between DPPH radical scavenging assay, NO scavenging assay, and TPC.Keywords: 1-1diphenyl-2-picryl-hydrazil, Total phenolic content, Endophytic fungus, Tectona grandis
