Endophytic fungi from medicinal plants are a rich source of new biologically active compounds. In the present study, an endophytic fungus Nigrospora sphaerica (Berk. & Broome) Petch was isolated from Dillenia indica L and was characterized morphologically and at molecular levels. The isolated fungus was investigated for antibacterial activity, antifungal activity, antioxidant activity, total phenolics and flavonoids content, and its responsible bioactive molecules. The toxicity test revealed that the crude extract of Nigrospora sphaerica inhibited the growth of pathogenic bacteria, i.e., E. coli, Staphylococcus aureus, Bacillus subtilis and Pseudomonas aeruginosa. The value of MIC (Minimum inhibitory concentration) ranges from 82–115 µg/mL for the selected bacteria. The isolated endophytic fungus exhibited the highest inhibition against the Fusarium oxysporum (72%) and the lowest inhibition against Aspergillus niger (55%). The maximum scavenging activity was 88.1% at 600 µg/mL with an IC50 value of 85 µg/mL. GC–MS (Gas chromatography-Mass spectroscopy) analysis of the ethyl acetate extract revealed the presence of more than 40 compounds. Some of the major compounds present in extract were 1H-Indene, 1-methylene-(3.64%), Dodecane (8.52%), Tetradecane (11.59%), (-)-Mellein (3.85%), Hexadecane (10.13%), 1,2,5-Oxadiazole-3,4-dicarboxamide (5.95%), Octadecane (6.46%) and Benzoic acid, 2-(dimethylamino) ethyl ester. The compounds present in the extracts have various biological activities such as antiviral, antioxidant, insecticidal, cytotoxic, antihyperglycemic, antibacterial, antifungal activity. The compounds present in the extract can be used in clinical trials for further applications. To the best of our knowledge, this is the first report on bioactive molecules produced by Nigrospora sphaerica isolated from Dillenia indica L. having antioxidant and antimicrobial activity.
