Antimicrobial and antioxidant activities of endophytic fungi extracts isolated from Carissa carandas

This is the first report of endophytic fungi derived from Carissa carandas producing bioactive compounds in Thailand. The aims of this research were to evaluate the antimicrobial and antioxidant activities of extracts from endophytic fungi, identify the potential fungal isolates by phylogenetic analysis and analyze the composition of the potential crude extract by gas chromatography-mass spectrometry (GC-MS). The endophytic fungus Nigrospora guilinensis TSU-EFHA009 produced the most active extracts. Broth ethyl acetate extract (BE) had the strongest activity against Cryptococcus neoformans at a minimum inhibitory concentration (MIC) of 4 µg/mL and a minimum fungicidal concentration of 8 µg/mL. Moreover, the antimicrobial activity was confirmed using scanning electron microscopy. The target cells were morphologically damaged. In addition, this active extract had the highest antioxidant activity with an inhibitory concentration (IC50) value of 0.03 mg/mL. The total phenolic content of the target extract was detected by using the colorimetric method. This extract contained a total phenolic content of 41.20±0.40 mg GAE/g of the extract. The results indicated that the endophytic fungi from C. carandas are good sources of antimicrobial and antioxidant substances.    Key words: Antimicrobial activity, antioxidant activity, endophytic fungi, active metabolites.