Antimicrobial activities of endophytic fungi of the Sri Lankan aquatic plant<i>Nymphaea nouchali</i>and chaetoglobosin A and C, produced by the endophytic fungus<i>Chaetomium globosum</i>

Twenty distinct endophytic fungi were isolated from the surface-sterilized plant parts of <i>Nymphaea nouchali</i> and were identified using morphological and molecular techniques. At 300 µg/disc concentration, eight of the 20 fungal extracts exhibited antimicrobial activities against <i>Staphylococcus aureus</i> (ATCC 25923) and <i>Bacillus cereus</i> (ATCC 11778) while two within the eight showed activity against <i>Pseudomonas aeruginosa</i> (ATCC 9027) and <i>Escherichia coli</i> (ATCC 35218). Furthermore, investigation of the crude extract of <i>Chaetomium globosum</i> resulted in the isolation of two known cytochalasans, chaetoglobosin A and C, and their structures were elucidated and confirmed by mass and nuclear magnetic resonance (NMR) (¹H, ¹³C, COSY, HSQC, HMBC and tROESY) spectral data. Chaetoglobosin A showed antibacterial activities against <i>Bacillus subtilis</i> (MIC 16 µg mL^-1), <i>Staphylococcus aureus</i> (MIC 32 µg mL^-1) and methicillin-resistant <i>Staphylococcus aureus</i> (MRSA, MIC 32 µg mL^-1). This is the first study to report the isolation, identification and antimicrobial properties of endophytic fungi of <i>N. nouchali</i> in Sri Lanka.