Bioactive compounds of endophytic fungi isolated from Mammea siamensis, Mesua ferrea, AND Calophyllum inophyllum

Abstract

In the present study, four endophytic fungal strains, Aspergillus terreus (MS1), Colletotrichum gloeosporioides (CI3), Phoma herbarum (CI4) and Ascomycete sp. (CI5) obtained from M. siamensis, M. ferrea and C. inophyllum, were selected for bioactive metabolite isolation. Investigation on chemical constituents of each fungus cultured on suitable medium led to the isolation of two novel butyrolactone derivatives, aspernolide D (4) and asperterone (5) from EtOAc extract of the fungus A. terreus, together with five known derivatives, butyrolactones I (1), II (2), aspernolide B (3), butyrolactones III (6) and IV (7). Furthermore, terrein (8) was found to be a major metabolite (relatively high yield) when cultured in malt extract broth. This indicated that cultured medium has much effect on chemical structure of metabolites produced. In the case of fungal strains CI3, CI4 and CI5, after ferment on solid rice medium, purification of their EtOAc extracts by chromatographic techniques led to the isolation of fiveteen known compounds (9-23). The structures of all isolated metabolites were established on the basis of spectroscopic data. Further, compounds obtained from the fungus A. terreus were evaluated for their cytotoxicity against cancer cell lines, antimalarial and antibacterial activities. Only compounds 5 and 8 exhibited cytotoxicity on cancer cell lines tested with IC₅₀ ranging of 2.70-5.63 µM, whereas compounds 1, 3-5 and 6 displayed weakly to moderately antibacterial activity. In addition, it was found that compound 8 could inhibit potent antimalarial activity with IC₅₀ value of 3.17 µM.