A new natural product diketopiperazine, antibiotically active compound from symbiotic fungus purpureocillium lilacinum isolated from mangrove sonneratia alba

Abstract

We performed the study of secondary metabolites from endophytic fungus Purpureocillium lilacinum. The fungus was isolated from the Mangrove Sonneratia alba which grows in Manado Bay North Sulawesi. Chemical investigation of fractions from Biomalt agar found compounds from diketopiperazines groups namely (3S,6R)-3-(4-hydroxybenzyl)-1,4-dimethyl-3,6-bis(methylthio)piperazine-2,5-dione (1), (3R,6S)-3-(4-hydroxybenzyl)-1,4-dimethyl-3,6-bis(methylthio)piperazine-2,5-dione (2), (3S,6S)-3-(4-hydroxybenzyl)-1,4-dimethyl-3,6-bis(methylthio)piperazine-2,5-dione (3) and (3S,6R)-3-(4-hydroxybenzyl)-1,4-dimethyl-3,6-bis(methylthio)piperazine-2,5-dione (4), where (1) and (2) are with an additional isoprene unit linked to their aromatic chain. Hence, we can define the relative stereochemistry of all isolated compounds by analyzing the1H chemical shift differences in comparison to the available literature. We proposed that compound (1) is a new natural product due to β-SMe position in C-10. The structure of the above compounds was characterized based on consecutive spectroscopic data including NMR, UV and MS. All isolated compounds showed a narrow spectrum antibacterial activity against Gram-positive bacteria Bacillus megaterium DSM32T. So far there has been no report about the antibacterial activity of all isolated compounds.