Bioactivity and secondary metabolite from the static cultures of mango endophytic fungi.

Abstract

The surge for endophytic fungi over the years have contributed immensely to the production of effective drug therapeutics to buttress the fighting race of various ailments caused by microorganisms. The discovery of secondary metabolites through the culturing of these fungi has been phenomenal, contributing enormously to the pharmaceutical industry in their quest to find lasting solutions to different kind of diseases that have engulfed our planet. Endophytic fungi obtained from mango leaf was cultured in a 3% malt extract and 6% glucose in two 2 dm3 flat-bottomed flask for eight weeks with a temperature range of 25-29 0C. The broth was harvested and extraction was carried out using ethyl acetate to obtain the organic layer. It was then concentrated using the rotary evaporator. Chromatographic study (TLC) was carried out on the crude extract to separate compounds present into their respective components in fractions. They were then triturated with hexane, chloroform, petroleum ether and methanol. After several weeks, yellowish solid crystals were seen at the bottom of the test tube labelled ABM-EN (15). It was filtered and dried for characterization using NMR and for antimicrobial and antioxidant activity testing. The following NMR analysis which consists of 1H NMR, 13C-NMR, COSY, DEPT-135, HSQC and HMBC showed a lactone ring with two carboxylic moieties, methyl, methylene and a methine group. The IR analysis as well confirmed the functional groups in the structure. From literature, the structure of the compound was identified as Spiculisporic acid. It is a microbial biosurfactant with anti-oxidative stress actions having the empirical formula, C17H28O6 with a formula mass of 328.405 g/mol. The antimicrobial test results showed that the crystal (ABM-EN) is not sensitive against four bacteria strains; E. faecalis (NCTC 13379), S. pyogenes (NCTC 12696), K. pneumoniae (NCTC 13348), S. aureus (NCTC 12973) and one fungus; C. albicans (ATCC 90028) but has a very high antioxidant activity of percentage inhibition (+/-MSD) 23.38(+/-0.88) at a concentration of 0.5 mg/mL at 517 nm.