Bioactive compounds produced by endophytic fungi isolated from beach morning glory Ipomoea pes-caprae Linn.

Abstract

150 endophytic fungi were isolated from leaves, stems, flowers and seeds of Ipomoea pes-caprae Linn. collected from beaches of Thailand. The genera of isolated endophytic fungi comprised of alternaria, aspergillus, collectotrichum, curvularia, eurotium, fusarium, geotrichum, penicillium, phomopsis, stemphylium, trichoderma, xylaria. and mycelia sterilia. All of selected endophytic fungi were tested antimicrobial activity against 5 microorganisms; Bacillus subtilis, staphylococcus aureus, escherichia coli, pseudomonas aeruginosa and candida albicans. Endophytic fungi isolate Cm1 and Ch109 were exhibited high antimicrobial activity against test microorganisms. Thus both fungi were selected for further studies. Based on light microscope identification and DNA sequencing of the ITS region, the fungus isolate Cm1 was identified as stemphylium solani and Ch109 was identified as eurotium amstelodami. Isolation of bioactive compounds from mycelial EtOAc extracted of Cm1 found that combined fraction ME-10 exhibited the best result of antimicrobial activity with 13-25 mm of clear zone width. The antioxidant test of ME-10 showed IC50 44 µg/ml and LC50 of brine shrimp lethality test was 414 µg/ml. The cytotoxicity test of ME-10 with 5 cell lines; BT474, CHAGO, HEP-G2, KATO-3 and SW620, IC50 were 14.05, 10.40, 8.41, 8.91 and 10.23 µg/ml, respectively. Isolation of bioactive compounds from mycelial EtOAc extract of Ch109 by column chromatography gave 4 compounds including tetrahydroauroglaucin, flavoglaucin, physcion and erythroglaucin. Antimicrobial and antioxidant assay of four compounds were tested. IC50 of compound 1 (tetrahydroauroglaucin), compound 2 (flavoglaucin), compound 3 (physcion) and compound 4 (erythroglaucin) were exhibited antioxidant with IC50 of 18, 35.5, 42 and 32 µg/ml, respectively while vitamin E was exhibited antioxidant with IC50 of 19 µg/ml. Antimicrobial activity of compound 1-2 against B. subtilis with MIC of 250 µg/ml and S. aureus with MIC of 250 µg/ml. Compound 3 and 4 showed antimicrobial activity against B. subtilis with the same MIC of 50 µg/ml and against S. aureus with MIC of 80 µg/ml.