Metabolites with phytopathogenic fungi inhibitory activities from the mangrove endophytic fungus Botryosphaeria ramose

Abstract

To check whether the endophytic fungus from the host plant could produce novel bioactive metabolites induced by the host-derived chemical components, a strategy called "Induction of Endophyte Metabolism by Adding Host Components" (IEMAHC) was put up and applied. Cultivation of the endophytic fungus Botryosphaeria ramosa L29 derived from Myoporum bontioides after adding (2R, 3R)-3, 5, 7-trihydroxyflavanone 3-acetate, a constituent of the same plant, into the culture medium, led to the separation of three new chromones, 5-hydroxy-2, 3-dihydroxymethyl-7-methoxychromone (1), 5-hydroxy-3-acetoxymethyl-2-methyl-7- methoxychromone (2), 5, 7-dihydroxy-3-hydroxymethyl-2-methylchromone (3), one new isocoumarin, 8-hydroxy-3-hydroxymethyl-6-methoxy-7-methylisocoumarin (4), two new δ-lactones, botryopyrone (8) and (5S, 8R)-simplicilopyrone (9), one new naturally rare 2 (7H)-oxepinone, botroxepinone (10), and three known compounds (5-7). They were identified through comprehensive analysis of spectroscopic data. HPLC comparative analysis indicated that compounds 8-10 were induced products after adding (2R, 3R)-3, 5, 7-trihydroxyflavanone 3-acetate as an inducer. Compound 3 exhibited more potent inhibitory activities on Fusarium oxysporum, Fusarium graminearum, Penicillium italicum, and Colletotrichum musae than triadimefon. Compounds 1, 2, 4-7 and 9 displayed potent antifungal activities towards two or three tested fungi with MIC values equal or superior to triadimefon. The induced products 9 and 10 both showing strong inhibitory activity against C. musae, might play a role in strengthening the host defense against the common mangrove invasive pathogenic fungal genera Colletotrichum.

Keywords: 2 (7H)-Oxepinone; Antifungal activity; Botryosphaeria ramose; Chromone; Induction fermentation.