Study On The Secondary Metabolites Of A Marine Mangrove Endophytic Fungus And An Insect Symbiotic Fungus

The metabolic pathway of endophytic fungi is unique because they are growing in a special marine environment.They can produce metabolites with novel structures and medicinal activities,which has great potential for developments of medicines and pesticides.In this paper,the metabolites of an endophytic fungus Botryosphaeria ramosa L29 derived from the marine mangrove plant Myoporum bontioides A.Gray were studied.In addition,the addition of specific compounds into the the culture medium has been recognized as an effective way to induce microorganisms to produce novel active metabolites in recent years.However,there is no report on the introduction of the constituents of the mangrove plant into the culture medium of an endophytic fungus from the same plant.Therefore,a chemical compound(2R,3R)-3,5,7-trihydroxyflavanone-3-acetate derived from M.bontioides was added to the culture medium fermented with the above-mentioned endophytic fungus Botryosphaeria ramosa L29.Then the metabolites were studied.Insect symbiotic microorganisms are also considered to be new microbial resources with special habitats in search of medicinal natural products.However,in contrast to the metabolites of marine fungi,the relating study of insect symbiotic microorganism is far from enough.Thus,the metabolites of an endophytic fungus Nigrospora sphaerica ZMT05 isolated from Oxya chinensis Thunber were also studied.In this paper,a total of 43 compounds were isolated by comprehensive silica gel column chromatography,sephadex LH-20 gel column chromatography,preparative thin layer chromatography,high performance preparative liquid chromatography and recrystallization.Their structures were identified by the techniques including nuclear magnetic resonance spectroscopy,high resolution mass spectrometry,infrared spectroscopy and ultraviolet spectroscopy,and by comparision of the reported literatures.The detailed results were listed as follows: 20 metabolites were isolated and identified from theendophytic fungus Botryosphaeria ramosa L29.They are botryospyrone A(1),botryospyrone B(2),botryospyrone C(3),botryospyrone D(4),4-ethoxy-2-hydroxy-3,6-dimethylbenzoic acid ethyl(5),6,8-dihydroxy-5-methoxy-3-methyl-1H-isochromen-1-one(6),emodin methyl ether(7),3-cyanopropyl Acid(8),2,4-dihydroxy-3,6-dimethylbenzoic acid ethyl ester(9),p-hydroxybenzaldehyde(10),3,4-Dihydro-8-hydroxy-3-methyl-1H-2-benzopyran-1-one-5-carboxylic Acid(11),similanpyrone B(12),5-hydroxytryptophan(13),ethyl 4-hydroxyphenyl(14),angelicoin(15),hyrtio Erectine C(16),penicipyran B(17),chrysogine(18),(11S)-1,3,6-trihydroxy-7-(1-hydroxyethyl)anthracene-9,10-dione(19),and 4,15-diacetoxynivaleno(20).Four metabolites were isolated and identified from the endophytic fungus Botryosphaeria ramosa L29 induced by the addition of(2R,3R)-3,5,7-trihydroxyflavanone-3-acetate into the culture medium.There are(3a S,8a S)-1-acetyl-1,2,3,3a,8,8a-hexahydropyrrolo [2,3-b]indole-3a-ol(21),simplicilopyrone(22),4-hydroxy honey mycin(23),uracil(24),respectively.Eighteen compounds were isolated and identified from the metabolites of the insect symbiotic fungus Nigrospora sphaerica ZMT05,which are(+)-nigrosporione A(+)-1(25),(-)-nigrosporione A(-)-1(26),nigrosporione B(27),nigrosporione C(28),nigrosporione D(29),nigrosporione E(30),ergosterol(31),9,11-dehydroperoxide ergosterol(32),pair hydroxybenzoic acid(33),myristic acid(34),methyl hydrazine-3-acetate methyl ester(35),indole-3-carbaldehyde(36),Nb-acetyltryptamine(37),hydrazine-3-acetic acid(38),linoleic acid glyceride(39),dibutyl phthalate(40),nicotinamide(41),L-dibutyl malate(42),sohirnone C(43).Among them,compounds 1,2,3,4,5,25,26,27,28,29 and 30 are new ones not reported in the literature,compound 21 is a new natural product.Compounds 6,9,12,13,15,16,17,19,20 and 22 were obtained for the first time from the genus Botryosphaeria ramosa,and 23 were obtained for the first time from the genus Botryosphaeria.Compounds 35,37,42,43 were obtained for the first time from the genus Nigrospora sphaerica.Studies on the antimicrobial activity of the isolated new compounds showed that compounds 1,2,3,4,5,21,25,26,27,28,29 and 30 had high antifungal effects against one or several plant pathogenic fungi among Fusarium graminearum,Colletotrichum musae,Fusarium oxysporum,Penicillium italicum.In summary,a total of 11 new compounds,a new natural product and 31 known compounds were isolated.Among them,11 compounds exhibited strong activity against the test plant pathogens,suggesting that they have potiential to be further studied to developnew agricultural antibiotics.