Screening Of Active Endophytic Fungi Isolated From Bruguiera Sexangula (Lour.)poir. And Study On Its Metabolites

Endophytic fungi, whose metabolites had high degree of diversity and showed high potential as sources of antibacterial, antioxidant, anti-tumor, immune suppression and other active compounds, were abundant microbial resources and could be regarded as a treasure trove for natural active substances. In order to futher explore natural products derived from endohytic fungi of Bruguiera sexangula （Lour.）Poir., this dissertation described the discovery of serveral products led by studies of antibacterial activity and antioxidant activity. The main contents included isolation and identification of Endophytic Fungi from Bruguiera sexangula （Lour.）Poir., screening of antibacterial and antioxidant activity strains and natural products of active strains. The results were concluded as follows:Ninty-six strains were isolated from roots, stems, leaves, flowers and hypocotyl of Bruguiera sexangula （Lour.）Poir., and the sixty-seven of them were screened out by their morphological characters and further indentified by Molecular identification technology.The final results showed that the endophytic fungi of Bruguiera sexangula （Lour.）Poir., we isolated, belonged to twenty species, thirteen genera, twelve families, and ten orders.Diaporthe sp.and Pestalotiopsis sp. were dominant endophytic fungi population in Bruguiera sexangula （Lour.）Poir.Four kind of culture medium were used to fermentation of endophytic fungi, and ethyl acetate was used to extract the products. The extracts were screened by antimicrobial assay and antioxidant assay to be futher evaluated by value of MIC and IC₅₀. Ten strains showed inhibition to growth of Escherichia coli, methicillin-resistant Staphylococcus aureus,Enterococcus faecalis, Pseudomonas aeruginosa and Candida albicans. Twelve strains were deemed with antioxidant activity, which showed strong scavenging capacity to 1,1 -Diphenyl-2-picrylhydrazyl and 2,2’-azino-bis（3-ethylbenzothiazoline-6-sulphonicacid）.Finally, Pestalotiopsis mangiferae was chosen as the aimed strain to explore its metabolites in this study by results of antimicrobial and antioxidant analysis.Five compounds, stigmast-4-en-3-one, 3-Heptadecyl-5-methoxy-phenol, Ergosta-4,6,8（14）, 22-tetraen-3-one, Stigmastanol trans-Ferulate, 5,8-epidioxy-5a,8a-ergosta-6,22 E-dien-3β-ol, were isolated from the strain by repeated column chromatography on silica gel, C18 column chromatography and Sephadex LH-20. The structures of thes e compounds were elucidated by means of spectroscopic methods including ESI-MS,1H NMR and 13C NMR. These compounds were evaluated by their antimicrobial and antioxidant activities. The results indicated that 3-Heptadecyl-5-methoxy-phenol could scavenge ABTS radical, with IC₅₀ less than 1.7mg/mL.