| With the progress of human society, people have to face a lot of serious problems, such as drug resistance in bacteria, the appearance of life threading viruses, the recurring problems with disease in person with organ transplants, and the tremendous increase in the incidence of fungal infections, human society is increasingly strong demand for new drugs. Meanwhile, as awareness of environmental protection, the use of chemical pesticides is more and more limited and study of microbial pesticides has been attracted widespread attention. Xylaria is the source of a large number of biologically active substances, and its metabolites including antibacterial, anti-tumor, anti-oxidation,anti-AIDS and novel structure of active compounds. Thus, the search for new natural products or biologically active substances has efficient ways to become an exploration of new resources from medicinal plants and their endophytic fungi. The host plant of Xylaria had a long history of civil records related medicinal knowledge in our country, different chemical compositions have been isolated from this kind of plants, including pregnane,lipids, sterols, flavanols, triterpenoids, sesquiterpene and double sugar. Studing on the Xylaria found that natural products are expected to develop the most promising pharmaceutical, high theoretical and practical significance.This study was based on endophyte Xylaria sp. T-4, by studying flat antibacterial test of the Xylaria sp. T-4 living colonies and its metabolites, antibacterial activity of Gram bacteria of ethyl acetate extract concentrate of the Xylaria sp. T-4, and isolation and structure elucidation of secondary metabolites, the following conclusions:1. The Xylaria sp. T-4 living colonies had inhibitory activity to all the selected 15 kinds of pathogenic fungi. Plant pathogens were inhibited rate of between 24.14% ~82.92%, and the range of relative inhibitory effect was 0.90 to 19.75. Among them, the strongest inhibitory effect was Phytophthora melonis Kalsura and pathogen inhibition ratewas 82.92%. While the suppressed rate of Xylaria sp. T-4 was 4.20%, the relative inhibitory effect was 19.75 resulting in a 2 mm antagonism and pathogen growth was completely inhibited.2. The medium was inoculated plant pathogens containing the Xylaria sp. T-4metabolites were observed for 15 kinds of pathogenic fungi inhibition. The results showed that the Xylaria sp. T-4 metabolites all inhibited the growth of pathogenic antagonistic, and the inhibition rate was between 22.91% and 100.00%. Among them, the inhibition of Phytophthora melonis Kalsura was the best, the inhibition rate was 100.00%. While Phoma sp. of the spider orchid, Colletotrichum lycopersici Ell. et Ev. and Alternaria alternata were inhibited significantly higher than other treatments, respectively, 84.09%, 74.90% and68.75%.3. The antibacterial activity of ethyl acetate extract concentrate of allowing to stand and flask of the Xylaria sp. T-4 for Gram bacteria showed that both the crude extract at a concentration of 20 mg/m L, against Gram-positive bacterium Staphylococcus aureus had a certain extent, inhibition zone was 2.6 mm and 2.0 mm.4.Five compounds were isolated from ethyl acetate extract of the fermentation filtrate of Xylaria sp.T-4 by chromatographic techinques, and their structures were determined by spectroscopic and chemical methods. They contained: LD1(1), 7-Isochromancarboxylic acid(2),Sordaricin(3), Cyclic pentapeptide(4) and Dibutyl phthalate(5). LD1 was a new compound and its structure was a relatively rare at C-3 and C-4 alkyl bit ergosterol type open loop.Sordaricin is a good anti-fungal agent.Therefore, endophytic fungi are isolated from medicinal plants, and study of secondary metabolites, and explore its role in the biological control and medical. It is expected to get with efficient biological activity or new structure of the compounds to meet the demand of pharmaceutical and agricultural production. The development potential of bioactive compounds or frame has also a great application prospect. |
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