Primary Studies On Antimicrobial And Antitumor Agents Of Endophytic Fungi Isolated From Mangroves

Mangroves are woody plant communities in the intertidal zone of tropical and subtropical coast. Endophytes of these special plants exhibit characteristic in distribution of species, process of metabolism and variety of metabolized products. These endophytes possess the potential ability in producing novel compounds, and they are important resources for the natural active products.Endophytes of mangroves, Kandelin canda, Avicennia marina and Aegiceras corniculatum, collected from Fujian were studied. Density and distribution of these endophytes in different mangroves are investigated. Endophytic population density of 40 to 220 was revealed in the endophytes of the investigated plants. The distribution of endophytes were influenced by the species, age and the growth environment of the host plants.One hundred and twenty-five endophytic fungi were isolated from the balk of three mangroves. 26 strains (about 20.8% of the total isolates) with antimicrobial activity, against one or more sensitive microbes, such as Bacillus subtilis, Escherichia coli, and Fusarium sp. etc, were screened out using the filter paper assay. The majority was Mycelia, accounting for 42.3 of all active strains. The proportions of active strains isolated from three different plants are similar, occupied about 20%.Using the method of MTT (Methyl Thiazolyltetrazolium), the isolates were screening for anticancer strains in vitro'. The result shows that 11 strains (about 8.8% of the total isolates) can inhibit the growth of KB and/or HL~60 cell lines. The proportions of antitumor strains from three mangrove plants were 11.6%, 5.7% and 4.8%, respectively. Two strains with excellent antitumoractivities were detected. Strain HQ1 exhibited nicer cytotoxic activity. IDjo of its fermentation broth against KB, HL-60, HeLa, BGC and SPC-A-1 cell lines were 3,600, 3,600, 5,400, 1,800 and 150, respectively. And the strain FQ1 inhibited the growth of KB, HL-60, HeLa and BGC with ID50 5,400, 3,600, 1,800 and 150.Two active strains HQ1 and FQ10 were investigated in detail. The culture product of strain FQ10 was isolated and purified. One pure component was observed. Though theESI-MS, IR and NMR detection, it was identified as cyclo(Tyr-Pro) dipeptide. This compound was isolated from microbes for the first time. And further study on its activity will be carried out in future.From the fermentation broth of strain HQ1, one lipophilic compound was isolated and identified as brefeldin A, which exhibit remarkable antitumor activity. BFA was reported to produce by many terrestrial fungus. This is the first report that BFA was isolated from marine fungi. In the fermentation broth, several other active components selectively inhibiting the growth of KB cell line were also detected, which are worthy of further study.