| The aims of this study are to isolate the endophytic actinomycetes from mangrove plant, and to further screen their bioactivities against human pathogens and tumor cells.A sterilization procedure including 5 min wash in 75% ethanol, followed by a 15 minute wash in 0.1% HgCl, then a final rinse in sterile ddH2O 5 times was employed, and then applied to selective media (1/10ATCC172) adding with different antibiotics.One huandred and thirty nine strains of endophytic actinomycetes were isolated from 18 species of real mangrove and 4 species of semi-mangrove collected from the mangrove reserve zone of Qinglan port, Hainan.One huandred and thirty nine isolates were primarily classified by their morphology on the agar plates and under microscope. Fourty two isolations were putatively identified to the genus level based on 16S rDNA sequence analysis and cell wall amino acid analysis by TLC. Neighbor-joining tree based on almost-complete 16S rRNA gene sequences showing the systematic relationship between the 42 strains.The 139 strains were classified to 2 genera of Micromonospora and, Streptomyces. The distributions of endophytic actinomycetes in different mangrove species of this research were different. In mangroves Micromonospora were of predominant genus under our isolation strategy.Through detection of bioactivities on the 139 endophytic actinomycetes isolates, 45 strains showed activity against liver cancer SMMC-7721 cell, which was 32.3% of total strains; 31 strains were active against MRSA which was 22.3% of total strains. Strains isolated from mangroves showed no bioactivity against Candida albicans.Our study indicated that mangrove endophytic actinomycetes were great resources for new structural metabolites with bio-activities. They are worth further researches. We studied two actinomycetes strain 0616208 and strain 124092 isolated from mangrove soil collected from the mangrove reserve zone of Qinglan port, Hainan.The two actinomycetes had cytotoxic activity and good genetic stability through generation transferring analysis. Salt tolerance of these two strains were observed by culturing on media with sea water and distilled water. The two strains grew better in YE medium with sea water than with distilled water. So they were mostly likely to be marine origin.Based on morphological and physiological characteristics, cell wall composition analysis and 16S rDNA sequence analysis, strain 0616208 was the most similar of 96 % to Streptomyces cinerochromogenes strain: NBRC 13822(AB184507) that had not be confirmed to be which species was; strain 124092 was preliminarily identified to Streptomyces parvus var. marinus.The two marine actinomycetes were fermented and their culture broth was extracted with MeOH. The extracts were subjected to column chromatography with various materials such as silica gel and Sephadex-LH 20. Five compounds were isolated from the fermentation broth of strain 124092, their structures were elucidated as p-tolyl-3-aminopropanoate (1), 6-amino-3-(4-hydroxybenzyl)-1,4-diazonane-2,5-dione (2), (1α,4aα,5α,7β,8aβ)-5,8a-dimethyldecahy- dronaphthalene-1,4a,7-triol (3), 7,4'-dihydroxy- isoflavone (4), and 1H-Indole-3-carboxylic acid (5) by ESI-MS, IR, 1D-, 2D-NMR and other spectra. Among them, compounds 1-2 were new ones, and compounds 1-4 showed antitumor activities by MTT methods. Meanwhile, two compounds, 1α,4aα,5α, 7β,8aβ)-5, 8a-dimethyldecahydronaphthalene-1,4a,7-triol (d) and uracil (e) were isolated and identified from the fermentation broth of stain 0616208. Compound d was a new compound which showed antitumor activity.From above evidences, mangrove actinomycetes were proved to be a great resource for new actinomycetes and new bio-activitive secondary metabolites.
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