Screening And Secondary Metabolites Studies Of Marine-derived Actinomycetes From Bohai And Yellow Sea

Actinomycetes have been concerned as an important resource of bioactivenatural product. Due to the unique living environment, marine-derived actinomycetesmust have special metabolic pathway differrent from terrestrial actinomycetes, whichprovides an important resource for the discovery of novel drug leading compounds.Marine-derived actinomycetes were isolated and screened by the integeratedmethod using chemical, genetic and bioactive screening model, and metabolitesstudies on two target strains were carried out. The research include isolation andscreening strains, purification and structural elucidation of the secondary metabolites,preliminary bioactivities evaluation of some pure compounds and metabolitesdiversity research using OSMAC strategy.142actinomycete strains were isolated from17sediment samples of Yellow Seaand Bohai Sea. Screening with another221strains from our laboratory,107actinomycetes were selected by chemical fingerprint methods, which has enrichedTLC and HPLC fingerprint library. By the PKS I gene fragments screening,2strainswere selected from13actinomycetes with enriched HPLC fingerprint library.Cytotoxity assay of P388cell line using SRB method,46strains were obtained fromthe107actinomycetes. Actinomycetes LXF-80, which possessed both PKS I genefragments and HPLC chromatogram characteristics, was selected as the target strain.Another targent strain was LXF-75that exhibited significant cytotoxity activity. Sincemetabolites produced by strain LXF-80were more particularly, OSMAC strategy wasused to develop diversity potential.26compounds were isolated and purified from the ethyl acetate extracts of2strains, by means of silica gel column, Sephadex LH20, HPLC, and etc. FromStreptomyces sp. LXF-80,12compounds (1-12) were separated, including a newnatural products YT87(b)(1), enterocin(2), a terpene compound(3),5cyclic dipeptidecompound(4-8), four benzene derivative(9-12); compound5-deoxyenterocin (13) and 3-epi-5-deoxyenterocin(14) were got from the extract which have added inhibitors ofLXF-80;12compounds have been isolated from LXF-75, including5diketopiperazine compounds (15-19), and the compound15is a new compound, oneother compound (20), and6benzene derivatives (21-26).The cytotoxity of compounds1-2,15-20to inhibit the growth of P388, Hela,A-549, HL-60and K562cells lines were measured by MTT and SRB assay. At aconcentration of50μM, the inhibition rate of compound15and16to Hela cells were90.58%and89.84%. The IC50values of compound15against Hela cell is30.1μMand compound16is15.6μM.In summary,26compounds have been isolated and elucidated from two marinederived actinomycetes strains, including a new compound and a new natural product.By activity evaluation, compounds15and16have a weak anti-Hela cell activity.Studies of marine actinomycetes natural products provide wealth of resources. Inaddition, with the development of molecular biology, genetic screening greatlyimproves the efficiency of looking for new natural products and binding studiesbiosynthetic pathway, taking OSMAC strategy not only overcome the compoundsreplication effectively by chemical-activitive screening, but also an effective way tofind out more novel structural analogues.