| Objective:In searching for biologically active natural products for drug discovery,the secondary metabolites of five endophytic streptomyces strains which were isolated from the medicinal plants or their rhizosphere soil were isolated and purified for structural identification and biological activity detection.Methods:At first,many streptomyces strains isolated from medicinal plants or their rhizosphere soil were cultured in small amounts.We screened the target strain combining the chemical compositions with the biological activity of the fermentation broth.Than these target strains were fermented on a large scale respectively.The main secondary metabolites were extracted with ethyl acetate from the fermentation broth,and further isolated and purified by means of chromatography over Silica gel column,RP-C18,sephadex LH-20,MCI column and semi-preparative HPLC.Their structures were identified through extensive NMR（1H-NMR,1C-NMR,HSQC,HMBC,COSY,ROESY）,ESI-MS,UV,IR Spectra,X-ray,chemical derivatization,and related literatures.The antibiotic activity of some monomeric compounds on Staphylococcus aureus,Escherichia coli,Bacillus subtilis,Saccharomyces cerevisiae,Penicillium decumbens,Xanthomonas orzae pv.oryzae and other plant pathogenic fungi by filter paper method.Results:Five target strains with plenty of products showing specific ultraviolet absorption,and good antibacterial activity were obtained.They are endogenous Streptomyces sp.KIB-1083 from Lycopodium japonicum,endogenous Streptomyces sp.KIB-2025 from Trigonostemon tuberculatum,Streptomyces sp.KIB-717 from the rhizosphere soil of Pteris vittata,endogenous Streptomyces sp.KIB-2054 from Campylotropis pinetorum,Streptomyces sp.KIB-717 from the rhizosphere soil of Maytenus graciliramula,respectively.The main secondary metabolites of five target strains were extracted with ethyl acetate from the fermentation broth,and further isolated and purified for structural identification.The structures of 32 compounds were identified.Among them there were 8 new compunds,including 2 piericidin glucosides,1 piericidin,2 tetraenoic acids,1 2（3H）-furanone,1 2（2H）-pyranone,1 naphthalenecarboxamide;2 compounds were isolated from Streptomyces for the first time,and they belong to naphthalenecarboxamide and naphthomycin respectively;23 known compounds,including 3 piericidin glucosides,9 piericidins,5 naphthomycins,1 macrolide dilactone compound with two oxazole ring,2 rubromycins,1 coumarin,and 14-Deoxy-ε-pyrromycinone and benzoic acid.The antibacterial test results showed that Glucopiericidin A（3）,compound 4,piericidin A5（14）,piericidin A3（15）and Mer-A2026A（16）can inhibit the growth of Staphylococcus aureus and Bacillus subtilis;piericidin C1（8）,piericidin C5（10）,piericidin C3（11）,Mer-A2026A（16）and piericidin A3（15）can inhibit the growth of Saccharomyces cerevisiae and Penicillium decumbens;Piericidin C1（8）,piericidin C3（11）,piericidin C5（10）and Piericidin A（1）had a strong inhibitory effect on Xanthomonas oryzae pv.oryzae,Mer-A2026A（16）,Piericidin A3（15）,Piericidin A5（14）and Piericidin D1（13）showed moderate inhibitory activity against Xanthomonas oryzae pv.oryzae;β-rubromycin（21）andγ-rubromycin（22）possessed significant antifungal activity against most of the tested plant pathogenic fungi.Conclusion:Piericidins have a strong and broad spectrum of bioactivity which is particularly significant for the antibacterial activity of Xanthomonas oryzae pv.oryzae.Rubromycins possessed significant antifungal activity against most of the tested plant pathogenic fungi.The growth cycle of Streptomyces is short,and it is easy to culture.The secondary metabolites of Streptomyces possessed significant biological activity.Streptomyces have a research value in the development of new medical and agricultural antibiotics. |
