Bioactive Secondary Metabolites Produced By Two Soil Actinomycetes

Actinomycetes have been one of the most important sources of microbes for discovering new antibiotics for decades.According to statistics,more than half of the commonly used antibiotics are produced by actinomycetes.Soil is the main habitat of actinomycetes.At present,exploitations and utilizations of the soil actinomycetes only account for 10%-20% of the total.Therefore,the research on secondary metabolites from soil actinomycetes is still the essential work of the development of new medicines and new pesticides.Two active strains,named Streptomyces sp.HS-NF-813 and Streptomyces sp.HS-HX-145,were screened by pathogen model as well as human colon cancer cell HCT-116 in vitro.The secondary metabolites of the two strains were isolated and extracted.The results are as follows:The strain Streptomyces sp.HS-NF-813 was fermented for 20 L.Nine compounds(1-9)were isolated from the fermentation broth of the strain Streptomyces sp.HS-NF-813 by silica gel,diaion HP20 column,preparative HPLC and semi-preparative HPLC.Their structures were determined by 1D and 2D NMR techniques,ESIMS,IR,UV,HRESIMS and comparison with data from the literature.At last,we found that three compounds are novel compounds,named CP-78545 free acid A(2),BE-52211 D(8)and BE-52211 E(9).The remaining six are known compounds,Conglobatin(1),Piericidin C1(3),Piericidin C5(4),Piericidin A3(5),Piericidin A1(6),Mer-A 2026 A(7),compounds 3-7 were belong to piericidin antibiotics.The strain Streptomyces sp.HS-HX-145 was fermented for 30 L,a new compound 4-(hydroxymethyl)-2-isopropylfuran-3-carboxamide(10)and three known compounds 5-prenyltryptophol(11),N-(2-(3-indolyl)ethyl)acetamide(12),and Nocardamine(13)were isolated by the same treatment and analysis methods.The absolute stereochemistry of 8 was elucidated by NMR data of the Mosher ester derivatives,the(S)-MTPA ester and(R)-MTPA ester of compound 8 were successfully derived by reaction.From the MTPA determination rule,the absolute configuration of C-2 was assigned as S.Compound 9 was unstable during the reaction of modified Mosher's experiment,thus the configuration at C-16 remained unresolved.Biological origin,the configuration of C-2 of 9 was considered to be S as that of 8.The result of the bioactivities of the obtained compounds 1-13 indicated that the new compounds 2,8 and 9 showed definite antimicrobial activity: compound 2 showed best inhibition of bacterial activity with the rate more than 20 mm against Micrococcus luteus and Staphalococcus aureus at a concentration of 1mg/m L,compounds 8 and 9 expressed antifungal activity against Bacillus subtilis and Staphalococcus aureus;in addition,compounds 2,8 and 9 also exhibited moderate cytotoxic activity against three human tumor cell lines,Hep G2,HCT-116 and K562,among which compound 2 showed best activity with IC50 values of less than 10ug/m L.Compound 1 showed weak anti-tumor activity,compounds 3-7 exhibited certain inhibitory effect on Staphalococcus aureus and Sclerotinia sclerotiorum,they also showed inhibitory activity on colon cancer cell HCT-116;compounds 10 and 12 displayed no biological activity.