Antibacterial Secondary Metabolites From Streptomyces Sp.D-4,D-11

Plant endophytic actinomycetes are special microorganisms that can grow in host plants without causing plant infection.These secondary metabolites from plant endophytic actinomy-cetes are usually abundant and diverse in structures and biological activities.They are important resources for searching and developing new lead compounds.Garlic has a broad spectrum of antibacterial activity for existence of allicin.Five strains of endophytic actinomycetes were obtained from garlic bulb and were identified as Streptomyces.The purified and identified strains were fermented by shaking flask on a small scale,and the crude extracts were analyzed by HPLC fingerprint and screened for antibacterial activity of Kirby-Bauer test.Actinomyces with antibacterial activity,rich chromatographic peaks in HPLC and characteristic UV absorption were selected for large-scale fermentation.Finally,two actinomyces strains were selected for large-scale fermentation,Streptomyces puniceus.D-4（Gen Bank:OP735464）、Streptomyces pratensis.D-11（Gen Bank:OQ592575）.Twenty compounds,including ten new compounds and ten known compounds,were isolated from the crude extracts of Streptomyces sp.D-4,D-11.The new compounds are Puniceusinene（1）、Butyl（3-hydroxypentanoyl）leucinate（2-5）、Pratensisopolyketidin A（13）、（±）-pratensisopolyketidin C（14-15）、（±）-pratensisopolyketidin D（16-17）.Puniceusinene（1）was a new heteroatom-free polyene dimer compound,which are rare in natural products.Butyl（3-hydroxypentanoyl）leucinates（2-5）were four new alkaloid enantiomers and their structures and absolute configurations were determined by chemical synthesis.Compounds 13-17 were polyketides with high carbon-proton ratio,including two pair of Enantiomers.Puniceusinene（1）showed inhibition the growth of Candida albicans and the MIC₅₀ value was 38.4μg/m L.