Study On The Secondary Metabolites From A Soil-derived Streptomyces Sp. KIB-H91

This dissertation is composed of two chapters.In the first chapter,isolation and identification of secondary metabolites from a soil-derived Streptomyces sp.KIB-H91 were described and the antimicrobial activities of six selected compounds were studied.In the second chapter,a review concerning the bioactive natural compounds and their discovery approaches from Streptomyces in recent years was given.Sanqi?Panax notoginseng Burk.F.H.Chen?,a well-known Chinese herbal medicine,is a typical biological resources in Yunnan Province.Its cultivation is severely inhibited by sequential cropping obstacles which is probably affected by the microbial community composition in the rhizosphere soil.We isolated the strain KIB-H91 from a soil sample collected from the Sanqi planting field in Kunming Botanical Garden.This strain was fermented and scaled up.As a result,25 natural products,including 5 new compounds and a quinazolin separated from nature for the first time,were isolated from the fermentation broth by varied chromatographic methods,such as silica-gel column chromatography,reverse-phase chromatography,HPLC and so on.Among them,the structures of 20 compounds were elucidated on the basis of spectroscopic evidence(¹H NMR,¹³C NMR,COSY,HSQC,HMBC,ROESY,etc.)and comparing with literature reports.In this study,we also conducted the antimicrobial susceptibility tests to determine the minimum inhibitory concentration values of several isolated compounds.Sarubicins A and B were the main antimicrobial components of strain KIB-H91with MIC values of 25?g/mL for sarubicin A against Escherichia coli ATCC 8099 and of 12.5?g/mL for sarubicin A against Bacillus subtilis ATCC 6633.Secondary metabolites produced by Streptomyces play a significant role in the discovery of antibiotic drugs.So far,natural products chemists have uncovered an array of bioactive NPs and established a series of approaches for mining novel compounds from Streptomyces resource.In chapter 2,the related advancements were reviewed and 94 references and 65 compounds were cited.