Studies On Antimicrobial Active Constituents From Oxytropis Hirta Bunge

The discovery of natural products with agricultural activity from plants is an effective way to discover new pesticides.Oxytropis hirta Bunge is a Traditional Chinese Medicinal from genus Oxytropis.Its secondary metabolites include flavonoids,alkaloids,triterpenes and their glycosides.This thesis using bioactive guided method to systematically isolation,structure elucidation and antimicrobial active evaluation of moderate polar secondary metabolites from the title plants.The main results of this thesis are as follow:1.The extraction rate of crude O.hirta was 7.71%by successive ethanol extraction method.After stepwise extraction with different polar solvents such as petroleum ether,ethyl acetate and n-butanol,it was found that the medium-polar ethyl acetate extracts of O.hirta had the highest content,and the highly polar n-butyl extraction was second,and the small polar petroleum ether extraction was the least.2.Eight compounds were isolated from O.hirta by column chromatography techniques such as silica gel and Sephadex LH-20.The structures of six compounds were identified by various spectroscopy methods,namely 20S-3-Oxo-azukisapogenol（JDY-3-1）,β-amyrin（JDY-2-1）,5α-stigmast-9（11）-en-3β-ol（JDY-4-1）,Stigmast-4-ene-3,6-dione（JDY-4-2）,soyasapogenol B（JDY-5-1）and azukisapogenol（JDY-7-1）.Among the isolates,JDY-3-1 is a new compound.3.The results of antimicrobial activity of the crude extracts of O.hirta and the related partitions on phytopathogenic fungi and plant pathogenic bacteria showed that:Ethyl acetate extract and n-butanol extract showed better inhibitory activity against phytopathogenic fungi and phytopathogenic bacteria,and the antimicrobial activity of ethyl acetate phase was better than that of n-butanol phase.4.Using Thanatephorus cucumeris,Fusahum graminearum,Colletotrichum gloeosporioides,Gaeumannomyces graminis var.tritici,Botrytis cinerea Pers and Phytophthora capsici Leonian as target pathogenic fungi,the antimicrobial activity of four compounds of JDY-2-1,JDY-4-1,JDY-5-1 and JDY-7-1 from the title plants was tested.The results showed that azukisapogenol（JDY-7-1）had a significant inhibitory effect on the mycelial growth rate of pathogens of T.cucumeris and B.cinerea,and their EC₅₀were 117.353μg/m L and 86.213μg/m L,respectively.5.Using Pseudomonas syringae pv.actinidae,Erwinia carotovora,Pseudomonas solanacearum Smith,Bacilus subtilis and Staphylococcus aureus as target pathogenic bacteria,the antimicrobial activity of four compounds of JDY-2-1,JDY-4-1,JDY-5-1 and JDY-7-1from the title plants was tested.The results showed thatβ-amyrin（JDY-2-1）had the best inhibitory effect on S.aureus with MIC value of 50μg/m L.It also inhibited E.carotovora,P.solanacearum and B.subtilis with MIC value of 100μg/m L.