Study On The Secondary Metabolites Of Both Streptomyces Pluricolorescens SN194 And Xenorhabdus Budapestensis SN84

As an important source of pesticide active lead compounds,natural products can provide a guarantee for the development of new and efficient and environmentally friendly pharmaceuticals.To this end,we have tried to discover new lead compounds for pesticides through the research and development of natural products.Both Streptomyces pluricolorescens SN194 and Xenorhabdus budapestensis SN84 were deposited in our laboratory.The previous results indicated that(1)dichloromethane extract from fermentation of S.pluricolorescens SN194 contained abundant secondary metabolites and showed inhibitory activity against Botrytis cinerea;(2)X.budapestensis SN84 produced abundant secondary metabolites,which could be a promising source of lead molecules for nematicidal chemicals by analyzing the symbiotic system of "insect-pathogen nematode-symbiotic bacteria".In this paper,the two strains of bacteria(S.pluricolorescens SN194,X.budapestensis SN84)were used as materials to carry out fermentation and culture,and then the secondary metabolites in the fermentation broth were systematically isolated,purified and elucidated.On the basis of previous research and literature,the secondary metabolites of S.pluricolorescens SN194 were tested for the activity against B.cinerea,and the secondary metabolites of X.budapestensis SN84 were tested for the activity against Meloidogyne incognita.According to the results of activity detection,the structure-activity relationship analysis was carried out to provide a theoretical basis for the discovery of new pesticide lead compounds.The main results are as follows:Two new diterpenoids,named chloroxaloterpin A(1),and B(2),along with four known diterpenoids,viguiepinol(3),and oxaloterpins C-E(4-6),were isolated from fermentation culture broth of S.pluricolorescens SN194.Their structures were elucidated based on extensive MS and NMR.All of them contained a viguiepinol skeleton.Both of compounds 1 and 2 contained rare chlorobenzene-containing side chains in natural products.The planar structure and absolute configuration of the new compounds 1 and 2 were confirmed by X-ray crystallography analyses,respectively.All six compounds were tested against B.cinerea.Pyrimethanil was selected as the positive control.Chloroxaloterpin A(1),and B(2),demonstrated strong inhibitory activity against spore germination of B.cinerea with EC50 of 4.40 and 4.96 ?g/mL,respectively,which was better than the positive control.Seven linear peptides named rhabdopeptides I-O,7-13,were isolated from fermentation culture broth of X.budapestensis SN84.The planar structures of these peptides were elucidated on the basis of extensive MS,and NMR analyses.According to the result of previous research and the pathway of biosynthesis,it is deduced that the amino acid residues in the seven compounds are all L-form,which was verified by Marfey's Method.9,10 and 13 were novel compounds.7,8,11,and 12 were isolated and purified for the first time,despite being previously elucidated from an extract mixture based on labeling and MS experiments.All seven compounds were tested for their nematicidal activities against the second-stage juveniles(J2)of Meloidogyne incognita using 24-microwell plates.Rhabdopeptide J(8),demonstrated a strong inhibitory activity with LC50 value of 27.8 ?g/mL.Rhabdopeptide K(9),and M(11),showed moderate inhibitory activity with LC50 values of 46.3 and 42.4 ?g/mL,respectively.