| Natural products and their derivatives have become valuable sources for the design and development of new pesticides due to their rich and unique biological activities.The natural products produced by endophytic fungi have a wide range of active and diverse structures,including the Nodulisporium sp.Ths endophytic fungi which have been reported can produce many natural products with novel structures and significant activity in the literature.Macroporous adsorption resin is a kind of adsorbent with large specific surface area,low cost,strong adsorption and reusability.It was first used in environmental protection,separation and purification of natural products.In recent years,studies have shown that adding macroporous resin can not only adsorb fermentation products,but also alleviate the degradation or further metabolism of secondary metabolites,protecting some unstable intermediates,and synthesize new metabolites.Therefore,it is a new idea that using the technique about macroporous resin during the microbial fermentation process to enrich and purify metabolites could discover new active natural products.In our previous study,a strain of endophytic fungi Nodulisporium sp.A21 was found and sixteen secondary metabolites were obtained.In order to further explore the structural types of the secondary metabolites of A21,macroporous adsorption resin was added during the fermentation of A21 to obtain compoudnds with unique structure and novel activity.The results are as follows:Four kinds of macroporous adsorption resins XAD16,XAD1600,XAD761 and D101 were screened,and the crude extracts were obtained by small batch fermentation.The antifungi activity,1H-NMR spectrum and HPLC spectrum of the crude extracts were compared to XAD16 resin was selected;The A21 was subjected to liquid fermentation,and add 3%XAD16 on the third day of fermentation.Hyphae and resin were partially dried,and the fermentation broth was extracted with methanol and dichloromethane respectively.The total crude extract of 130 g.The compounds were separated and purified using various column chromatography techniques HPLC,and identifiend using spectral data analysis,ECD calculation and X-ray single crystal diffraction techniqu es.A total of 11 compounds(1-11)were isolated from the secondary metabolites off A21,and 4 of which were new structural compounds(8-11).The results of bacterial test showed that compounds 7,8,9,11 have different degrees of inhibition against Xanthomonas oryzae pv.oryzicola,Pseudomonas solanacearum,Xanthomonas oryzae,and Bacillus subtilis Bacillus subtilits.Compound 7(1-undecen-2,3-dicarboxylic acid)has the best antibacterial effect against Bacillus subtilis,and the MIC value reaches 16 μg/mL,compound 8(Sporothric acid B)MIC value of 16μg/mL against Xanthomonas oryzae pv.oryzicola.The results of antifungi activity showed that compound 7 could inhibite the growth of Sclerotinia sclerotiorum.The inhibition rate is 87.4%at 50 μg/mL.The compound had certain control effect on the in vitro leaf infection of S.sclerotiorum,reaching 26.2%at 200μg/mL.At 200 μg/mL,Compound 7 was almost completely inhibited the germination of Fusarium graminearum spores and Magnaporthe oryzae spores.Compound 9 was measured it herbicidal activities against two weeds species,such as Echinochloa crusgalli,Eclipta prostrate.The results showed it can inhibite the growth at 400μg/mL.In summary,this paper uses macroporous resin in situ adsorption technology,and XAD16 resin was added during the fermentation of A21,and obtains the active metabolite of new structure,which provides a new idea for the discovery of new pesticide lead compounds. |
PDF Full Text Request