Study On The Insecticidal Active Ingredients Of Two Endophytes Isolated From Tripterygium Wilfordii Hook.f.

Plant endophytes have a wide variety of secondary metabolites with multiple biological activities.Two endophytes F4-20(Streptomyces blastomycetica strain NRRL B-5480)and F4-3(Pestalotiopsis malicola JF501649)were screened and isolated from 3-years-old root of Tripterygium wilfordii Hook.f.with insecticidal activity.In order to further clarify the insecticidal components of these two strains and find compounds with similar structure to the alkaloids of Tripterygium wilfordii Hook.f.This study conducted the separation of active ingredients,identification of isolated compounds and evaluation of insecticidal activity of theses two strains F4-20 and F4-3.The results were as follows:1.Six compounds were isolated from the metabolite of Streptomyces blastomycetica strain NRRL B-5480,and five of them were identified as Olivoretin A,Teleocidin B,Olivoretin C,Benzoic Acid and Betulin by NMR according to related literature.Two compounds were isolated from the fermentation of Pestalotiopsis malicola JF501649 and one was identified as Brefeldin A by NMR according to related literature.2.Acaricidal activity of extracts and 6 compounds isolated from F4-20 and F4-3 against Tetranychina harti were tested with slide-dip method at the concentration of 2 mg/mL.The result showed that the mycelium extracts and fermentation broth of F4-20 had high toxicity against Tetranychina harti with the corrective mortality(24 h)of 86.59% and 62.19%,respectively.However,the mycelium extracts and fermentation broth of F4-3 had no obvious effects against Tetranychina harti.Compounds N3 and N2 showed higher toxicity against Tetranychina harti with their LC50 values of 333.41 and 40.34 ?g/mL,respectively.4.The toxicity of fermentation extracts and 6 compounds isolated from F4-20 and F4-3 were tested against Myzus persicae by insect-dipping method.The results showed that the mycelium extracts and fermentation broth of F4-20 and F4-3 had no obvious insecticidal activity after treated 24 h at the concentration of 5 mg/mL.And the corrective mortality(24 h)were 31.71%,26.83%,29.27% and 25.61%,respectively.Six compounds showed no obvious insecticidal activities against the 3rd larva of Myzus persicae.5.The toxicity of fermentation extracts and 6 compounds isolated from F4-20 and F4-3 were evaluated against the 3rd larva of Mythimna separata by insect-dipping method at the concentration of 5 mg/mL.The results showed that the mycelium extracts and fermentation broth of F4-20 and F4-3 had no obvious insecticidal activity after treated 24 h and 48 h.And the corrective mortality(24 h and 48 h)were all lesser than 20%.Six compounds showed no obvious insecticidal activities against the 3rd larva of Mythimna separata.6.Fermentation extracts of F4-20 and F4-3 had great antifeedant activity against the 3rd larva of Plutella xylostella(Linnaeus)by leaf disc method at the concentration of 5 mg/mL,and the inhibition rate were 65.31% and 80.95%,respectively.The 6 compounds and mycelium extracts of F4-20 and F4-3 showed no obvious antifeedant activity.In conclusion,In this study,we separated 8 compounds from F4-20 and F4-3 of Tripterygium wilfordii and six compound structures were identified and then tested their insecticidal activities.These results provided a theoretical foundation for the further study of these two endophytes and development of new pesticides.