Extraction of secondary metabolites of Penicillium sp.in Derris plants and bioactivity assay against Lipaphis erysimi

Objective To screen out one strain of endophytic fungi which might produce insecticidal secondary metabolites and test its insecticidal activity against Lipaphis erysimi.

Method Endophytic fungi in insecticidal plants, including Derris elliptica, D.alborubra, D.thyrsiflora and D.hacei, were studied. Endophytic fungi isolated from Derris plants were identified by classical morphological method, and their secondary metabolites were identified using high-performance liquid chromatograph(HPLC) to obtain the objective strains. Various extraction methods and extraction solvents were used to optimize the extraction of secondary metabolites. Insecticidal activity against L.erysimi was studied by immersion of the insect bodies.

Result One strain of endophytic fungi of Penicillium sp., which produced insecticidal metabolites, was screened out from the roots of D.elliptica. Extracting tests on the mycelia and fermentation of endophytic Penicillium sp. indicated that chloroform was the best extracting solvent, and bioactive compounds could be effectively extracted using supersonic method with an extracting rate of 4.156%. Chloroform extract had the highest efficiency against the adults of L.erysimi, of which LC₅₀ was 1.570 mg·mL^-1 after 24 h and 0.953 mg·mL^-1 after 48 h.

Conclusion This study determines the extraction method of the secondary metabolites from endophytic fungi of Derris plants, and confirmes that these metabolites have insecticidal activity similar to rotenone. However, the specific chemical structures of the secondary metabolites remains to be further confirmed.