Study On Secondary Metabolites And Biological Activities Of An Endophytic Fungus From Pogostemon Cablin And An Entomopathogenic Fungus

Endophytic fungus are plentiful and diverse in species,which are capable of producing the same or similar active metabolites with their hosts and other biological properties.Pogostemon cablin is an authentic herb from Guangdong,which is widely used in traditional Chinese medicine as its vital medicinal and economic values.However,the endophytic fungus from Pogostemon cablin and their metabolites were rarely reported.Thus,to explore the endophytic fungus and active metabolites from Pogostemon cablin has great theoretical and practical significance.In this study,6 compounds were isolated from Daldinia eschscholzii A630,an endophytic fungus from Pogostemon cablin,by MCI column chromatography,Sephadex LH-20 gel column chromatography,reverse phase silica gel column chromatography and high performance liquid phase reversed phase preparative column chromatography methods.Their structures were determined by extensive spectroscopic analysis,including ¹H-NMR,¹³C-NMR and ESI-MS.The compounds were identified as Dihydrosphaerolone?M01?,8-methoxy-1-naphthol?M02?,1-?2,6-dihydroxyphenyl?-butan-1-one?M03?,helicascolide A?M04?,6-hydroxymellein?M05?and 8-dihydroxy-1-tetralone?M06?,and compound M03 was first isolated from the genus Daldinia for the first time.All of the compounds?M01-M06?were evaluated for their cytotoxic activities against SF-268?glial cells?,MCF-7?breast cancer cells?,NCI-H460?non-small cell lung cancer cells?,HepG-2?hepatocarcinoma cells?by the SRB method.The results indicated that compounds M01,M03 and M07had cytotoxic activities against the tumor cells mentioned above with the inhibitory rates ranging from 72.68%to 98.56%at the concentration of 100 ug/mL.CompoundM02 show cytotoxic acticities on SF-268,MCF-7,NCI-H460.Bio-pesticides have drawn a lot of attention because of low residue,strong selectivity,low risk of human and animal diseases and difficulty to cause resistance.The representatives are Beauveria bassiana,Metarhizium and other entomopathogenic fungus.Cordyceps cardinalis is a pathogenic fungus,which is parasitic on Lepidoptera larvae.Previous studies have found that its asexual strain C033 can produce oosporein.Therefore,strain C033 may have certain application prospect in biological control since oosporein is the main metabolite of Beauveria bassiana.In this study,we first explored the preparation of the oosporein and studied the antifeedant activity of the oosporein to the common agricultural pests Spodoptera litura and S.exigua,also we test the insecticidal activity of Plutella xylostella,then further studied the optimum fermentation conditions for the high yield of oosporein.Preliminary investigation showed that oosporein was difficult to dissolve in the common pesticide emulsifiers.The bioactivity assay showed that oosporein exhibited antifeeding activity with LC₅₀ values of 2907.17 and 1419.38 ppm against Spodoptera litura in the selective and non-selective tests,respectively,and displayed antifeeding activity with LC₅₀ values of 1541.35,2055.63 ppm against S.exigua in the selective and non-selective tests,respectively.Oosporein also showed no significant lethal activity against Plutella xylostella with LC₅₀ value of 2569.8463 ppm?48 h?.Finally,optimal conditions of strain C033 for producing high yield of oosporein were investigated.The result indicated the PPD was the most optimal medium among 8media by single factor screening and orthogonal experiment.The optimum conditions were as follows:the culture time was 6 days,the amount of inoculation was 6%,the initial pH was 7,the culture temperature was 24^oC,the amount of liquid was 100 mL?500 mL Erlenmeyer flask?and the rotational speed was 120 r/min.Under the optimum conditions,the density of oosporein in the fermentation broth of strain C033reached 448.70?g/ml.