Study On The Conversion Of Methylglycosylation Of Plant Flavonoids By Isaria Fumosorosea

Plant flavonoids are a class of important secondary metabolites with complex and diverse structures and activities.They are widely used in the fields of medicine,agriculture and food processing.Special physiological characteristics such as low solubility,low bioavailability,and phytotoxicity greatly limit the function of flavonoids.Flavonoids can be converted to flavonoid glycosides under mild conditions through microbial transformation,which can improvewater solubility and bioavailability.Filamentous fungi such as Isaria fumosorosea can utilize intracellular glucosyltransferase and oxymethyltransferase to catalyze organic compounds and produce glycoside derivatives with different physiological characteristics and biological activities.In this study,through microbial transformation,a strain I.fumosorosea which efficiently transformed different flavonoid compounds was screened from four entomogenous filamentous fungi and a series of novel glycoside derivatives were obtained,and the lipid-lowering and anti-inflammatory activity of these compounds was initially explored,specific progress is as follows:1.Through the microbial transformation experiment of four filamentous fungi I.fumosorosea ACCC 37814,Metarhizium robertsii ARSEF 23,Clavieps purpurea ACCC 37002,Cordyceps militaris ACCC 50985,it was found that I.fumosorosea ACCC 37814 could efficiently transform 10 flavonoids(1-10).Among them,I.fumosorosea ACCC 37814 had higher conversion efficiency to naringenin 1,luteolin 2,geraniol 3,and formononetin 4.2.The compounds(1-4)were transformed by I.fumosorosea ACCC 37814 and glycoside products were isolated and purified as 1a(2.3 mg),1b(3.2 mg),1c(6.5 mg),1d(1.5 mg),2a(2.3 mg),2b(2.8 mg),3a(2.0 mg)and 4a(4.0 mg),and then the structure of each glycoside derivative was analyzed by NMR technology.Among them,six were novel methylglucopyranosides(1b,1d,2a,2b,3a,4a),two were known methylglucopyranoside(1a)and glucopyranoside(1c).3.The lipid-lowering experiment of 3T3-L1 preadipocytes and the anti-inflammatory experiment of RAW 264.7 macrophages were performed by using four flavonoids(1-4)and their eight glycoside derivatives(1a-1d,2a,2b,3a,4a),It was found that within the allowable toxicity range,when the test concentration was 100 ?g/mL,compound 1b and compound 3a could significantly inhibit the proliferation of 3T3-L1 preadipocytes and significantly reduce the number of lipid droplets generated during cell differentiation(P<0.05),compound 1b could significantly reduce the amount of NO release and had the strongest anti-inflammatory effect,up to 97%(P<0.05).In this study,the fungus I.fumosorosea ACCC 37814 which could efficiently methylglycosylate plant flavonoids was screened by the microbial transformation.A series of glycoside derivatives with novel structure,good lipid-lowering and anti-inflammatory effects were obtained by using this bacterium to transform four flavonoids,which expanded the structural space of such compounds and provided resources for the screening of active compounds.The research results of the paper are helpful for mining efficient strain resources,expanding the structural space and biological functions of flavonoids,and providing choices for quality breeding of coarse grain crops and drug screening.