Chemical Constituents From Faeces Of Philosamia Cynthia And Their Antibacterial Activities

Silkworm faeces is the excrement of silkworm larvae,which is rich in chemical constituents and has a wide range of biological activities.However,the utilization rate of silkworm faeces is not high at present.Except a small part of silkworm faeces is used as traditional Chinese medicine,most of silkworm faeces is discarded as waste,which belongs to a kind of biological resources to be developed.Through consulting the relevant literature of silkworm faeces,we know that silkworm faeces can enrich the chemical substances in food.Using this characteristic,Philosamia cynthia,which likes to eat the leaves of Phellodendron amurense,was fed with Phellodendron amurense,which is rich in fungicidal active substances.The faeces of Philosamia cynthia was used as the test material to explore the possibility of using silkworm faeces as the source of botanical fungicides,to broaden the scope of application of silkworm faeces and to improve the efficiency of resource utilization.We used methanol extraction,methanol-water-dichloromethane extraction,silica gel column chromatography,gel column chromatography and high performance liquid chromatography to separate and purify 9 monomer compounds from faeces of Philosamia cynthia.The structures of the nine monomers were identified by high resolution mass spectrometry,carbon and hydrogen NMR spectroscopy and related literature.The antimicrobial activities of these nine compounds were studied.The results are as follows:1.The silkworm faeces of Philosamia cynthia was separated and purified by column chromatography and semi-preparative high performance liquid chromatography,and nine monomer compounds were obtained.By mass spectrometry and nuclear magnetic resonance spectroscopy,the names of nine compounds were analyzed and determined as follows: vomifoliol(compound 1),(3S,5R,6S,7E,9R)-5,6-epoxy-3,9-dihydroxy-7-megastigmene(compound 2),obacunone(compound 3),neophellamuretin(compound 4),phellamurin(compound 5),clerosterol(compound 6),clerosterol 3-O-β-D-glucoside(compound 7),α-linoleate phytol(compound 8)and phytol(compound 9),all of which were first found in the silkworm faeces of Philosamia cynthia.2.The antimicrobial activity of compound 1-9 with concentration of 50μg/m L was studied by broth dilution method.The results showed that compound 1-3,5-9 had certain antimicrobial activity against 11 plant pathogenic fungi,and compound 1(vomifoliol)showed antimicrobial activity against many plant pathogenic fungi.Compounds 1-5 exhibited certain bacteriostatic activities against five bacteria,of which compound 1(vomifoliol)and compound 2((3S,5R,6S,7E,9R)-5,6-epoxy-3,9-dihydroxy-7-megastigmene)exhibited good bacteriostatic activity against bacillus subtilis,and the bacteriostatic rate was more than 70%.3.Through preliminary screening of compounds with better activity for further study,mycelial growth rate method was used to test the inhibition of compounds such as compound 1(vomifoliol)and compound 3(obacunone)on the mycelium of Exserohilum turcicum,Pythium aphanidermatum,Thanatephorus cucumeris and Sclerotinia sclerotiorum.The EC50 value was calculated by SPSS and the independent regression equation was obtained.The results showed that vomifoliol showed good antimicrobial activity against four plant pathogenic fungi,and had the best antimicrobial activity against the mycelium of Sclerotinia sclerotiorum.The EC50 value was about 47.144μg/m L.Obacunone has certain inhibitory activity against Pythium aphanidermatum and Sclerotinia sclerotiorum.The chemical composition of silkworm faeces of philosamia cynthia was analyzed for the first time in this experiment.The results of bacteriostasis test showed that silkworm faeces is rich in many kinds of antimicrobial active substances and has a broad spectrum of antimicrobial activity.It shows that silkworm faeces of philosamia cynthia has the potential to become a new type of botanical fungicide or a source of botanical fungicide,broadens the utilization mode of silkworm faeces,and provides a new idea for the comprehensive utilization of silkworm faeces.