Studies On The Secondary Metabolites Of Three Symbiotic Microbes From Odontotermes Formosanus

Insect symbiotic microbes are a type of microorganisms that have been symbiotic with insects for a long time,and have a very rich diversities of species and metabolic pathways.According to related reports,insect symbiotic microbes can produce active compounds with a completely new structure,which is one of the important source of new active compounds.In this paper,Odontotermes formosanus were used as the research object.Two strains of actinomycetes?BYTB63 and BYF48?from the body surface of O.formosanus and one strain of bacillus?BYJP72?from the nest of O.formosanus,were isolateded and identified.Separation and purification of secondary metabolites using various chromatographic separation techniques?silica gel column chromatography,gel column chromatography,reverse phase column chromatography?,and various spectroscopy techniques(¹H NMR,¹³C NMR,¹H-¹HCOSY,HMQC,HMBC and ESI-MS,etc.),and through a variety of database searches?Microspectral database,SCI-Finder database?to identify the structure of the compounds.In this paper,a total of 9 monomer compounds were isolated,and 7 compounds were identified,of which4 compounds were new metabolites;the new compounds were furtherly tested for their antibacterial and cytotoxic activities.The results are summarized as follows:1.BYTB63 was identified by morphological observation and molecular biology.It was identified as Streptomyces tanashiensis BYTB63.Five new active compounds were isolated and purified from the secondary metabolites of S.tanashiensis BYTB63:termstrin A?1?,termstrin B?2?,termstrin C?3?,and termstrin D?4?.The filter paper diffusion method was used to test the antibacterial activities of five new compounds against Escherichia coli,Micrococcus tetragenus and Staphylococcus aureus.Under the concentration of 30?g/disc,the results showed that compounds 1 and 4 have the best bacteriostatic effect against S.aureus with disc diameters of zone of inhibition?ZOI?of of 12.85 and 11.17 mm,which is comparable to the positive sodium penicillin with a diameter of 13.15 mm.In addition,compound 2 had moderate bacteriostatic effects against S.aureus,with ZOI of 9.13 mm.Compounds 1 and 2 had weak antibacterial activities against M.tetragenus,with ZOI of 8.52 and 8.77 mm,respectively,which were smaller than those of the positive penicillin sodium and gentamicin with ZOI of 73.18 and 41.98 mm,respectively.In addition,the MTT method was used to determine the cytotoxic activity on cancer cells and normal human cells.The experiment showed that compound 1 showed moderate cytotoxic effects on human melanoma tumor cells?A375?and human gastric cancer tumor cells?MGC-803?,with IC₅₀ of 22.76 and 36.65?M,respectively,which were less than those of the positive doxorubicin,with IC₅₀ values of 1.01±0.48 and 0.48±0.61?M.2.Using morphological observation and molecular biology methods to identify BYF48 and BYJP72,They were identified as Streptomyces enissocaesili BYF48,Bacillus siamensis BYJP72 respectively.The antifungal activity of the crude extract of S.enissocaesili BYF48 and B.siamensis BYJP72 strains against five pathogenic fungi of crops was determined by growth rate method.The results shown that both crude extract have a good inhibitory effect against plant pathogenic fungi.The strain S.enissocaesili against Alternaria solani,Fusarium oxysporum f.Sp.Mornordicae,Curvularia lunata,Fusarium oxysporum f.Sp.Vesinfectum,and Gibberella sanbinetti.The inhibition rates were 75.8%,78.7%,71.4%,59.7%,and 24.5%,respectively;further purify the crude extract was furtherly purified to obtain two monomer compounds 5?BYF48-1?and 6?BYF48-2?,which were identified as pyrrole-2-carboxylic acid and borrelidin,respectively.The inhibition rates of the B.siamese BYJP72 strain on the above five plant pathogenic fungi are 75.8%,57.9%,72.8%,70.0%and 17.1%,respectively;further,the BYJP72 strain crude extract was separated and purified to obtain one monomer known compound uracil?7?and two suspected new compounds?BYJP72-2 and BYJP72-3?.Therefore,the new compounds 1 and 4 can be used as a new antibiotic lead compound,and compound 1 can be used as an anti-cancer lead compound;the strains S.enissocaesili BYF48 and B.siamensis BYJP72 as a plant-derived fungicide deserves further study.