Investigation On Bioactive Secondary Metabolites Of Dragonflies And Termite' Symbionts

Insects are the largest animals in the human living environment with features of great varieties of species,complex habitats,different feeding mode,and they keep close coevolution relationship with symbionts for a long time,which results in a certain differences on the type,quantity of insect symbionts.Many scholars have begun to pay attention to symbiotic microorganisms and gradually isolated new strains and novel skeleton natural products from insect symbionts.This kind of special symbionts will increasingly display its potential.This paper mainly deals with two fungi QTYC-1 and QTYC-44 from the gut of Pantala flavescens larvae along with Actinomycetes associated with the Odontotermes formosanus' nest.We conducted the process of column chromatography including Silica gel chromatography,LH-20 Sephadex column chromatography and C18-column chromatography to isolate and purify the active secondary metabolites from these strains.There were 11 compounds including.a new one compound and 10 known compounds determined though 1H-NMR,13C-NMR,HMQC,1H-1HCOSY,HMBC and ESI-MS.The biological characteristics of compounds such as herbicidal,antimicrobial activities was studied.The details were described as follows:1.Chemical investigations about the strain Curvularia crepinii QTYC-1 in the gut of P.flavescens larvae led to the isolation of five bioactive metabolites(1-5)from the ethyl acetate extracts of solid fermentation,including zeaenol(1),new compound 3,4,7,8,9,10-hexahydro-7,8,9,14,16-pentahydroxy-3-methyl-(1)(2),mannitol(3),adenosine(4)and ergosta-5,7,22-trien-3b-ol(5).The phytotoxic bioassay of these compounds indicated the five compounds have certain degrees of inhibition effects on Echinochloa crusgalli or Amaranthus retroflexus under the concentration of 100?g/mL.Compound 1 and 2 possessed best activities with inhibition rates 85.5%and 85.6%against E.crusgalli,then calculated IC50 of 28.8 ?g/mL and 4.8 ?g/mL respectively;they have slightly lower inhibition effects on the radical growth of A.retroflexus with inhibition rates 70.0%and 66.7%respectively.Both compounds 3 and 4 exhibited phytotoxic activities against A.retroflexus with the inhibition rates of more than 50%.The antifungal test declared that under the concentration of 100?g/mL,new compounds 2 exhibited significant activity against the growth of Valsa mali with the inhibition rate of 100%,which were comparable to that of positive cycloheximide.2.The morphology observation were degined for the strain Trichoderma sp.QTYC-44 associated with the gut of P.flavescens larvae,and the characteristics of conidia and conidiophore were described.The depiction accorded with the basic characteristics of genus Trichoderma.Bio-activity guided fractionation for isolating and identifying secondary metabolite from solid-state fermentation product were employed as to the target strain QTYC-44.We obtained four compounds:d-(+)-galactose(6),uracil(7),a-D-glucopyranose(8),adenosine(9).The results of antioxidant activity bioassay showed that the compound 9 has potent DPPH radical scavenging activity with radical scavenging inhibition rate 87.3%under the concentration of 250 ?g/mL,the other compounds' activities were relatively weaker.3.The diversity and related activity of Actinomycetes associated with the termites'nest were primary investigated via a culture dependent method and identification on account of morphology and molecular biology characteristics.43 Actinomycetes were isolated from termites' nest,and 26 of them were selected according to their morphology feature to construct phylogenetic tree for identification.The result illustrated they were in the same Streptomyces genera,seven different species.The result of antifungal tests showed 20 Actinobacteria inhibited the Xylaria more severely than the Termitomyces,and two Actinobacteria had a selectively antifungal effect on Xylaria strain;the remaining 21 strains showed no effects for Xylaria and Termitomyces.Biological activities of the strains' were tested against three pathogenic bacteria and Canidia albicans though the method of oxford cup.About 50%of the strains had good activities against the tested strains.Strain T29 was chose for its good activity,and fermentation product was isolated and purified though the method described above.The main antimicrobial ingredients of T29 fermentation broth consisted in the ethyl acetate fraction of moderate polar part.The ethyl acetate extract of T29 had strong activity against Staphylococcus aureus and C.albicans with inhibition zone of 20.1 mm and 17.4 mm respectively under the concentration of 30 jig/filter paper.Two compounds geldanamycin(10)and 17-O-demethylgeldanamycin(11)were charactered from the fermentation production of the strain.Bioassay test showed that under concentration of 30 ?g/filter paper,compounds 10 and 11 revealed good activities against S.aureus with inhibition of diameters 14.6 mm and 14.5 mm respectively,so as to C.albicans with inhibition of diameters 14.5 mm and 13.9 mm respectively,which were compared to that of the positive control.