Insect gut microbes have been considered as a resource for bioactive metabolites. The aim of this study was to characterize the compounds of a fungus Aspergillus terreus QT122 associated with the gut of dragonfly. Five main phytotoxic, antifungal, and immunosuppressive substances were isolated from the fungus QT122. The structures of such compounds were identified as emodin (1), 1-methyl emodin (2), terrein (3), methyl 6-acetyl-4-methoxy-7,8-dihydroxynaphthalene-2-carboxylate (4), and dihydrogeodin (5) on the basis of spectroscopic analysis and by comparison of the corresponding data to those reported in the literature previously. The compound 3 exhibited the best phytotoxic activity against the radicle growth of A. retroflexus L. and E. crusgalli L. with their IC50 values of 11.2 and 3.1 μg/mL, which were comparable to that of the positive control of 2,4-dichlorophenoxyacetic acid (2,4-D) with the IC50 values of 8.1 and 1.6 μg/mL, respectively. The compounds 2–3 showed potent antifungal activity in the growth of Alternaria solani with the IC50 value of less than 0.1 μg/mL and the compound 2 also had great inhibitory effect against the growth of Fusarium oxysporum f. sp. cucumerinum (IC50 < 0.1 μg/mL), which was comparable to that of referenced cycloheximide with IC50 value of below 0.1 μg/mL. The compounds 3–5 exhibited strong immunosuppressive activities against the T cell viability with the inhibition rates of more than 99%, which were comparable to positive cyclosporin A under the concentration of 20 μM. These results suggest that the compounds 2–5 have the potential to be used as bio-control agents in agriculture or immunosuppressive agents.

In the proceeding of screening new bioactive natural products, the ethyl acetate extract of the fermentation broth of Fusarium proliferatum ZS07, a fungus residing in the gut of long-horned grasshoppers (Tettigonia chinensis), was found possessing selective phytotoxic activity against the radicle growth of Amaranthus retroflexus L. Bioactivity-guided fractionation lead to the isolation of six fungal metabolites 1–6, including a new polyketide derivate O-methylated SMA93 (2) and five known compounds SMA93 (1), rhodolamprometrin (3), radicinin (4), dehydroallogibberic acid (5), and 3-methyl-6,8-dihydroxyisocoumarin (6). Their structures were identified on the basis of spectroscopic analysis and by comparison of the corresponding data to those reported in the literature previously. Phytotoxic effects of the four isolated compounds 1–4 on the radicle growth of A. retroflexus L. seeds were investigated under laboratory conditions, and compounds 2 and 4 showed good phytotoxic activity in the concentration of 100 μg/mL, with the inhibition rates of 83.0 and 65.2%, respectively. Furthermore, the antibacterial activity of compounds 1–5 were evaluated against selected bacteria. Compounds 1–3 were found to possess potent antibacterial activity against Bacillus subtilis (ATCC 6633), with the minimum inhibitory concentration (MIC) values of 3.13–12.50 μg/mL, while Escherichia coli (ATCC 8739) and Salmonella typhimurium [CMCC(B) 50115] were not susceptible. These results suggest that the new polyketide derivate 2 and known compounds 1, 3, and 4 have potential to be used as biocontrol agents in agriculture.

Two main antifungal metabolites resistomycin and tetracenomycin D were isolated and purified from a termite-associated Streptomyces canus BYB02 by column chromatography. The structures of isolated compounds were determined on the basis of extensive spectroscopic analysis. Resistomycin possessed strong activities against mycelial growth of Valsa mali (IC50 = 1.1 μg/mL) and Magnaporthe grisea (IC50 = 3.8 μg/mL), which were comparable to those of referenced cycloheximide, with IC50 values of 2.3 and 0.3 μg/mL, respectively. A further spore germination test showed that resistomycin exhibited potent reduction in spore germination for M. grisea, with an IC50 value of 5.55 μg/mL. Finally, the in vivo antifungal activity experiment showed that resistomycin possessed significant preventive efficacy against rice blast, which was more potent than that of referenced carbendazim, with control efficacies of 66.8 and 58.7%, respectively. The present results suggest that resistomycin has potential to be used as a fungicide.

Aqueous enzymatic extraction (AEE) of oil from Myrica rubra kernels was performed. The four AEE parameters namely mixed enzyme (cellulose/neutral protease = 1/2, w/w) amount, liquid/solid ratio, extraction time, and temperature, were optimised by response surface methodology. The statistical analysis indicated that the enzyme amount, liquid/solid ratio, time, and the quadratics of liquid/solid ratio, and enzyme amount, as well as the interactions between time and temperature, showed significant effects on oil yield. The optimal extraction conditions for oil yield were mixed enzyme amount, liquid/solid ratio, time, temperature as 3.17% (w/w), 4.91 ml/g, 4 h and 51.6 °C. Under the optimum conditions, the experimental oil extraction yield was 31.15%. The GC–MS analysis showed that the oil was abundant in the unsaturated fatty acids (9-octadecenoic acid and 9,12-octadecadienoic acid accounting for more than 80%), and the AEE was more efficient method to extract polyunsaturated fatty acid than the organic solvent process.Highlights► AEE eliminates organic solvent consumption. ► The extraction conditions of bayberry kernel oil by AEE are optimised. ► The predicted and experimental values are in good agreement. ► The bayberry kernel oil contains more than 80% total unsaturated fatty acids. ► AEE is more efficient method to extract PUFA than the organic solvent process.

The optimised extraction conditions of red pigments (RP) from Camellia japonica obtained with an orthogonal design L9(34) were solid/liquid ratio, temperature, pH and extraction time as 1/10, 60 °C, 1.5 and 4 h, respectively. The RP were then purified by the macroporous resin method, which showed the resin LX-68 was appropriate for purifying the pigments from C. japonica. The antioxidant activities of these pigments were also investigated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl radical in vitro model systems. The DPPH scavenging activity of pigment extract was comparable to that of standard butylated hydroxyanisole (BHA). The IC50 values of the RP and BHA were 4.55 and 4.17 μg ml−1, respectively. The pigments showed higher hydroxyl radical-scavenging activities than that of mannitol at the same concentration. Following activity-oriented separation, (−)-epicatechin was isolated as an active principle, which exhibited excellent DPPH free radical scavenging activities with IC50 5.08 μg ml−1.Research highlights► We got the optimised extraction conditions of red pigments (RP) from Camellia japonica. ► The resin LX-68 was appropriate for purifying the pigments from C. japonica. ► The red pigments showed high DPPH and hydroxyl radical scavenging activities. ► Following activity-oriented separation, (−)-epicatechin was isolated as an active principle.

Three main phytotoxic compounds including lunatoic acid A (1), 5Z-7-oxozeaenol (2) and zeaenol (3) were isolated from the fermentation broth of Cladosporium oxysporum DH14, a fungus residing in the locust (Oxya chinensis) gut. Two additional derivative compounds, compound 1a and 1b, were synthesized by methylation and chlorination of compound 1, respectively. The structures of such compounds were identified on the basis of spectroscopic analysis and by comparison of the corresponding data to those previously reported in the literature. Compounds 1-3 exhibited significantly phytotoxic activities against the radicle growth of Amaranthus retroflexus L. with the 50% inhibitory concentrations (IC50 values) of 4.51, 4.80 and 8.16 μg mL−1, respectively, which is comparable to that positive control 2,4-dichlorophenoxyacetic acid (IC50=1.95 μg mL−1). Furthermore, the compound 1 showed selective phytotoxic activity with the inhibition rate of less than 22% against the crops of Brassica rapa L., Sorghum durra, Brassica campestris L., Capsicum annucm and Raphanus sativus L. under the concentration of 100 μg mL−1. Both derivatives of compound 1 had moderate phytotoxic activity against the radicle growth of A. retroflexus L. The findings of our present study suggest that these compounds provide new promising candidates for the potential management strategies of weeds.