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A series of steroidal piperidone derivatives were synthesized, and their agricultural activities were evaluated against Myzus persicae, Aphis citricola, Brevicoryne brassicaeLinn., and Bemisia tabaci(Gennadius). Most of the tested compounds exhibited potent insecticidal activity against these four pests. Compound I-9displayed the highest activity against M. persicae, A. citricola,and Brevicoryne brassicae, with LC50values of 11.3, 10.4, and 8.68 μg/mL, respectively. The mode of action test indicated that these derivatives had superior contact and systemic insecticidal activity against M. persicae. In addition, we initially explored whether the foregut and midgut might be the action sites of the target derivatives against M. persicae. Furthermore, a field trial showed that the control of compound I-9was similar to that of acetamiprid against M. persicae, at a dose of 50 μg/mL; the control rates were 97.8 and 99.2% after 14 and 21 days, respectively. The structure–activity relationship of these analogues provided some important insights for the discovery and development of new insecticides to solve the current pesticide resistance crisis.

A series of novel steroidal derivatives with a substituted 1,3,4-oxadiazole structure was designed and synthesized, and the target compounds were evaluated for their insecticidal activity against five aphid species. Most of the tested compounds exhibited potent insecticidal activity against Eriosoma lanigerum(Hausmann), Myzus persicae, and Aphis citricola. Compounds 20gand 24gdisplayed the highest activity against E. lanigerum, showing LC50values of 27.6 and 30.4 μg/mL, respectively. Ultrastructural changes in the midgut cells of E. lanigerumwere detected by transmission electron microscopy, indicating that these steroidal oxazole derivatives might exert their insecticidal activity by destroying the mitochondria and nuclear membranes in insect midgut cells. Furthermore, a field trial showed that compound 20gexhibited effects similar to those of the positive controls chlorpyrifos and thiamethoxam against E. lanigerum, reaching a control rate of 89.5% at a dose of 200 μg/mL after 21 days. We also investigated the hydrolysis and metabolism of the target compounds in E. lanigerumby assaying the activities of three insecticide-detoxifying enzymes. Compound 20gat 50 μg/mL exhibited inhibitory action on carboxylesterase similar to the known inhibitor triphenyl phosphate. The above results demonstrate the potential of these steroidal oxazole derivatives to be developed as novel pesticides.

To explore novel lead compounds for botanical pesticides from natural sources, a new pregnane glycoside (periplocoside) P2as well as its isomer, a known pregnane glycoside P1, were isolated from the root barks of Periploca sepiumusing a bioactivity-guided method, and their structures were confirmed by 1D NMR, 2D NMR, IR, ESI-MSn and HRMS. Their insecticidal activities were evaluated against 3rdinstar larvae of M. separata, and the results indicated that P2exhibited excellent insecticidal activity with LC50values of 2.9 and 2.2 mg/mL after 24 and 48 h, respectively, much lower than those of the positive control celangulin-V (24.7 and 21.0 mg/mL after 24 and 48 h, respectively). This work demonstrated that pregnane glycosides from Periploca sepiumcould be promising lead compounds for developing botanical pesticides urgently needed in agriculture.

The essential oil from the roots of Bupleurum longiradiatum, obtained by hydrodistillation was analyzed by gas chromatography/mass spectrometry (GC/MS) and evaluated for antimicrobial activity and antioxidant activity. Fifty-one compounds were identified, representing 99.3% of the total oil. The major constituents were thymol (7.0%), butylidene phthalide (6.8%), 5-indolol (5.6%), heptanal (5.3%), 4-hydroxy-2-methylacetophenone (5.3%), 4,5-diethyl-octane (5.3%), bormeol (5.1%) and hexanoic acid (5.1%). The oil was tested against 4 bacteria at different concentrations using disc diffusion and 96-well dilution methods. The inhibition zones and minimum inhibitory concentration values for bacterial strains were in the range of 7.0–18.0 mm and 250 −500 μg/mL, respectively. The in vitroantioxidant activity was assessed by DPPH radical scavenging and inhibition of lipid peroxidation methods. The oil showed a potent free radical scavenging activity, as evidenced by the low IC50value for DPPH radical (566.2μg/mL) and inhibition of lipid peroxidation (induced by FeSO4, H2O2and CCl4) with IC50values of 275.2 μg/mL, 296.9 μg/mL and 118.7 μg/mL, respectively.

Three new insecticidal sesquiterpene polyol esters with dihydro-β-agarofuran skeletons, Kupiteng esters A (1), B (2) and C (3), were isolated from the methanol extracts of the root bark of Celastrus angulatusand their structures elucidated by analyses of MS and NMR spectral data. The insecticidal activities of these compounds against the 4thinstar larvae of Mythimna separatawere evaluated. The KD50values of compounds 1-3, were 260.2, 445.5 and 1260.0 μg-g−1, respectively.