Bruceine D Isolated from Brucea Javanica (L.) Merr. as a Systemic Feeding Deterrent for Three Major Lepidopteran Pests.

Systemicity is a desirable property for insecticides. Many phytochemicals show good systemic properties and thus are natural sources of novel systemic insecticidal ingredients. Bruceine D, a quassinoid, was identified in Brucea javanica (L.) Merr. and displayed outstanding systemic properties and excellent antifeedant activity against the diamondback moth (DBM, Plutella xylostella L.), beet armyworm ( Spodoptera exigua Hübner), and cotton leafworm ( Spodoptera litura Fabricius). Its antifeedant effect on third instar larvae of DBM was approximately 6.2-fold stronger than that of azadirachtin. When bruceine D was applied to roots at a concentration of 100 µg/mL for 24 and 48 h, its concentration in flowering Chinese cabbage ( Brassica campestris L. ssp. chinensis var. utiliz Tsen et Lee) leaves was 38.69 µg/g (fresh weight, FW) and 108.45 µg/g (FW), respectively. These concentrations could achieve 93.80% and 96.83% antifeedant effects, which were significantly greater than those of azadirachtin. Similar to azadirachtin, bruceine D also posed a potent growth inhibition effect on insect larvae. After feeding with 20 µg/g bruceine D, no pupae were observed. The results demonstrated that bruceine D is an effective botanical insect antifeedant with outstanding systemic properties, causing potent pest growth inhibitory activity.

Flavonoids from Pronephrium megacuspe.

A chemical investigation of the whole plant of Pronephrium megacuspe (Bak.) Holtt. led to the isolation of four flavonoids, pronephrones A-D (1-4), which were firstly reported. The chemical structures of four compounds were established using spectroscopic methods. These isolates were further evaluated for cytotoxicity to ovarian cells of Spodoptera litura Fabricius.

Insect spontaneous ultraweak photon emission as an indicator of insecticidal compounds.

The influence of beta-cypermethrin, a commercial insecticide, and Cicuta virosa L. var. latisecta Celak (Umbelliferae:Cicutal), an insecticidal plant, on the spontaneous ultraweak photon emissions from larvae of Spodoptera litura Fabricius and Zophobas morio Fabricius were studied. The increased percentages of spontaneous photon emission intensities from S. litura treated with 0.1 and 1 µg/ml beta-cypermethrin were both lower than those of the control in the 24 post-treatment hours, remarkable difference could also be observed during the same period from Z. morio treated with beta-cypermethrin at 0.156, 0.313 and 0.625 µg/ml. The increased percentages of spontaneous photon emission intensities from the two mentioned insects treated with 10,100 and 1000 µg/ml petroleum ether fraction of C. virosa L. var. latisecta, which displayed little activity against whole insects, could also be changed noticeably. The present study indicated that change in the intensity of spontaneous ultraweak photon emission from insect could be used as a novel method for screening insecticidal compounds with very low content in plant.

Photoactivated insecticidal thiophene derivatives from Xanthopappus subacaulis.

Three new photoactivated insecticidal thiophene derivatives, xanthopappins A-C (1-3), were isolated from Xanthopappus subacaulis, along with three known thiophene acetylenes, 5-hydroxymethyl-2-(E)-hept-5-ene-1,3-diynylthiophene (4), 5-(1,2-dihydroxyethyl)-2-(E)-hept-5-ene-1,3-diynylthiophene (5), and 5-(1,2-diacetoxyethyl)-2-(E)-hept-5-ene-1,3-diynylthiophene (6). The structures of 1-3 were elucidated by spectroscopic methods. Compounds 1-6 exhibited significant photoactivated insecticidal activity against the fourth-instar larvae of the Asian tiger mosquito.