Glucosinolate breakdown products as insect fumigants and their effect on carbon dioxide emission of insects

BACKGROUND: Glucosinolate breakdown products are volatile, therefore good candidates for insect fumigants. However, although they are insecticidal, the mode of action of such natural products is not clear. We studied the insecticidal effect of these compounds as fumigants, and monitored the production of carbon dioxide by the insects as a probe to the understanding of their mode of action. RESULTS: The fumigation 24-h LC(50) against the house fly (Musca domestica L.) of allyl thiocyanate, allyl isothiocyanate, allyl cyanide, and l-cyano-2-hydroxy-3-butene was 0.1, 0.13, 3.66, and 6.2 μg cm(-3), respectively; they were 0.55, 1.57, 2.8, and > 19.60 μg cm(-3), respectively, against the lesser grain borer (Rhyzopertha dominica Fabricius). The fumigation toxicity of some of the glucosinolate products was very close to or better than that of the commercial insect fumigants such as chloropicrin (LC(50): 0.08 and 1.3 μg cm(-3) against M. domestica and R. dominica, respectively) and dichlorovos (LC(50): < 0.02 and 0.29 μg cm(-3) against M. domestica and R. dominica, respectively) in our laboratory tests. Significantly increased CO(2) expiration was found in insects exposed to the vapor of allyl isothiocyanate, allyl thiocyanate and allyl isocyanate. Allyl isothiocyanate was also found to increase the CO(2) expiration of the American cockroach (Periplaneta americana L.). CONCLUSIONS: Glucosinolate breakdown products have potential as biodegradable and safe insect fumigants. They may act on the insect respiratory system in their mode of action

Insecticidal Activity of Monoterpenoids to Western Corn Rootworm (Coleoptera: Chrysomelidae), Twospotted Spider Mite (Acari: Tetranychidae), and Fouse Fly (Diptera: Muscidae)

Acute toxicities of 34 naturally occurring monoterpenoids were evaluated against 3 important arthropod pest species; the larva of the western corn rootworm, Diabrotica virgifera virgifera LeConte; the adult of the twospotted spider mite. Tetranychus urticae Koch; and the adult house fly. Musca domestica L. Potential larvicidal or acaricidal activities of each monoterpenoid were determined by topical application, leaf-dip method, soil bioassay, and greenhouse pot tests. Phytotoxicity was also tested on a corn plant. Citronellic acid and thymol were the most topically toxic against the house fly, and citronellol and thujone were the most effective on the western corn rootworm. Most of the monoterpenoids were lethal to the twospotted spider mite at high concentrations; carvomenthenol and terpinen-4-ol were especially effective. A wide range of monoterpenoids showed some larvicidal activity against the western corn rootworm in the soil bioassay. Perillaldehyde, the most toxic (LC50 = 3 micrograms/g) in soil, was only 1/3 as toxic as carbofuran, a commercial soil insecticide (LC50 = 1 microgram/g). Selected monoterpenoids also effectively protected corn roots from attack by the western corn rootworm larvae under greenhouse conditions. alpha-Terpineol was the best monoterpenoid in the greenhouse pot test. The acute toxicity of monoterpenoids was low relative to conventional insecticides. Some monoterpenoids were phytotoxic to corn roots and leaves. l-Carvone was the most phytotoxic, whereas pulegone was the safest. The results with thymyl ethyl ether, one of the synthetic derivatives of thymol, showed a potential of derivatization to reduce monoterpenoid phytotoxicity

Osajin and Pomiferin, Two Isoflavones Purified from Osage Orange Fruits, Tested for Repellency to the Maize Weevil (Coleoptera: Curculionidae)

The fruit of the osage orange tree, Maclura pomifera (Raf.) Schneid (Moraceae), has long been thought to be repellent to insects. A preliminary study reported here confirmed repellency of fruit extracts to the maize weevil, Sitophilus zeamais Motschulsky. Two isoflavones, osajin and pomiferin, were isolated from the mature fruit of M. pomifera in high purity (≥95%). Testing of purified osajin and pomiferin failed to show repellency. Repellency is likely caused by factors other than isoflavones in the fruit

Plant growth regulatory effect and insecticidal activity of the extracts of the Tree of Heaven (Ailanthus altissima L.)

BACKGROUND: There is an urgent need to explore and utilize naturally occurring products for combating harmful agricultural and public health pests. Secondary metabolites in the leaves of the Tree of Heaven, Ailanthus altissima L. have been reported to be herbicidal and insecticidal. The mode of action, however, of the active compounds in A. altissima are not understood. In this paper, we report the chemical characteristics of the herbicidal and insecticidal components in this tree, and will discuss the effect of light on the bioactivity of the active components. RESULTS: Extracts from the fresh leaves of A. altissima showed a strong plant germination/growth inhibitory effect in laboratory bioassays against alfalfa (Medicago sativa). The effect was dose-dependent. The growth inhibitory components were in the methylene chloride soluble fraction of the extract. The effect was greater in the light than in the dark. Other fractions had plant growth enhancing effect at lower concentrations. The extract was slightly insecticidal against yellow fever mosquito larvae (Aedes aegypti). CONCLUSIONS: The extract or its semi-purified fractions of A. altissima were strong plant growth inhibitors, therefore good candidates as potential environmentally safe and effective agricultural pest management agents. The finding that light affects the activity will be useful in the application of such natural products

A unified constitutive model for asymmetric tension and compression creep-ageing behaviour of naturally aged Al-Cu-Li alloy

A set of unified constitutive equations is presented that predict the asymmetric tension and compression creep behaviour and recently observed double primary creep of pre-stretched/naturally aged aluminium-cooper-lithium alloy AA2050-T34. The evolution of the primary micro- and macro-variables related to the precipitation hardening and creep deformation of the alloy during creep age forming (CAF) are analysed and modelled. Equations for the yield strength evolution of the alloy, including an initial reversion and subsequent strengthening, are proposed based on a theory of concurrent dissolution, re-nucleation and growth of precipitates during artificial ageing. We present new observations of so-called double primary creep during the CAF process. This phenomenon is then predicted by introducing effects of interacting microstructures, including evolving precipitates, diffusing solutes and dislocations, into the sinh-law creep model. In addition, concepts of threshold creep stress σth and a microstructure-dependant creep variable H, which behave differently under different external stress directions, are proposed and incorporated into the creep model. This enables prediction of the asymmetric tension and compression creep-ageing behaviour of the alloy. Quantitative transmission electron microscopy (TEM) and related small-angle X-ray scattering (SAXS) analysis have been carried out for selected creep-aged samples to assist the development and calibration of the constitutive model. A good agreement has been achieved between the experimental results and the model. The model has the potential to be applied to creep age forming of other heat-treatable aluminium alloys

Monoterpenoids and Their Synthetic Derivatives as Leads for New Insect-Control Agents

Monoterpenoids are natural substances which are found in many higher plant species. These plant secondary metabolites are generally considered as self-defense tactics against the plants\u27 enemies. Our study was aimed at the anticipation of improved biological activities through the synthesis of derivatives of the natural monoterpenoids. We have also developed a systematic bioassay system to evaluate the spectrum of toxicities of the monoterpenoids. The results show that the monoterpenoids, either natural or synthetic, have a relatively wide spectrum of activity against agricultural and public health insect pests. Derivatization, especially, to the acyl derivatives of the monoterpenoids, has significantly improved the acute, fumigant, larvicidal and ovicidal activities against the above insects. The ether derivatives also showed enhanced insecticidal activity. When mosquito larvae were treated with the monoterpenoids at sublethal dosages, insect growth and development activity was observed. The enhanced biological activity of the synthetic derivatives of monoterpenoids indicates that optimal chemical structures for insecticides can be possibly elucidated through the study of structure-activity relationships

Chemistry and Biochemistry of Dietary Polyphenols

Polyphenols are the biggest group of phytochemicals, and many of them have been found in plant-based foods. Polyphenol-rich diets have been linked to many health benefits. This paper is intended to review the chemistry and biochemistry of polyphenols as related to classification, extraction, separation and analytical methods, their occurrence and biosynthesis in plants, and the biological activities and implications in human health. The discussions are focused on important and most recent advances in the above aspects, and challenges are identified for future research