Mosquitoes act as a vector for most of the life threatening diseases like malaria, yellow fever, dengue fever, chikungunya ferver, filariasis, encephalitis, West Nile Virus infection, etc. Under the Integrated Mosquito Management (IMM), emphasis was given on the application of alternative strategies in mosquito control. The continuous application of synthetic insecticides causes development of resistance in vector species, biological magnification of toxic substances through the food chain and adverse effects on environmental quality and non target organisms including human health. Application of active toxic agents from plant extracts as an alternative mosquito control strategy was available from ancient times. These are non-toxic, easily available at affordable prices, biodegradable and show broad-spectrum target-specific activities against different species of vector mosquitoes. In this article, the current state of knowledge on phytochemical sources and mosquitocidal activity, their mechanism of action on target population, variation of their larvicidal activity according to mosquito species, instar specificity, polarity of solvents used during extraction, nature of active ingredient and promising advances made in biological control of mosquitoes by plant derived secondary metabolites have been reviewed.

Plant extracts as potential mosquito larvicides

Genomics of secondary metabolite production by Pseudomonas spp.

Direct Oxidative Allylic and Vinylic Amination of Alkenes through Selenium Catalysis Bringing “N” into the game: The direct chemoselective nitrogenation of unactivated alkenes can be achieved through oxidative selenium catalysis (see scheme). This protocol provides a broad variety of allylic imides in yields of up to 89 % using N-fluorobenzenesulfonimide (NFSI) as the terminal oxidant and nitrogen source. Furthermore, an unprecedented selenium-catalyzed vinylic C(sp)–H nitrogenation was discovered. Angewandte Chemie

Direct Oxidative Allylic and Vinylic Amination of Alkenes through Selenium Catalysis

The Natural Anticancer Compounds Rocaglamides Inhibit the Raf-MEK-ERK Pathway by Targeting Prohibitin 1 and 2

On the basis of chronic feeding bioassays with neonate larvae of Spodoptera littoralis reared on an artificial diet, the methanolic leaf and root extracts from Stemona collinsae displayed very high insect toxicity compared to those of two Aglaia species, a commercial Pyrethrum extract, and azadirachtin, whereas S. tuberosa extracts demonstrated low activity in roots and no activity in leaves. Beyond that, in leaf disk choice tests against fifth instar larvae, S. collinsae showed strong antifeedant activity, whereas S. tuberosa was characterized by remarkable repellency. The anti-insect properties of both species were based on pyrrolo[1,2-a]azepine alkaloids, from which didehydrostemofoline (asparagamine A) was the major compound of the roots of S. collinsae, exhibiting the highest toxicity in feeding assays. Saturation and hydroxylation of the side chain in the co-occurring stemofoline and 2'-hydroxystemofoline, respectively, led to an increasing loss of activity. Contact toxicity tests with stemofoline and didehydrostemofoline exhibited even higher activities than those of Pyrethrum extract. Tuberostemonine was the dominating alkaloid in the roots of S. tuberosa, showing outstanding repellency but no toxic effects.

Feeding deterrence and contact toxicity of Stemona alkaloids-a source of potent natural insecticides.

Insecticidal piperidine alkaloid from Microcos paniculata stem bark.

Identification and structure of a family of syringolin variants : Unusual cyclic peptides from Pseudomonas syringae pv. syringae that elicit defense responses in rice

A process of formula (I):
 [in which: R¹ is hydrogen, halogen, cyano, nitro, optionally substituted alkyl, alkoxy, alkoxyalkoxy, or a group of formula: in which: m is 1 or 2; n is 0, 1 or 2; R⁶ is hydrogen or a variety of organic groups; R⁷ is alkyl, cycloalkyl, or aralkyl; R⁹ is hydrogen or alkyl; R¹¹ is any of R⁶, or cyano, nitro, -COOR⁷ or -COR⁶; Y is an oxygen or a sulphur; Z is -COOR⁷, -COR⁶ or -SO₂R⁶; 
A is a group of formula: 
        -CHR²-CHR³-CHR⁴- 
        -CR²=CR³-CHR⁴- 
or
 in which R², R³ and R⁴ are hydrogen, halogen, alkyl or alkoxy; 
R⁵ is methyl, ethyl, isopropyl or sec-butyl; and X is hydroxy, optionally substituted alkanoyloxy or hydroxyimino] and salts and esters thereof have valuable anthelmintic, acaricidal and insecticidal activities. Methods of preparing the compounds are also provided.

Milbemycin ether derivatives, their preparation and their anthelmintic uses

An Erratum for this article has been published in Pest Management Science 56(5) 493 (2000).



In the course of the screening for novel, naturally occurring pesticides from the plant family Meliaceae, an extract of the stem bark of Aglaia roxburghiana was found to exhibit significant insecticidal activity. In addition to rocaglamide, a known insecticide isolated from several species of the genus Aglaia, 15 new natural products were isolated from this plant. Isolation and structure elucidation of the natural products is described. The outstanding insecticidal activities of some of the compounds as well as a structure–activity relationship study are presented.



© 1999 Society of Chemical Industry

Insecticidal natural products: new rocaglamide derivatives from Aglaia roxburghiana.

Compounds of formula (I) wherein R1, R2, R3, R4 and R5 are as defined in claim 1, can be used as agrochemical active ingredients and can be prepared by extraction of Aglaia roxburghiana.

Louis-Pierre Molleyres

Papers

Insecticidal piperidine alkaloid from Microcos paniculata stem bark.

Identification and structure of a family of syringolin variants : Unusual cyclic peptides from Pseudomonas syringae pv. syringae that elicit defense responses in rice

Milbemycin ether derivatives, their preparation and their anthelmintic uses

Insecticidal natural products: new rocaglamide derivatives from Aglaia roxburghiana.

Insecticidal polycyclic compounds