New mosquito larvicidal tetranortriterpenoids from Turraea wakefieldii and Turraea floribunda

The crude methanol extracts of the root barks of Turraea wakefieldii and Turraea floribunda were found to show mosquito larvicidal activity against third-instar larvae of Anopheles gambiae sensu stricto. Four new limonoids comprising a vilasininoid 1 and three havanensinoids 2-4 were isolated from the chloroform fractions of the methanol extracts of T. wakefieldii and T. floribunda, respectively. The structures of the compounds were elucidated by NMR spectroscopy. Compounds 1, 2, and 4 had LD50 values of 7.1, 4.0, and 3.6 ppm, respectively, and were more potent than azadirachtin, which had an LD50 value of 57.1 ppm when tested against larvae of A. gambiae.     

Semiochemical modulation of oviposition behaviour in the gregarious desert locust Schistocerca gregaria

Bioassays have shown that sand freshly contaminated by ovipositing females of the gregarious desert locust Schistocerca gregaria (Forskal) is more effective in inducing further oviposition from conspecifics than contaminated sand stored for three or six months, which contrasts with results obtained previously with Locusta migratoria (Reiche & Farmaire). The activity of contaminated sand correlated with the levels of three unsaturated aliphatic ketones, (Z)-6-octen-2-one, (E,E)-3,5-octadien-2-one and its geometric isomer (E,Z)-3,5-octadien-2-one present in the volatile emissions from the sand.     

Innovative approaches to exploit host plant metabolites in malaria control

Malaria is the most important vector‐borne disease in sub‐Saharan Africa (SSA). Recent reports indicate that the levels of malaria‐associated mortality and morbidity in SSA have remained the same. Malaria vectors have modified their feeding behavior in response to the selective pressure from indoor‐based interventions, and there is emerging malaria parasite resistance to artemisinin‐based combination therapies. These challenges have created an altered malaria landscape, especially within local scales in some malaria‐endemic countries in SSA. To address these challenges, complementary new strategies are urgently required for malaria control. This paper argues that to develop the next generation of vector and chemotherapeutic tools for malaria control, especially based on natural products with novel modes of action, a better understanding of mosquito bioecology and, more importantly, plant sugar feeding is needed. © 2019 Society of Chemical Industry