Evaluation of selected South African ethnomedicinal plants as mosquito repellents against the Anopheles arabiensis mosquito in a rodent model

<p>Abstract</p> <p>Background</p> <p>This study was initiated to establish whether any South African ethnomedicinal plants (indigenous or exotic), that have been reported to be used traditionally to repel or kill mosquitoes, exhibit effective mosquito repellent properties.</p> <p>Methods</p> <p>Extracts of a selection of South African taxa were tested for repellency properties in an applicable mosquito feeding-probing assay using unfed female <it>Anopheles arabiensis</it>.</p> <p>Results</p> <p>Although a water extract of the roots of <it>Chenopodium opulifolium </it>was found to be 97% as effective as DEET after 2 mins, time lag studies revealed a substantial reduction in efficacy (to 30%) within two hours.</p> <p>Conclusions</p> <p>None of the plant extracts investigated exhibited residual repellencies >60% after three hours.</p

Atividade de três Piper spp. contra adultos de Stegomyia aegypti (Diptera: Culicidae)

Three Piper species, Piper longum, P. ribesoides and P. sarmentosum, were selected for investigation of adulticidal potential against Stegomyia aegypti, a main vector of dengue and dengue haemorrhagic fever. Successive extraction by maceration with 95% ethanol showed percentage yields of ethanolic extracts, which derived from P. longum, P. ribesoides and P. sarmentosum, of 8.89, 3.21 and 5.30% (w/w), respectively. All Piper extracts illustrated an impressive adulticidal activity when tested against female mosquitoes by topical application. The susceptibility of St. aegypti females to ethanol-extracted Piper was dose dependent and varied among the plant species. The highest adulticidal effect was established from P. sarmentosum, followed by P. ribesoides and P. longum, with LD50 values of 0.14, 0.15 and 0.26 µg/female, respectively. The potential of these Piper species, as possible mosquitocides, established convincing activity for further researches to develop natural substances for combat against adult mosquitoes.Três espécies de Piper, Piper longum, P. ribesoides e P. sarmentosum, foram selecionadas para investigação da potencialidade contra Stegomyia aegypti adultos, principal vetor de dengue e febre do dengue hemorrágico. Sucessivas extrações por maceração com etanol a 95% mostraram uma porcentagem de extratos etanólicos, derivados de P. longum, P. ribesoides e P. sarmentosum, de 8,89, 3,21 e 5,30% (w/w), respectivamente. Todos os extratos de Piper mostraram atividade adulticida expressiva quando testados contra fêmeas de mosquitos através de aplicação tópica. A suscetibilidade das fêmeas do St. aegypt ao extrato de Piper etanólico foi dose dependente e variou entre as espécies de plantas. O mais elevado efeito adulticida foi demonstrado a partir do P. sarmentosum, seguido pelo P. ribesoides e P. longum, valores LD50 de 0,14, 0,15 e 0,26 µg/fêmea, respectivamente. O potencial destas espécies de Piper, como possíveis mosquiticidas, estabeleceu atividade convincente para futuras pesquisas a fim de desenvolver substâncias naturais para o combate a mosquitos adultos

Chemical Constituents and Combined Larvicidal Effects of Selected Essential Oils against Anopheles cracens (Diptera: Culicidae)

A preliminary study on larvicidal activity against laboratory-colonized Anopheles cracens mosquitos revealed that five of ten plant oils at concentration of 100 ppm showed 95–100% larval mortality. The essential oils of five plants, including Piper sarmentosum, Foeniculum vulgare, Curcuma longa, Myristica fragrans, and Zanthoxylum piperitum, were then selected for chemical analysis, dose-response larvicidal experiments, and combination-based bioassays. Chemical compositions analyzed by gas chromatography coupled to mass spectrometry demonstrated that the main component in the oil derived from P. sarmentosum, F. vulgare, C. longa, M. fragrans, and Z. piperitum was croweacin (71.01%), anethole (63.00%), ar-turmerone (30.19%), safrole (46.60%), and 1,8-cineole (21.27%), respectively. For larvicidal bioassay, all five essential oils exerted promising efficacy in a dose-dependent manner and different performances on A. cracens after 24 hours of exposure. The strongest larvicidal potential was established from P. sarmentosum, followed by F. vulgare, C. longa, M. fragrans, and Z. piperitum, with LC50 values of 16.03, 32.77, 33.61, 40.00, and 63.17 ppm, respectively. Binary mixtures between P. sarmentosum, the most effective oil, and the others at the highest ratio were proved to be highly efficacious with a cotoxicity coefficient value greater than 100, indicating synergistic activity. Results of mixed formulations of different essential oils generating synergistic effects may prove helpful in developing effective, economical, and ecofriendly larvicides, as favorable alternatives for mosquito management

Adulticidal activity against Stegomyia aegypti (Diptera: Culicidae) of three Piper spp.

Three Piper species, Piper longum, P. ribesoides and P. sarmentosum, were selected for investigation of adulticidal potential against Stegomyia aegypti, a main vector of dengue and dengue haemorrhagic fever. Successive extraction by maceration with 95% ethanol showed percentage yields of ethanolic extracts, which derived from P. longum, P. ribesoides and P. sarmentosum, of 8.89, 3.21 and 5.30% (w/w), respectively. All Piper extracts illustrated an impressive adulticidal activity when tested against female mosquitoes by topical application. The susceptibility of St. aegypti females to ethanol-extracted Piper was dose dependent and varied among the plant species. The highest adulticidal effect was established from P. sarmentosum, followed by P. ribesoides and P. longum, with LD50 values of 0.14, 0.15 and 0.26 µg/female, respectively. The potential of these Piper species, as possible mosquitocides, established convincing activity for further researches to develop natural substances for combat against adult mosquitoes

Karyotypic variation and geographic distribution of Anopheles campestris -like (Diptera: Culicidae) in Thailand

Seventy-one isolines of Anopheles campestris -like were established from wild-caught females collected from human-biting and animal-biting traps at 12 locations in Thailand. All isolines had an average branch summation of seta 2-VI pupal skins ranging from 20.3-30.0 branches, which is in the range of An. campestris (17-58 branches). They showed three different karyotypes based on the amount of extra heterochromatin in the sex chromosomes, namely Forms B (X2, Y2), E (X1, X2, X3, Y5) and a new karyotypic Form F (X2, X3, Y6). Form B has been found only in Chaing Mai and Kamphaeng Phet populations, while Forms E and F are widely distributed throughout the species range. Genetic crosses between the 12 isolines, which were arbitrarily selected as representatives of An. campestris-like Forms B, E and F, revealed genetic compatibility that provided viable progeny through F2 generations, suggesting a conspecific nature of these karyotypic forms. These results are supported by the very low intraspecies variation (genetic distance < 0.005) of ITS2, COI and COII from genomic DNA of the three karyotypic forms

Incorporation of Gas Chromatography–Mass Spectrometry into the Undergraduate Organic Chemistry Laboratory Curriculum

Gas chromatography–mass spectrometry (GC–MS) is a powerful analytical tool for detection, identification, and quantification of many volatile organic compounds. However, many colleges and universities have not fully incorporated this technique into undergraduate teaching laboratories despite its wide application and ease of use in organic chemistry. In this article, a set of experiments are provided to educators for the purposeful integration of the GC–MS technique into undergraduate organic chemistry laboratories. The laboratories provide students experimental opportunities to use GC–MS as the main analytical tool for (a) identification and quantification of major and minor product(s) formed in three common organic synthesis reactions and (b) extraction, separation, and identification of multiple natural products found in fruits and vegetables