Identification of mosquito repellent odours from Ocimum forskolei

<p>Abstract</p> <p>Background</p> <p>Native mosquito repellent plants have a good potential for integrated mosquito control in local settings. <it>Ocimum forskolei</it>, Lamiaceae, is used in Eritrea as a spatial mosquito repellent inside houses, either through crushing fresh plants or burning dry plants. We verified whether active repellent compounds could be identified using gas-chromatography coupled electroantennogram recordings (GC-EAD) with headspace extracts of crushed plants.</p> <p>Results</p> <p>EAD active compounds included (R)-(-)-linalool, (S)-(+)-1-octen-3-ol, trans-caryophyllene, naphthalene, methyl salicylate, (R)-(-)-α-copaene, methyl cinnamate and (E)-ocimene. Of these compounds (R)-(-)-linalool, methyl cinnamate and methyl salicylate reduced landing of female <it>Aedes aegypti </it>on human skin-odor baited tubes. The latter two are novel mosquito repellent compounds.</p> <p>Conclusions</p> <p>The identification of mosquito repellent compounds contributes to deciphering the mechanisms underlying repulsion, supporting the rational design of novel repellents. The three mosquito repellent compounds identified in this study are structurally dissimilar, which may indicate involvement of different sensory neurons in repulsion. Repulsion may well be enhanced through combining different repellent plants (or their synthetic mimics), and can be a locally sustainable part in mosquito control efforts.</p

Chemical Composition and Larvicidal Activities of the Himalayan Cedar, Cedrus deodara Essential Oil and Its Fractions Against the Diamondback Moth, Plutella xylostella

Plants and plant-derived materials play an extremely important role in pest management programs. Essential oil from wood chips of Himalayan Cedar, Cedrus deodara (Roxburgh) Don (Pinales: Pinaceae), was obtained by hydrodistillation and fractionated to pentane and acetonitrile from which himachalenes and atlantones enriched fractions were isolated. A total of forty compounds were identified from these fractions using GC and GC-MS analyses. Essential oils and fractions were evaluated for insecticidal activities against second instars of the diamondback moth, Plutella xylostella L. (Lepidoptera: Yponomeutidae), using a leaf dip method. All samples showed promising larvicidal activity against larvae of P. xylostella. The pentane fraction was the most toxic with a LC50 value of 287 µg/ml. The himachalenes enriched fraction was more toxic (LC50 = 362 µg/ml) than the atlantones enriched fraction (LC50 = 365 µg/ml). LC50 of crude oil was 425 µg/ml and acetonitrile fraction was LC50 = 815 µg/ml. The major constituents, himachalenes and atlantones, likely accounted for the insecticidal action. Present bioassay results revealed the potential for essential oil and different constituents of C. deodara as botanical larvicides for their use in pest management

In vitro Anticancer Screening of 24 Locally Used Nigerian Medicinal Plants

Background: Plants that are used as traditional medicine represent a relevant pool for selecting plant candidates that may have anticancer properties. In this study, the ethnomedicinal approach was used to select several medicinal plants native to Nigeria, on the basis of their local or traditional uses. The collected plants were then evaluated for cytoxicity. Methods: The antitumor activity of methanolic extracts obtained from 24 of the selected plants, were evaluated in vitro on five human cancer cell lines. Results: Results obtained from the plants screened indicate that 18 plant extracts of folk medicine exhibited promising cytotoxic activity against human carcinoma cell lines. Erythrophleum suaveolens (Guill. & Perr.) Brenan was found to demonstrate potent anti-cancer activity in this study exhibiting IC50 = 0.2-1.3 $\mu$g/ml. Conclusions: Based on the significantly potent activity of some plants extracts reported here, further studies aimed at mechanism elucidation and bio-guided isolation of active anticancer compounds is currently underway.Chemistry and Chemical Biolog

COMPARATIVE STUDY OF TOXICITY OF SOME ESSENTIAL OILS TO LARVAE OF THREE MOSQUITO SPECIES

The toxicity of the essential oils from the leaves of Lantana camara L., Eugenia uniflora L. and fruits of Aframomum daniellii K. Schum to the fourth instar larvae of Aedes aegypti, Anopheles gambiae and Culex pipiens fatigans was investigated. The results indicated that 0.02-0.04% of the oils produced 90-100% mortality on the larvae of all the three mosquitoes. The oils from E. uniflora and L. camara at a concentration of 0.02% were more toxic to Culex pipiens fatigans and Aedes aegypti (producing 100% mortality at 24h.) than Anopheles gambiae. Key Words: Lantana camara, Eugenia uniflora, Aframomum daniellii, essential oils, toxicity, mosquito larvae. Nig. J. Nat Prod. And Med. Vol.3 1999: 74-7

Essential Oil Analysis of the Peel and Leaf Oils of Citrus Medica L. (Rutaceae) from Nigeria

The essential oils isolated from peel and leaves of Citrus medica L. grown in Nigeria were analyzed by GC-MS. Thirty three compounds were identified in the peel oil and thirty in the leaf oil, constituting 99.3% and 99.6% of the oils, respectively. The major constituent of the peel oil was found to be limonene (67.7%), while the leaf oil contained predominantly linalool (27.1%), &#225;-terpineol (21.3%) and linalyl acetate (21.7%). The other minor constituents differed both qualitatively and quantitatively among peel and leaf oils

CALLUS INDUCTION AND MORPHOGENESIS IN DIOSCOREA DUMETORUM FOR STEROID PRODUCTION

Diosgenin is characteristic of the genus Dioscorea (Dioscoreaceae), which is used in partial synthesis of steroid drugs. It was not detected in the crude sapogenin extract of Dioscorea dumetorum and in the calluses. Callus was induced from the meristem of the two genotypes and maintained successfully on Murashige and Skoog's medium (MS) supplemented with 0.1mg/l of 2, 4-dichlorophenoxyacetic acid (2,4-D). Shoots induced from nodal cuttings of the white and yellow genotypes regenerated plantlets, which were subsequently maintained on MS medium, and Linsmaier and Skoog's medium (LS) supplemented with 0.5mg/l kinetin. Control of microbial contamination was achieved with tetracycline. Microtubers were also obtained from the yellow genotype plantlet growing on the MS medium. Steroids, especially the &Delta;5, 3-hydroxy steroids were detected only in the yellow genotype callus. Keywords: Dioscorea dumetorum; diosgenin; 3-hydroxy steroids; callus; shoot culture; meristem culture; yellow genotype Nigerian Journal of Natural Products and Medicine Vol.7 2003: 5-