Smoke of Capsicum baccatum L. var. baccatum (Solanaceae) repels nymphs of triatoma infestans (Klug) (Hemiptera: Reduviidae) / Humo de capsicum baccatum L. var. baccatum (Solanaceae) repele las ninfas de Triatoma infestans (Klug) (Hemiptera: Reduviidae)

Control of the Chagas disease vector, Triatoma infestans (Klug) (Hemiptera: Reduviidae) with synthetic pesticides in Bolivia has become increasingly inefficient due to the development of resistance in the insects. In the Chaco region of Bolivia, guaraní populations have approached the problem by fumigating their houses with the smoke of native plants. Through interviews and field work with local guides, the main plant used by the guaraníes was collected and later identified as Capsicum baccatumL. var. baccatum (Solanaceae). In choice bioassays, filter papers exposed to the smoke of the plant repelled nymphs of T. infestans. Activity remained significant after storing the exposed filter papers for 9 days. Chemical analysis of smoke and literature data suggested that capsaicinoids present in the smoke were responsible for the repellent effect. The data presented provide a rationale for the use of C. baccatumvar. baccatumto control the Chagas vector bythe guaraní populations.

El control del vector de la enfermedad de Chagas, Triatoma infestans (Klug) (Hemiptera: Reduviidae) con plaguicidas sintéticos en Bolivia se ha vuelto cada vez más ineficiente debido al desarrollo de resistencias en los insectos. En la región del Chaco de Bolivia, las poblaciones guaraníes han abordado el problema fumigando sus casas con el humo de las plantas nativas. A través de entrevistas y trabajo de campo con guías locales, se recogió la principal planta utilizada por los guaraníes y posteriormente se identificó como Capsicum baccatumL. var. baccatum (Solanaceae). En bioensayos selectos, los papeles de filtro expuestos al humo de la planta repelieron a las ninfas de T. infestans. La actividad siguió siendo significativa después de almacenar los papeles de filtro expuestos durante 9 días. El análisis químico del humo y los datos de la literatura sugieren que los capsaicinoides presentes en el humo eran responsables del efecto repelente. Los datos presentados proporcionan una justificación para el uso de C. baccatum var. baccatum para el control del vector Chagas por las poblaciones guaraníes.

Efectividad de repelentes comerciales disponibles contra el mosquito Aedes aegypti (L ) en Yucatán, México / Effectiveness of commercial repellents against Aedes aegypti (L ) in Yucatan, México

Resumen: Objetivo: Determinar la eficacia de repelentes comerciales disponibles en Yucatán contra el mosquito Aedes aegypti, vector del dengue, Chikungunya y Zika. Material y métodos: Se determinó el tiempo de protección con base en el protocolo WHO/CTD/WHOPES/IC y la NOM-032-SSA2-2014. Resultados: Sólo el repelente con DEET (N, N-dietil-3-metilbenzamida) al 25% cumplió con la protección recomendada. La eficacia fue directamente proporcional a la concentración del DEET; aquéllos con componentes botánicos fueron poco o nada protectores. Conclusiones: Los resultados muestran que los repelentes con DEET proveen protección contra Ae. Aegypti; los repelentes botánicos, incluyendo las pulseras impregnadas, ofrecen nula protección.

Abstract: Objective: We assessed the efficacy of commercial repellents available in Yucatan against Aedes aegypti, vector of dengue, Chikungunya and Zika. Materials and methods: Protection time was determined based on WHO/CTD/ WHOPES/IC y la NOM-032-SSA2-20I4. Results: Products with DEET (N, N-diethyl-3-methylbenzamide) at 25% met the recommended protection. Efficacy was directly proportional to the concentration of DEET; botanicals repellents resulted no protective. Conclusions: Repellents with DEET provided more protection against Ae. aegypti and botanical repellents, including impregnated wristbands, provided no protection.

Bioactividad del aceite esencial de croton trinitatis millsp colombiano / Bioactivities of essential oil from colombian croton trinitatis millsp

Los aceites esenciales son motivo de estudio debido a propiedades bioactivas, las cuales varían de acuerdo con su composición química. Los objetivos de este trabajo fueron el estudio de la composición química volátil del aceite esencial (AE) de Croton trinitatis Millsp (Euphorbiaceae) obtenido de plantas colectadas en el municipios Maria La Baja (Bolívar). Además, evaluar sus propiedades antioxidante y repelente. AEs fueron aislados mediante la técnica de hidrodestilación e identificados por cromatografía de gases acoplada a un detector de espectrometría de masas (GC-MS). Los compuestos mayoritarios encontrados en C. trinitatis fueron sesquiterpenos: cariofileno (15,3 por ciento), dihidrocurcumeno (14,5 por ciento), cis y trans calameneno (4.0 y 13.7.0 por ciento, respectivamente), ipsilon-cadina-1,4-dieno (7.4 por ciento), alaskeno (6.4 por ciento), gerrmacreno A (5.8 por ciento), biciclogermacreno (5.3 por ciento); y monoterpenos como fenchona (4.4 por ciento) y eucaliptol (1,8-cineol) (2.4 por ciento). La actividad antioxidante de los AEs se determinó por el método del radical DPPH. El porcentaje de inhibición de DPPH del aceite esencial de C. trinitatis fue del 92.2 por ciento comparado con la del ácido ascórbico (96.4 por ciento). El AE presentó la mayor actividad repelente frente al gorgojo Tribolium castaneum, a una concentración de 0.1 μL/cm2 a 2 y 4 horas de exposición (86.0 y 92.0 por ciento, respectivamente).

Essential oils are being studied because bioactive properties, which vary according to their chemical composition. The objectives of this work were to study the volatile chemical composition of essential oil (EO) from Croton trinitatis Millsp (Euphorbiaceae), obtained from plants collected in Maria la Baja (Bolívar). Also, evaluate their antioxidant and repellent properties. EOs were isolated by hydrodistillation technique and identified by gas chromatography coupled to a mass spectrometric detector (GC-MS). The major compounds found in C. trinitatis were sesquiterpens: Caryophyllene (15,3 percent), dihydrocurcumene (14,5 percent), cis and trans calamenene (4.0 y 13.7.0 percent, respectively), upsilon-cadina-1,4-diene (7.4 percent), alaskene /6.4 percent), gerrmacrene A (5.8 percent), bicyclogermacrene (5.3 percent); and monoterpens as fenchone (4.4 percent) and eucalyptol (1,8-cineol) (2.4 percent). The antioxidant activity of the EOs were determined using the method of DPPH radical. The percentage of inhibition of DPPH from C. trinitatis was 92.2 percent compared with ascorbic acid (96,4 percent). The EO from Turbaco had the highest repellent activity against Tribolium castaneum, at a concentration of 0.2 uL/cm2 at 2 and 4 hours of exposure (86.0 and 92.0 percent, respectively).

Chemical composition of the essential oil from Ageratina jocotepecana and its repellent effect on drywood termite incisitermes marginipennis / Composición química del aceite esencial de Ageratina jocotepecana y su efecto repelente en termitas de madera seca incisitermes marginipennis

Essential oils obtained from new plant species with metabolomes unexplored or poorly known are a natural resource to find molecules with deterrent (irritant) effect. The aim of this study was to evaluate the chemical composition and the termite repellent activity of the essential oils from Ageratina jocotepecana. The repellent effect was determined by the pine drywood termite Incisitermes marginipennis behavior of to sense the contact of the tunnel wall in the wooden colony in the presence of an irritant obstacle caused by essential oils. Gas chromatographic analysis of the essential oils from flower, leaf, and stem showed quantitative and qualitative differences in components. Twenty-eight volatile components were identified by their mass spectra (MS). beta-caryophyllene, carvacrol, spathulenol, and terpinen-4-ol were the four major components, of them in relation 0.1 M citronellol, the 0.1 M carvacrol was the best repellent of the termite. Essential oils from A. jocotepecana exhibited a termite repellent effect due to their major components. Additionally, more research about the termite repellent action of carvacrol is still needed.

Los aceites esenciales obtenidos de nuevas especies de plantas con metabolomas inexplorados o poco conocidos son un recurso natural para encontrar moléculas con efecto disuasivo (irritante). El propósito del estudio fue evaluar la composición química de los aceites esenciales de Ageratina jocotepecana y su actividad repelente de termitas. El efecto repelente fue determinado por el comportamiento de las termitas de la madera seca de pino Incisitermes marginipennis de sentir el contacto de la pared del túnel en la colonia de madera en la presencia de un obstáculo irritante causado por los aceites esenciales. El análisis de cromatografía de gases de los aceites esenciales de flores, hojas y tallo mostró diferencias cuantitativas y cualitativas en componentes. Veintiocho componentes volátiles fueron identificados por sus espectros de masas (MS). beta-cariofileno, carvacrol, spathulenol y terpinen-4-ol fueron los cuatro componentes mayoritarios, de ellos en relación con 0,1 M citronelol el control positivo, el carvacrol 0,1 M fue el mejor repelente de la termita. Además, más investigación sobre la acción repelente de termitas de carvacrol se necesita realizar.

Repellent activity of essential oils against cockroaches (Dictyoptera: Blattidae, Blattellidae, and Blaberidae) in Thailand.

Seven commercial essential oils extracted from the plant species Boesenbergia rotunda (L.) Mansf., Citrus hystrix DC., Curcuma longa L., Litsea cubeba (Lour.) Pers., Piper nigrum L., Psidium guajava L. and Zingiber officinale Roscoe, and naphthalene as a control, were evaluated for repellent activity against the three cockroach species Periplaneta americana (L.), Blattella germanica (L.) and Neostylopyga rhombifolia (Stoll) under laboratory conditions. The essential oil derived from Citrus hystrix showed the best repellency over other candidate essential oils and naphthalene. The essential oil of Citrus hystrix exhibited complete repellency (100%) against P. americana and B. germanica, and also showed the highest repellency (among the essential oils tested) of about 87.5% against N. rhombifolia under laboratory conditions. In the field, Citrus hystrix essential oil formulated as a 20% active ingredient in ethanol and some additives provided satisfactory repellency of up to 86% reduction in cockroaches, mostly P. americana and N. rhombifolia with a residual effect lasting a week after treatment. Citrus hystrix essential oil has good potential for being used as a cockroach repellent. Further improvements in efficacy and residual activity may be realized with appropriate formulations.

Larvicidal and mosquito repellent activities of Pine (Pinus longifolia, family: Pinaceae) oil.

BACKGROUND AND OBJECTIVES: Various plant-based products are safe and biodegradable alternatives to synthetic chemicals for use against mosquitoes. Oil of Pinus longifolia is traditionally used for protection against mosquitoes in some rural areas but there is no documented report of its use against mosquitoes. The present study was undertaken to scientifically evaluate the activity of Pine oil against mosquitoes. METHODS: The oil was procured from the market and its contents were chemically analysed. Larvicidal activity of oil was tested in laboratory bioassays, while repellent action was studied during whole night bait collections in field by direct application on the skin and after its impregnation on mats. RESULTS: Results showed varying degree of larvicidal activity of Pine oil against mosquitoes with LC50 values ranging between 82 and 112 ppm. The Pine oil had strong repellent action against mosquitoes as it provided 100% protection against Anopheles culicifacies for 11 h and 97% protection against Culex quinquefasciatus for nine hours respectively. Electrically heated mats prepared from Pine oil provided, 94 and 88% protection against An. culicifacies and Cx. quinquefasciatus for 10 and seven hours respectively. INTERPRETAION AND CONCLUSION: Pine oil is effective against mosquito larvae at very higher doses which are not of any practical utility. However, Pine oil showed strong repellent action against An. culicifacies (malaria vector) and Cx. quinquefasciatus (pest mosquito). Thus its use could be popularised as mosquito repellent.

Comparative repellent properties of certain chemicals against mosquitoes, house flies and cockroaches using modified techniques.

Several terpenoids were assessed for their repellent/toxic properties against mosquitoes (Aedes aegypti), house flies (Musca domestica) and cockroaches (Periplaneta americana). Impregnated wide mesh netting was used in the case of the Dipterans, while treated filtered paper was employed for the bioassays with cockroaches. Persistence of the repellent chemicals was studied. Doses ranged from 5-20 gm/M2 for the Dipterans and 25-100 mg per 4 x 4 cm filter paper for the cockroaches. Dimethyl phthalate (DMP) offered the maximum protection of the chemicals tested against mosquitoes but was not so effective against house flies and cockroaches. Citral and Eugenol were effective against all the three test insects. Other test compounds afforded varying degrees of protection. Application strategy and utility of the findings are discussed.