Biological effects of essential oils - A review

Repellent activity of essential oils: a review.

Plant-based repellents have been used for generations in traditional practice as a personal protection measure against host-seeking mosquitoes. Knowledge on traditional repellent plants obtained through ethnobotanical studies is a valuable resource for the development of new natural products. Recently, commercial repellent products containing plant-based ingredients have gained increasing popularity among consumers, as these are commonly perceived as “safe” in comparison to long-established synthetic repellents although this is sometimes a misconception. To date insufficient studies have followed standard WHO Pesticide Evaluation Scheme guidelines for repellent testing. There is a need for further standardized studies in order to better evaluate repellent compounds and develop new products that offer high repellency as well as good consumer safety. This paper presents a summary of recent information on testing, efficacy and safety of plant-based repellents as well as promising new developments in the field.

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Plant-based insect repellents: a review of their efficacy, development and testing

A review of botanical phytochemicals with mosquitocidal potential.

Mosquitoes in the larval stage are attractive targets for pesticides because mosquitoes breed in water, and thus, it is easy to deal with them in this habitat. The use of conventional pesticides in the water sources, however, introduces many risks to people and/or the environment. Natural pesticides, especially those derived from plants, are more promising in this aspect. Aromatic plants and their essential oils are very important sources of many compounds that are used in different respects. In this study, the oils of 41 plants were evaluated for their effects against third-instar larvae of Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus. At first, the oils were surveyed against A. aegypti using a 50-ppm solution. Thirteen oils from 41 plants (camphor, thyme, amyris, lemon, cedarwood, frankincense, dill, myrtle, juniper, black pepper, verbena, helichrysum and sandalwood) induced 100% mortality after 24 h, or even after shorter periods. The best oils were tested against third-instar larvae of the three mosquito species in concentrations of 1, 10, 50, 100 and 500 ppm. The lethal concentration 50 values of these oils ranged between 1 and 101.3 ppm against A. aegypti, between 9.7 and 101.4 ppm for A. stephensi and between 1 and 50.2 ppm for C. quinquefasciatus.

Larvicidal effects of various essential oils against Aedes, Anopheles, and Culex larvae (Diptera, Culicidae).

Aromatic plant-derived essential oil: an alternative larvicide for mosquito control.

Pharmacological effect and toxicity of alkaloids from Gelsemium elegans Benth.

Anti-gastric ulcer effect of Kaempferia parviflora.

Crude seed extract of celery, Apium graveolens, was investigated for anti-mosquito potential, including larvicidal, adulticidal, and repellent activities against Aedes aegypti, the vector of dengue haemorrhagic fever. The ethanol-extracted A. graveolens possessed larvicidal activity against fourth instar larvae of Ae. aegypti with LD50 and LD95 values of 81.0 and 176.8 mg/L, respectively. The abnormal movement observed in treated larvae indicated that the toxic effect of A. graveolens extract was probably on the nervous system. In testing for adulticidal activity, this plant extract exhibited a slightly adulticidal potency with LD50 and LD95 values of 6.6 and 66.4 mg/cm2, respectively. It showed repellency against Ae. aegypti adult females with ED50 and ED95 values of 2.03 and 28.12 mg/cm2, respectively. It also provided biting protection time of 3 h when applied at a concentration of 25 g%. Topical application of the ethanol-extracted A. graveolens did not induce dermal irritation. No adverse effects on the skin or other parts of the body of human volunteers were observed during 3 mo of the study period or in the following 3 mo, after which time observations ceased. A. graveolens, therefore, can be considered as a probable source of some biologically active compounds used in the development of mosquito control agents, particularly repellent products.

Potential of crude seed extract of celery, Apium graveolens L., against the mosquito Aedes aegypti (L.) (Diptera: Culicidae).

Four fractions of Kaempferia galanga (hexane fraction, dichloromethane fraction 1, dichloromethane fraction 2 and methanolic fraction) were tested for larvicidal activity toward fourth instar Culex quinquefasciatus The hexane fraction was found to exhibit the highest larvicidal effect with the LC50 of 4233 ppm Testing for adulticidal activity, the hexane fraction did not show any promising adulticidal effect However, it caused a knockdown effect which might be useful as a repellent It was then tested for repellent activity in human volunteers both in laboratory and field studies In a laboratory study, the hexane fraction possessed repellency against Aedes aegypti (ED50 value of 3073 microg/cm2), and provided biting protection for 3 hours In a field study, it could protect against certain mosquitos, ie, Armigeres subalbatus, Anopheles barbirostris, An aconitus, Mansonia uniformis, Cx quinquefasciatus, Cx gelidus, Cx tritaeniorhynchus and Ae aegypti The hexane fraction did not cause dermal irritation when applied on human skin

Duangta Kanjanapothi

Papers

Aromatic plant-derived essential oil: an alternative larvicide for mosquito control.

Pharmacological effect and toxicity of alkaloids from Gelsemium elegans Benth.

Anti-gastric ulcer effect of Kaempferia parviflora.

Potential of crude seed extract of celery, Apium graveolens L., against the mosquito Aedes aegypti (L.) (Diptera: Culicidae).

Larvicidal, adulticidal and repellent effects of Kaempferia galanga.