Constituents of the essential oil of Suregada zanzibariensis leaves are repellent to the mosquito, Anopheles gambiae s.s.

Ester Innocent1,2, Cosam C. Joseph3, Nicholas K. Gikonyo4, Mayunga H.H. Nkunya3, and Ahmed Hassanali2,5

1Institute of Traditional Medicine, Muhimbili University of Health and Allied Sciences, P.O. Box 65001, Dar es Salaam, Tanzania
2International Centre of Insect Physiology and Ecology, P.O. Box 30772-00100, Nairobi, Kenya
3Department of Chemistry, University of Dar es Salaam, P.O. Box 35061, Dar es Salaam, Tanzania
4Department of Pharmacy & Complementary /Alternative Medicine, Kenyatta University, P.O. Box 43844- 00100, Nairobi, Kenya
5Current address: Department of Chemistry, Kenyatta University, P.O. Box 43844-00100, Nairobi, Kenya

Abstract

In traditional African communities, repellent volatiles from certain plants generated by direct burning or by thermal expulsion have played an important role in protecting households against vectors of malaria and other diseases. Previous research on volatile constituents of plants has shown that some are good sources of potent mosquito repellents. In this bioprospecting initiative, the essential oil of leaves of the tree, Suregada zanzibariensis Verdc. (Angiospermae: Euphobiaceae) was tested against the mosquito, Anopheles gambiae s.s. Giles (Diptera: Culicidae) and found to be repellent. Gas chromatography (GC), GC-linked mass spectrometry (GC-MS) and, where possible, GC-co-injections with authentic compounds, led to the identification of about 34 compounds in the essential oil. About 56% of the constituents were terpenoid ketones, mostly methyl ketones. Phenylacetaldehyde (14.4%), artemisia ketone (10.1%), (1S)-(-)-verbenone (12.1%) and geranyl acetone (9.4%) were the main constituents. Apart from phenylacetaldehyde, repellent activities of the other main constituents were higher than that of the essential oil. The blends of the main constituents in proportions found in the essential oil were more repellent to An. gambiae s.s. than was the parent oil (p < 0.05), and the presence of artemisia ketone in the blend caused a significant increase in the repellency of the resulting blend. These results suggested that blends of some terpenoid ketones can serve as effective An. gambiae s.s. mosquito repellents.

Keywords: Methyl ketone terpenes, traditional uses of plants, Verbenaceae
Abbreviations: GC, gas chromatography; MS, mass spectrometry

Correspondence: einnocent@muhas.ac.tz
Associate Editor: Sonny Ramaswamy was editor of this paper.

Received: 17 April 2008 | Accepted: 18 September 2009 | Published: 9 June 2010

ISSN: 1536-2442 | Volume 10, Number 57

Innocent E, Joseph CC, Gikonyo NK, Nkunya MHH, Hassanali A. 2010. Constituents of the essential oil of Suregada zanzibariensis leaves are repellent to the mosquito, Anopheles gambiae s.s. Journal of Insect Science 10:57, available online: insectscience.org/10.57


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