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Chemical composition and mosquito repellency of essential oil of Conyza newii propagated in different geographical locations of Kenya
Author(s) -
MAYEKU W. P.,
OMOLLO N. I.,
ODALO O. J.,
HASSANALI A.
Publication year - 2014
Publication title -
medical and veterinary entomology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 82
eISSN - 1365-2915
pISSN - 0269-283X
DOI - 10.1111/mve.12039
Subject(s) - geraniol , essential oil , biology , anopheles gambiae , limonene , toxicology , botany , malaria , immunology
Abstract Previously, essential oil of Conyza newii (Asterale: Asteracea, Oliv. & Hiern) growing in the northern part of West Pokot (35°E, 1°N) of Kenya was shown to be highly repellent [ RD 50 = 8.9 × 10 −5 mg/cm 2 , 95% confidence interval ( CL )] to Anopheles gambiae s.s . Fumigant toxicity of the oil to the mosquito was also demonstrated. The major constituents of the oil were found to be monoterpenoids, including ( S )‐(‐)‐perillyl alcohol, ( S )‐(‐)‐perillaldehyde, geraniol, ( R )‐(+)‐limonene, trans‐β ‐ocimene and 1,8‐cineol. In this study, the chemical composition and repellency of essential oils of the plant seedlings collected from West Pokot (35°E, 1°N) and propagated in seven different geographical regions of Kenya [West Pokot (35°E, 1°N), Kilome (37°E, 1°S), Naivasha (36°E, 0°), Webuye (34°E, 1°N), Nyakach (34°E, 0°), Kericho (35°E, 0°) and Nairobi (36°E, 1°S)] were compared. There were significant variations ( P < 0.01, 95% CL ) in the relative proportions of the six constituents and this was reflected in the repellency of the essential oils ( P < 0.01, 95% CL ). Higher repellency of the oil was associated with greater proportions of ( S )‐(‐) perillyl alcohol, ( S )‐(‐)‐perillaldehyde and geraniol, and lower repellency was associated with an increased proportion of ( R )‐(+)‐limonene. The results suggest significant epigenetic (chemotypic) variations in the repellency and composition of C. newii essential oils growing in different regions of Kenya.