Publication Type

Journal Article

Journal Name

Phytochemistry

Publication Date

2-10-1998

Abstract

The repellency of the essential oil of the previously reported anti- tick pasture shrub Gynandropsis gynandra and identified constituents of the oil were evaluated against the livestock tick, Rhipicephalus appendiculatus. In a tick-climbing repellency bioassay, the oil of G. gynandra exhibited a repellency effect which at the highest treatment levels was higher than that of the commercial arthropod repellent N,N-diethyltoluamide. Twenty eight compounds were identified in the G. gynandra oil by GC, GC-MS and coinjection with authentic samples. Carvacrol was found to occur in largest quantity (29.2%), followed by trans-phytol (24.0%), linalool (13.3%), trans-2- methylcyclopentanol (7.2%) and β-caryophyllene (4.4%). m-Cymene, nonanal, 1- α-terpineol, β-cyclocitral, nerol, trans-geraniol, carvacrol, β-ionone, trans-geranylacetone, and nerolidol were the most repellent components against R. appendiculatus. Methyl isothiocyanate which occurred in the G. gynandra oil at a relative percentage of 2.1 and which was not tested in the bioassay due to its toxicity may also contribute significantly to the repellency of the oil. The repellency of the oil of G. gynandra supported earlier findings by other workers that G. gynandra repelled R. appendiculatus ticks.

Keywords

Anti-tick pasture, Brown-ear tick, Capparidaceae, Essential oil, Gynandropsis gynandra, Repellents, Rhipicephalus appendiculatus, Tick

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