Chemical compositions and mosquito repellency of essential oils from Artabotrys hexapetalus and Artabotrys rupestris

The two Tanzanian Artabotrys species were investigated to establish the chemical composition and mosquito repellent properties of their essential oils. Hydrodistillation of leaves and stem bark of Artabotrys hexapetalus (L.f.) (Annonaceae) and stem bark of Artabotrys rupestris Diels (Annonaceae) gave essential oils which were analyzed by Gas Chromatography – Mass Spectrometry (GC-MS). While the oil from the stem bark of A. hexapetalus contained high amount of β-caryophyllene oxide, the oil from the leaves had both β- caryophyllene oxide and 11-hexadcyn-1-ol as the main components. The oil from the root barks of A. rupestris contained large amount of 6-(p-tolyl)-2-methyl-2-heptanol and (-)-spathulenol. β-Caryophyllene oxide, cadinol, cubenol, (-)-spathulenol and 7-methyl-4-methylene-1-(1-methylethyl)-naphthalene were identified as common constituents of the essential oils from the two plant species investigated. On evaluation for mosquito repellency, the essential oil from the leaves of A. hexapetalus was found to exhibit strong activity with RC50 = 1.81×10-5 mg/cm2 and 2.79×10-5 mg/cm2 for the first and the second fractions, respectively against female Anopheles gambiae s.s. mosquitoes. The repellency activity of essential oil from leaves were significantly higher than from stem bark, but less than that of the standard citronella oil used (RC50 = 4.1×10-6 mg/cm2). The observed high mosquito repellent activity for the essential oil fractions from A. hexapetalus could be attributed to the presence of β-caryophyllene oxide.Keywords: Essential oils, mosquito repellent properties, Annonaceae, β-caryophyllene oxide, cadinol, cubenol.