Bio-active principles in Commiphora africana resin dichloromethane extract and their insecticidal activity against bed bugs

Abstract

Abstract Bed bugs (Cimex lecturalius Linnaeus) are ecto-parasite pests that wholly feed on human and domestic animals’ blood and can cause anemia to the host on heavy feeding. Bed bug control has proved difficult due to various challenges including; development of insecticide resistance, high associated cost and environmental pollution. Natural herbal-based phytochemicals remain unexploited and we focused on Commiphora africana (A. Rich.) Engl. resin traditionally used in bed bug control in the coastal region of Kenya. We previously showed that dichloromethane extract of C. africana resin is highly repellent and toxic against bed bugs. In this study, we isolated compounds from the dichloromethane extract using column chromatographic techniques. The isolated compounds were evaluated for repellency and toxicity against bed bugs; and identified using Gas chromatography linked to mass spectrometer (GC-MS), Fourier Transform Infra-red (FTIR), 13C- and 1H Nuclear Magnetic Resonance techniques. Five compounds: taraxasterol, pseudo-taraxasterol, beta-sitosterol, fungisterol and guggusterol were isolated and characterized for the first time in this plant. Fungisterol had the highest repellency (75%) against bed bugs which was not significantly different (P>.05) to the positive control (neocidol) (74%) after > one-hour exposure. Fungisterol also elicited highest toxicity against bed bugs with LC50 of 25.73 mg/L after 24 h exposure. Blending fungisterol with other identified active terpenes did not synergize the overall repellent/toxic responses. This study identifies active compounds in C. africana resin and therefore lays a solid background in bed bug control using isolated compounds.