Repellent and mosquitocidal effects of leaf extracts of Clausena anisata against the Aedes aegypti mosquito (Diptera: Culicidae)

Abstract

Mosquitoes are rapidly developing resistance to insecticides that millions of people relied on to protect themselves from the diseases they carry, thereby creating a need to develop new insecticides. Clausena anisata is used traditionally as an insect repellent by various communities in Africa and Asia. For this study, the repellency and adulticidal activities of leaf extracts and compounds isolated from this plant species were evaluated against the yellow fever mosquito, Aedes aegypti. In the topical application assays, using total bites as an indicator, repellency was dose-dependent, with the acetone crude extract (15% ) having 93% repellence and the hexane fraction (7.5%) 67% repellence after 3 h. Fractionation resulted in a loss of total repellence. As mosquito-net treating agents, the acetone and hexane extracts of C. anisata, both at 15%, had average repellences of 46.89 ± 2.95 and 50.13 ± 2.02 %, respectively, 3 h after exposure. The C. anisata acetone extract and its hexane fraction caused mosquito knockdown and eventually death when nebulised into the testing chamber, with an EC 50 of 78.9mg/ml (7.89%) and 71.6 mg/ml (7.16%) in the first 15 minutes after spraying.Clausena anisata leaf extracts have potential to be included in protection products against mosquitoes due to the repellent and cidal compounds contained therein.

The use of Clausena anisata in insect pest control in Africa: A review

“…Adult mortality ranging from 4 to 10% after 24 hours of exposure was reported. A report from India further affirms this adulticidal activity (Ramkumar et al, 2015) In the study by Mukandiwa et al (2016b) the acetone and hexane leaf extracts of C.…”

“…The adulticidal activity of C. anisata against mosquitoes has been reported by Mavundza et al (2014) and Mukandiwa et al (2016b). Of note again, is the fact that the different researchers used different methods to demonstrate the cidal effect of C.…”

“…Innocent and Hassanali (2015) reported that estragole, which was the main component of the C. anisata oil tested, had a lower protective efficacy (between 10% and 38%) compared to the crude essential oil (between 13 and 57%). Similarly, Mukandiwa et al, (2016b) found that fractionation of the crude C. anisata extract resulted in a loss of total repellency. This loss of activity may imply that there is more than one bioactive compound acting synergistically to produce the observed activity.…”

“…Innocent and Hassanali (2015), also reported that the crude essential oil of C. anisata had a protective efficacy ranging between 14 and 57% against A. gambiae. Mukandiwa et al (2016b) evaluated leaf extracts of C. anisata against A. aegypti for their possible value as mosquito-net repellent agents, as topical repellents in a guinea pig model and as aerosol insecticide sprays. As mosquito-net treating agents, the acetone and hexane extracts of C. anisata, both at 15%, had average repellences of 46.9 ± 2.95 and 50.1 ± 2.02 %, respectively, 3 h after exposure.…”

Chemical constituents of Clausena lenis

“…Hook. f. ex Benth., are widely used by local people for ethnomedicinal and other purposes (Albaayit et al 2016;Mukandiwa et al 2016aMukandiwa et al , 2016b. Phytochemical studies on Clausena species revealed the preponderance of prenylated/geranylated coumarins and carbazole alkaloids with interesting bioactivities (Ito et al 2000;Sripisut et al 2012;Cao et al 2018;Yan et al 2019).…”