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 EC50 of 78.9 mg/ml (7.89 %) and 71.6 mg/ml (7.16 %) in the first 15 min after
spraying. C. anisata leaf extracts have potential to be included
in protection products against mosquitoes due to the repellent
and cidal compounds contained therein.
