Repellency Effect of Hydro-Alcoholic Ricinus communis (Castor) Leaf Extract against Phlebotomus papatasi Under Laboratory Conditions.

Background: The extract of seed and leave of Ricinus communis (castor plant) is rich in glycerides and fatty acids, including ricin, oleic acid, palmitic acid, linoleic acid and dihydroxy-stearic. This study aimed to evaluate the repellency effect of R. communis leaf extract (castor extract, CE) on Phlebotomus papatasi sand flies and compare its effectiveness with a commercial insect repellent, 10% DEET spray (positive control), under laboratory conditions.

Methods: Hydro-alcoholic extract of castor leaves was prepared, and the repellency effect and mortality rates were evaluated at different doses. The study also assessed 10% DEET (positive control) and 50 μl of 70% ethanol (negative control). The modified Wirtz method was applied using the K and D apparatus.

Results: The repellency effect of various doses of hydro-alcoholic castor extract (CE) on Ph. papatasi sand flies were evaluated. The ED₅₀ (95% CL) was calculated as 4.17 mg/cm², and ED₉₀ (95% CL) as 7.9 mg/cm² after 24 hours of exposure. At 1.6 mg/cm², the repellency effect of hydro-alcoholic CE was greater than that of 10% DEET. However, DEET exhibited higher repellency than CE at concentrations below than 1.6 mg/cm² (i.e. 0.1, 0.2, 0.4 and 0.8 mg/cm²). Mortality among sand flies was observed only at high doses (1.6mg/cm²) of hydro-alcoholic CE, with the highest mortality rate recorded at 17.7%.

Conclusion: This study demonstrated that 10% DEET and hydro-alcoholic castor extract exhibit strong repellency effects against Ph. papatasi sand flies, the primary vector of zoonotic cutaneous leishmaniasis. The findings highlight castor extract's potential as an effective sand fly repellent.