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Lethal and sublethal effects of essential oil of Lippia sidoides  (Verbenaceae) and monoterpenes on Chagas’ disease vector Rhodnius prolixus
Figueiredo, Marcela B; Gomes, Geovany A; Santangelo, Jayme M; Pontes, Emerson G; Azambuja, Patricia; Garcia, Elói S & Carvalho, Mário G de
Abstract
The aim of this study was to identify the composition of the essential oil from leaves of Lippia sidoides (EOLS), a
typical shrub commonly found in the dry northeast of Brazil, popularly known as “alecrim-pimenta”. Additionally, we
investigated the nymphicidal, ovicidal, phagoinhibitory and excretion effects of EOLS, its major constituent thymol and
its isomer carvacrol, on fourth instar nymphs and eggs of Rhodnius prolixus, the Chagas’ disease vector. The nymphicidal
and ovicidal activity of thymol, carvacrol, and EOLS was assessed by tests using impregnated Petri dishes. The
lethal concentration values (LC50) for EOLS, carvacrol, and thymol were 54.48, 32.98, and 9.38 mg/cm2, respectively. The
ovicidal test showed that both carvacrol and thymol (50 mg/cm2) inhibited hatching (50% and 23.3%, respectively), while
treatments with 10 mg/cm2 or 50 mg/cm2 EOLS did not affect the hatching rate at all (80% and 90%, respectively). We
observed an anti-feeding effect in insects fed with blood containing natural products at the higher concentrations (100 μg/
mL). Finally, excretion rate was affected by EOLS and carvacrol, but not by thymol. These findings offer novel insights into
basic physiological processes that make the tested natural compounds interesting candidates for new types of insecticides.
Keywords
Rhodnius prolixus; natural compounds; biological activity; Lippia sidoides
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