Potencial de óleos essenciais no controle da esquistossomose: estado da arte e avaliação das atividades moluscicida e cercaricida do óleo volátil de Dysphania ambrosioides (L.) Mosyakin & Clemants (mastruz)

Abstract

Schistosomiasis mansoni is a parasitic disease caused by the helminth Schistosoma mansoni, which requires snails of the genus Biomphalaria as intermediate hosts to develop its evolutionary cycle. One of the ways to combat parasitosis is the control of transmitting molluscs through molluscicide products. Dysphania ambrosioides (L.) Mosyakin & Clemants, synonym and basionym Chenopodium ambrosioides L., is an herbaceous plant with a strong aroma and popularly known as mastruz. Its essential oil has biological potential and has shown lethal effects on Schistosoma haematobium transmitting snails. Thus, the present work aimed to carry out a review study on the molluscicidal action of essential oils (EO) in snails that transmit schistosomiasis, as well as to evaluate the chemical composition, molluscicide and cercaricide effects, and the ecotoxicity of the essential oil of aerial parts of D. ambrosioides (DAEO). This thesis was divided into two chapters. Chapter I consists of a review article of scientific studies about the molluscicidal potential of EO, carried out between 1984 and 2019. This article demonstrated that 50 volatile oils from 46 plant species, distributed among 29 genera and 13 families, were evaluated in transmitter snails of schistosomiasis. More than 80% of these EO were active against snails of the genera Bulinus and Biomphalaria (LC90 or LC100 ≤100 µg/mL or LC50 <40 µg/mL). The EO with greater toxicity to molluscs had high levels of monoterpenes in their composition. Some components of these EO were tested isolated in vector molluscs and, among them, the compounds of the monoterpene class exhibited significant molluscicidal activity, with emphasis on thymol, camphene and geraniol. Less than half of the EO studied underwent acute toxicity testing with nontarget organisms. Among those evaluated, only the EO of Curcuma longa L., Citrus limon (L.) Osbeck and Citrus sinensis (L.) Osbeck demonstrated low ecotoxicity, meeting the parameters of the World Health Organization (WHO). The review article confirmed the importance of EO as a raw material for the development of natural molluscicide products and highlighted the potential of monoterpenic compounds for the control of snails that transmit schistosomiasis. Chapter II reports the experimental study of the chemical constitution, molluscicide and cercaricide potential, and environmental toxicity of DAEO. To obtain the studied oil, aerial parts of D. ambrosioides were collected in the city of Paço do Lumiar-MA in October 2016, dried at room temperature and submitted to the hydrodistillation technique using a Clevenger-type device. The chemical composition of DAEO was analyzed by gas chromatography coupled with mass spectrometry (GC-MS). The molluscicide and cercaricide activities were evaluated by the immersion method, while the ecotoxicity was investigated by means of bioassays with Artemia salina larvae and Danio rerio fish. DAEO showed a yield of 0.8%. GC-MS analysis revealed the predominance of hydrocarbon monoterpenes (66.87%) in the oil, followed by oxygenated monoterpenes (25.46%). The main compounds identified were α-terpinene (50.69%), p-cymene (13.27%) and ascaridol (10.26%). The studied volatile product showed bioactivity on Biomphalaria glabrata snails and S. mansoni cercariae, with LC90 values of 48.60 and 87.21 μg/mL, respectively. Furthermore, the toxicity of DAEO to nontarget aquatic organisms was considered low when compared to the ecotoxicity of the synthetic molluscicide niclosamide. DAEO has shown potential to be used in the control of snails in areas of transmission of schistosomiasis, contributing to a reduction in the number of cases of the disease.