Atividade antiplasmódica e composição química de óleos essenciais e extratos fixos de Croton sacaquinha Croizat

Abstract

Due to the frequent acquisition of resistance by parasites to current drugs, it is important to discover new substances that can give rise to new treatments for this disease that affects millions of people every year. The study of medicinal plants is a promising alternative as a source of antimalarial substances and the Amazon is an invaluable source for this. This work investigated the chemical composition and antimalarial (antiparasitic) potential of the Amazonian plantCroton sacaquinha Croizat. Essential oils (EOs) from the leaves, stems and bark of C. sacaquinha were prepared by hydrodistillation and their chemical composition was qualitatively characterized by gas chromatography using flame ionization detection (GC-FID) and mass spectrometry (GC-MS). Fifty, fifty-five and fifty-six substances were respectively identified in the EOs of the bark (11-15% of the total peak area: caryophyllene, spathulenol; 5%: ledol, linalool), stems (8-12%: caryophyllene oxide, cyperene, spathulenol) and leaves (8-11%: b- elemene, germacrene D, linalool, selin-11-en-4-ol). Extracts of this species were prepared using various solvents and the extracts were evaluated for in vitro inhibitory activity against the K1 strain (chloroquine and pyrimethamine resistant) of Plasmodium falciparum Welch (the species that causes the most lethal form of malaria). Initially, 13 extracts from the leaf and bark of C. sacaquinha were screened for antiplasmodial potential in two concentrations (5.0 and 50 µg/mL). Hexane, ethyl acetate (EtOAc), ethyl alcohol and ethyl alcohol-water extracts of the bark and hexane extract of the leaves exhibited antiplasmodial potential (inhibition ≥80%). Due to the antiplasmodial potential and thin layer chromatography (TLC) profile, the bark EtOAcextract was prepared on a larger scale and fractionated by column chromatography, resulting in the isolation of 3-acetyl aleuritolic acid, identified on the basis of its nuclear magnetic resonance (NMR) data. For IC50 determinations, 7 concentrations of extract (from 100 to 1.56 µg/mL) were used. The bark ethanol and EtOAc extracts were respectively active (IC50 = 4.92 µg/mL) and partially active (IC50 = 16.3 µg/mL) while the leaf EtOAc extract was inactive (IC50 = 23.4 µg/mL). The following are unprecedented results of this study: 1) the very existence of OEs in the bark and stem and their chemical composition; 2) the presence of the triterpene, 3-acetyl aleuritolic acid, in the bark and 3) the antiplasmodial activity of the bark of C. sacaquinha, used in traditional medicine.