Leishmanicidal activity of Vernonanthura nebularum (Asteraceae)

SOSA, AM; VERA NR; BARDON, A; BORKOSKY SA; BARROSO, PA

Buenos Aires

Congreso; 4th Scientific Meeting of the Research Network Natural Products against Neglected Diseases; 2018

Leishmaniasis are a group of tropical diseases caused by parasites belonging to the genus Leishmania. According to the latest reports from the World Health Organization (WHO), the disease is present in 97 countries, affecting approximately 12 million people and with 350 million people at risk [1,2]. There are two main forms of the disease: visceral leishmaniasis (VL), and tegumentary forms (ATL). The ATL occurs in warm and wet regions of northern Argentina. Theantimonial drugs employed in the treatment of leishmaniasis causes serious toxic effects in patients, besides they must be administered parenterally and treatments are long and expensive, which limit their use in endemic areas [3].In the past few decades, there has been a growing interest in the search for alternative medicinal therapies based on natural products. Vernonanthura nebularum (Cabrera) H. Rob. (Asteraceae) is an endemic species from northernArgentina, very rich in elephantopus type sesquiterpene lactones [4] (SLs).Continuing with our study of V. nebularum as a source of antiparasitic products, in the present work, we evaluated the leishmanicidal activity of a dichloromethane flowers extract (DFE), a chromatographic fraction rich in lactones (CF) and the main SL isolated from CF (Vn1).Proton nuclear magnetic resonance (1H-NMR) spectra of the V. nebularum DFE and the CF were performed for the identification of diagnostic value signals. The main compound of CF (Vn1) was isolated by RP-HPLC and identified as 2-methoxy-2,5-epoxy-8-methacryloxygermacra-3Z, 11 (13) -dien-6,12-olide through mono and bidimensional 1H-NMR and 13C-NMR spectra. The leishmanicidal activity of DFE, CF and Vn1 was assessed against the promastigote and amastigote forms of Leishmania (L.) amazonensis (MHOM/BR/73/M2269), quantifying the number of parasites withan optic microscopy. The toxicity of the substances in macrophages of the cell line RAW 264.7 was also assessed with the Cell Counting Kit-8®. DFE, CF and Vn1 presented a strong leishmanicidal effect against the promastigote and amastigote forms of L. (L.) amazonensis with IC50 values between 2.72 and 0.66 μg/mL. As previously was reported, the compounds that possess at least one α,β unsaturated carbonyl group as pharmacophore, usually show significant antiprotozoal activity4. The SL Vn1 showed a powerful activity against intracellular amastigotes of L. (L.) amazonensis with an IC50 value of 0.78 μg/mL (2.15 μM), three times lower than the cytotoxic activity (IC50=6.05 μM). Different strategies could be applied to increase the Vn1 selectivity and to explore its antiparasitic activity in an animal model of ATL in the near future.