Previous studies had shown that different extracts obtained from Mitracarpus frigidus (Willd. ex Roem. & Schult.) K. Shum, an annual shrub commonly found in South America, present antimicrobial, leishmanicidal, cytotoxic, laxative, and anti-inflammatory activities. Thus, this study aimed to isolate the bioactive compounds from the hexane extract of the aerial parts of this plant and to evaluate some of their biological activities. The bioactivity guided fractionation of the hexane extract of M. frigidus afforded two pentacyclic triterpenoids, ursolic acid and methyl ursolate. Their identities were confirmed unambiguously by way of H-1, C-13, H-1 COSY, HMBC, HMQC, Dept 135, IR and UV-Vis spectroscopy, and mass spectrometry. These compounds, hitherto unknown in the species, were evaluated for their in vitro biological activities against four tumor cell lines (HL60, Jurkat, MCF-7, and HCT) and four Leishmania species (L. amazonensis, L. major, L. braziliensis, and L. chagasi). Also, their in vivo anti-inflammatory effect was evaluated using carrageenan-induced paw edema and carrageenan-induced peritonitis. Ursolic acid was active for all tumor cell lines with ED50 values varying from 4.2 to 35.7 mu g/mL, and methyl ursolate was active only for HL60 cells with an ED50 value of 22.7 mu g/mL. A pronounced antileishmanial potential was verified for amastigote form of L. major, with IC50 values of 1.3 and 2.1 mu g/mL for ursolic acid and methyl ursolate, respectively. They also presented in vivo anti-inflammatory effects in the carrageenan-induced paw edema test. Oral administration of these triterpenoids at 1 mg/kg significantly inhibited edema formation induced by carrageenan by 80 % and peritoneal leukocyte migration by 85 %. The results obtained reinforced that pentacyclic triterpenoids are an important class of natural products for investigation in the search of new bioactive compounds.
