ABSTRACT
Wedelia paludosa D.C. (Asteraceae) is an ornamental species occurring in many regions of Brazil. Aiming to find new cytotoxic compounds, the hydromethanol extract of W. paludosa (HME), as well as the dichloromethane (DF) and water (WF) fractions resulting from its partition, were submitted to the brine shrimp lethality bioassay (BSLB) in order to evaluate their cytotoxicity. Dichloromethane fraction (DF) was shown to be the most cytotoxic fraction (LC50 = 140.6 μg/mL), and its analysis by reversed phase high performance liquid chromatography (RP-HPLC) revealed ent-kaurenoic (1, 6.22 ± 0.23 percent) and grandiflorenic (2, 3.22 ± 0.31 percent) acids as important constituents. HME (LC50 = 980 μg/mL), DF (LC50 = 140.6 μg/mL), 1 (LC50 = 15.9 μg/mL) and 2 (LC50 = 29.8 μg/mL) were found to be cytotoxic, while the water fraction (WF, LC50 >> 1000 μg/mL) was inactive. As conclusion, the cytotoxicity observed for HME and DF is mainly due to the presence of 1 and 2 in their constitution.
Wedelia paludosa D.C. (Asteraceae) é uma planta ornamental facilmente encontrada em várias regiões do Brasil, principalmente nos estados de Santa Catarina, São Paulo, Minas Gerais, Bahia e Pernambuco. Objetivando descobrir novas substâncias citotóxicas a partir desta espécie, o extrato hidrometanólico de W. paludosa (HME) e as frações diclorometânica (FD) e aquosa (FA) resultantes de sua partição em CH2Cl2-H2O foram avaliados utilizando-se o bioensaio em Artemia salina. A fração diclorometânica (FD) apresentou a maior atividade citotóxica (CL50 = 140,6 μg/mL), e sua análise por cromatografia líquida de alta eficiência empregando-se fase reversa (FR-CLAE) revelou os ácidos caurenóico (1, 6,22 ± 0,23 por cento) e grandiflorênico (2, 3,22 ± 0,31 por cento) como constituintes majoritários. As amostras HME (CL50 = 980 μg/mL), FD (CLC50 = 140,6 μg/mL), 1 (CL50 = 15,9 μg/mL) e 2 (CL50 = 29,8 μg/mL) foram citotóxicas contra A. salina, enquanto que a fração aquosa (FA, CL50 >> 1000 μg/mL) mostrou-se inativa. Conclui-se que a citotoxidade observada para HME e FD pode ser atribuída à presença dos ácidos caurenóico (1) e grandiflorênico (2) nestes extratos.
ABSTRACT
There are several reports of biological activity for kaurenoic acid (1), which is found in the aerial parts of Wedelia paludosa D.C., a herbaceous plant of the Asteraceae family abundant in Brazil, and that contains grandiflorenic acid (2) also. Both of these diterpenes were shown to cause lysis of trypomastigotes of the protozoa Trypanosoma cruzi, the causative agent of Chagas' disease (American trypanosomiasis). This paper reports the quantitative determination of these diterpene acids in the aerial parts of W. paludosa by an isocratic RP-HPLC method employing 60 percent acetonitrile in water and UV detection (220 nm). Kaurenoic acid (1) was found to be more abundant (0.85 ± 0.08 percent) while the amount of grandiflorenic acid (2) determined was almost three times lower (0.32 ± 0.02 percent). No significant seasonal variation was observed for these compounds in W. paludosa growing in Belo Horizonte (MG, Brazil) what points out to the aerial parts of this species are a good source of these biologically active diterpenes along all the year.