In vitro trypanocidal and leishmanicidal activities of the flavonoids hispidulin, from Ambrosia tenuifolia, and santin, from Eupatorium buniifolium, are reported. A sensitive technique that takes advantage of ((3)H)thymidine uptake by dividing trypanosomatids has been adjusted for quantification of the parasiticidal effect of the natural products. The IC(50) values for hispidulin and santin on Trypanosoma cruzi epimastigotes were 46.7 and 47.4 muM, respectively. On trypomastigotes, the IC(50) values were 62.3 microM for hispidulin and 42.1 microM for santin. Hispidulin was more active than santin on promastigotes of Leishmania mexicana (IC(50) = 6.0 microM versus 32.5 microM). No cytotoxic activity was observed on lymphoid cells, making hispidulin and santin potential lead compounds for the development of new natural drugs. This is the first report on the trypanocidal and leishmanicidal activities of these flavonoids and on the presence of santin in E. buniifolium.
BackgroundDue to the high prevalence of viral infections having no specific treatment and the constant appearance of resistant viral strains, the development of novel antiviral agents is essential. The aim of this study was to evaluate the antiviral activity against bovine viral diarrhea virus, herpes simplex virus type 1 (HSV-1), poliovirus type 2 (PV-2) and vesicular stomatitis virus of organic (OE) and aqueous extracts (AE) from: Baccharis gaudichaudiana, B. spicata, Bidens subalternans, Pluchea sagittalis, Tagetes minuta and Tessaria absinthioides. A characterization of the antiviral activity of B. gaudichaudiana OE and AE and the bioassay-guided fractionation of the former and isolation of one active compound is also reported.MethodsThe antiviral activity of the OE and AE of the selected plants was evaluated by reduction of the viral cytopathic effect. Active extracts were then assessed by plaque reduction assays. The antiviral activity of the most active extracts was characterized by evaluating their effect on the pretreatment, the virucidal activity and the effect on the adsorption or post-adsorption period of the viral cycle. The bioassay-guided fractionation of B. gaudichaudiana OE was carried out by column chromatography followed by semipreparative high performance liquid chromatography fractionation of the most active fraction and isolation of an active compound. The antiviral activity of this compound was also evaluated by plaque assay.ResultsB. gaudichaudiana and B. spicata OE were active against PV-2 and VSV. T. absinthioides OE was only active against PV-2. The corresponding three AE were active against HSV-1. B. gaudichaudiana extracts (OE and AE) were the most selective ones with selectivity index (SI) values of 10.9 (PV-2) and >117 (HSV-1). For this reason, both extracts of B. gaudichaudiana were selected to characterize their antiviral effects. Further bioassay-guided fractionation of B. gaudichaudiana OE led to an active fraction, FC (EC50=3.1 μg/ml; SI= 37.9), which showed antiviral activity during the first 4 h of the viral replication cycle of PV-2 and from which the flavonoid apigenin (EC50 = 12.2 ± 3.3 μM) was isolated as a major compound.ConclusionsThe results showed that, among the species studied, B. gaudichaudiana seemed to be the most promising species as a source of antiviral agents.
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