Inhibition of α-Glycosidase by Lippia dulcis Trevir. (Verbenaceae) Preparations, Quantification of Verbascoside, and Study of Its Molecular Docking.

This study aimed to quantify verbascoside (VEB), perform molecular docking studies of VEB with the α-glucosidase (GL) of Bacillus stearothermophilus, and evaluate the inhibition of the enzyme by L. dulcis preparations. The substrate concentration and presence of reduced glutathione were evaluated for their effect on the in vitro inhibition of the GL enzyme. Assays were also performed in the presence and absence of simulated gastric fluid. The antidiabetic fractions 2 and 3 were the most inhibited GL, but their activity were significantly decreased in the presence of gastric fluid. Chromatographic analyses confirmed the predominant presence of VEB in the samples. The samples had VEB concentrations between 49.9 and 243.5 mg/g. Simulation of the molecular docking of VEB were consistent with its GL-inhibitory activity. It can conclude that the crude ethanol extract and fractions show inhibitory activity against the GL enzyme.

Anti-Zika virus activity and chemical characterization by ultra-high performance liquid chromatography (UPLC-DAD-UV-MS) of ethanol extracts in Tecoma species.

BACKGROUND: Plant species from the genus Tecoma are found in tropical and subtropical regions around the world. Some of them are grown as ornamental plants and others can be used as medicinal plants. In the present study, ethanolic extracts from trunks and leaves of Tecoma species were tested in vitro using assays against the Zika virus. METHODS: There was a total of 8 extracts obtained from different anatomical parts of three Tecoma species. The Tecoma castaneifolia, T. garrocha, T. stans var. angustata and T. stans var. stans were prepared by percolation with ethanol. The antiviral activity was assayed in vitro against the Zika virus by the MTT colorimetric method (n = 3). The UPLC-DAD-MS analysis of ethanolic extracts was performed from all the studied species. The biofractionation of T. stans var. stans trunk extract using different separation techniques led to the isolation of crenatoside compound. RESULTS: Ethanolic extract from Tecoma species leaves were more active against the Zika virus (EC50 149.90 to 61.25 µg/mL) when compared to the trunk extracts tested (EC50 131.0 to 66.79 µg/mL and two were not active). The ethyl acetate and aqueous fractions obtained from T. stans var. stans trunk were active against the Zika virus with EC50 values of 149.90 and 78.98 µg/mL, respectively. Crenatoside is a phenylethanoid glycoside isolated from the ethyl acetate of T. stans var. stans trunk extract. This compound was tested and exhibited EC50 34.78 µM (21.64 µg/mL), thus demonstrating a better result than the original ethanolic extracts as well as others extracts of Tecoma species, and it was more active than the positive control, ribavirin (386.84 µM). Furthermore, its selectivity index was at least 2.5 times higher than the tested ethanolic extracts and 11.1 times more potent than ribavirin. CONCLUSION: The Tecoma species demonstrated interesting in vitro activity against the Zika virus. The crenatoside, phenylethanoid glycoside that was for the first time isolated from Tecoma stans var. stans, exhibited a potent and relevant anti-Zika virus activity, being more active than ribavirin (positive control). The data show that crenatoside, was a promising compound with in vitro antiviral activity against the Zika virus.