Ethanol extracts of Cassia grandis and Tabernaemontana cymosa inhibit the in vitro replication of dengue virus serotype 2

Abstract

ObjectiveTo determine the antiviral activity of ethanol extracts derived from Cassia grandis leaves and Tabernaemontana cymosa bark against two dengue virus (DENV) serotype 2 strains DENV-2/NG and DENV-2/16681 in two cell lines susceptible to infection, VERO and U937. MethodsThe cytotoxic concentration 50 (CC50) was assessed using the MTT method, and the effective concentration 50 (EC50) was determined using the technique of inhibiting the production of infectious viral particles by the plating method. Further testing of dose-response inhibition was performed, and three experimental approaches were evaluated (pre-, trans- and post-treatment) to determine the effect of the extracts according to the time of administration. Finally, a preliminary phytochemical analysis for both extracts was performed. ResultsThe cytotoxicity of the extracts was low (CC50>300 μg/mL), and the U937 cell line was more sensitive to the antiproliferative effect of both extracts. When the virus strain-dependent selectivities of the extracts were compared, it was found that both extracts were more selective in cultures infected with the DENV-2/NG strain than in those infected with the DENV-2/16681 strain. A dose-dependent inhibitory effect of the extracts was not observed in any of the evaluations. Finally, the highest inhibition was detected with the post-treatment approach with the Tabernaemontana cymosa extract (99.9% in both cell lines). ConclusionsA therapy with compounds derived from these extracts would inhibit viral replication and affect steps after viral internalization.