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

Abstract Objective To 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. Methods The cytotoxic concentration 50 (CC 50 ) was assessed using the MTT method, and the effective concentration 50 (EC 50 ) 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. Results The cytotoxicity of the extracts was low (CC 50 >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). Conclusions A therapy with compounds derived from these extracts would inhibit viral replication and affect steps after viral internalization.