Preliminary study on the effect of Munronia pinnata (Wall) Theob. (Meliaceae) aqueous extract on functional change in endothelial cells infected by dengue virus

Infection of endothelial cells (ECs) and their dysfunction has been implicated in the immunopathogenesis leading to severity in dengue virus (DENV) disease and rationalize the therapeutic targeting of the endothelium. Munronia pinnata is a rare medicinal plant which is commonly used to treat fever in traditional systems of medicine in Sri Lanka. The objective of the present study was to investigate the effect of aqueous plant extract (APE) of M. pinnata on the interaction between DENV-3 and ECs in inducing any changes. The effect of DENV-3 on metabolic activity of ECs was evaluated by using MTT. The effect of APE of M. pinnata on interaction between DENV-3 and ECs was assessed in three different ways to determine the potential of M. pinnata to protect the endothelial cells in a dengue infection; i) pre-treatment of DENV-3 with APE on ECs, ii) sequential treatment of DENV-3 followed by APE on ECs and iii) sequential treatment of APE followed by DENV-3 on ECs. A 49.8% reduction of EC viability was recorded following interaction with DENV-3 as opposed to that in the absence of DENV-3 (p < 0.001). A significant protection of ECs was observed at almost all concentrations of APE in treatment strategies. Interestingly, an increased significant protection was observed during the pre-treatment of DENV-3 with APE prior to the interaction with ECs (lowest p = 0.0003), and highest protection of EC at 15.6 and 31.3 µg/mL of APE (p < 0.0001). The present study suggests that the APE of M. pinnata exhibits an antiviral effect against DENV-3 by protecting the metabolic activity of ECs. Further studies are needed to understand the underlying mechanism of the direct inhibitory activity of M. pinnata against DENVs and to characterize the active compounds in the origin of its efficacy