Avaliação do teor de geranina como marcador de um derivado vegetal de Spondias mombin L. e do seu potencial efeito antiherpético

Abstract

The herpes simplex virus type-1 (HSV-1) promotes a permanent infection of high prevalence in adults, with potential implications in immunocompromised individuals. Standard therapy for the treatment of symptoms of HSV infections includes acyclovir and its analogues, which have the same mechanism of action, act by inhibiting the DNA polymerase enzyme involved in the synthesis of new virions in the infected cell. Medicinal plants have shown promising antiviral effect as Spondias mombin species (Anacardiaceae), popularly known as cajazeira, is a fruitful plant, distributed in Brazil and other countries in the Americas. S. mombin presents non-clinical evidence of antiviral effect, added to popular use to treat herpes. Its antiviral action is mainly related to the presence of hydrolyzable tannins which act against HSV-1 and coxsakie virus, and one of the bioactive metabolites appears to be geraniin. In this sense, this study aimed to investigate the mechanism of antiviral action of the extract and fractions of the leaves of S. mombin and geraniin against HSV-1, as well as to identify the substances present in the extract and quantify the content of geraniin. For this, the phytochemical profile of the extract by LC-MS and the geraniin content was quantified by a method developed and validated by UFLC-DAD. For biological assays, different concentrations of samples were used to evaluate the in vitro antiherpes activity (anti-HSV-1) in virucidal, post-infection, attachment, and penetration assays. The mechanism of action of geraniin was investigated considering the glycoproteins gB and gD of HSV-1 surface as potential molecular targets. Molecular docking simulations were carried out for both in order to determine the possible binding mode position of geraniin at the activity sites. The binding mode position was posteriorly optimized considering the flexibility of the glycoproteins. The chemical analysis of samples was performed by LC‑MS and revealed the presence of 22 substances, which are hydrolysable tannins, O-glycosylated flavonoids, phenolic acids, and a carbohydrate. The extract, tannin-rich fraction and geraniin showed important in vitro virucidal activity through blocking viral attachment but showed no relevant inhibition of viral penetration. The in silico approaches demonstrated a high number of potential strong intermolecular interactions as hydrogen bonds between geraniin and the activity site of the glycoproteins, particularly the glycoprotein gB. In silico experiments indicated that geraniin is at least partially responsible for the anti-herpes activity through interaction with the viral surface glycoprotein gB, which is responsible for viral adsorption. Additionally, the quantitative analyses of geraniin in the extract by UFLC-DAD presents a content of 193.8 µg of geraniin per mg of extract. These results highlight the therapeutic potential of S. mombin antiherpes treatment and provides support for its popular purposes. However, further studies are required to validate the antiviral activities in vivo, as well as efficacy in humans.