Avaliação da atividade antiviral de extratos obtidos da folha e fruto de Morinda citrifolia contra o vírus dengue

Abstract

Dengue is an arbovirosis which affects mankind, causing problems in the public health worldwide, especially in tropical countries which present conditions that favor the spread of the mosquito Aedes aegypti. Currently, among the various strategies to control the disease, there is no effective vaccine or antiviral capable of combating this infection. Thus, the aim of the present study was to evaluate the antiviral activity of leaf and fruit extracts of the plant Morinda citrifolia L. in Vero cells culture infected with dengue-2 virus (DENV-2). Initially, the crude extracts (hydroethanolic) and their fractions were obtained: hexane, chloroform and ethyl acetate, followed by chromatographic analysis. The cytotoxicity test of the crude extract, the aqueous residue and its fractions were performed in culture of Vero cells by the MTT method, at concentrations of 1000; 500; 250; 125; 62.5; 31.2 μg/mL. The antiviral assay results were conducted through the following strategies: cells infected with DENV-2 (positive control); cells maintained with culture medium (negative control); cells infected with DENV-2 and treated with the extract or fractions. After five days of infection, cell viability was evaluated by the MTT method and culture supernatant was used for viral quantification by plaque forming unit (PFU) assay. The results showed that the chromatographic analysis of extracts and fractions present distinct bands, which could be suggestive of saponins, terpenes and flavonoids. Such extracts and fractions were not toxic to cell cultures, except for the cells treated with the chloroform fraction obtained from leaf, hexane and ethyl acetate fractions of the green fruit, leading to a near 65% viability. In the antiviral assay the positive control had 60% of cell viability after five days of infection. Among the leaf extract treatments, it was observed that infected cells treated with ethyl acetate fraction, maintained their cell viability around 100% in the concentration of 1000μg/mL and up to 85% in the concentrations of 500 and 250μg/mL. The hexane fraction treatment showed higher viability in comparison to the positive control at all concentrations. However, in the chloroform fraction, viability remained high only at concentrations of 500 and 250 μg/mL. Crude extract and residual aqueous fraction did not show any antiviral activity. Cells treated with the extract and different fractions obtained from the mature and green fruits, presented an overall cell viability close to 100% in 500 and 1000 μg/mL in the mature fruit and only 1000 μg/mL in the green fruit. However, for the cells treated with the chloroform fraction, it was not possible to observe any significant difference when compared to the positive control. In the viral quantification it was observed that cells treated with hexane and chloroform fractions obtained from leaf, as well as crude extracts obtained from mature and green fruits had antiviral effect, resulting in a total viral load decrease. Finally, identified from this study, a possible antiviral activity of the compounds obtained from Morinda citrifolia against dengue virus.