Avaliação das propriedades farmacológicas e farmacogenéticas do extrato e frações da planta Pavonia xanthogloea (Malvaceae)

Abstract

The Pampa Biome has a great biodiversity of plants, among them the Family Malvaceae. Despite the medicinal use of many of these plants, studies on the biological activity of these are still very scarce. This is the case of the plant known as "erva de ovelha", which is traditionally used in therapy against prostate cancer, used as tea and prepared from two species of the genus Pavonia, highlighting the Pavonia xanthogloea. Therefore, this study aimed to identify bioactive compounds in the extract and five fractions of P. xanthogloea, evaluating their antioxidant and antitumor action in the lineage of prostate cancer DU145. Additionally, the potential cytotoxic effect via pharmacogenetic studies on human red blood cells (RBCs) bearers of different genotypes of the polymorphism found in the gene of the enzyme superoxide dismutase manganese dependent (Ala16Val-SOD2). These RBCs afterwards were exposed to extract and fractions of P. xanthogloea. The results were arranged and shown as three scientific papers. Manuscript 1: The chemical composition of the extract and fractions (ethyl acetate, hexane, n-butanol, aqueous and dichloromethane) was determined by liquid chromatography of high efficiency. The antioxidant activity was determined by DPPH assay. The antioxidant activity and the cytotoxicity evaluated by exposure of human lymphocytes exposed to different concentrations of extract/fractions with and without sodium nitroprusside and H2O2. Tiliroside was found in all extracts. The aqueous and ethyl acetate fractions showed high antioxidant capacity. The crude extract (ethanol) and hexane, n-butanol and aqueous fractions reverts the ROS levels generated by H2O2. The crude extract and hexane, ethyl acetate and n-butanol fractions do not cause cytotoxicity. The aqueous fraction was cytotoxic at concentration of 300 μg/mL. The reversal of the cytotoxicity caused by SNP was dependent on the concentration and extract/fraction. The dichloromethane fraction was cytotoxic at all concentrations. The results suggest potential medicinal use of this species. Manuscript 2: The study evaluated in vitro the hemolytic effect of chelerythrine (CHE), alkaloid extracted from Zanthoxylum rhoifolium, and the possible pharmacogenetic influence of SOD2-Ala16Val in RBCs. The CHE inhibits protein kinase C activity decreasing the RBCs deformation and causing oxidative stress. Blood was collected from healthy subjects previously genotyped for the polymorphism Ala16Val-SOD2. The CHE was incubated with RBCs (1 × 109 cell/mL) at concentrations 0.1 μM, 2 μM and 8 μM. Pharmacogenetic effect was evaluated through spectrophotometric analysis of indicators of oxidative stress, lipid peroxidation, catalase, advanced oxidation protein products (AOPP) and nitrate/nitrite (NOx), and hemolysis. The RBCs were maintained under controlled conditions. The response to treatment with CHE was genotype dependent and AA RBCs were more sensitive than VV. The SOD2 plays an important role in erythropoiesis and causes an impact on the quality of RBC. Therefore, the results presented here suggest toxicogenetic influence of SOD2 in hemolytic assay using human cells. Manuscript 3: To evaluate the antitumor effect viability assays of (24 hour exposure) and cell proliferation (72 hour exposure) were performed by MTT assay and spectrophotometric analisys. The pharmacogenetic effect through the hemolysis assay by spectrophotometry. Blood was collected from healthy subjects previously genotyped for the polymorphism Ala16Val-SOD2. Both erythrocytes and tumor cells were grown under controlled conditions. Study the pattern of hemolysis associated with different genotypes of the polymorphism Ala16Val-SOD2 suggests pharmacogenetic effect. When hemolysis assay was performed for different concentrations of extract and fractions of P. xanthogloea the anti-hemolytic protective effect observed was independent of the gene SOD2. Cytotoxic and antiproliferative activity was observed in the cell lineage of prostate cancer DU145 was dependent on the type of extract/fraction and concentration, highlighting n-butanol fraction that showed strong antiproliferative activity. These results showed great similarity to antitumor activity of doxorubicin chemotherapeutic and also seem to be associated with tiliroside isolated from P. xanthogloea. The overall results match with the popular use of P. xanthogloea regarding the prostate cancer therapy. However, further investigations should be performed to evaluate the antitumor action mechanisms of P. xanthogloea.