Propriedades biológicas e toxicológicas de Bauhinia forficata Link (Fabaceae)

Abstract

Bauhinia forficata Link (Fabaceae), known as "pata-de-vaca", is a medicinal plant native in South America, traditionally used as hypoglycemic, diuretic, hypocholesterolemic, and in the treatment of cystitis, intestinal parasites, elephantiasis and other organic disturbs. These disorders are associated with oxidative stress and cellular damage. The major secondary metabolites present in this species are phenolic compounds, particularly flavonoids. In this context, the aims of this study were to evaluate the antioxidant, antibacterial and genotoxic activities of B. forficata leaves and to determine the total phenols and flavonoids contents. Dried and powdered plant material was subjected to static maceration in ethanol followed by liquid/liquid partition to obtain the ethanol extract (EE) and the hexane (HF), dichloromethane (DF), ethyl acetate (EF) and butanol (BF) fractions. The total phenols and flavonoids contents were determined by spectrophotometry using gallic acid and rutin calibration curves, respectively. The antioxidant activity was evaluated by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging, the ferric reducing power and the β-carotene bleaching assays. The antibacterial activity was investigated by determining the 100% Minimal Inhibitory Concentration (MIC100) using the broth microdilution according to Clinical Laboratory Standards Institute (CLSI) recommendations against seven ATCC reference strains. After that, the bactericidal or bacteriostatic pharmacological effect was established and the Minimal Bactericidal Concentration (MBC) was also determined. The genotoxic potential was assessed by the comet assay using HepG2 cells. Analyses were performed in triplicate and the results presented as mean ± standard deviation, when appropriate. Data were statistically analyzed by one-way ANOVA followed by Tukey’s post-test (p < 0.05). The total phenolic and flavonoid contents ranged from 9.20 ± 0.87 to 87.35 ± 0.92 mg/g gallic acid equivalents, and from 2.51 ± 0.06 to 56.76 ± 0.81 mg/g rutin equivalents, respectively. The Effective Concentration 50% values in the DPPH and ferric reducing power assays were 27.95 ± 0.33 to 193.62 ± 1.12 μg/mL, and 21.12 ± 0.52 to 328.45 ± 3.23 μg/mL, respectively. The percentage inhibition of lipid peroxidation obtained by β-carotene bleaching method ranged from 26.80 ± 2.26 to 67.07 ± 1.48, 36.30 ± 5.38 to 73.66 ± 3.91 and 48.70 ± 5.08 to 81.93 ± 3.45 at 250, 500 and 1000 μg/mL concentrations, in that order. The EF was active against Staphylococcus aureus ATCC 29213 and ATCC 6538, with MIC100 and MBC values of 2.5 mg/mL and 5 mg/mL, and 5 mg/mL and > 5 mg/mL, respectively, showing bacteriostatic effect. The EE induced significant genetic damage to HepG2 cells by the comet assay at concentrations of 125 and 250 μg/mL. The results of this study indicate that B. forficata contains phenolic compounds, including flavonoids, possessing antioxidant and antibacterial effects. The genetic damage revealed by EE requires additional studies to confirm its genotoxic potential.