Antioxidant properties of leaves and steams from Bauhinia microstachya (Raddi) J.F. Macbr.

Abstract

This paper describes in vitro antioxidant activities of different extracts (EBHF, EBHC, EBCF, EBCC, EBEF and EBEC) and fractions (FAEF and FAEC) obtained from leaves and stems of Bauhinia microstachya (Fabaceae), using two distinct methodologies: the formation of a phosphomolibdenum complex (a) and the chemical reduction of DPPH free radical (b). When assayed by the phosphomolibdenum complex formation method, EBEF, EBEC, FAEF and FAEC (200 μg.mL-1) showed the highest antioxidant activities with regard to standard ascorbic acid (Vitamin C) (45% ± 1.55, 47% ± 1.10, 49% ± 2.06, 43% ± 3.14, respectively). Similarly, when assayed by the DPPH reduction method, FAEF and FAEC showed that they are highly efficient as antioxidants (EC50 = 2.75 and 2.86 mg.mL-1 respectively) with regard to standard ascorbic acid (EC50 = 36 ± 0.35 mg.mL-1), quercetin (EC50 = 1.60 ± 0.17 mg.mL-1) and rutin (EC50 = 8.13 ± 0.13 mg.mL-1). Phytochemical studies, as well as 1H and 13C NMR analysis of the most active fractions (FAEF and FAEC) established the presence of polyphenols (tannins and flavonoids). The percentage of total flavonoids from the leaves of B. microstachya was shown to be 0.12 g% ± 0.03 (n = 5). These results not only demonstrate the high in vitro antioxidant potential of this plant species, but prompt further chemical, pharmacological and biotechnological research studies with a view to producing new phytotherapics for medical use which are aimed at combating free radicals.