Abstract

MUEDAS TAIPE, Golfer; LA ROSA TORO GOMEZ, Adolfo  and  ROBLES CAYCHO, Juana. Electrochemical Evaluation of the antioxidant activity of alcoholic extract of Bauhinia guianensis var. kuntiana Aubl.. Rev. Soc. Quím. Perú [online]. 2008, vol.74, n.4, pp.233-246. ISSN 1810-634X.

The evaluation of the antioxidant activity was carried out using two methods: the chemical method, by neutralizing free radical 2,2-diphenyl-1-picrylhidracyl (DPPH) and the electrochemical method, using cyclic voltammetry. The alcoholic extract (EBO) was evaluated from the bark of the Bauhinia guianensis var. kuntiana Aubl. and fractions derived from the EBO: hexane, ethyl acetate, methanol, water and insoluble. Furthermore, 4 synthetic polyphenols standards were used: quercetin, rutin, butylated hydroxyanisole (BHA) and resorcinol. According to the analysis by DPPH, the rutin and quercetin showed more antioxidant activity (84,08 and 83,83 % respectively) compared to resorcinol and BHA that showed less than 72 %. The EBO showed a good antioxidant activity of 87,02 % and ethyl acetate (88,52 %) and insoluble (84,83 %) fractions. According to these results, alcoholic extract and its fractions tested were classified in group G-IV. The aqueous fraction presented an activity of 70,41 % (G-III) and fractions of methanol and hexane showed a low antioxidant activity of less than 7 % (G-I). In the electrochemical analysis by cyclic voltammetry (reference electrode Ag/AgCl), the synthetic polyphenols showed an oxidation potential between 0,156 and 0,638 V, where the quercetin presented the lowest value. The EBO presented a lower value of oxidation potential of 0,171 V, while the fractions showed an oxidation potential between 0,147 and 0,494 V, where the lowest value showed corresponds to fractions of ethyl acetate. The cyclical voltamograms (VC) did not present any oxidation peaks for the hexane fraction. Comparing the potential of oxidation and antioxidant properties, we conclude that at a very low potential of oxidation (between 0,14 and 0,15 V), polyphenolic compounds showed a good antioxidant activity (between 84 and 88 %).

Keywords : antioxidant; cyclic voltammetry; oxidation potential; Bauhinia guianensis.

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