Evaluation of antioxidant, DNA cleavage and α-amylase inhibitory activity of polyphenolics from the root bark of Bauhinia racemosa

Bauhinia racemosa Lamk. (Caesalpiniaceae) is a small tree where bark and leaves are used extensively for the treatment of inflammation, headache, fever, malaria, skin infections, dysentery and diarrhea. The primary objective of this study was to evaluate the antioxidant, DNA cleavage and α-amylase inhibitory effects of the phenolic compounds: racemosol (BR-I), de-O-methyl racemosol (BR-II), 1,7,8,12b-tetrahydro-2,2,4-trimethyl-2Hbenzo[6,7]cyclohepta [1,2,3-de][1]benzopyran-5,10,11-triol (BR-III) and racemosolone (BR-IV), isolated from ethanolic extract of root bark of B. racemosa and their structures were determined by spectroscopic analysis. Further the total phenolic contents were also determined. The antioxidant activities were evaluated using the scavenging of 2-2-diphenyl-1-picrylhydrazyl radical (DPPH) and FRAP total reduction capability methods where BR-II exhibited most significant antioxidant effect at all concentrations while others were active at high concentrations only. In DNA cleavage activity measured using gel electrophoresis method, BR-I, BR-II and BR-III displayed partial cleavage of DNA at all concentrations while in BR-IV results were inconclusive as the compound was fluorescent under UV. The α-amylase inhibitory assay was performed using the chromogenic DNSA method where BR-IV showed 88.4% and 100% inhibition at 250 μg and 500 μg concentration respectively. The total phenolics were found to be 0.75 mg/ g catechol which could be correlated with the antioxidant capacity established by two different methods suggesting that these may be the active antioxidant ingredients of B. racemosa.