Isolation and characterization of gallic acid and methyl gallate from the seed coats of Givotia rottleriformis Griff. and their anti-proliferative effect on human epidermoid carcinoma A431 cells

Gallic acid (GA) and its derivative methyl gallate (MG) are well studied plant phenolics. They have exhibited anticancer effects in several cancer cell lines. However, the presence of GA/MG in the seed coats of Givotia rottleriformis and their inhibitory effect on human epidermoid carcinoma (A431) skin cancer cells were not reported. In this study we have isolated and chemically characterized the bioactive compounds GA and MG from the bioassay guided methanolic (MeOH) seed coat extracts of G. rottleriformis. The fractions obtained from open silica column chromatography were subjected to in vitro enzymatic assays. Among seven fractions we found that only fractions 5 and 6 showed significant inhibition activity toward COX -1 with an IC50 value of 28 tig/mL and 9.3 tig/mL and COX -2 with an IC50 value of 35 tig/mL and 7.0 tig/mL respectively. However, we could not find 5 -LOX enzyme inhibition activity. MG (10 mg/g DW) and GA (6 mg/g DW) were the major compounds of seed coats. Cell viability was analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, which showed that GA/MG significantly reduced the growth of A431 cells with an IC50 value of 25 tig/mL and 53 tig/mL and 11 tig/mL and 43 tig/mL at 24 h and 48 h, respectively. However the cytotoxic effect of GA/MG on HaCaT normal skin keratinocyte cell line was found to be less. Western blot analysis has shown that GA/MG treatment down regulated Bcl-2 and up regulated cleaved caspa se -3 with respect to increasing doses. Our results conclude that GA and MG have potential anticancer effects and can be used as therapeutic agents for skin cancers. (C) 2015 The Authors. Published by Elsevier Ireland Ltd. This is an open access article under the CC BY -NC -ND license.