Content of gallic acid in selected plant extracts
2006
Karamac, M., E-mail: [email protected] | Kosinska, A. (Polish Academy of Sciences, Olsztyn (Poland). Inst. of Animal Reproduction and Food Research, Div. of Food Science) | Pegg, R. B. (University of Saskatchewan, Saskatoon (Canada). Dept. of Applied Microbiology and Food Science)
Ethanolic extracts of phenolic compounds were prepared from green teas (Camellia sinensis L.), bearberry leaves (Arctostaphylos uva-ursi L.), hazelnuts (Corylus avellana), evening primrose (Oenothera biennis) and grape seeds (Vitis vinifera L.). All crude extracts were examined for their gallic acid content by HPLC. The bearberry-leaf preparation was also fractionated by a Sephadex LH-20 column chromatographic method with 95 percent (v/v) ethanol and acetone:water (1:1; v/v) as mobile phases: one fraction consisted of low molecular-weight phenolics and the other of tannins. To all samples tannase was applied in an effort to liberate gallic acid from the phenolic esters and hydrolysable tannins. The content of free gallic acid in the extracts ranged from 1 to 15 mg/g with the highest quantity being found in evening primrose. The content of gallic acid liberated by tannase ranged from 5 to 309 mg/g with the highest content being found in the tannin fraction from the bearberry-leaf extract
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