R. Amarowicz et al., Antioxidant activity of condensed tannins of beach pea, canola hulls, evening primrose, and faba bean, J FOOD LIPI, 7(3), 2000, pp. 195-205
Condensed tannins were extracted from beach pea, Cyclone canola hulls, even
ing primrose and faba bean using 70% aqueous acetone. The dried crude tanni
n extracts were purified on a Sephadex LH-20 column using first 95% ethanol
as a mobile phase for elution of nontannin phenolics and then 50% aqueous
acetone to elute tannins. The total content of polyphenolics in tannin extr
acts ranged between 10 and 405 mg catechin equivalents per 1 g extract. All
tannins extracts displayed a marked antioxidant activity in a beta-caroten
e-linoleate model system. Evening primrose and faba bean tannin extracts ex
hibited the best preventive effect against the bleaching of beta-carotene a
fter a 120 min period. The scavenging effect of tannin extracts on alpha,al
pha-diphenyl-beta-picrylhydrazyl (DPPH) radical, at a dose of 0.5 mg, range
d from 35% to 75.4%. The condensed tannins of evening primrose exhibited a
significantly (P<0.01) greater scavenging effect far DPPH radical than othe
r tannin extracts. The reducing power of beach pea and evening primrose tan
nin extracts on potassium ferricyanide was greater than that of other tanni
n extracts examined.