Antioxidant activity of crude tannins of canola and rapeseed hulls |
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Authors: | R Amarowicz M Naczk F Shahidi |
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Affiliation: | (1) Department of Biochemistry, Memorial University of Newfoundland, A1B 3X9 St. John's, Newfoundland, Canada;(2) Department of Human Nutrition, St. Francis Xavier University, P.O. Box 5000, B2G 2W5 Antigonish, Nova Scotia, Canada;(3) Present address: Division of Food Science, Institute of Animal Reproduction and Food Research of Polish Academy of Sciences, Olsztyn, Poland |
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Abstract: | The antioxidant activity of crude tannins of canola and rapeseed hulls was evaluated by β-carotene-linoleate, α,α-diphenyl-β-picrylhydrazyl
(DPPH) radical, and reducing power assays. Crude tannins were extracted from three samples of Cyclone canola (high-tannin)
hulls and Kolner, Ligaret, and Leo Polish rapeseed (low-tannin) hulls with 70% (vol/vol) acetone. The total phenolic content
in crude tannin extracts ranged between 128 and 296 mg of sinapic acid equivalents per 1 g of extract. The ultraviolet spectra
of methanolic solution of canola extracts showed two absorption maxima (282 and 309 nm), whereas those of rapeseed extracts
exhibited a single maximum (326 nm). Crude tannins isolated from canola hulls exerted significantly (P<0.025) greater antioxidant activity than those from rapeseed in all three assays. The scavenging effect of all crude tannins,
at a dose of 1 mg, on the DPPH radical ranged from 35.2 to 50.5%. The reducing power of Cyclone canola hull extracts on potassium
ferricyanide was significantly (P≤0.0025) greater than that of rapeseed hull extracts, and the observed data correlated well (r=0.966; P=0.002) with the total content of phenolics present. |
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Keywords: | Antioxidative properties canola condensed tannins hulls rapeseed reducing power scavenging effects |
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