Polyphenolic composition and antioxidant capacity of Japanese and American walnuts in vitro
2015
Toida, E. (Nagano Prefectural College, Nagano, Nagano (Japan). Department of Living Sciences) | Tajima, M.
The proximate composition (%) of Japanese walnut (Shinano) was determined to be as follows : crude protein, 13.6; crude fat, 67.5; carbohydrate, 14.3; ash, 1.7; and moisture, 2.9. 1-1-diphenyl-2-picrylhydrazyl radical scavenging activity was 186.2 and 144.8 micro mol of Trolox equivalent per gram dry weight in Japanese and American walnuts, respectively, indicating that Japanese walnuts exhibit slightly stronger antioxidant capacity than American walnuts. The total polyphenol content was 2 202.3 and 1 855.0 mg of gallic acid equivalent per 100g dry weight in Japanese and American walnuts, respectively, indicating that Japanese walnuts have a slightly higher polyphenol content than American walnuts. The principal ellagitannin compounds were 445.7 and 473.5 mg of ellagic acid equivalent 100 gram dry weight in Japanese and American walnuts, respectively, indicating that American walnuts have slightly higher ellagitannin content than Japanese walnuts. The results presented above indicate that polyphenolic compounds contribute to the antioxidant capacity. The data also suggest that the antioxidants in walnuts include both identified ellagitannins and unidentified polyphenolic compounds. The study also demonstrates differences in polyphenolic composition between Japanese and American walnuts, which reflect antioxidant capacity. These observations are likely related to differences between the two countries in cultivation region and horticultural practices, as well as genetic factors and post-harvest processing.
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