Glucosinolate Profiles in Cabbage (Brassica oleracea var. capitata) Cultivars and Their Effect on the Induction of a Phase II Detoxification Enzyme

Abstract

This study presents a profile of glucosinolate (GSL) levels in the edible portions of 31 cultivars of cabbage cultivated in Japan, and compares potential bioactivity levels on the basis of their ability to induce quinone reductase (QR), a phase II detoxification enzyme. Cabbage (Brassica oleracea var. capitata) seeds were sown in early March 2005 (summer-harvest) and early August 2005 (winter-harvest) and grown under uniform culture conditions. Total GSL concentration varied from 1.07 to 12.14 (mean 5.73) μmol·gDW⁻¹ in the summer-harvest, and from 3.42 to 10.26 (mean 6.16) μmol·gDW⁻¹ in the winter-harvest. The most predominant GSL was 3-indolylmethyl glucosinolate, 2-propenyl glucosinolate or 2-hydroxy-3-butenyl glucosinolate, depending on the cultivar. The values of relative QR activity were positively correlated only with 4-methylsulfinylbutyl glucosinolate (glucoraphanin, GR) content in both the summer-harvest (r = 0.51) and winter-harvest (r = 0.77). GR concentration ranged from 0.04 to 1.70 (mean 0.43) μmol·gDW⁻¹ in the summer-harvest, and from 0.11 to 1.39 (mean 0.44) μmol·gDW⁻¹ in the winter-harvest. There was no significant correlation between GR content and total GSL in either the summer-harvest (r = 0.31) or winter-harvest (r = 0.24). Among the same cultivars, there was a significant positive correlation between GR content in the summer-harvest and that in the winter-harvest (r = 0.63). These results suggest that the inducing activity of QR increased with GR content independent of total GSL, and that there are some inherent differences between cabbage cultivars in the intensity of this activity.