Glucosinolates Profile and Antioxidant Capacity of Romanian Brassica Vegetables Obtained by Organic and Conventional Agricultural Practices

Abstract

The profile of glucosinolates in relation to the antioxidant capacity of five Brassica vegetables (Broccoli, Cauliflower, Kohlrabi, White and Red Cabbage) grown by organic and conventional agricultural practices in Transylvania region-Romania, were determined and compared. The qualitative and quantitative compositions of glucosinolates were determined by HPLC-PDA technique. The antioxidant capacity was comparatively determined by ABTS, DPPH, FRAP and Folin-Ciocalteu assays. The highest glucosinolates levels were found in the Broccoli samples grown under conventional practices (14.24 μmol/g dry weight), glucoraphanin, glucobrassicin and neo-glucobrassicin being the major components. The total glucosinolates content was similar in Kohlrabi and Cauliflower (4.89 and 4.84 μmol/g dry weight, respectively), the indolyl glucosinolates were predominant in Kohlrabi, while the aliphatic derivatives (sinigrin and glucoiberin) were major in Cauliflower. In Cabbage samples, the aliphatic glucosinolates were predominat against indolyl derivatives, glucoraphanin and glucoiberin being the main ones in Red Cabbage. The principal component analysis was applied to discriminate among conventional and organic samples and demonstrated non-overlaps between these two agricultural practices. Meanwhile it was shown that glucosinolates may represent appropriate molecular markers of Brassica vegetables, their antioxidant capacity being higher in organic crops, without significant differences among different Brassica varieties.