Postharvest variation of major glucosinolate and their hydrolytic products in Brassicoraphanus ‘BB1’

Abstract

Brassicoraphanus ‘BB1’ is an inter-generic hybrid vegetable between Chinese cabbage (Brassica rapa L. ‘Bulam 3’) and radish (Raphanus sativus L. ‘Taebaek’), maintaining high glucosinolates during their development. Postharvest changes in glucosinolate content and their corresponding hydrolytic products were determined between root and leaf tissues of Brassicoraphanus ‘BB1’ during storage at 2 °C. Among the glucosinolates, glucoraphasatin was the major glucosinolate (34–45% and 49–59% of total glucosinolates content in leaves and roots, respectively). Total glucosinolates content was higher in root (13,439 to 16,233 μmol kg−1 dry matter) than in leaf (3,506 to 6,146 μmol kg−1 dry matter) tissues during storage. Total glucosinolates content in leaves of Brassicoraphanus ‘BB1’ decreased approximately 40% in 3 d of storage; however, it regained up to 85% of the initial value after storage for 28 d. Glucosinolates content in root tissue decreased steadily during the eight weeks of storage. Sulforaphene and raphasatin were the most abundant isothiocyanates in leaves, whereas the main isothiocyanates in roots were raphasatin and 2-phenethyl isothiocyanate. Total isothiocyanates content in the leaves increased, but little change was exhibited in the roots during storage. Total isothiocyanates content was highly correlated with total glucosinolates content (r = 0.976, n = 10, P < 0.01) in leaf and root tissues combined, but not in those tissues separately. Nitriles and epithionitriles were not detected from glucosinolate hydrolysis in Brassicoraphanus ‘BB1’. These results indicated that glucosinolates in Brassicoraphanus ‘BB1′ are exclusively converted to isothiocyanates with little activity of epithiospecifier protein. This study is the first to provide basic information on glucosinolates and their hydrolytic products in Brassicoraphanus ‘BB1’.