Glucosinolates, Degradation Products and Myrosinase Activity in Raphanus sativus Linn.

This research was conducted to assess the gluocosinolate (GSL), isothiocyanate (ITC) and myrosinase content in two cultivars of Raphanus sativus Linn. (white and red) roots. LC-ESIMS investigation was done on desulfated GSLs since this methodology has been previously established for efficient GSL analyses. The major GSLs: sinigrin (1) 1,2-dihydroxy-2-phenylethyl glucosinolate (2), 4-hydroxyglucobrassicin (3), glucoraphasatin (4) and 4-methoxyglucobrassicin (5) were found in red radishes; whereas, only 1 and 4 were obtained in white radishes. Myrosinase was analyzed in the tubers due to its ability to catalyze and hydrolyze GSLs into ITCs. This β-thioglucosidase enzyme was found to be over 10 times more active in red tubers (2.05E-02 units) than in white radishes (1.55E-03 units) and the results were linked to the presence/absence of the outer covering of the tubers. Due to the promising medicinal properties of the aglucone derivative of compound 4, 4-methylthio-3-butenyl isothiocyanate (6), the ITC analog was monitored using gas chromatographic mass spectral analyses after myrosinase-mediated hydrolysis. From the results, it can be construed that the occurrence of GSLs 1-5 and the bioactive agent 6 were inherent in the R. sativus cultivars evaluated.