Extraction and Characterization of Glucosinolates and Isothiocyanates from Rape Seed Meal

Abstract

While some isothiocyanate (ITCs) are attractive targets for the agricultural and pharmaceutical industries, the presence of goitrin and ITCs has hampered the widespread utilization of rapeseed meal. ITCs are the products of the myrosinase-mediated hydrolysis of glucosinolate (GSLs). As such, a study was conducted in order to gain a better understanding into the identity of the GSLs contained in rapeseed meal. Extraction of the GSLs was carried out with 20% ethanol, affording 3.0% GSL content. The resulting GSL extracts were purified via silica gel column chromatography resulting in the isolation of main three pure GLSs (GSL A, B, and C) and a final GSL content of 39.8%. The indirect-identification of the GSLs in rapeseed meal was also carried out via GC/MS analysis of ITCs. The GSLs, progoitrin and gluconapin, were present in the highest concentration in these extracts. Interestingly, only goitrin was produced when GSL A was the substrate for the defatted rapeseed meal mediated hydrolysis reaction. This indicates GSL A is a progoitrin. Conversely, 3-butenyl ITC was produced only when GSL B was used as substrate, indicating GSL B is gluconapin. These results will be helpful for opening the doors for the use of rapeseed meal in the agricultural or pharmaceutical sectors.