Enzyme-Triggered Chromogenic and Fluorogenic Probes for Myrosinase Activity Detection

Myrosinase, a thioglucosidase, is a key enzyme in the mechanism of defense of plants that hydrolyzes glucosinolates (GSLs) into isothiocyanates. These isothiocyanates are the main bioactive molecules exerting protective effect in Brassicales plants. These plants that contain this specific enzyme-substrate couple belong to our daily human diet and have demonstrated health benefits, such as chemopreventive effects. Thus, the detection of myrosinase activity is a key aspect of the production of isothiocyanates from glucosinolates. Two novel chromogenic and fluorogenic GSLs, GSL p-nitrophenoxy (GSL-pNP) and GSL-4-methylumbelliferone (GSL-4MU), were designed and synthesized to be used as simple and reliable molecular tools to spectrophotometrically detect myrosinase activity in simple and complex mixtures. Notably, the chromogenic GSL enabled the UV-vis detection and quantification of isolated myrosinase activity, while fluorogenic GSL could be used for in vitro activity monitoring of more complex plant materials, such as seeds.