Glucosinolates redox activities: can they act as antioxidants?

Glucosinolates are a class of secondary plant metabolites particularly occurring in Cruciferae with potential health-promoting properties, as their hydrolysis products, isothiocyanates, possess chemopreventive and antioxidant activities. In the present study, we systematically studied the in vitro redox behaviour of 15 glucosinolates, by using a range of analytical methods measuring different activities: (i) radical scavenging activity toward peroxyl and toward ABTS radical (chain-breaking activity); (ii) capacity in modulating the in vitro resistance of human low-density lipoprotein (LDL) catalysed by copper (chelating and chain-breaking activity). Data obtained from different assays were compared and analysed by principal component analysis (PCA). PCA allowed us to identify a big cluster of glucosinolates (10 out 15 tested) that do not possess any antioxidant capacity; while, the other five glucosinolates showed moderate and specific antioxidant capacity. Notably, sinalbin and gluconasturtiin were highly active in scavenging ABTS radical and in protecting LDL from copper-catalysed oxidation, respectively. The overall results of this study indicate that just few glucosinolates can act as antioxidants.