Biologically important thiols in aqueous extracts of spices and evaluation of their in vitro antioxidant properties

The levels of the biologically important thiols in aqueous extracts of different spices were determined using a sensitive high performance liquid chromatography (HPLC) technique. The spices analysed: turmeric, ginger, cardamom, mustard, fenugreek, and coriander showed different levels of thiols. Biologically important thiols or biothiols measured in these spices included glutathione (GSH), cysteine (CYS), N-acetylcysteine (NAC), homocysteine (HCYS), and γ-glutamyl cysteine (GGC). Our results showed that thiol levels varied from 4 to 1089 nM/g weight (dry or wet). Furthermore, none of the biothiols analysed were found in cumin, nutmeg, clove or star anise. We also studied the antioxidant abilities of these aqueous extracts using various in vitro antioxidant methods to correlate between the levels of these thiols and their antioxidant effects. Our results suggested that antioxidant activities may be independent of thiol content and may be, in part the combination of all the phytochemicals present. These results may be useful in explaining the effect of spices on thiol levels in in vitro and in vivo studies.