The determination of low-molecular-weight aminothiol
based biological molecules, such as cysteine (Cys) and glutathione
(GSH) (Scheme 1), in human plasma are becoming increasingly
important, due to exploration of their crucial role in
many biological pathways. Cysteine is sulfur containing nonessential
amino acids, which is critical to the metabolism of a
number of essential biochemicals, including coenzyme A, heparin,
biotin, and glutathione. The tripeptide glutathione (GSH),
a master antioxidant which is supplied by the cysteine, is the
main intracellular defence against oxidative stress, in addition
to regulating the action of antioxidants, such as vitamins C
and E, in the body