Determination of NAC, GSH, CYS, HCYS, and GGC by the HPLC
method
An HPLC method for determining thiols was developed in this
laboratory by analysing c-glutamyl cycle intermediates (Winters,
Zukowski, Ercal, Matthews & Spitz; 1995). All spices (0.1 g each)
were placed in a 1 mL of serine borate buffer and homogenised
on ice for 2 min. Ginger samples were prepared as described above.
The slurry was centrifuged at 5000g for 1 min at 4 C and supernatant
(250 lL) was derivatized with 750 lL of NPM (1 mM in acetonitrile).
This compound reacts with the free sulfhydryl groups to
form fluorescent derivatives. The resulting solution was mixed
and incubated at room temperature for 5 min. Ten micro litres of
2 N HCl were added to stop the reaction. After filtration through
a 0.2 lm acrodisc, the derivatized samples were injected onto a
5 lm C18 column in a reverse phase HPLC system. NAC, GGC,
CYS, and HCYS were determined concurrently with GSH since they
also form fluorescent derivatives with NPM.