Extracts were prepared according to the literature procedure
described by Demirkol et al. (2004). Ginger (0.1 g/ml) and tomatoes
(0.5 g/ml) were placed in a serineborate buffer solution
(100 mM Tris–HCl, 10 mM borate, 5 mM serine, and 1 mM diethylenetriaminepentaacetic
acid, pH 7.0) to prevent artifactual oxidation.
The samples were homogenised with a tissue tearor
(Wiggen Hauser, model D-130 handheld disperser) on ice for
2 min, with 5 s intervals of homogenisation, and then centrifuged
at 2000g for 15 min; supernatants were used for the thiol content.