A microsomal fraction was
obtained from rat liver as indicated in . One part of microsome
(5 mg/mL) treated with 100 mM of dithiothreitol (DTT) at 30 C for
30 min and ultracentrifuge at 100,000 g at 4 C twice to remove the
dithiothreitol (DTT). It will reduce disulfide bond to thiol groups.
GST activity was probed for unmodified and DTT-modified lots of
microsomes, by a standard assay involving the conjugation of
glutathione to chloro-dinitro benzene (CDNB). CDNB is a substrate
of choice because the conjugation product can be monitored spectrophotometrically
at 340 nm. GST activity was measured using
the modified method of Habig et al. [24]. It was checked that the
phenolic compounds used in the study did not interfere with the
assay.