The possible effect of the different extracts on the activity of two detoxifying enzymes, NAD(P)H:quinone oxidoreductase (QR) and glutathione S-transferase (GST), was tested by exposing HT29 human colonic adenocarcinoma cells to non-toxic doses (0.01 μg mL−1) of the extracts for 48 h of treatment (Figure 2). Here, NQO1 is linked to colon adenocarcinoma.