The chemical background of the
biological activities of vegetables of the Cruciferae family is considered. These vegetables contain
alkaloids of the
glucobrassicin group that are decomposed by the
enzyme myrosinase (
thioglucosidase, EC 3.2.3.1) released upon damage to the plant cells. This results in several
indole derivatives, with
ascorbigen and
indole-3-carbinol predominating. In the gastrointestinal tract, these compounds form 5H,11H-indolo[3,2-b]
carbazole, natural
ligand of the
aromatic hydrocarbon receptor (Ah receptor) and a functional analogue of
2,3,7,8-tetrachlorodibenzo-p-dioxin, a dangerous
xenobiotic. The indolocarbazole-
Ah receptor complex activates the gene of
CYP1A1, an
isoenzyme of
cytochrome P450-dependent
monoamine oxidase, which enhances the 2-hydroxylation (inactivation) of
estrogens. In its turn, the resulting lowered level of
estrogens inhibits the growth of
hormone-dependent
tumors or prevents their appearance. The mechanism of
xenobiotic inactivation, underlying the anticarcinogenic action of food products including vegetables of Cruciferae family and some homogeneous
indole compounds, is similar. Some other effects of nutrient
indole compounds, e.g., the inhibition of expression of the
cyclin-dependent kinase 6 (CDK6) by
indole-3-carbinol that leads to the cell cycle arrest in G1 phase, are also considered. Analysis of the
biological effects of the Cruciferae diet has helped start clinical studies of
indole-3-carbinol as an antitumor and anticarcinogenic remedy for patients with a high risk of
tumor diseases.