Molecule

Description

Metabolic Disease

Description

Alizarin strongly inhibits P450 isoform CYP1A1, CYP1A2 and CYP1B1 with IC50 of 6.2 μM, 10.0 μM and 2.7 μM, respectively.

Targets

IC₅₀

In Vitro

Alizarin weakly inhibits CYP2A6 and CYP2E1. Alizarin shows competitive inhibition against CYP1B1 with K_i of 0.5 μM. Alizarin deduces the mutagenicity of MeIQx, which induced by each CYP1A2 or CYP1B1, while does not effectively reduce the mutation induced by B[a]P. ^[1] Alizarin exhibits antioxidants against iodophenol-derived phenoxyl radicals, superoxide anion radicals and lipid peroxidation in rat liver microsomes. ^[2]

In Vivo

Alizarin also reduces the hepatic content of thiobarbituric acid-reactive substances and the serum level of alanine aminotransferase in poisoned animals. ^[2]

Clinical Trials

Features

Measurement of enzyme activities of CYPs

Enzyme activities are measured by fluorometric quantification of each metabolite produced by O-deethylation of 7-ethoxycoumarin by CYP1A1 and CYP1B1, O-deethylation of 7-ethoxyresorufin by CYP1A2 and 7-hydroxylation of coumarin by CYP2A6, using Hitachi F-2000 fluorescence spectrophotometer. The fluorescence of metabolite is not influenced by the presence of anthraquinone pigments at the doses tested in these experiments. 7-Ethoxycoumarin is used at 40 μM for CYP1A1 and at 20 μM for CYP1B1. In the cases of CYP2C19, CYP2E1, CYP3A4 and CYP3A5, the amount of each metabolite derived from the catalytic reaction by individual CYPs is determined by HPLC equipped with a UV detector. The activities of CYP2C19 and CYP2E1 are determined by 4′-hydroxylation of (S)-mephenytoin and by 6-hydroxylation of chlorzoxazone, respectively. In the case of CYP3As, their activities are determined by 1′-hydroxylation of midazolam with a modification in which the metabolites are extracted from the incubation mixture before injection to HPLC. Briefly, 1 μM diazepam is added to the reaction mixture as an internal standard with an excess amount of ammonium sulfate and 5 volumes of ethyl acetate immediately after the incubation. After shaking for 10 min, 1′-hydroxymidazolam and diazepam are extracted into the ethyl acetate layer by centrifugation at 2000×g for 10 min, at 4 °C. Then ethyl acetate is removed by evaporation and the residue is used for HPLC after dissolving in methanol. A volume of 20 μM of midazolam is used for the detection of CYP3A4 activity and 7 μM for CYP3A5. To evaluate the K_m value of CYP1B1, the measurement of activity is carried out at substrate doses from 2.5 to 40 μM. K_i value of Alizarin against the activity of CYP1B1 is calculated from the enzyme activities in the presence of 0.2-1.6 μM Alizarin.