Effects on the Cytochrome P450 Enzyme System
In vivo tests performed using human test subjects taking 1000 mg curcumin once daily for 14 continuous days showed that curcumin inhibited the cytochrome P450 enzyme CYP1A2 by 28.6% and induced CYP2A6 by 48.9%. [4]
Curcumin was found to inhibit CYP3A4 in the small intestine but induce it in the liver and kidneys in rats in vivo.[3]
Curcuminoids were found to inhibit human CYP2C19, CYP2B6, and CYP3A4 in vitro with IC50 values ranging from 0.99 +/- 0.04 to 25.3 +/- 1.3 microM. CYP2D6, CYP1A2, and CYP2E1 activities were less affected (IC50 values > 60 microM).[2]
Rats fed a diet of 1% turmeric showed inhibition of CYP1A1, CYP1A2 and CYP2B1.[1]
Effects on Other Enzymes and Biological Compounds
Curcuminoids were found to inhibit human UGT and SULT in vitro.[2]
Curcumin was found to inhibit intestinal P-glycoprotein (P-gp) and induce hepatic P-glycoprotein in rats in vivo.[3]
In one study curcumin was found to inhibit glutathione S-transferase (GST) by 96% and reduce levels of glutathione by 50% in vitro.[5]