A xenobiotic (Greek, xenos "foreign"; bios "life") is a compound that is foreign to a living organism. Principal xenobiotics include: drugs, carcinogens and various compounds that have been introduced into the environment by artificial means.
Any EC 1.1.1.* (oxidoreductase acting on donor CH-OH group, NAD+ or NADP+ acceptor) inhibitor that inhibits HMG-CoA reductases. Hydroxymethylglutaryl-CoA reductase inhibitors have been shown to lower directly cholesterol synthesis. The Enzyme Commission designation is EC 22.214.171.124 for the NADPH-dependent enzyme and EC 126.96.36.199 for an NADH-dependent enzyme.