(±)-α-CMBHC

Vitamin E is a well known antioxidant that exists in eight natural forms: four tocopherols (α, β, δ, and γ) and four tocotrienols (α, β, δ, and γ). α-Tocopherol is the major lipid soluble antioxidant in vivo and protects against lipid peroxidation. α-CEHC is the major urinary metabolite of α-tocopherol following vitamin E supplementation. α-CMBHC is the longer side-chain precursor of α-CEHC and a minor metabolite of α-tocopherol. HepG2 cells release α-CEHC, α-CMBHC, and α-CMHHC into the medium when treated with all rac α-tocopherol. Pretreatment of Hep-G2 cells with rifampicin, an inducer of the CYP3A family of cytochrome P450s, results in a 5-fold increase in α-CEHC. This indicates that metabolism of α-tocopherol proceeds by initial ω-oxidation to precursors of α-CMBHC followed by β-oxidation to shorter chain metabolites such as α-CEHC.