Differential Metabolic Stability of 4α,25- and 4β,25-Dihydroxyvitamin D3 and Identification of Their Metabolites

Vitamin D3 (1) is metabolized by various cytochrome P450 (CYP) enzymes, resulting in the formation of diverse metabolites. Among them, 4α,25-dihydroxyvitamin (6a) and 4β,25-dihydroxyvitamin (6b) are both produced from 25-hydroxyvitamin (2) CYP3A4. However, 6b detectable serum, whereas 6a not. We hypothesized that reason for this a difference susceptibility to CYP24A1-mediated metabolism. Here, we synthesized 6b, confirmed has greater metabolic stability than 6a. also identified 4α,24R,25- 4β,24R,25-trihydroxyvitamin (16a 16b) as metabolites respectively, HPLC comparison with authentic samples. Docking studies suggest β-hydroxy group at C4 contributes blocking crucial hydrogen-bonding interaction between C25 hydroxy Leu325 CYP24A1.