Synthesis and biological activities of 1α,4α,25- and 1α,4β,25-trihydroxyvitamin D3 and their metabolism by human CYP24A1 and UDP-glucuronosyltransferase

Abstract

A previous report has demonstrated the existence of a C4-hydroxylated vitamin D2 metabolite in serum of rats treated with pharmacological doses of vitamin D2. However, the biological significance and metabolic fate of this metabolite have not been described. To explore its potential biological activities, we therefore synthesized 1α,4 α,25-trihydroxyvitamin D3 and its diastereoisomer, 1α,4β,25-trihydroxyvitamin D3, using Trost Pd-mediated coupling reaction, and studied their vitamin D receptor (VDR) binding affinity, osteocalcin promoter transactivation activity, and their further metabolism by human CYP24A1 as well as by human liver microsomal fraction based on CYP- and UDP-glucuronosyltransferases (UGTs)-reactions. © 2012 The Pharmaceutical Society of Japan.