TY - JOUR T1 - The metabolism of avermectins B1a, H2B1a, and H2B1b by liver microsomes. JF - Drug Metabolism and Disposition JO - Drug Metab Dispos SP - 268 LP - 274 VL - 10 IS - 3 AU - G T Miwa AU - J S Walsh AU - W J VandenHeuvel AU - B Arison AU - E Sestokas AU - R Buhs AU - A Rosegay AU - S Avermitilis AU - A Y Lu AU - M A Walsh AU - R W Walker AU - R Taub AU - T A Jacob Y1 - 1982/05/01 UR - http://dmd.aspetjournals.org/content/10/3/268.abstract N2 - The avermectins area a new class of structurally related antiparasitic agents isolated from Streptomyces avermitilis. The major polar metabolites isolated from in vitro incubations of [3H]avermectins B1a, H2B1a, and H2B1b with either rat or steer liver microsomes have been isolated and identified as the C24-methyl alcohols of the parent compounds. A smaller quantity of a more polar metabolite has also been identified as the monosaccharide of the C24-methyl alcohols of avermectin H2H1b from rat liver microsomal incubation and avermectin H2B1a from steer liver microsomal incubation. The mass spectra and 300-MHz 1H-NMR spectra permitted assignment of structures to these metabolites. Together these two metabolites represent 50-80% of the total radioactivity more polar than the parent compounds. The metabolite profiles on reverse-phase HPLC demonstrate that the rat and steer are qualitatively similar in the production of these two polar metabolites. ER -