%0 Journal Article %A G T Miwa %A J S Walsh %A W J VandenHeuvel %A B Arison %A E Sestokas %A R Buhs %A A Rosegay %A S Avermitilis %A A Y Lu %A M A Walsh %A R W Walker %A R Taub %A T A Jacob %T The metabolism of avermectins B1a, H2B1a, and H2B1b by liver microsomes. %D 1982 %J Drug Metabolism and Disposition %P 268-274 %V 10 %N 3 %X 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. %U https://dmd.aspetjournals.org/content/dmd/10/3/268.full.pdf