Triples with object Enzyme system: human liver microsomes NADPH added: assumed based on the date of the article and authors substrate used: coumarin reaction: coumarin 7-hydroxylation Quote: No inhibition was found in microsomal preparations made from human livers with adequate CYP2D6 activity or with expressed CYP2D or with adequate activity of CYPs 1A2, 2A6, 2C9, 2E1, and 3A4.