phase I reaction

of biotransformation
https://doi.org/10.1351/goldbook.PT06836
Enzymic modification of a substance by @O04362@, reduction, @H02902@, @H02876@, dehydrochlorination, or other reactions catalyzed by @E02159@ of the cytosol, of the endoplasmic reticulum (microsomal @E02159@) or of other cell @O04324@.
Source:
PAC, 2004, 76, 1033. (Glossary of terms used in toxicokinetics (IUPAC Recommendations 2003)) on page 1064 [Terms] [Paper]