Open AccessStereospecific reduction of the original anticancer drug oracin in rat extrahepatic tissues
Author(s) -
Szotáková Barbora,
Skálová Lenka,
Jílek Petr,
Buchta Vladimír,
Wsól Vladimír
Publication year - 2003
Publication title -
journal of pharmacy and pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.745
H-Index - 118
eISSN - 2042-7158
pISSN - 0022-3573
DOI - 10.1211/0022357021260
Subject(s) - stereospecificity , microsome , caecum , chemistry , biotransformation , enantiomer , small intestine , large intestine , drug metabolism , biochemistry , cytosol , lumen (anatomy) , metabolism , biology , stereochemistry , enzyme , medicine , catalysis , microbiology and biotechnology
ABSTRACT The liver is the major site of drug metabolism in the body. However, many drugs undergo metabolism in extrahepatic sites and in the gut wall and lumen. In this study, the distribution and activity of reductases in rat that reduced potential cytostatic oracin to its principal metabolite 11‐dihydrooracin (DHO) were investigated. The extension and stereospecificity of oracin reduction to DHO were tested in microsomal and cytosolic fractions from the liver, kidney, heart, lung and wall of small intestine, caecum and large intestine. Intestinal bacterial reduction of oracin was studied as well. The amount of DHO enantiomers was measured by HPLC with Chiralcel OD‐R as chiral column. Reductive biotransformation of oracin was mostly stereospecific for (+)‐DHO, but the enantiomeric ratio differed significantly among individual tissues and subcellular fractions (from 56% (+)‐DHO in heart microsomes to 92% (+)‐DHO in liver cytosol). Stereospecificity for (‐)‐DHO (60%) was observed in bacterial oracin reduction in the lumen of small intestine, caecum and large intestine. Shift of the (+)‐DHO/(‐)‐DHO enantiomeric ratio from 90:10 (in liver subcellular fractions) to 60:40 (in‐vivo) clearly demonstrated the importance of the contribution of extrahepatic metabolism to the total biotransformation of oracin to DHO.