This document discusses metabolism of xenobiotics, or foreign compounds in the body. It defines xenobiotics as exogenous compounds from foods/drugs or endogenous compounds produced in the body. Xenobiotic metabolism occurs in two phases - phase 1 involves reactions like hydroxylation and phase 2 involves conjugating compounds with substances like glucuronic acid to make them more polar and excretable. The liver is the main organ that contains enzymes to process xenobiotics through these two phases and detoxify potentially harmful compounds. Factors like diet, drugs, and disease can influence an individual's biotransformation of xenobiotics.

1. Metabolism of Xenobiotics
Dr Rupali Sengupta
Coordinator-MScCND
Dr BMN College of Home Science
Affiliated to SNDT women’s University
338 R.A.Kidwai Road Matunga

2. Xenobiotics
• A xenobiotic (Gk xenos "stranger") is a
compound that is foreign to the body.
• Types of Xenobiotics:
• Exogenous & Endogenous

3. Types of Xenobiotics
• Exogenous- The foreign molecules which gain
entry through dietary food stuffs, or in the
form of certain medicines/ drugs used for a
therapeutic cause or are inhaled through
environment .
• Examples: Drugs, food additives, pollutants,
insecticides,etc

4. • Endogenous
These are synthesized in the body or are
produced as metabolites of various processes in
the body.
Examples-Bilirubin, Bile acids, Steroids,
Eicosanoids and certain fatty acids.

5. Metabolism of Xenobiotics
• Metabolism of xenobiotics occurs in two phases-
• Phase 1, the major reaction involved is hydroxylation. In addition to
hydroxylation, a wide range of reactions also take place including-
 Deamination,
 Dehalogenation,
 Desulfuration,
 Epoxidation,
 Peroxygenation,
 Reduction

6. • Phase 2, the hydroxylated or other compounds produced in
phase 1 are converted by specific enzymes to various polar
metabolites by conjugation with-
 Glucuronic acid,
 Sulfate, acetate,
 Glutathione, or
 Certain amino acids,
 By methylation.

7. Detoxification Reactions
 All the biochemical reactions involved in the
conversion of foreign, toxic and water insoluble
molecules to non toxic, water soluble and excretable
forms are called Detoxification / Biotransformation
reactions
 The overall purpose of the two phases of metabolism of
xenobiotics is to increase their water solubility
(polarity) and thus excretion from the body.

8. • Significance
– Converts lipophilic to hydrophilic compounds
– Facilitates excretion
• Consequences
– Changes in solubility characteristics
– Detoxification
– Metabolic activation

9. Function of Liver
 Main organ involved-Liver
 Hepatocytes contain wide variety of enzymes to
process xenobiotics
 Enzymes are present in cytosol, endoplasmic reticulum
and to lesser extent in other organelles
 Each enzyme represents a large family of gene product

10. Phase 1 reactions can also convert xenobiotics from inactive to
biologically active compounds.
Phase 2/conjugation reactions can convert the active products of phase 1
reactions to less active or inactive species, which are subsequently excreted in
the urine or bile.

11. Factors affecting Biotransformation of drugs
 Prior administration of the drug or Co administration of other drugs
 Diet
 Hormonal status
 Genetics
 Disease (e.g., decreased in cardiac and pulmonary disease)
 Age and developmental status
 Functional status of Liver and Kidney

12. Effects of Xenobiotics

13. References
• Review of Biochemistry .Harold A.Harper.30th
Edition.ISBN 9780870410376.
• Biochemistry . Dawn B.Marks. ISBN 978068305979.
• www.pubmed.com