comprehensive presentation on Detoxification of xenobiotics in human body.This presentation is designed for undergraduate medical ,dental ,biotechnology & pharmacology students for self study.Presentation has Definition of detoxification , classification of toxic substances .Detoxification of endogenous & exogenous toxic substances along with molecular mechanism involved is presented here.Metabolism of xenobiotic (detoxification) by oxidation. reduction , hydrolysis& conjugation is illustrated with suitable examples.Characteristics of cytochrome P450& its mode of action are described.Google images are used to support the text for better understanding.

1. DETOXIFICATION
DR ROHINI C SANE

2. DETOXIFICATION
DEFINATION OF DETOXIFICATION :
Reactions which convert certain substances into compounds which are more
water soluble &thus readily excreted from the body. (Toxic to less toxic)
• Toxicity may not be eliminated but reduced.
• Detoxification is also called drug metabolism or biotransformation.

3. DETOXIFICATION
Definition –series of biochemical reactions occurring in body to
convert foreign ( often toxic )compounds to nontoxic or less toxic
more easily excretable forms.
• Word DETOXIFICATION IS MISLEADING
• Detoxified products may be more toxic than original form but more
water soluble (polar) and easily excretable compounds.
• Methanol Formaldehyde

6. CLASSIFICATION OF TOXIC SUBSTANCES
CLASSIFICATION OF TOXIC SUBSTANCES
(A)ENDOGENOUS
(B)EXOGENOUS

7. DETOXIFICATION OF ENDOGENOUS TOXIC SUBSTANCES
(A)ENDOGENOUS –
Substances produced in large intestine from bacterial enzymatic action
INTESTINAL PUTREFACTION
Unabsorbed food
bacteria
Altered unabsorbed food
Easily execrable form

8. DETOXIFICATION OF EXOGENOUS TOXIC SUBSTANCES
(B)EXOGENOUS –
DRUGS ,DYES,POLLUTANTS ,ADDITIVES,COSMETICS ,PESTICIDES
LIVER (ENZYME MACHINERY)
UNWANTED COMPOUNDS

12. EXCRETION OF ENDOGENOUS XENOBIOTICS IN TOXIC FORMS
1. Tryptophan Indol
2. Lysine  Cadaverine
3. TYROSINE  Tyramine
4. Phenylalanine  Phenol
5. Hemoglobin  Bilirubin

14. METABOLISM OF XENOBIOTICS (DETOXIFICATION)
XENOBIOTICS (XENOS = STRANGE /FOREIGN)
Metabolism of foreign compounds decreased permeability into
cell increased excretion.
• Site of detoxification Liver
• Excretion kidney/ faeces /expired air
• PHASE I oxidation ,reduction, hydrolysis
• PHASE II  Conjugation( using Glucoronic Acid, Glycine, Glutathione
sulphate ,Acetates & Methyl group )
Oxidation Conjugation ( the most common mechanism)

17. DETOXIFICATION BY OXIDATION
I ALCOHOLACIDS
(1) Methanol  Formic acid (CH3OHHCOOH)
(2) Ethanol  Acetic acid (C2H5OH CH3COOH )
(3) Benzyl alcohol Benzoic acid (C6H5CH2OH C6H5COOH)
II ALDEHYDESACIDS
(1) Benz aldehyde  Benzoic acids
(2) Chloral Trichloro acetic acids

18. DETOXIFICATION BY OXIDATION
III AMINES & THEIR DERIVATIVES
(1) Aliphatic amines  Aliphatic acids +Urea
(RCH2NH2)  RCOOH+ NH2CONH2
(2) Aniline P- Amino Phenol
C6H5NH2 OH –C6H5NH2

19. DETOXIFICATION BY OXIDATION
IV AROMATIC HYDROCARBON
Benzene  Phenol+ Quinol+ Catechol+ Hydroxy Quinol
(Mono Hydroxy )+(P-di Hydroxy) + (O-di Hydroxy )+(1,2,4 Trihydroxy )
Toluene (C₆H₅CH₃)  Benzoic acid(C ₆ H ₅ COOH)(Oxidation)
V SULPHUR  H2SO4
VI Meprobamate(tranquilizers  OH-Meprobamate (excreted in urine)

20. DETOXIFICATION BY OXIDATION
 Role of Cytochrome P450 in detoxification by oxidation
Oxidation reactions catalyzed by Mono- oxygenase or Cytochrome P450
Site  Microsomal
Absorption peak = 45Onm—the enzyme exposed to CO
X-H +O₂ + NADPH + H⁺+ Cytochrome P450  X-OH + H₂0 + NADP⁺
( Xenobiotics) ( Hydroxylated Xenobiotics)

21. Characteristicsof Cytochrome P450
1. Exists in Multiple forms
2. Hemoprotein (Heme prosthetic group)
3. Present in Microsomes from liver ,adrenal gland mitochondria
4. Cofactor need is NADPH (for addition of OH-group)
5. Phospholipid ---Phosphotidyl Choline is a constituent of Cytochrome
P450—essential for action of this enzyme
6. Cytochrome P450 inducible enzyme (Phenobarbitone induces it)
7. Cytochrome P448 –absorption peak 448 nm
8. metabolism of polycyclic aromatic hydrocarbon (Aromatic Hydrocarbon
Hydroxylase )

22. MODE OF ACTION OF CYTOCHROME P450
NADPH+H+ NADPH CYTOCHROME P450 REDUCTASE REDUCED CYTOP450 O2+XH
(OXIDIZED)
NADP + NADPHCYTOCHROME P 450 REDUCTASE OXIDIZED CYTO P450 XOH
(REDUCED)
HYDROXYLATED XENOBIOTICS

23. DETOXIFICATION BY REDUCTION
(A) Picric acid  Picramic acid
C₆H₅OH(NO₂)₃  C ₆H₂OH(NO₂)₂NH ₂
(B)chloral  Trichloro ethanol
CCl₃CH(OH)  CCl₃CH₂OH
( C ) Nitro benene  Amino Benzene
C₆H₅NO₂  C₆H₅NH ₂

24. DETOXIFICATION BY HYDROLYSIS
(1) Aspirin (Acetyl Salicylic acids )  Salicylic acid + Acetic acid
(2) Acetanilide  Aniline + Acetic Acid
(3) Di isopropyl Fluorophosphate (DFP)  HF + Di -Alkyl phosphate
(Nerve gas  Serine Protease  Acetyl Choline Esterase inhibitor)
(4) Atropine  Tropic acid + Tropine
(5) Procaine (anesthetia) P- Amino Benzoic acid + Diethylamino Ethanol
(6) Digitalis  Sugar + (Aglycan)
(7) Detoxification of Arsenic ,Mercury, Cadmium ( Xeno biotics )
BAL (BRITISH ANTI LEWISITE) IIND WORLD WAR
BAL+ METAL EXCRETED IN URINE
Active enzyme with Cystein at active site + Heavy Metal Inactive Enzyme + BAL
(ANTIDOTE)

25. DETOXIFICATION BY CONJUGATION
• PHASE I : Oxidation / Reduction / Hydrolysis Of Xeno biotics
• PHASEII : Conjugation of Xeno biotics Excretion
• PHASE I –foreign substances + Substances in body Excretion
I Glucoronic acid UDP- Glucoronic acid (Active)
X-OH +UDP- Glucoronic acid---OX---Glucoronide +UDP
Barbiturates induce Glucoronyl transferase Increases Glucoronide
formation
DRUGS :Morphine /Dapsone / Chloramphenicol/ Indomethacin
detoxified by conjugation with Glucoronic acid

26. DETOXIFICATION BY CONJUGATION
I UDP- Glucoronic acid
1. Phenol + Glucoronic acid  Phenyl Glucoronide +UDP
2. Benzoic acid + Glucoronic acid  Benzoyl Glucuronide + UDP
3. Bilirubin + Glucoronic acid  Bilirubin Di-glucoronide
II Glycine
1. Benzoyl+ Glycine Hippuric acid  excreted in urine
2. Cholic acid + Glycine  Glycocholic acid
3. Deoxy Cholic acid + Glycine  Deoxy glycocholic acid
4. Phenyl Acetic acid + Glycine  Phenyl Aceturic acid

27. DETOXIFICATION BY CONGUGATION III CYSTEIN FROM GLUTATHIONE

29. DETOXIFICATION BY CONJUGATION
IV- GLUTAMINE
Phenyl Acetic acid + Glutamine Phenyl Glutamine
V- METHYL GROUP OF S –Adenosyl Methionine
XOH+ S-Adenosyl Methionine XO-CH₃ (Methylated Xenobiotics)+S-Adenosyl Homocysteine
Following hormones adopt this method for their detoxification in human body
Eg Thyroxine
Estrogen
Epinephrine (methylated )
Norepinephrine( no methyl group )

30. DETOXIFICATION BY CONJUGATION
Sulphate3 Phospho Adenosine  5- P- Sulphate
V PAPS (Phospho Adenosyl Phosphate)
PAPPS involved in sulphtation of aliphatic & aromatic compounds
Phenol  Phenyl Sulphate ( catalyzed by Sulpho transferase )
VI ACETIC ACID
Acetylation
X + Acetyl COA  Acetyl –X + CO-A-SH
Sulphanamide (₂HNC₆H₅SO₂NH₂-an antibiotic )  Acetyl Sulphnamide + CoA SH
Isoniazide (used for treatment of Tuberculosis ) Acetyl Sulphnilamide

31. DETOXIFICATION BY CONJUGATION
VII THIO SULPHATES
Cyanide (toxic) + Sodium Thiosuphate Thiocynates* + Na-sulphate
 Thiocynates* (less toxic ) =SCN
HCN + Na₂S ₂O₃  NaSCN +NaHSO₃ ( catalyzed by Thio transferase )
Cyanide poisoning  Meth-hemoglobin (treatment with Sodium Nitrite –
pulls Cyanide from Cytochrome oxidase –Nitroglycerine

32. DETOXIFICATION BY CONJUGATION
SOURCE CONJUGATING
MOLECULE
PRODUCT
CARBOHYDRATES Glucoronic acid Glucoronides of Bilirubin , Phenyl ,Benzyl
Glucose Glucoside
AMINO ACIDS Glycine Hippuric acid
Glycocholic acid
Deoxycholic acid
Glutamine
Cysteine
Acetyl Glutamine
Mercapturic acid
DERIVATIVES OF
AMINOACIDS
Glutathione Mercapturic acid
Acetyl COA Acetylated derivatives of SULPHA DRUGS/INH
AROMATIC
AMINES/STEROIDS/ETHERS
PAPPS Sulphate esters
Phenol /Cresol / Skatole

33. DETOXIFICATION BY CONJUGATION
SOURCE CONJUGATING
MOLECULE
PRODUCT
Thio sulphate NACNS(HCN)
BAL (BRITISH ANTI
LEVISITE )
Heavy metals
(Mercury/Arsenic/Lead )
Hormones (Estrogen
/Thyroxine/Epinephrine/Nor –
epinephrine)
SAM Methylated derivatives of Estrogen
/Thyroxine/epinephrine/Nor -
epinephrine
GGGG ABC ,STP