DETOXIFICATION
DR ROHINI C SANE
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.
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.
• MethanolFormaldehyde
CLASSIFICATION OF TOXIC SUBSTANCES
CLASSIFICATION OF TOXIC SUBSTANCES
(A)ENDOGENOUS
(B)EXOGENOUS
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
DETOXIFICATION OF EXOGENOUS TOXIC SUBSTANCES
(B)EXOGENOUS –
DRUGS ,DYES,POLLUTANTS ,ADDITIVES,COSMETICS ,PESTICIDES
LIVER (ENZYME MACHINERY)
UNWANTED COMPOUNDS
EXCRETION OF ENDOGENOUS XENOBIOTICS IN TOXIC FORMS
1. TryptophanIndol
2. Lysine Cadaverine
3. TYROSINE Tyramine
4. Phenylalanine Phenol
5. Hemoglobin Bilirubin
METABOLISM OF XENOBIOTICS (DETOXIFICATION)
XENOBIOTICS (XENOS = STRANGE /FOREIGN)
Metabolism of foreign compounds decreased permeability into cell increased excretion.
• Site of detoxificationLiver
• Excretionkidney/ 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)
DETOXIFICATION BY OXIDATION
I ALCOHOLACIDS
(1) Methanol Formic acid (CH3OHHCOOH)
(2) Ethanol Acetic acid (C2H5OHCH3COOH )
(3) Benzyl alcoholBenzoic acid (C6H5CH2OHC6H5COOH)
II ALDEHYDESACIDS
(1) Benz aldehyde Benzoic acids
(2) ChloralTrichloro acetic acids
DETOXIFICATION BY OXIDATION
III AMINES & THEIR DERIVATIVES
(1) Aliphatic amines Aliphatic acids +Urea
(RCH2NH2) RCOOH+ NH2CONH2
(2) Aniline P- Amino Phenol
C6H5NH2 OH –C6H5NH2
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)
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)
Characteristics of 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 )
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
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
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)
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 Glucoronideformation
DRUGS :Morphine /Dapsone / Chloramphenicol/ Indomethacin
detoxified by conjugation with Glucoronic acid
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
DETOXIFICATION BY CONGUGATION III CYSTEIN FROM GLUTATHIONE
DETOXIFICATION BY CONJUGATION
IV- GLUTAMINE
Phenyl Acetic acid + Glutamine Phenyl Glutamine
V- METHYL GROUP OF S –Adenosyl Methionine
XOH+ S-Adenosyl MethionineXO-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 )
DETOXIFICATION BY CONJUGATION
Sulphate3 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
DETOXIFICATION BY CONJUGATION
VII THIO SULPHATES
Cyanide (toxic) + Sodium ThiosuphateThiocynates* + 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
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
GlutamineCysteine
Acetyl GlutamineMercapturic acid
DERIVATIVES OF AMINOACIDS
Glutathione Mercapturic acid
Acetyl COA Acetylated derivatives of SULPHA DRUGS/INH
AROMATIC AMINES/STEROIDS/ETHERS
PAPPS Sulphate estersPhenol /Cresol / Skatole
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