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