Antimicrobial agents - Pharmaceutical Inorganic Chemistry B. Pharma 1st Semester
Antimicrobial agents
Contents
• Antimicrobial agents
• The various mechanism of action of anti-microbial agents
• The monograph analysis of:
Boric acid
Hydrogen peroxide
Iodine and its preparation
Potassium permanganate
Chlorinated lime
Learning Objectives
At the end of this lecture, the student will be able to:
• Define antimicrobial agents
• Describe the various mechanism of action of anti-microbial agents
• Explain the monograph analysis of:
Boric acid
Hydrogen peroxide
Iodine and its preparation
Potassium permanganate
Chlorinated lime
Antimicrobial Agents
• kills or inhibits the growth of microorganisms such as bacteria, fungi, or protozoans
• Antimicrobial drugs either kill microbes (microbiocidal) or prevent the growth of microbes (microbiostatic)
Specific terminology
• Antiseptic
• Disinfectants
• Germicides
• Bacteriostatics
• Bactericidal
• Sanitizers
An antimicrobial agent should possess the following characteristics:
• Broad spectrum of activity
• Posses antiseptic or germicide activity
• Rapid onset and sustained activity
• Good therapeutic index
• Should not cause local cellular damage
• Should not interfere with body defence mechanism
Mechanism of action of antimicrobial agents:
Oxidative mechanism
Halogenations mechanism
Protein precipitation mechanism
Monograph of potassium permanganate
Name: potassium permanganate
Chemical formula:KMnO4
Molecular weight: 158.0
Standards:Potassium Permanganate contains not less than 99.0 per cent and not more than 100.5 per cent of KMnO4
Method of Preparation:
2MnO2 + 4 KOH +O2 à 2K2MnO4 + 2H2O
KOH + MnO2 + KCLO3 à KCl + K2MnO4 + 3H2O
K2MnO4 + 3Cl2 à KMnO4 + KCl
Properties of potassium permanagante:
Description:
• A dark purple or brownish black, granular powder or dark purple or almost black slender, prismatic crystals
• Having a metallic lustre
• Odourless
• It decomposes on contact with certain organic substances
Test for purity
• Appearance of solution
• Water-insoluble matter
• Sulphates
• Chlorides
Assay:
Principle
Iodometric titration, Direct titration
2KMnO4 + 10KI + 8H2SO4 à 6K2SO4 + MnSO4 + 8H2O + 5I2
I2 + 2Na2S2O3 à 2NaI + Na2S4O6
Indicator: starch solution
Colour change: Blue to colourless
Storage: Store protected from moisture
Medicinal uses:
• Anti-microbial agent
• Antiseptic in mouth wash
• Anti dote: Barbiturates, chloral hydrate
• Veterinary practice: antiseptic
Monograph of Boric acid
Name: Boric acid
Chemical formula:H3BO3
Molecular weight: 61.8
Standards: Boric Acid contains not less than 99.5 per cent and not more than 100.5 per cent of H3BO3, calculated on the dried basis
Synonyms:Borarcic acid, ortho boric acid
Method of Preparation:
Boric acid may be prepared by reacting borax (sodium tetraboratedecahydrate) with a mineral acid, such as Sulphuric acid
Na2B4O7 + H2SO4 + H2O à 4H3BO3 + Na2SO4
Properties of boric acid:
Description:
• A white, crystalline powder or colourless shiny plates unctuous to the touch or white crystals
• Odourless
• Slightly acidic and bitter in taste
• Stable in air
• Weak acid pKa=9.19
Test for purity
• Appearance of solution
• Heavy metals
• Solubility in ethanol
• Arsenic
• Loss on drying
• Acidity/Alkalinity
• Sulphates
Assay: Principle
Neutralization titration, Indirect titration alkali metric
Indicator:phenolphthalein
Reagent:Glycerine
Colour change:colourless to pale pink
Storage: Store protected from moisture
Medicinal uses:
• Anti-microbial agent: weak germicide
• Local anti-infective
• Aqueous solution: eye wash and mouth wash
• Dusting powder
Monograph of Hydrogen peroxide
Name: Hydrogen peroxide
Chemical formula:H2O2
Molecular weight: 34.0
Standards:Hydrogen Peroxide Solution (20 Vol) contains not less than 5.0 per cent w/v and not more than 7.0 per cent w/v of H2O2, corresponding to about 20 times its volume of available oxygen.
Method of Preparation:
1. By adding barium or sodium peroxide to a solution of sulphuric acid
Na2O2 + H2SO4 à H2O2 + Na2SO4
2. By electrolysis of 50 percent ice cold sulphuric acid
2H2SO4 à H2S2O8
H2S2O8 + 2H2O à 2H2SO4 + H2O2
Properties of hydrogen peroxide:
Description:
• A clear, colourless liquid; odourless
• It decomposes in contact with oxidisable organic matter and with certain metals and also if allowed to become alkaline
Test for purity
• Organic stabilizers
• Non-volatile matter
• Acidity/Alkalinity
Assay: Principle
Redox Permanganometry titration
2 KMnO4 + 3 H2SO4 + 5H2O2 à K2SO4 + MnSO4 + 5O2 + 8H2O
Indicator:potassium permanganate
Media: sulphuric acid
Colour change:colorless to permanent pink
Storage: Store protected from light in containers resistant to hydrogen peroxide at a temperature not exceeding 30°. If the solution does not contain a stabilising agent, it should be stored in a refrigerator (2° to 8°). It should not be stored for long periods
Medicinal uses:
• Anti-microbial agent
• Bleaching agent
• Anti-dote for phosphorus and cyanide poisoning
Monograph of Iodine
Name: Iodine
Chemical formula:I2
Molecular weight:253.8
Standards: Iodine contains not less than 99.5 per cent and not more than 100.5 per cent of Iodine
Method of Preparation:
Iodine is obtained by natural source
• By extracting kelp (seaweed’s ash)
• Concentrated – to remove salts of sulphate and chloride
• Add sulphuric acid: removes sulphur and sulphides
• Mother liquor is decanted
• To this solution manganese di oxide is added
• Iodine distils over
2NaI + 3H2SO4 + MnO2 à MnSO4 + 2NaHSO4 + I2 + 2H2O
Properties of Iodine:
Description:
• Heavy, bluish-black, rhombic prism or plates having metallic lusture
• Peculiar odour
• Irritant
• It volatilises at ordinary temperature
• Freely soluble in chloroform and ether, soluble in water in presence of potassium iodide
Test for purity
• Chlorides and bromides
• Cyanogen
• Nonvolatile matter
Assay: Redox titration
I2 + 2Na2S2O3 à 2NaI + Na2S4O6
Indicator: Starch
Colour change:blue -colourless
Formulations of Iodine
• Aqueous iodine solution
• Weak iodine solution
• Strong iodine solution
• Povidone-Iodine solution
Storage: Store in ground-glass-stoppered containers or in earthenware containers with waxed bungs.
Medicinal uses:
• Counter irritant
• Disinfectant
• Proper thyroid functioning
Monograph of Chlorinated Lime
Name: Chlorinated lime
Chemical formula:Ca(OCl) Cl
Molecular weight:142.98
Standards: It contains not less than 30 per cent w/w of chlorine
Synonym: Calcium hypochlorite, Calcium oxychloride, Bleaching powder
Method of Preparation:
By action of chlorine gas on calcium hydroxide
Ca(OH)2 + Cl2 à Ca(OCl2)
Assay: Redox titration, Iodometric
Ca(OCl)2 + CH3CHOOH à (CH3CHOO)2Ca + Cl2 + H2O
2KI + Cl2 à 2KCl + I2
I2 + 2Na2S2O3 à 2NaI + Na2S4O6
Indicator: Starch
Colour change:blue -colourless
Storage: Store in well closed container in a cool place
Medicinal uses:
• Disinfectant
• Bleaching agent
Summary
• Antimicrobial agents: Kills the microbes
• Antiseptics:Kill or prevent the growth of microbes
• Disinfectants:Applied on inanimate objects
• Mechanism of action: Oxidative, halogenation and protein precipitation
• Monograph analysis of Potassium permanganate: prepared by, using potassium hydroxide and manganese di oxide, assayed by iodometric titration in acidic media, medicinally used as antidote, antiseptic, antimicrobial agent and as strong oxidizing agent
• Monograph analysis of Boric acid: In lab it is prepared by adding sulphuric acid water mixture to a solution of borax, assayed by neutralization indirect titration, glycerine is used in the assay to increase the acidity of boric acid. Medicinally it is used as germicide and anti-infective agent
• Monograph analysis of hydrogen per oxide: prepared by electrolysis process of sulphuric acid, assayed by permangnometric titration in acidic media, medicinally used as antidote and as strong oxidizing agent
• Monograph analysis of Iodine: Prepared by sea weed, assayed by redox titration using sodium thio sulphate as titrant
• Povidone iodine is widely used as anti-bacterial agent
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