1. Characteristics of bulk powders

• Uniform particle size and good flow property.
• Chemically and physically stable.
• Non-hygroscopic or protected from moisture.
• Non-irritant when intended for external use.
• Free from contamination and microbial growth.
• Easily dispersible or soluble when meant for internal use.
• Pleasant taste or suitably flavoured/sweetened for oral use.
• Properly labelled with dose, method of use, and storage directions.

• Simple and economical to prepare.
• More stable than liquid dosage forms.
• Flexible dose adjustment.
• Suitable for large doses.

• Dose may be inaccurate if measured by the patient.
• Unsuitable for potent drugs and unpleasant-tasting drugs.
• Moisture-sensitive powders may cake.
• Not suitable where sterility is required.

2. Preparation of medicinal castor oil

1. Select mature, clean castor seeds.
2. Remove the outer seed coat and crush the kernels.
3. Express the oil mechanically, preferably by cold expression, to avoid decomposition.
4. Filter or clarify the expressed oil to remove suspended particles.
5. Purify the oil, commonly by treatment with adsorbents such as activated charcoal or bleaching earth, followed by filtration.
6. Remove traces of moisture by gentle heating under controlled conditions.
7. Store in well-closed, light-resistant containers.

3. Gelatin

• Type A gelatin: Produced by acid treatment of collagen.
• Type B gelatin: Produced by alkaline treatment of collagen.

• Pale yellow to amber, transparent sheets, flakes, granules, or powder.
• Odourless and almost tasteless.
• Swells in cold water.
• Dissolves in hot water and forms a gel on cooling.
• It is a protein and is amphoteric in nature.
• Gel strength depends on concentration, temperature, pH, and bloom value.

• Hard and soft capsule shells.
• Tablet binder and coating material.
• Preparation of gels, jellies, suppositories, and wound dressings.
• Stabilizer in some pharmaceutical and food products.
• Culture media in microbiology.

4. Antirheumatic oil

• Methyl salicylate
• Menthol
• Camphor
• Eucalyptus oil
• Turpentine oil
• Wintergreen oil
• Sesame oil, coconut oil, or another fixed oil as a base

1. Measure the required base oil.
2. Dissolve or mix volatile ingredients, such as menthol and camphor, in a small amount of suitable oil.
3. Add methyl salicylate and other essential oils gradually with stirring.
4. Make up to final volume with the base oil.
5. Filter if necessary and pack in an amber, tightly closed bottle.

5. Analysis of protein by the Kjeldahl method

Principle

Steps

A. Digestion

• Weigh a known amount of sample in a Kjeldahl flask.
• Add concentrated sulfuric acid and catalyst mixture, such as potassium sulfate with copper sulfate or selenium.
• Heat until the solution becomes clear.
• Organic nitrogen is converted to ammonium sulfate.

B. Distillation

• Cool the digest and dilute with water.
• Add excess sodium hydroxide.
• Ammonia gas is released.

• Distil the ammonia into boric acid or a known volume of standard acid.

C. Titration

• Titrate the absorbed ammonia with standard hydrochloric acid or sulfuric acid.

Calculation

• (V_s) = volume of acid used for sample, in mL
• (V_b) = volume of acid used for blank, in mL
• (N) = normality of acid
• (W) = weight of sample in g

6. Methods of extraction of lipids

A. Mechanical expression

• Oil is obtained by pressing oil-containing seeds.
• It may be cold pressing or hot pressing.
• Used for oils such as castor, sesame, coconut, and groundnut oil.

B. Solvent extraction

• Dried and powdered material is extracted using non-polar solvents such as hexane, petroleum ether, ether, or chloroform.
• Solvent is removed by evaporation or distillation.

C. Soxhlet extraction

1. Dry and powder the sample.
2. Place it in a porous thimble in a Soxhlet apparatus.
3. Heat solvent in a flask.
4. Solvent vapour condenses and repeatedly washes the sample.
5. The extract siphons back into the flask repeatedly.
6. Evaporate the solvent and weigh the lipid residue.

D. Folch method

• Uses chloroform:methanol in a 2:1 ratio.
• Especially useful for extracting total lipids from animal tissues.

E. Bligh and Dyer method

• Uses chloroform, methanol, and water.
• Commonly used for biological samples, tissues, microorganisms, and lipid analysis.

F. Supercritical fluid extraction

• Uses supercritical carbon dioxide.
• Produces solvent-free extracts and is useful for heat-sensitive materials, but requires costly equipment.

7. Chemistry of lipids

Classification

1. Simple lipids

• Fats and oils: Esters of fatty acids with glycerol, also called triglycerides.
• Waxes: Esters of fatty acids with higher monohydric alcohols.

2. Compound or complex lipids

• Phospholipids
• Glycolipids
• Lipoproteins
• Sphingolipids

3. Derived lipids

• Fatty acids
• Glycerol
• Sterols, such as cholesterol
• Steroid hormones
• Fat-soluble vitamins A, D, E, and K

Fatty acids

• Saturated fatty acids: No double bond, for example palmitic acid and stearic acid.
• Unsaturated fatty acids: One or more double bonds, for example oleic acid, linoleic acid, and linolenic acid.
• Essential fatty acids: Linoleic acid and alpha-linolenic acid must be supplied in the diet.

Important reactions

• Hydrolysis: Breakdown of triglycerides into glycerol and fatty acids.
• Saponification: Alkaline hydrolysis of fats/oils to form soap and glycerol.
• Hydrogenation: Addition of hydrogen to unsaturated bonds.
• Oxidation: Leads to rancidity.
• Esterification: Fatty acids react with alcohols to form esters.

8. Natural pesticides

Plant-derived pesticides

• Pyrethrum: Obtained from Chrysanthemum cinerariifolium. It contains pyrethrins and acts on insect nervous systems.
• Neem: Obtained from Azadirachta indica. Azadirachtin acts as an antifeedant, repellent, and insect growth regulator.
• Rotenone: Obtained from roots of Derris species. It affects cellular respiration in insects.
• Nicotine: Obtained from tobacco. It acts on nicotinic receptors but is highly toxic and restricted in many settings.
• Essential oils: Citronella, clove, eucalyptus, and peppermint oils may have repellent or insecticidal actions.

Microbial pesticides

• Bacillus thuringiensis (Bt): Produces proteins toxic to specific insect larvae.
• Beauveria bassiana: Entomopathogenic fungus used against insects.
• Nuclear polyhedrosis viruses: Used for selected agricultural insect pests.

Advantages

• Often biodegradable.
• Usually produce less persistent environmental residue.
• Some have selective action.
• Useful in integrated pest management.

Limitations

• May act more slowly.
• Can be degraded by sunlight and rain.
• May require repeated application.
• “Natural” does not mean harmless. Correct dose and safety precautions remain necessary.

9. Chemistry of proteins

Amino acid structure

• Amino group: (-NH_2)
• Carboxyl group: (-COOH)
• Hydrogen atom
• Variable side chain, (R)

Peptide bond

Classification of proteins

• Simple proteins: Yield only amino acids on hydrolysis, for example albumin and globulin.
• Conjugated proteins: Protein combined with a non-protein group, for example glycoproteins, lipoproteins, phosphoproteins, and haemoproteins.
• Derived proteins: Products of protein denaturation or hydrolysis, for example proteoses, peptones, and peptides.

• Fibrous proteins: Long, insoluble proteins, for example collagen, keratin, and elastin.
• Globular proteins: Compact, generally soluble proteins, for example enzymes, albumin, and haemoglobin.

Levels of protein structure

1. Primary structure: Amino-acid sequence.
2. Secondary structure: Alpha-helix or beta-pleated sheet.
3. Tertiary structure: Three-dimensional folding of one polypeptide chain.
4. Quaternary structure: Arrangement of two or more polypeptide subunits.

Protein denaturation

Functions

• Enzymes and hormones
• Structural support, such as collagen and keratin
• Transport, such as haemoglobin and albumin
• Immunity, such as antibodies
• Muscle contraction, such as actin and myosin
• Tissue repair and growth

10. Analysis of lipids, including animal-source lipids

Physical tests

• Colour, odour, and taste.
• Specific gravity.
• Refractive index.
• Melting point or solidification point.
• Viscosity.

Chemical tests

A. Acid value

B. Saponification value

C. Iodine value

D. Ester value

E. Peroxide value

F. Reichert-Meissl value

G. Acrolein test

Animal-source lipids: examples

• Cod liver oil: Obtained from the liver of cod fish; contains vitamins A and D.
• Shark liver oil: Contains squalene and fat-soluble vitamins.
• Lanolin: Wool fat obtained from sheep wool; used in ointments and cosmetics.
• Beeswax: A wax of animal origin used in ointments and creams.
• Lard: Purified fat from pig adipose tissue.
• Butter fat: Milk fat containing triglycerides and volatile fatty acids.

1. Extraction of Proteins

Definition

Principle

• pH
• Ionic strength
• Temperature
• Solvent composition
• Charge and isoelectric point

General steps in protein extraction

1. Selection and preparation of sample

• Select fresh material such as seeds, legumes, animal tissue, milk, egg, microorganisms, etc.
• Wash if necessary.
• Dry or keep cold, depending on the sample.
• Grind, homogenize, or powder the material to increase surface area.

2. Removal of unwanted material

• Defatting may be done with petroleum ether, hexane, or acetone.
• In animal tissues, fat and connective tissue are removed.
• Keep the sample cold to prevent protein degradation by enzymes.

3. Cell disruption

• Grinding with mortar and pestle
• Homogenization in a blender/homogenizer
• Freeze-thaw cycles
• Sonication
• French press or high-pressure homogenization
• Enzyme treatment, for example lysozyme for bacteria
• Mild detergents for membrane proteins

4. Extraction using suitable solvent/buffer

• Distilled water
• Salt solution, for example sodium chloride
• Buffer solution, such as phosphate buffer or Tris buffer
• Dilute alkali, for example sodium hydroxide
• Dilute acid
• Detergent-containing buffer for membrane proteins

5. Centrifugation or filtration

• Centrifuge the mixture.
• Insoluble material forms a pellet.
• The protein-containing liquid above it is called the supernatant.
• The supernatant is collected for further purification.

6. Protein precipitation

7. Collection and purification

• Collect the precipitated protein by centrifugation.
• Redissolve it in a suitable buffer.
• Further purify by dialysis, chromatography, or electrophoresis if required.

Important methods of protein extraction

A. Water extraction

Principle

Procedure

1. Powder the sample.
2. Mix with cold distilled water.
3. Stir for a suitable time.
4. Filter or centrifuge.
5. Collect the aqueous protein extract.

Examples

• Albumins from seeds
• Some whey proteins from milk

Advantages

• Simple
• Cheap
• No toxic solvent is required

Limitation

B. Salt extraction or salting-in

Principle

• Sodium chloride
• Ammonium sulfate
• Sodium sulfate

Procedure

1. Homogenize the sample in dilute salt solution.
2. Stir under cold conditions.
3. Centrifuge.
4. Collect the supernatant containing solubilized protein.

Use

C. Alkaline extraction

Principle

Procedure

1. Defat and powder the material, such as soybean or groundnut meal.
2. Add dilute sodium hydroxide, usually at alkaline pH.
3. Stir for a fixed time.
4. Centrifuge or filter.
5. Collect the alkaline extract containing protein.
6. Adjust the pH to the protein's isoelectric point to precipitate the protein.

Advantages

• High extraction yield
• Commonly used for plant proteins

Limitation

D. Acid extraction

Principle

Procedure

1. Treat the powdered sample with dilute acid such as hydrochloric acid or acetic acid.
2. Stir at low temperature.
3. Filter or centrifuge.
4. Collect the protein extract.

Example

Limitation

E. Isoelectric precipitation

Principle

Procedure

1. First dissolve protein in alkaline or salt solution.
2. Add dilute acid slowly with stirring.
3. Adjust the pH to the isoelectric point.
4. Protein precipitates.
5. Centrifuge and collect the precipitate.
6. Wash and dry or redissolve in buffer.

Example

F. Salting-out method

Principle

Procedure

1. Add ammonium sulfate gradually to the protein solution.
2. Maintain low temperature and stir continuously.
3. Allow protein to precipitate.
4. Centrifuge and collect the protein precipitate.
5. Dissolve the precipitate in buffer.
6. Remove salt by dialysis.

Advantages

• Simple and economical
• Helps concentrate protein
• Suitable for initial protein purification

Limitation

G. Organic solvent precipitation

Principle

• Ethanol
• Acetone
• Methanol

Procedure

1. Cool the protein solution.
2. Add chilled organic solvent slowly.
3. Keep the mixture cold.
4. Centrifuge.
5. Collect the protein precipitate.

Precaution

H. Extraction of membrane proteins

Method

• Use detergents such as Triton X-100, sodium deoxycholate, or sodium dodecyl sulfate.
• Detergents dissolve membrane lipids and release membrane proteins.

I. Enzyme-assisted extraction

Principle

• Cellulase and pectinase for plant materials
• Lysozyme for bacterial cell walls

Advantages

• Improves yield
• Can be carried out under mild conditions
• Helpful for plant and microbial samples

Factors affecting protein extraction

1. pH: Determines protein charge and solubility.
2. Temperature: Low temperature prevents denaturation and enzyme degradation.
3. Ionic strength: Low salt may improve solubility, while high salt may precipitate proteins.
4. Extraction time: Excessive extraction may cause degradation.
5. Particle size: Smaller particle size improves extraction.
6. Solvent-to-sample ratio: Adequate solvent increases protein recovery.
7. Presence of fat and phenolic compounds: Can reduce purity and yield.

2. Chemistry of Proteins

Definition

• Carbon: 50-55%
• Hydrogen: 6-7%
• Oxygen: 20-23%
• Nitrogen: 15-18%
• Sulfur: 0-3%

Amino acids

General structure

• Amino group: (-NH_2)
• Carboxyl group: (-COOH)
• Hydrogen atom
• Variable side chain: (R)
• Central alpha carbon atom

Examples

• Glycine
• Alanine
• Valine
• Leucine
• Lysine
• Arginine
• Phenylalanine
• Tyrosine
• Cysteine
• Methionine

Essential amino acids

• Leucine
• Isoleucine
• Valine
• Lysine
• Methionine
• Threonine
• Tryptophan
• Phenylalanine

Peptide bond

• Two amino acids form a dipeptide.
• Three amino acids form a tripeptide.
• Many amino acids form a polypeptide.
• One or more polypeptide chains form a protein.

Classification of proteins

A. Classification according to composition

1. Simple proteins

• Albumins
• Globulins
• Glutelins
• Prolamins
• Histones
• Protamine
• Scleroproteins

2. Conjugated proteins

3. Derived proteins

• Proteoses
• Peptones
• Peptides
• Coagulated proteins
• Denatured proteins

B. Classification according to shape

1. Fibrous proteins

• Long, thread-like molecules
• Usually insoluble in water
• Mainly structural in function

• Collagen
• Keratin
• Elastin
• Fibroin

2. Globular proteins

• Compact and spherical molecules
• Usually soluble in water or dilute salt solutions
• Perform dynamic functions

• Albumin
• Haemoglobin
• Enzymes
• Insulin
• Antibodies

Levels of protein structure

1. Primary structure

• Stabilized by peptide bonds.
• Determines all higher levels of protein structure.
• Even a single amino-acid change can alter protein function.

2. Secondary structure

• Alpha helix
• Beta-pleated sheet
• Beta turns

3. Tertiary structure

• Hydrogen bonds
• Ionic bonds
• Hydrophobic interactions
• Van der Waals forces
• Disulfide bonds between cysteine residues

4. Quaternary structure

• Haemoglobin has four subunits.
• Many enzymes have multiple subunits.

Important properties of proteins

1. Amphoteric nature

2. Isoelectric point

• Solubility is minimum.
• Protein may precipitate.
• It is useful in protein separation.

3. Solubility

• pH
• Salt concentration
• Temperature
• Nature of solvent

4. Denaturation

• Heat
• Strong acids or alkalis
• Alcohol and organic solvents
• Heavy metals
• Radiation
• Detergents
• Mechanical agitation

• Coagulation of egg white on heating
• Curd formation from milk by acid

5. Coagulation

Chemical reactions and tests of proteins

Functions of proteins

• Form body structures: collagen, keratin, elastin
• Act as enzymes
• Transport substances: haemoglobin, albumin
• Provide immunity: antibodies
• Regulate functions: peptide hormones
• Help blood clotting: fibrinogen
• Contract muscle: actin and myosin
• Maintain fluid balance and buffering action
• Supply energy when required: approximately 4 kcal/g

Short exam conclusion

Powder Characteristics of Bark Drugs

Definition

1. Organoleptic characters of bark powder

• Colour: Brown, reddish-brown, yellowish-brown, greyish-brown, etc.
• Odour: Characteristic, aromatic, faint, or odourless.
• Taste: Bitter, astringent, pungent, sweetish, or aromatic.
• Texture: Coarse, fibrous, gritty, or fine.
• Fracture: Short, fibrous, splintery, or granular.

2. Microscopic powder characteristics

A. Cork cells

• Found in the outer bark.
• Brown, polygonal, rectangular, or tabular cells.
• Cell walls may be suberized and sometimes thickened.
• Usually arranged in rows.

B. Cortical parenchyma

• Thin-walled, polygonal or rounded living cells.
• May contain starch grains, tannins, calcium oxalate crystals, or other cell contents.

C. Phloem parenchyma

• Thin-walled cells of the inner bark.
• May contain tannins, starch, oil droplets, mucilage, or crystals.

D. Sieve tubes

• Elongated conducting cells of phloem.
• May be seen with companion cells and sieve plates in some bark powders.

E. Phloem fibres or bast fibres

• Long, narrow, thick-walled fibres.
• Usually lignified.
• Give mechanical strength to bark.
• May occur singly or in groups.

F. Stone cells or sclereids

• Thick-walled, hard, lignified cells.
• Their shape may be isodiametric, elongated, branched, or irregular.
• They have narrow lumen and visible pits.
• Commonly important diagnostic features of bark powders.

G. Medullary rays

• Radially elongated parenchymatous cells.
• May contain starch or crystals.
• Seen as bands or strips in bark fragments.

H. Vessels

• Fragments of xylem vessels may occur in bark powder.
• Types include spiral, annular, scalariform, reticulate, and pitted vessels.
• Vessels are often lignified.

I. Calcium oxalate crystals

• Prismatic crystals
• Acicular crystals or raphides
• Rosette crystals
• Cluster crystals or druses
• Crystal sand

J. Starch grains

• Simple or compound grains.
• May be round, oval, or polygonal.
• Hilum may be central or eccentric.
• Detected using iodine solution, which gives a blue colour.

K. Tannin-containing cells

• Brownish-red contents may be present in cells.
• Common in astringent bark drugs.
• Ferric chloride test gives a blue-black or greenish-black colour depending on tannin type.

L. Secretory cells, oil cells, or resin ducts

• Some bark drugs contain volatile oil, resin, gum, or mucilage.
• These structures can aid identification.

General powder-character table

Short answer for exam