UNIT 3

Carbohydrates and
Related Compounds

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 Awareness of the importance of carbohydrates in living systems and medicine is growing due to the increasing
understanding of their biological and pharmacological relevance. Carbohydrates are ubiquitous and perform a wide
array of biological roles. Carbohydrate-based or -modified therapeutics are used extensively in cardiovascular and
hematological treatments ranging from inflammatory diseases and anti-thrombotic treatments to wound healing.
(Carbohydrates in therapeutics: Michelle Kilcoyne, Lokesh Joshi. Retrieved from https://pubmed.ncbi.nlm.nih.gov/)

At the end of this lesson, you should be able to:

1. Discover natural drug

substances and the general properties of
each carbohydrate and related compounds
2. Illustrate the general biosynthetic pathway of the natural substances
3. Classify drugs related to each of the natural drug substances
4. List the chief constituent and use of representative drugs with natural drug substances
5. Classify the different sources of the natural drug products

The Germans first and foremost introduced the word ‘kohlenhydrates’ which was later on coined to
carbohydrates. The name obviously suggests that these compounds are essentially the hydrates of carbon. In reality, all
carbohydrates comprise of carbon, hydrogen and oxygen; whereas, the last two elements are found to exist in the same
proportions as in water ( i.e., H2O – 2:1). However, it has been observed that there are certain compounds that do
conform to the said ‘hydrate rule’ i.e., maintain the ratio of H and O (2:1) but do not belong to the category of
carbohydrates.

▪ Compounds with same proportions as in water but are not hydrates of carbon:
o Formaldehyde [HCHO]
o Acetic Acid [CH3COOH]
o Lactic Acid [C3H6O3]
▪ Carbohydrates that do not abide in the “rule of H 2O”
o Cymarose C7H14O4
o Digitoxose C6H12O4
o Rhamnose C6H12O5
o Sarmentose C7H14O4
o Oleandrose C7H14O4
o Digitalose C7H14O5

Under this unit, carbohydrates represent not only the sugars but also those substances that are related to them
basically in structure and other characteristic features. They belong to the chemical class of the aldehydes, ketone
alcohols, and also the condensation polymers of these partially oxidized polyalcohol collectively known as
‘Polysaccharides’ or ‘Oligosaccharides’. It is important to recall the properties and classifications of carbohydrates
discussed in Pharmaceutical Biochemistry.

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 Physical Properties

Solubility – with increasing complexity of the chemical structure, the water solubility decreases. This means that
monosaccharides and disaccharides are soluble in water while polysaccharides are insoluble, hence, heat is required
to dissolve them.

Shape - monosaccharides and disaccharides (like sucrose) appear as white crystalline while polysaccharides (like starch)
are amorphous

Taste – with increasing complexity of the chemical structure, the level of sweetness decreases). This means that
monosaccharides and disaccharides taste sweet while polysaccharides taste bland.

Chemical Properties

1. Can undergo hydrolysis - e.g. Starch hydrolyzes to amylodextrin → erythrodextrin → achrodextrin → maltose → 2
glucose
2. Can reduce metals – e.g. reducing sugars can reduce cupric ion from Fehling’s solution to produce cuprous ion.
3. Form osazones with phenylhydrazine
4. Can be fermented to produce ethanol and carbon dioxide:
▪ Initiated by yeast (Saccharomyces cerevisiae)
▪ Fruits and flowers are made into wine
▪ Honey is made into mead (alcoholic beverage)
▪ Malted barley is made into beer
▪ Apple is made into cider (alcoholic beverage made from the fermented juice)
▪ Molasses is made into rhum (distilled from fermented molasses)
5. Can be metabolized
a. When sugars undergo oxidation, they produce sugar acids – e.g. glucose to gluconic acid
b. When sugars undergo reduction, they produce sugar alcohols – e.g. mannose to mannitol

How is carbohydrate synthesized? (watch the video “Photosynthesis”)

The synthesis of carbohydrates takes place due to photosynthesis wherein carbon dioxide (CO2) is one of the starting
materials. This chemical process occurs abundantly both in all plants and in certain purple bacteria.

nCO2 + n H2O + Light Energy → (CH2O)n Carbohydrate + nO2

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 Biosynthesis of sucrose:

Sucrose is the first sugar produced in photosynthesis and serves as the

main transport material. It is the usual precursor for polysaccharides
synthesis.

Steps:
1. Fructose 6-phosphate is converted to glucose 1-phosphate
2. Glucose 1-phosphate reacts with UTP uridylyltransferase to form UDP-
glucose Uridine diphosphate glucose
3. UDP-glucose reacts with fructose 6-phosphate to form sucrose
phosphate then sucrose or:
4. UDP-glucose reacts with fructose to form sucrose directly
5. Sucrose may remain as sucrose or be utilized to form
monosaccharides then oligosaccharides or polysaccharides

Sugars and sugar containing drugs

1. Dextrose (aka  -D-glucopyranose, D-glucose)

Biological Source: Grapes; Starch
Uses:
▪ Nutrient (oral, enema, SC inj., IV inj.) injection of fluid into the lower bowel
▪ Ingredient in:
✓ dextrose injection
✓ alcohol and dextrose injection
✓ dextrose and sodium chloride injection
✓ Dextrose and sodium Chloride tablets
✓ Dopamine HCl and dextrose injection Vasopressor and inotropic action
✓ Lidocaine HCl and dextrose injection
✓ Potassium chloride in dextrose injection (treatment of hypokalemia)
✓ Anticoagulant citrate dextrose solution (Anticoagulant for the storage of whole blood)
✓ Anticoagulant citrate phosphate dextrose solution (Anticoagulant for the storage of whole blood)

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 *Dextrose excipients

A. Dextrose excipient (aka Dextrose monohydrate, dextrates)

Biological Source/Source: Starch
Description: Crystalline, solid

Uses:
▪ Sweetening agent (substitute for sucrose in syrup)
▪ Tablet binder
▪ Coating agent
▪ Replacement for liquid glucose as pharmaceutic aid

B. Liquid glucose

Biological Source/Source: starch

Description: Colorless/yellowish, thick, syrupy liquid; nearly odorless; sweet
Chemical Constituents: Dextrose, dextrins, maltose, water
Uses: Agent of pharmaceutic necessity

C. Calcium gluconate (aka Calcium salt of gluconic acid)

Biological Source/Source: from Gluconic acid
Description: Soluble in cold water; less irritating for parenteral use than calcium chloride
Uses:
▪ Electrolyte replenisher (accounts for the therapeutic use of calcium)
✓ Dose: 1 g orally 3x or more in a day or IV infusion 1 to 3 days intervals

D. Calcium gluceptate and calcium levulinate (aka Calcium salts of 7- and 5-carbon acids)
Biological Source/Source:
▪ Calcium gluceptate: glucose
▪ Calcium levulinate: starch and cane sugar
Description: Salts are calcemic
Uses: Electrolyte replenisher (accounts for the therapeutic effect of calcium)

E. Ferrous gluconate (aka Ferrous salt of gluconic acid)

Biological Source/Source: Gluconic acid

Uses
▪ Hematinic increase the amount of hemoglobin in the blood
✓ Prophylactic dose: 325 mg 4x a day
✓ Less gastric distress than inorganic ferrous salts
▪ Products:
o Fergon®; Feralet®; Simron®

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 2. Fructose (aka D-fructose, levulose, B-D (-)-fructopyranose, B-D (-) – fructofuranose, fruit sugar
because it is present in most sweet fruits)
Biological Source/Source: Inversion of sucrose; honey; hydrolysis of inulin; enzymatically
prepared high fructose syrup inverted sugar glucose and fructose
Description:
▪ Ketone sugar carbonyl group (CO) bonded to an R group
▪ Colorless crystals or white crystalline or granular, odorless powder that has sweet taste
▪ Freely soluble in water
▪ Half as sweet to the taste as glucose
Uses:
▪ Food for diabetic patients (particularly diabetic acidosis)
▪ Infant feeding formulas
▪ Intravenously, less urinary secretion than glucose
▪ Fluid, nutrient and electrolyte replenisher (IV or SC)
▪ Ingredient in: fructose injection; fructose and NaCl injection

* High-fructose sweetener
Biological Source/Source: prepared by controlled enzymatic isomerization of Glucose (derived from starch)

3. Xylose (aka D-Xylose, wood sugar)

Biological Source/Source: Corn cobs, straw
Description:
▪ Sweet taste; absorbed from the small intestine
▪ Not metabolized by mammalian enzymes (to significant extent)
Uses:
▪ Diagnostic agent (FDA approved) for the evaluation of intestinal absorption
✓ Relative excretion of xylose in urine is indicative of intestinal malabsorption (celiac disease,
sprue, Crohn’s disease, pellagra, radiation enteritis, surgical resection
✓ D-xylose is normally easily absorbed by the intestines
▪ Products: Xylo-Pfan®

4. Sucrose (aka Saccharum, sugar)

Biological Source
▪ Sugarcane: Saccharum officinarum Linne (Gramineae)
▪ Sugar beet: Beta vulgaris Linne (Chenopodiaceae)
▪ Sugar maple: Acer saccharum (Aceraceae)
▪ Residual dark-colored syrup is called molasses (Use: animal food
and production of ethyl alcohol)
▪ Sugar beets: Beets are dug, washed and sliced into small, limp
slivers called cossettes like thin
Uses
▪ Pharmaceutic necessity (syrups)
▪ Demulcent relieves irritation of the mucous membranes in the mouth by forming a protective film.
▪ Nutrient
▪ Bacteriostatic and preservative (sufficient concentration in aqueous solution)

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 ▪ Sweetening agent to troches and tablets
▪ Retards oxidation to some preparations

5. Lactose (aka Milk sugar)

Biological Source/Source: Cow’s milk from Bos taurus, Bovidae
Chemical Constituents: Cow’s milk (80-90 % water; 3% casein; 5% lactose;
0.1 to 1 % mineral slats; 2.5 to 5 % fat (butter); vitamins)
Description:
▪ Cow’s milk
✓ White, opaque liquid
✓ Emulsion of minute fat globules suspended in a solution of casein,
albumin, lactose, and inorganic salts
✓ Slight but pleasant odor
✓ Agreeable sweet taste
✓ Specific gravity: 1.029 – 1.034
▪ Lactose
✓ Odorless, faintly sweet taste
✓ Stable in air; readily absorbs odor
✓ Hydrolysis: yields D-glucose and D-galactose
✓ Reduces Fehling’s solution; undergoes mutarotation; forms osazone change in the optical rotation
✓ Hydrolyzed by lactase
✓ Undergoes lactic and butyric acid fermentation
Uses:
▪ Cow’s milk
✓ Nutrient: Source of lactose, yoghurt and kumyss (fermented milk)
✓ Source of casein: Sodium caseinate is employed in culture media
▪ Lactose
✓ Nutrient: Nutrient in infant food; Easily hydrolyzed than sucrose
✓ Pharmaceutic necessity: Inert diluent for other drugs; Tablet diluent
✓ Provides substrate for lactobacilli: Minor role in establishing intestinal microflora

6. Lactulose
Biological Source/Source: lactose
Description:
▪ Semisynthetic sugar
▪ Yields fructose and galactose upon hydrolysis
▪ Poorly absorbed; remains unchanged in the colon
Uses:
▪ Laxative
o Bacteria in the colon metabolizes lactulose to acetic and lactic acid
o Accumulation of these irritating acids causes laxative effect
▪ Decreases blood ammonia concentration in portal systemic encephalopathy
o Acidified stools trap ammonia (ammonium ion), reabsorption is prevented
o Blood ammonia levels may be decreased by 25 to 50 %
▪ Product: Cephulac®; Chronuac ®; Duphalac ®; Lilac ®

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 Drugs containing compounds metabolically related to sugars

Certain pharmaceutic products, such as ethanol and citric acid, are produced by the cellular respiration of
carbohydrates, especially glucose.

Pathways:
1. Embden-Meyerhof pathway: anaerobic conversion of glucose to pyruvic acid by glycolysis. In the absence of air,
pyruvic acid may be converted to lactic acid or to ethanol. Lactic acid can be converted to energy without oxygen.
Accumulation of it in the blood results to muscle cramps

2. Oxidative decarboxylation of pyruvic acid: pyruvic acid undergoes oxidative decarboxylation to yield acetyl
coenzyme A (acetyl-CoA or active acetate) which can be utilized in a variety of reactions including the acetylation of
aromatic amines and alkaloids or the biosynthesis of fatty acids or steroids.

3. Tricarboxylic acid cycle: most of the acetyl-CoA undergoes condensation with oxaloacetate to form citrate, thereby
entering the TCA cycle where it is oxidized to CO2 and water with the liberation of energy

4. Other mechanism: hexose monophosphate shunt/pentose phosphate pathway

2 Phases of Pentose Phosphate Pathway (watch the video “Pentose Phosphate Pathway”)
1. Oxidative phase: G6P is oxidized and decarboxylated to ribulose-5-Phosphate; products: 2 equivalents NADPH
2. Regenerative “sugar-shuffle” phase: Conversion of ribulose-5-phosphate to G-6-Phosphate

Products of glycolytic and oxidative metabolism

1. Plant juices

A. Cherry Juice aka Succus cerasi

L-malic acid
Biological Source/Source: Prunus cerasus Linne (Rosaceae)
Chemical Constituents: Malic acid (1%)
Uses: Preparation of cherry syrup, a flavored vehicle that disguises agent in
pharmaceutic mixtures (esp. acidulous in nature)

B. Others: Raspberry juice

2. Acids

A. Citric acid (First isolated in crystal form from lemon juice by Sheele
1784)
Biological Source/Source: Lemons, limes, pineapples; Fermentation of
sucrose
Description:
▪ Colorless, odorless, translucent crystals Citric acid
▪ Readily soluble in water and alcohol
▪ Tricarboxylic acid

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 Uses:
▪ Used in buffering systems
▪ Acidulant in effervescent formulations confer a tart, sour, or acidic flavor
▪ Ingredient in potassium citrate and citric acid solution; sodium citrate and citric acid solution; systemic alkalinizers;
anticoagulant citrate dextrose solution; anticoagulant citrate phosphate dextrose solution

B. Lactic acid
Biological Source/Source: sugar
Description:
▪ Colorless or yellowish, nearly odorless, syrupy liquid
▪ Miscible with water, alcohol, and ether
Chemical Constituents:
▪ Lactic acid (85-90 %by weight), lactic acid lactate
Uses:
▪ Acidulant: infant feeding formulas
▪ Electrolyte replenisher: sodium lactate injection
▪ Treatment of metabolic acidosis kidneys are not removing enough acid from the body
▪ Calcium replenisher: Calcium lactate (dose: 1 to 5 g 3x a day)

C. Tartaric acid
Biological Source/Source: wine Tartaric acid

Description:
▪ Dicarboxylic acid
▪ Soluble in water; freely soluble in alcohol
Uses: Used as a substitute for citric acid in buffer systems and effervescent formulations

D. Ferrous fumarate
Description: Comparable to ferrous gluconate
Uses:
▪ Hematinic agent (Dose: 200 mg 3-4x a day)
▪ Products: Feco-T®; Feostat®; Fumasorb®; Fumerin®; Hemocyte®; Ircon®; Palmiron®
E. Others: FUMARIC ACID, MALIC ACID

3. Alcohol

A. Alcohol (aka Ethanol)

Description: Liquid containing NLT 92.3 % by weight or 94.9% by volume of ethanol at 15.56⁰C
Uses
▪ 70% w/v: anti-infective
▪ Ethanol 5-10% and dextrose (5%) IV: increases caloric intake and replenish fluids

B. Diluted alcohol
Description
▪ Mixture of alcohol and water
▪ 48.4 to 49.5 % by volume at 15.56⁰ C
Uses: solvent
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 Products of Reductive metabolism

Dulcitol, mannitol, sorbitol and other sugar alcohols are widely distributed in plants but enzymes or enzyme systems
capable of reducing sugars to sugar alcohols have never been isolated from higher plant sources. Use of microbial
enzymes indicates that sugar alcohol (glycitol) phosphates may be formed by reduction of ketose phosphates (e.g.
glycitols are produced by the action of the enzyme phosphatase).

1. Mannitol (aka D-mannitol)

Biological Source/Source
▪ Manna: Fraxinus ornus Linne (Oleaceae)
▪ Fungi
Description:
▪ Hexahydric alcohol
▪ White, crystalline, odorless powder, sweet tasting
▪ Orthorhombic prisms or aggregates of fine needle
▪ Freely soluble in water and boiling alcohol; almost insoluble in cold alcohol
Uses:
▪ Manna: Laxative
▪ Diagnostic aid: mannitol is not absorbed from the gastrointestinal tract
▪ Osmotic diuretic: when administered parenterally, not metabolized and eliminated by glomerular filtration (80% of
approximately 100g dose appear in urine in 3 hours)
▪ Product: Osmitrol®

2. Sorbitol (aka D-glucitol)

Biological Source/Source:
▪ Ripe Berries of Mountain ash: Sorbus aucuparia Linne (Rosaceae)
▪ Glucose
Description:
▪ Hexitol: hexahydric alcohol
▪ Developed during World War I: Mannitol Hexanitrate used as substitute
for mercury fulminate (short supply)
▪ Crystalline and soluble
▪ Compatible with syrup, alcohol and other polyols
▪ Half as sweet as sucrose; humectant property; not absorbed on oral ingestion; not metabolized readily
Uses:
▪ Ingredients in: toothpaste; chewing gums and dietetic products
▪ Dietetic beverages: in conjunction with saccharin because it acts as osmotic laxative
▪ In combination with mannitol for urologic irrigation

3. Others: Xylitol

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 Polysaccharides and Polysaccharide-containing Drugs

Classification of polysaccharides
▪ More accurate and precise demarcation of polysaccharides
▪ This classification is based on position and configuration of the glycosidic linkage involved and type of
monosaccharide building unit.
Homoglycan
o The polysaccharide is termed as homoglycan when it contains only one type of monosaccharide unit
o Ex: Cellulose - expressed as β-1, 4 –D-glycan
Heteroglycan
o The polysaccharide is known as heteroglycan when it involves more than one kind of monosaccharide unit.
o ex: D-gluco-D-mannose is a diheteroglycan

Starch is the most widely distributed compound in plants. It is produced in large quantities in green leaves as the
temporary storage form of photosynthetic products. Starch occurs in seeds and in pith, medullary rays and cortex of the
stems and roots of perennial and other plants. It constitutes

HOMOGLYCANS

1. Honey (aka Mel or Madhu)

Biological Source: Honey is a viscid and sweet secretion stored in the honey comb by various species of bees, such as:
Apis dorsata, Apis florea, Apis indica, Apis mellifica, belonging the natural order Hymenoptera (Family: Apideae).
Description:
▪ Appearances: Pale yellow to reddish brown viscid fluid
▪ Odour: Pleasant and characteristic
▪ Taste: Sweet, Slightly acrid
▪ Specific gravity 1.35-1.36
▪ Specific rotation: +3 o to –15o Total Ash: 0.1-0.8%

▪ On prolonged storage it usually turns opaque and granular due to

the crystallization of dextrose and is termed as ‘granular honey’.
Chemical Constituents
▪ Moisture 14-24%, Dextrose 23-36%, Levulose (Fructose) 30-47%,
Sucrose 0.4-6%, Dextrin and Gums 0-7% and Ash 0.1-0.8%.
▪ small amounts of essential oil, beeswax, pollen grains, formic acid,
acetic acid, succinic acid, maltose, dextrin, colouring pigments,
vitamins and an admixture of enzymes eg; diastase, invertase and
inulase

Uses:
▪ It is used as a sweetening agent in confectionaries.
▪ Being a demulcent, it helps to relieve dryness and is, therefore, recommended for coughs, colds, sore-throats and
constipation.
▪ Because of its natural content of easily assimilable simple sugars, it is globally employed as a good source of
nutrient for infants, elderly persons and convalescing patients.

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 2. Starch
Biological Source: Zea mays (Poaceae); Triticum aestivum (Poaceae), Solanum tuberosum (Solanaceae)

Biosynthesis of Starch (watch video https://www.youtube.com/watch?v=b723qrc6VrU)

1. Amylose
▪ Effected by an enzyme known as transglycosylases – addition of single glucose residue
2. Amylopectin
▪ Formed from amylose by the action of a transglycosylase designated Q-enzyme
▪ The enzyme effects the splitting of a monosaccharide chain containing at least 40 glucose units into 2 fragments
▪ The fragment carrying the newly exposed residue end first forms an enzyme-substrate complex
▪ Fragment is then transferred to an acceptor chain forming -1,6 branch

Chemistry and property of starch: generally, a mixture of structurally different polysaccharides

1. Amylose
▪ linear molecule; composed of 250-300 D-glucopyranose units linked by -1, 4 glucosidic bonds; helix like shape
▪ more soluble in water
▪ complexed and precipitated with suitable agents (alcohols and nitroparaffins)
▪ reacts with iodine to form deep blue complex
▪ 25% in starch
▪ Hydrolyzed by -amylase or -1,4-glucan 4-glucano-hydrolase (pancreatic juice and saliva) – random splitting of
-1, 4 glucosidic bonds
▪ Products: glucose, maltose and amylopectin

2. Amylopectin

▪ consists of 1000 or more glucose units linked by -1,4 linkages and a number of -1,6 linkages at branch points
(appears to about 4% of the total linkages or 1 in every 25 glucose units)
▪ less soluble in water
▪ reacts with iodine to form blue-violet or purple color
▪ 75% in starch
▪ Hydrolyzed by B-amylase or -1,6-glucan maltohydrolase by removing maltose units
▪ Products: polysaccharide fragments known as dextrins (product of incomplete hydrolysis)

Zea mays Triticum aestivum Solanum tuberosum

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 3. Hetastarch: semisynthetic material (contains 90% amylopectin)
Uses:
▪ a 6% solution is used as plasma expander to treat shock due to hemorrhage, burns,
etc.
▪ It is employed in the management and treatment of hypovolemic shock (Shock
caused due to diminished blood volume).
▪ It is also used as a suspension medium for leukapheresis (The separation of leukocytes
from blood, which are then transfused back into the patient).
▪ It is employed as a cryoprotective (A chemical that protects cells from the effect of
cold) agent for erythrocytes.

4. Inulin
Biological sources: Inula helenium; Eupatorium cannabinum; Cynara scolymus;
Carpesium cernuum; Calendula officinalis; Aretium lappa
Uses:
▪ it is a D-fructan used in culture media as fermentative identifying agent for certain
bacteria.
▪ it is employed as a diagnostic agent for evaluation of glomerular filteration i.e., renal–
function test (or kidney function test).

5. Dextran
Description: a-1,6-linked polyglucan that is formed from sucrose by the action of an
enzyme system, transglucosylase, present in Leuconostoc mesenteroides
Uses:
▪ plasma expander (6% solution).
▪ NOTE: May interfere with some laboratory tests and significantly increase clotting
time

6. Cellulose
Biological source/source: Gossypium hirsutum (Malvaceae)

A. Purified cotton
Description: white, soft, fine, filament -like hairs that appear under microscope as
hollow, flattened and twisted bands. (see image)
Uses:
▪ Surgical dressing – mechanical protection to absorb blood, mucus or pus
▪ Source of pure cellulose in the manufacture of cellulose acetate

B. Powdered cellulose
Description: purified, mechanically disintegrated cellulose prepared by processing a-
cellulose obtained as a pulp
Uses:
▪ Self-binding tablet diluent and disintegrating agent

C. Microcrystalline cellulose
Description: purified, partially depolymerized cellulose prepared by treating a-cellulose with mineral acids
Use: tablet diluent

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 D. Cellulose derivatives

▪ Methylcellulose - obtained by the reaction of cellulose with caustic soda and methyl chloride used as bulk
laxative, suspending agent, topical protectants marketed as “artificial tears”
▪ Ethylcellulose – an ethyl ester of cellulose used tablet binder and film coating
▪ Hydroxyethylcellulose – used as thickening agent and as an ingredient in some formulations for artificial tears
▪ Hydroxypropylcellulose – used as stabilizer and thickener in liquid preparations; binder and film coating in tablet
formulations
▪ Hydroxypropylmethylcellulose – used as a suspending agent, thickening agent, a tablet excipient and topical
protectant for contact lenses
▪ Pyroxylin or soluble guncotton – obtained from the mixture of nitric and sulfuric acid on cotton. It is a mixture of
cellulose nitrates. It is used as a pharmaceutic aid in the manufacture of collodion and flexible collodion (topical
protectants)
▪ Oxidized cellulose and oxidized regenerated cellulose – usually available in the form of sterile pads, pledgets and
strips and are used as local hemostatics.
▪ Cellulose acetate phthalate – a free-flowing, white powder and is used for enteric coating of tablets.
▪ Sodium carboxymethylcellulose – used as suspending agent, thickening agent, tablet excipient and bulk laxative

HETEROGLYCANS: GUMS & MUCILAGES

These are natural plant hydrocolloids that may be classified as anionic (examples: arabic, karaya, tragacanth, gellan,
agar, algin, carrageenan, pectic acids) or non-ionic (examples: guar, locust bean, tamarind, xanthan, amylose,
arabinan, cellulose, galactomannan) polysaccharides or salts of polysaccharides.

What are hydrocolloids?

▪ Hydrocolloids forms a gel or viscous solution in the presence of water

▪ Produced in plants naturally or as a protective after injury (or unfavorable conditions like drought)
▪ Sources: Seed embryos or other plant parts (example: pectin- group of polysaccharides derived from plant cell
walls), marine algae and microorganisms
▪ Physical Characteristics: Translucent, amorphous
▪ COMMON SOURCES:
o Shrub or Tree exudates (e.g. Acacia, Karaya, Tragacanth)
o Marine Gums (e.g. Agar, Algin, Carrageenan)
o Seed gums (e.g. Guar, Locust bean, Psyllium)
o Plant extracts (e.g. pectins)
o Starch and Cellulose derivatives (e.g. Hetastarch, CMC, Ethylcellulose, Hydroxypropyl methylcellulose,
Methylcellulose)
o Microbial gums – dextrans. Xanthan

May be linear or branched

a. Linear hydrocolloids
▪ Less soluble than branched polymers (like algin, amylose, cellulose, pectin)
▪ Yields solutions with greater viscosity:
o These features are related to the increased possibility for good alignment and considerable intermolecular
hydrogen boding among linear polymers. This tendency for intermolecular associations also explains why

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 solutions of linear polysaccharides are less stable, especially with reductions in temperature that may result to
precipitation and insoluble in cold water.
o This phenomenon influences the shelf life or product formulations problem like recrystallization of these solutions.
b. Branched hydrocolloids
▪ Form gels rather than viscous solutions at higher concentrations
o Examples: xanthan, xylan, galactomannan, gum arabic, tragacanth
o They tend to be tacky (retaining a slightly sticky feel; not fully dry) when moist which is advantageous for
adhesive purposes.
o Gluemamela is an alternative for commercialized synthetic glue that is made out of gumamela mucilage.
▪ They rehydrate more readily than linear ones which is a property of importance in drug formulations that must be
reconstituted immediately before use (like suspensions).

They may be acidic, basic or neutral

a. Acidic and neutral: widely used

b. Basic: limited commercial importance

What are the chemical components of gums and mucilage?

1. Upon hydrolysis, these substances yield arabinose, galactose, glucose, mannose, xylose and various uronic acids,
class of sugar acids with both carbonyl (C=O) and carboxylic acid (COOH) functional groups
2. Because of the numerous components, this makes gums heterogenous in composition
3. The uronic acids may form salts with Calcium, Magnesium and other cations

What are the general uses of gums and mucilage?

1. Ingredient in dental and other adhesives

2. Bulk laxative - Bulk-forming laxatives are not digested but absorb liquid in the intestines and swell to form a soft,
bulky stool. The bowel is then stimulated normally by the presence of the bulky mass. (www.mayoclinic.org)
3. Pharmaceutic Use:
▪ Tablet binders (due to hydrophilic or water-loving properties)
▪ Emulsifiers
▪ Gelling agents - used to thicken & stabilize liquid solutions
▪ Suspending agents
▪ Stabilizers - ex. Seaweed gums and guar gums in ice cream and cheese
▪ Thickeners

What are the differences between gums and mucilage?

POINT OF COMPARISON GUMS MUCILAGES

Solubility in water Readily dissolves in water Forms slimy masses with water
Nature of origin Pathologic products from upon injury Physiologic products or normal
due to unfavorable conditions such products of metabolism form within
as drought, breakdown of cell walls the cells and may represent storage
material, water storage reservoir or
protection for germinating seeds

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 Sources

PLANT EXUDATES

1. Acacia Gum aka Gum Arabic

Description: gum Arabic came from a misnomer because little acacia is produced on the
Arabian Peninsula and none is exported. The name reflects the drug’s extensive use by the
early Arabian physicians
Biological source/source: Acacia senegal, Fabaceae
Constituent: Arabin (complex mixture of Calcium, Magnesium and Potassium salts of
Arabic acid)
Uses: Emulsifying agents, Suspending Agent, Demulcent, Emollient, Adhesive, binder,
Emollient

2. Indian Gum (aka Ghatti gum)

Biological source/source: Anogeissus latifolia, Combretaceae
Use/s: Used as a substitute for Acacia gum

3. Karaya Gum aka Sterculia gum, Indian tragacanth (Sterculia is from the Latin word Sterculius meaning fetid odors and
has a marked odor of acetic acid
Biological source/source: Sterculia urens, Sterculiaceae
Properties: One of the least soluble exuded plant gums. It absorbs and swells and forms a
discontinuous type of mucilage
Use/s:
▪ Bulk laxative, Agents forming emulsions and suspensions, dental adhesives
▪ Used extensively in skin lotions, textile and printing industries and food productions
▪ Found in Movicol® (Laxative)

4. Tragacanth aka Gum Tragacanth

Biological source/source: Astragalus gummifer, Fabaceae
Method of collection:
The gums exuding from natural injuries is more or wormlike and is twisted into coils (formerly known as
Vermiform tragacanth) or is shaped irregularly in a tear-shape (tragacanth sorts).
The better grade, ribbon gum and flake gum, comes from a transverse
Constituent/s: 60 to 70% bassorin (swells in water but do not dissolve) and 30% Tragacanthin (demethoxylated bassorin
and is more water soluble)
Uses:
▪ Suspending agent for insoluble powders in mixtures, emulsifying agent for oils and resins, adhesive, employed in
cosmetics as demulcent and emollient, cloth printing, confectionery (binder and emulsifier in lozenges production
to bring cohesion to the tablet and better release of the flavor)
▪ The most resistant of the hydrocolloids to acid hydrolysis and thus is preferred for use in highly acidic conditions

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 MARINE GUMS

1. Agar aka Japanese isinglas

Biological source/source: Gelidium cartilagineum, Gelidiaceae
Description: Insoluble in cold water
Constituent: Agarose and agaropectin
Uses:
▪ laxative, suspending agent, emulsifier, gelling agent for suppositories and surgical
lubricants, disintegrant, culture media

2. Algin aka Sodium alginate

Description: From Brown seaweeds extracted using a dilute alkali
Biological source/source: Macrocystis pyrifera, Lessoniaceae (Harvested from the Pacific
ocean)
Constituents: Mannuronic acid (major component), Sodium salt of alginic acid (a polymer
of L-glucoronic acid and D-mannuronic acid).
Uses: suspending agent, tablet binder and thickening agent

3. Carrageenan (aka Irish Moss, Chondrus)

Description: From red algae / seaweeds; It has higher sulfate ester content than agar
Biological source/source: Chondrus crispus, Gigartinaceae
Components:
▪ K-carrageenan (kappa) – good gelling agent*
▪ i-carrageenan (iota) - good gelling agent*
▪ λ-carrageenan (lambda) – non-gelling agent and used as thickener
*orients in stable helices in solution
Uses: Stabilizing agent for emulsions and suspensions, Toothpaste formulation (due to firm
texture and rinsability), demulcent, bulk laxative

4. Danish Agar

Biological source/source: Furcellaria fastigiata, Furcellariaceae

Description: From red algae; Similar to K-carrageenan
Uses: Gelling agent and suspending agent

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 SEED GUMS

1. Psyllium aka Plantago seed, Plantain seed

Biological source/source: Plantago psyllium, Plantaginaceae

Constituents: 10-30% hydrocolloid (localized in the outer seed coat)
Uses: Cathartic (action: swelling of the seed coat thus giving bulk and lubrication)
Dose: 7.5 g and should be taken with a considerable amount of water
Additional information: Solutions of purified psyllium gum are thixotropic

2. Cydonium / Quince Seed

Biological source/source: Cydonia vulgaris, Rosaceae
Forms viscous solutions with thixotropic properties

3. Guar gum
Biological source/source: Cyamopsis tetragonolubus,
Fabaceae Cydonia vulgaris Cyamopsis tetragonolubus Ceratonia siliqua
Uses: bulk forming laxative, thickening agent, tablet binder,
disintegrating agent
In fast dissolving tablet (The result is that it released the 99.21% drug in 15min as compared to Sodium Starch Glycolate).

4. Locust bean gum aka St. John’s bread (legendary use as the food of St. John the Baptist), Carob Pulp
Biological source/source: Ceratonia siliqua, Fabaceae
Uses: thickener, stabilizer

MICROBIAL GUMS

Xanthan Gum

Description: High molecular weight microbial gum produced from the action of Xanthamonas
campestris on suitable carbohydrates
Component: branched, partially acetylated polysaccharide (d-glucose, d-glucuronic acid, d-
mannose)
Uses: Emulsifying and suspending agent

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 PLANT EXTRACTIVES

Pectin
▪ Purified carbohydrate product obtained from the dilute acid extract of the inner portion of the rind of citrus fruits or
from apple pomace
o Citrus peel is rich in pectin with the amounts varying from the season and variety
o Pectin in fruit is found in an insoluble form known as Protopectin and is converted to the soluble form
Pectin by heating the fruit with dilute acid
▪ From Greek word meaning congealed or curdled
▪ Consists of partially methoxylated polygalacturonic acid
▪ Pharmaceutic pectin is pure pectin with no additions made

Uses: protectant and suspending agent, antidiarrheal formulations

▪ As colloidal solution it has the property to conjugate toxins (through adsorption) and enhance physiologic
functions of the digestive tract
▪ Kaopeptate is a preparation consisting of Kaolin + Pectin (antidiarrheal)

Types of pectin
▪ Protopectin – obtained from unripe sources
▪ Pectin – obtained from ripe sources
▪ Pectinic acid – obtained from over ripe sources

Sources of pectin:

Pomelo – Citrus grandis, Dalanghita – Citrus nobilis, Ponkan – Citrus sinensis, Orange – Citrus aurantium,
Rutaceae Rutaceae Rutaceae Rutaceae

Calamansi – Citrus Grapefruit – Citrus paradisi, Lemon – Citrus limon, Apple – Malus domestica,
microcarpa, Rutaceae Rutaceae Rutaceae Rosaceae

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