Comprehensive Study Guide: Carbohydrates, Derived Products, and Glycosides in Pharmacognosy

Introduction and Classification of Carbohydrates

• Chemical Definition and Historical Context:

  • Carbohydrates were historically defined as a group of compounds composed of carbon, hydrogen, and oxygen, where hydrogen and oxygen exist in the same 2:1 ratio as found in water ($2:1$). They were expressed by the general chemical formula $(CH_2O)_n$ or $C_x(H_2O)_y$, leading to the term "hydrates of carbon" (e.g., glucose $C_6H_{12}O_6$, sucrose $C_{12}H_{22}O_{11}$).
  • Limitations of the Historical Definition:
  • Not all organic compounds following the $2:1$ hydrogen-to-oxygen ratio are carbohydrates. Examples include formaldehyde $HCHO$ (expressible as $C(H_2O)$), acetic acid $CH_3COOH$ (expressible as $C_2(H_2O)_2$), and lactic acid $CH_3CHOHCOOH$ (expressible as $C_3(H_2O)_3$).
  • Many true carbohydrates do not conform to the traditional formula, such as rhamnose ($C_6H_{12}O_5$), cymarose ($C_7H_{14}O_4$), and digitoxose ($C_6H_{12}O_4$).
  • Certain carbohydrates contain additional elements such as nitrogen or sulfur alongside carbon, hydrogen, and oxygen.
  • Modern Chemical Definition: Carbohydrates are defined chemically as polyhydroxy aldehydes or polyhydroxy ketones, or substances that yield polyhydroxy aldehydes or polyhydroxy ketones upon hydrolysis.

• Biological and Pharmacognostical Role:

  • Carbohydrates are primary products of plant photosynthesis, converting electromagnetic energy into chemical energy.
  • They form a major portion of plant biomass, serving structural functions as cellulose in cell walls and energy storage functions as starch.
  • Sugars combine with diverse secondary metabolites to form glycosides. Mucilages (such as those in marshmallow root and psyllium seeds) act as water-retaining vehicles.
  • Gums and mucilages are produced due to plant injury or stress, occurring as solidified exudates composed primarily of uronic acid and sugar units.
  • Brown seaweed cell walls and higher plant middle lamellae contain polysaccharides consisting almost entirely of polyuronides/uronic acid units.

• Physical Properties by Molecular Weight:

  • Low Molecular Weight Carbohydrates: Crystalline, water-soluble, and sweet-tasting (e.g., glucose, fructose, sucrose).
  • High Molecular Weight Carbohydrates (Polymers): Amorphous, tasteless, and relatively insoluble or less soluble in water (e.g., starch, cellulose, inulin).

• Classification of Carbohydrates:

  • Monosaccharides: Simple sugars that cannot be further hydrolyzed into lower sugars. General chemical formula: $C_n H_{2n} O_n$. Subdivided according to carbon chain length:
  • Bioses: Contain $2$ carbon atoms; do not occur free in nature.
  • Trioses: Contain $3$ carbon atoms; exist as phosphoric acid esters (e.g., D-(+)-glyceraldehyde).
  • Tetroses: Contain $4$ carbon atoms (e.g., D-(-)-erythrose, D-(-)-threose).
  • Pentoses: Contain $5$ carbon atoms; common products of polysaccharide hydrolysis (hemicelluloses, mucilages, gums). Examples include D-(-)-ribose, D-(-)-arabinose, D-(+)-xylose.
  • Hexoses: Contain $6$ carbon atoms; most abundant in plants. Subclassified into Aldoses (e.g., D-(+)-glucose, D-(+)-mannose, D-(+)-galactose) and Ketoses (e.g., D-(-)-fructose, sorbose).
  • Heptoses: Contain $7$ carbon atoms; important intermediates in photosynthesis and animal glucose metabolism, rarely accumulating in free forms (e.g., glucoheptose, manoheptose).
  • Disaccharides: Yield $2$ monosaccharide molecules on hydrolysis:
  • Sucrose $\rightarrow$ Glucose + Fructose (found in sugarcane).
  • Maltose $\rightarrow$ Glucose + Glucose (malt sugar).
  • Lactose $\rightarrow$ Glucose + Galactose (cow's milk).
  • Trisaccharides: Yield $3$ monosaccharide molecules on hydrolysis:
  • Raffinose $\rightarrow$ Glucose + Fructose + Galactose (found in beet and sugarcane).
  • Gentianose $\rightarrow$ Glucose + Glucose + Fructose (found in gentian roots).
  • Tetrasaccharides: Yield $4$ monosaccharide molecules on hydrolysis (e.g., Stachyose, found in manna).
  • Polysaccharides: High polymers yielding an indefinite number of monosaccharides upon hydrolysis. Produced by condensation with elimination of water:
  • Pentosans: Yield pentoses on hydrolysis (e.g., Xylan).
  • Hexosans: Yield hexoses on hydrolysis (e.g., Starch, Inulin, Cellulose).
    • Cellulose consists of glucose units linked by $\beta\text{-}1,4$ glycosidic bonds.
    • Starch consists of glucose units connected by $\alpha\text{-}1,4$ and $\alpha\text{-}1,6$ glycosidic bonds.

• Qualitative Chemical Identification Tests:

  • Reduction of Fehling's Solution: Equal volumes of Fehling's solution A and B are added to the carbohydrate solution and heated. Formation of a brick-red precipitate of cuprous oxide ($Cu_2O$) indicates reducing sugars.
  • Molisch Test: Reagent consists of $\alpha\text{-}naphthol$ and concentrated sulfuric acid ($H_2SO_4$). Soluble carbohydrates yield a purple ring at the liquid junction when acid is layered gently. Insoluble carbohydrates (e.g., cotton wool cellulose) develop the purple color upon shaking acid in contact with the sample.
  • Osazone Formation Test: Carbohydrate solution is heated with phenylhydrazine hydrochloride, sodium acetate, and acetic acid. Yellow crystalline osazones form with characteristic shapes under microscopic examination. Glucose and fructose form identical osazones (glucosazone, melting point $205^\circ\text{C}$). Sucrose undergoes partial hydrolysis under test conditions to form glucosazone.
  • Resorcinol Test for Ketoses (Selivanoff's Test): Resorcinol crystal is added to the sample and warmed on a water bath with an equal volume of concentrated hydrochloric acid ($HCl$). Formation of a rose color indicates ketoses (e.g., fructose, honey, hydrolyzed inulin).
  • Test for Pentoses: Sample solution is heated with an equal volume of $HCl$ containing phloroglucinol. A red color indicates pentoses.
  • Keller-Kiliani Test for Deoxysugars: Deoxysugar sample is dissolved in acetic acid with a trace of ferric chloride ($FeCl_3$) and layered over concentrated $H_2SO_4$. A reddish-brown ring forms at the junction, gradually turning blue.
  • Furfural Test: Sample is heated in a test tube with syrupy phosphoric acid ($H_3PO_4$). Filter paper disk moistened with $10\%$ aniline in $10\%$ acetic acid placed over the tube mouth turns pink or red within $30\text{--}60\,\text{seconds}$.

Biosynthesis of Carbohydrates

• Photosynthetic Production of Monosaccharides:
  • Photosynthesis converts electromagnetic energy into chemical energy via light reactions (converting light to chemical potential) and dark enzymatic reactions (fixing carbon dioxide $CO_2$ into sugars using light reaction energy).
  • Overall photosynthetic equation:

$2H_2O + CO_2 + \text{light} \xrightarrow{\text{chlorophyll}} (CH_2O) + H_2O + O_2$

• Calvin cycle pathway: $CO_2$ fixation $\rightarrow$ Glucose-6-phosphate / Hexose-6-phosphate / Pentose-5-phosphate $\rightarrow$ Metabolic pool / Pyruvate / Aldose-1-phosphate / UDP-Sugars $\rightarrow$ Disaccharides, Oligosaccharides, Polysaccharides, Glycosides.

  • Pathways of Sucrose Biosynthesis:

• Sucrose is the principal transport sugar and initial photosynthetic product in higher plants.

• Biosynthetic sequence in higher plants:

  • Fructose 6-phosphate (derived from photosynthesis) is converted to Glucose 1-phosphate.
  • Glucose 1-phosphate reacts with UTP to yield UDP-glucose.
  • UDP-glucose reacts with Fructose 6-phosphate to produce sucrose phosphate, which is dephosphorylated to free sucrose (or UDP-glucose reacts directly with fructose to yield sucrose and UDP).
  • Free sucrose is translocated via sieve tubes or converted back to monosaccharides via invertase enzymes or pathway reversal.

Pharmacognostic Profiles of Carbohydrate Drugs

• Acacia Gum (Gum Arabic):
  • Synonyms: Acacia gum, Acacia vera, Egyptian thorn, Gummi africanum, Gum Senegal, Gummae mimosae, Kher, Sudan gum arabic, Somali gum, Yellow thorn, Indian Gum, Gum Arabic.
  • Biological Source: Dried gummy exudation from stems and branches of Acacia senegal (L.) Willd or other African species of Acacia. In India, collected from Acacia arabica Willd (Family Leguminosae).
  • Geographical Distribution: Drier parts of Anglo-Egyptian Sudan, northern Sahara, Senegal, Red Sea, Nigeria, Uganda, Kenya, Tanzania, Arabia, Sri Lanka, Morocco, and India (Punjab, Rajasthan, Western Ghats). Sudan produces $\sim 85\%$ of world supply.
  • Cultivation, Collection, and Ripening: Tapped from $6\text{--}8$ year old trees twice a year (Nov or Feb--March). Transverse incisions ($2\text{--}3\,\text{ft}$ long, $2\text{--}3\,\text{inches}$ wide) are made, removing outer bark while preserving cambium and xylem. Exudation occurs in $6\text{--}8$ weeks (winter) or $3\text{--}4$ weeks (summer). Sun drying for $3\text{--}4$ weeks causes uneven contraction, forming cracks/fissures ("ripening") converting transparent gum into opaque tears.

• Morphology: Spheroidal or ovoid tears ($2.5\text{--}3.0\,\text{cm}$ diameter) or off-white to light-brown powder. Color ranges from white to pale-yellow or creamish-brown/red. Odourless; bland and mucilaginous taste. Brittle fracture with glossy exposed surface.

• Chemical Constituents: Principal component is arabin (complex mixture of $Ca^{2+}$, $Mg^{2+}$, and $K^+$ salts of arabic acid). Hydrolysis of arabic acid yields L-arabinose, D-galactose, D-glucuronic acid, and L-rhamnose. Backbone consists of $1,3$-linked D-galactopyranose units. Contains $12\text{--}15\%$ water, oxidases, peroxidases, and pectinases. Total ash: $2.7\text{--}4.0\%$.

• Chemical Identification Tests:

  • Lead acetate test: Aqueous solution + lead acetate solution $\rightarrow$ heavy white precipitate.
  • Reducing sugars test: Hydrolyzed with dilute $HCl$ + boiled with Fehling's solution $\rightarrow$ brick-red $Cu_2O$ precipitate.
  • Enzyme test: Aqueous solution + alcoholic benzidine + $H_2O_2$ $\rightarrow$ distinct blue color (due to oxidases).
  • Borax test: Aqueous solution + borax $\rightarrow$ stiff translucent mass.
  • Specific distinctions: $10\%$ aqueous solution yields NO precipitate with dilute lead acetate (distinction from Agar and Tragacanth); NO color with Iodine (distinction from starch and dextrin); NO bluish-black color with $FeCl_3$ (distinction from tannins).

• Uses: Demulcent, emulsifying agent, thickening agent, tablet binder, micro-encapsulation, colloidal stabilizer, intravenous fluid in hemodialysis.

• Toxicology & Incompatibilities: Peroxidase destroys readily oxidizable drugs (vitamins, alkaloids) unless heat-inactivated. Reduces antibacterial efficacy of methyl-p-hydroxybenzoate against Pseudomonas aeruginosa. Contains a trypsin inhibitor.

  • Guar Gum:

• Synonyms: Guar gum, Jaguar gum, Guar flour, Decorpa.

• Biological Source: Powdered endosperm of seeds of Cyamopsis tetragonolobus Linn. (Family Leguminosae).

• Geographical Distribution: India (produces $80\%$ of global supply, $70\%$ from Rajasthan), Pakistan, USA, Australia, Africa.

• Processing: Seeds contain endosperm ($35\text{--}40\%$), germ/embryo ($45\text{--}50\%$), and husk ($14\text{--}17\%$). Mechanical splitting and winnowing separates bitter cotyledons/germ from endosperm, followed by micro-pulverization.

• Morphology: Colourless or pale yellowish-white powder; characteristic odour; gummy taste.

• Chemical Constituents: Guaran (high molecular weight galactomannan hydrocolloid composed of $(1\rightarrow 4)\text{-}\beta\text{-D-}$mannopyranosyl chain with $(1\rightarrow 6)\text{-}\alpha\text{-D-}$galactopyranosyl side chains; D-galactose to D-mannose ratio is $1:2$). Contains $5\text{--}7\%$ proteins.

• Chemical Identification Tests:

  • Iodine solution ($0.1\,\text{N}$) $\rightarrow$ fails to give olive-green color.
  • Ruthenium Red $\rightarrow$ NO pink color (distinction from sterculia gum and agar).
  • $2\%$ Lead acetate $\rightarrow$ instant white precipitate (distinction from sterculia gum and acacia).
  • Aqueous solution + alcoholic benzidine + $H_2O_2$ $\rightarrow$ NO blue color (distinction from acacia).
  • Borax addition $\rightarrow$ converted to a gel.

• Uses: Bulk laxative, appetite depressant, peptic ulcer therapy, protective colloid, tablet binder/disintegrant. Lowers total serum cholesterol ($10\text{--}15\%$) and LDL-cholesterol (up to $25\%$). Hypoglycemic agent in non-insulin-dependent diabetes.

• Toxicology: Fermented in colon to short-chain fatty acids; causes flatulence ($50\%$ of patients). May cause luminal/esophageal obstruction if taken without sufficient fluids (swells $10\text{--}20\text{-fold}$).

  • Honey:

• Synonyms: Madhu, Madh, Mel, Purified Honey.

• Biological Source: Viscid sweet secretion stored in honeycombs by hive bees Apis mellifera, Apis dorsata, Apis florea, Apis indica (Family Apidae, Order Hymenoptera).

• Processing: Floral nectar ($25\%$ sucrose, $75\%$ water) ingested by bees is converted to invert sugar by salivary invertase. Extracted by expression or centrifugation, heated to $80^\circ\text{C}$ to prevent fermentation and clear impurities, adjusted to density $1.35\,\text{g/cm}^3$ (natural density $1.47\,\text{g/cm}^3$).

• Morphology: Pale yellow to reddish-brown viscid fluid; pleasant, characteristic odour; sweet, slightly acrid taste. Turns opaque and granular ("Granulated honey") on storage due to dextrose crystallization.

• Chemical Constituents: Moisture ($14\text{--}24\%$), Dextrose ($23\text{--}36\%$), Levulose/Fructose ($30\text{--}47\%$), Sucrose ($0.4\text{--}6\%$), Dextrin and gums ($0\text{--}7\%$), Ash ($0.1\text{--}0.8\%$). Contains essential oils, pollen, formic acid, acetic acid, succinic acid, maltose, diastase, invertase, inulase, and antibacterial peptides (apidaecins, abaecin, royalisin).

• Chemical Tests:

  • Fiehe's Test for Artificial Invert Sugar: Ether extract + $1\%$ resorcinol in $HCl$ $\rightarrow$ transient red color in natural honey; persistent red color in artificial invert sugar.
  • Reduction of Fehling's Solution $\rightarrow$ brick-red precipitate.

• Toxicology: Infant botulism hazard when administered to infants under $1$ year old due to endospores of Clostridium botulinum colonizing the gut.

  • Tragacanth:

• Synonyms: Goat's thorn, gum dragon, gum tragacanth, hog gum.

• Biological Source: Air-dried gummy exudation from stems and branches of Astragalus gummifer Labill. and other species of Astragalus (Family Leguminosae).

• Geographical Distribution of Species:

  • A. gummifer: Anatolia and Syria.
  • A. kurdicus: Northern Iraq, Turkey, Syria.
  • A. brachycalyx: Western and Southwestern Iran.
  • A. eriostylus: Southwestern Iran.
  • A. verus: Western Iran.
  • A. leioclados: Western and Central Iran.
  • A. echidnaeformis, A. gossypinus: Isfahan region of Iran.
  • A. microcephalus: Shiraz/Kerman (Iran), Turkey.
  • A. adscendens: Southwestern/Southern Iran.
  • A. strobiliferus: Eastern Iran.
  • A. heratensis: Khorasan to Afghanistan.

• Collection & Commercial Grades: Tapped in 2nd year. Bark incised, wooden wedge inserted for $12\text{--}24\,\text{hours}$. Exudate collected after $2$ days. Commercial grades include Ribbon (Nos. 1, 2, 3, 4, 5) and Flake (Nos. 26, 27, 28, 55).

• Morphology: White or pale yellowish-white ribbons or flakes ($25 \times 12 \times 2\,\text{mm}$). Horny, translucent with longitudinal and transverse ridges. Short fracture. Odourless; mucilaginous taste.

• Chemical Constituents: Composed of two fractions:

  • Bassorin: Water-insoluble fraction ($60\text{--}70\%$); swells in water to form a gel; contains $\sim 5.38\%$ methoxyl moieties.
  • Tragacanthin: Water-soluble fraction ($30\text{--}40\%$); forms colloidal solution; contains no methoxyl groups.
  • Hydrolysis of tragacanthic acid yields galactose, xylose, and galacturonic acid.

• Chemical Identification Tests:

  • Boiling with concentrated $HCl$ $\rightarrow$ NO red color.

  • Ruthenium Red solution $\rightarrow$ NO red color.

  • $10\%$ Aqueous $FeCl_3$ + heat $\rightarrow$ deep-yellow precipitate.

  • Lead acetate solution $\rightarrow$ heavy precipitate.

  • Sodium Alginate:

• Synonyms: Algin, Alginic acid sodium salt, Sodium polymannuronate, Kelgin, Minus, Protanal.

• Biological Source: Sodium salt of alginic acid (polyuronic acid composed of reduced mannuronic and guluronic acids) extracted from brown seaweeds (Family Phaeophyceae): Macrocystis pyrifera, Laminaria hyperborea, Laminaria digitata, Ascophyllum nodosum, Durvillaea lessonia.

• Morphology & Solubility: White to buff-colored coarse or fine powder. Tasteless and odourless. Soluble in water forming a viscous colloidal solution ($1\%$ solution viscosity: $20\text{--}400\,\text{centipoises}$ at $20^\circ\text{C}$). Insoluble in alcohol, ether, chloroform, and strong acids.

• Identification Tests:

  • $0.5\%$ solution in $NaOH$ + $2.5\%$ $CaCl_2$ ($1/5$ volume) $\rightarrow$ voluminous, gelatinous precipitate (distinction from gum arabic, carboxymethyl cellulose, carrageenan, gelatin, ghatti, karaya, tragacanth).
  • $0.5\%$ solution in $NaOH$ + saturated $(NH_4)_2SO_4$ ($1/2$ volume) $\rightarrow$ NO precipitate (distinction from agar, carrageenan, methyl cellulose, starch).
  • Sample + acid ferric sulphate $\rightarrow$ cherry-red color developing to deep purple within $5\,\text{minutes}$.
  • $1\%$ aqueous solution + dilute $H_2SO_4$ $\rightarrow$ heavy gelatinous precipitate.

• Chemical Constituents: Linear copolymer of $1,4$-linked $\beta\text{-D-}$mannopyranosyluronic acid and $1,4$-linked $\alpha\text{-L-}$gulopyranosyluronic acid units.

• Uses: Suspending/thickening agent, tablet binder/disintegrant. Forms protective alginic acid/$CO_2$ raft in stomach acid over inflamed gastric mucosa.

  • Pectin:

• Biological Source: Purified polysaccharide obtained from inner peel of citrus fruits (Citrus lemon, Citrus aurantium - Rutaceae), apple pomace (Pyrus malus - Rosaceae), papaya (Carica papaya - Caricaceae), sunflower heads (Helianthus tuberosum - Asteraceae), guava (Psidium guyava - Myrtaceae), beets (Beta vulgaris - Chenopodiaceae), carrot (Daucus carota - Apiaceae), and mangoes (Mangifera indica - Anacardiaceae).

• Extraction Procedure: Peels boiled with $20\text{-fold}$ water at $90^\circ\text{C}$ ($30\,\text{min}$, pH $3.5\text{--}4.0$ using citric/lactic acid). Centrifuged, treated enzymatically to remove starch/protein, decolorized with charcoal, and precipitated using organic solvents (methanol/ethanol/acetone).

• Chemical Constituents: Molecular weight $20,000\text{--}400,000$. Core chain of $1,4$-linked D-polygalacturonate and L-rhamnose units with side chains of D-galactose, L-arabinose, D-xylose, and L-fructose. Graded by "Gelly-grade" ($100$, $150$, $200$).

• Identification Tests:

  • $10\%$ solution sets into a solid gel on cooling.
  • $1\%$ solution ($5\,\text{ml}$) + $2\%$ $KOH$ ($1\,\text{ml}$) set for $15\,\text{min}$ $\rightarrow$ gel. Acidification with dilute $HCl$ and shaking yields a voluminous gelatinous precipitate turning white and flocculent on warming.

• Uses: Antidiarrhoeal agent, enteroabsorbent, plasma lipoprotein-lowering agent, emulsifier, gelling agent.

  • Karaya Gum (Sterculia Gum):

• Synonyms: Indian tragacanth, Sterculia gum, Karaya gum, Bassora tragacanth, kadaya, mucara, kadira, katila, kullo.

• Biological Source: Dried gummy exudates from Sterculia urens Roxb., Sterculia villosa Roxb., Sterculia tragacantha Lindl. (Family Sterculiaceae).

• Morphology: Irregular tears or vermiform pieces; white, pink, or brown; slight acetic acid-like odour; bland, mucilaginous taste.

• Chemical Constituents: Partially acetylated polysaccharide ($\sim 8\%$ acetyl groups, $\sim 37\%$ uronic acid residues). Main chain of $1,4$-linked $\alpha\text{-D-}$galacturonic acid and $1,2$-linked L-rhamnopyranose units.

• Chemical Identification Tests:

  • Powder + water ($1\,\text{g}$ in $50\,\text{ml}$) $\rightarrow$ acidic viscous solution.
  • Powder + ethanol-water ($3:2$) $\rightarrow$ swells markedly.
  • Ruthenium Red solution $\rightarrow$ produces pink color.

• Uses: Bulk laxative (swells $60\text{--}100\text{-fold}$ in water), denture adhesive (reduces bacterial adhesion by $98\%$), ostomy appliance adhesive.

  • Bael:

• Synonyms: Bael fruits, Bel, Indian Bael, Bengal Quince, Belan.

• Biological Source: Unripe or half-ripe fruits, fruit slices, or irregular pieces of Aegle marmelos Corr. (Family Rutaceae).

• Chemical Constituents: Furocoumarins including marmelosin A, B, and C ($0.5\%$), marmesin, psoralin, umbelliferone; alkaloids (O-methylhalfordinol, isopentylhalfordinol, angelenine, marmeline, dictamine); carbohydrates ($11\text{--}17\%$), vitamins A and C.

• Uses: Antidiarrhoeal, antidysenteric, antidiabetic. Uterine stimulant in high doses (abortifacient hazard in pregnancy).

• Substitutes: Mangosteen (Garcinia mangostana - Guttiferae), Wood apple (Limonia acidissima - Rutaceae), Pomegranate rind (Punica granatum - Punicaceae).

  • Agar:

• Synonyms: Agaragar, Japanese Isinglass, Vegetable gelatin.

• Biological Source: Dried gelatinous substance extracted with water from Gelidium amansii, Gracilaria species, and Pterocladia species (Families Gelidaceae and Gracilariaceae).

• Chemical Constituents: Complex heterosaccharide composed of:

  • Agarose: Neutral, non-sulfated galactose polymer composed of D-galactose and 3,6-anhydro-L-galactose units (responsible for gel strength).
  • Agaropectin: Sulfated polysaccharide composed of galactose and uronic acid units partially esterified with sulfuric acid (responsible for viscosity).

• Chemical Identification Tests:

  • Fehling's test $\rightarrow$ positive (reducing sugar response after processing).
  • Molisch test $\rightarrow$ positive.
  • Hydrolyzed with concentrated $HCl$ + $BaCl_2$ solution $\rightarrow$ white precipitate of barium sulfate ($BaSO_4$) due to organic sulfate groups (distinction from starch, acacia, tragacanth).
  • Ruthenium Red $\rightarrow$ red color.
  • Heated with $KOH$ solution $\rightarrow$ canary-yellow color.
  • $1\%$ aqueous solution in boiling water sets into a jelly upon cooling.
  • $N/20$ Iodine solution $\rightarrow$ deep crimson to brown color (distinction from acacia and tragacanth).
  • $0.2\%$ solution + aqueous tannic acid $\rightarrow$ NO precipitate (distinction from gelatin).

• Uses: Culture media gelling agent, bulk laxative, surgical lubricant, tablet disintegrant.

  • Manna:

• Biological Source: Saccharine exudation from stem of Fraxinus ornus Linn. (Family Oleaceae).

• Chemical Constituents: Mannitol ($40\text{--}60\%$), mannotriose ($5\text{--}15\%$), mannotetrose ($10\text{--}15\%$), fraxin, dextrose, mucilage.

• Uses: Laxative.

  • Xanthan Gum:

• Biological Source: High molecular weight exopolysaccharide produced via bio-fermentation by Xanthomonas campestris.

• Chemical Constituents: Cellulosic backbone ($1,4$-linked $\beta\text{-D-}$glucose) with trisaccharide side chains (mannose--glucuronic acid--mannose) forming a repeating pentasaccharide unit. Contains pyruvate acetal and O-acetyl moieties.

• Uses: Viscosity modifier, emulsion stabilizer, pseudoplastic rheology modifier.

  • Ghatti Gum (Indian Gum):

• Synonyms: Ghati, Gutty.

• Biological Source: Gummy exudate from bark of Anogeissus latifolia Wallich (Family Combretaceae).

• Chemical Identification Tests:

  • $5\%$ solution + Millon's reagent $\rightarrow$ fine precipitate.
  • Solution + $2\%$ gelatin solution $\rightarrow$ white precipitate.
  • Solution + $10\%$ tannic acid $\rightarrow$ white precipitate.

• Uses: Emulsifier, tablet binder, calico printing stabilizer.

  • Ispaghula (Psyllium):

• Synonyms: Ispaghula, Ispagol, Ishabgula, Spongel seeds.

• Biological Source: Dried seeds of Plantago ovata Forskal (Family Plantaginaceae).

• Microscopy: Epidermis composed of single-layered, tangentially elongated cells filled with mucilage; yellow collapsed pigment layer; endosperm with aleurone grains and fixed oil; embryo with two cotyledons.

• Chemical Tests & Swelling Factor:

  • Treated with Ruthenium Red $\rightarrow$ red mucilage stain.
  • Swelling Factor: $1\,\text{g}$ seed placed in a $25\,\text{ml}$ graduated cylinder with $20\,\text{ml}$ water, shaken periodically for $23\,\text{hours}$ and rested for $1\,\text{hour}$. Official swelling factor for P. ovata seeds is $10\text{--}13$.

• Uses: Mechanical bulk laxative, demulcent in dysentery, irritable bowel syndrome, hypercholesterolemia.

  • Tamarind:

• Biological Source: Dried ripe fruits (freed from brittle epicarp) of Tamarindus indica Linn. (Family Leguminosae).

• Chemical Constituents: Fruit acids ($\sim 10\%$; mainly L-(+)-tartaric acid and maleic acid), potassium bitartrate ($\sim 8\%$), invert sugars ($25\text{--}40\%$), pectin.

• Uses: Osmotic laxative, acid refrigerant.

  • Chitin and Chitosan:

• Biological Source: Nitrogenous polysaccharide isolated from arthropod exoskeletons (crabs, lobsters, shrimp), insects, and fungal cell walls.

• Chemical Structure: Linear polymer of $1,4$-linked N-acetyl-$\beta\text{-D-}$glucosamine. Partially or fully deacetylated derivative is termed chitosan.

• Chemical Tests:

  • Soaked in iodine solution + $10\%$ $H_2SO_4$ $\rightarrow$ deep violet color.
  • Dissolved in $50\%$ nitric acid and crystallized $\rightarrow$ sphaerocrystals of chitosan nitrate showing a distinct Maltese cross under polarized light with crossed nicols.

• Uses: Wound dressing, artificial skin, hemostatic, ophthalmic corneal bandages, wastewater heavy metal chelator.

  • Carrageenan (Irish Moss Extract):

• Biological Source: Sulfated galactan polysaccharide extracted from red seaweeds, primarily Chondrus crispus Linn. and Gigartina species (Family Gigartinaceae, Class Rhodophyceae).

• Chemical Fractions: Fractionated into Kappa-carrageenan, Iota-carrageenan, and Lambda-carrageenan based on ester sulfate position and presence of 3,6-anhydro-D-galactose rings.

• Uses: Emulsifier, thickener; widely used as a phlogistic agent to induce experimental rat paw edema in pharmacological anti-inflammatory screening.

  • Locust Bean Gum:

• Synonyms: Arobon, Carob gum, Ceratonia.

• Biological Source: Powdered endosperm of seeds of Ceratonia siliqua Linn. (Family Leguminosae).

• Chemical Constituents: D-galacto-D-mannoglycan ($88\%$), with a D-galactose to D-mannose ratio of 20:80$.\n - **Chemical Identification Test:** Mucilage boiled with 5\%$$KOH$solution$\rightarrow becomes clear with NO yellow color (distinction from agar/tragacanth) and NO brown color (distinction from sterculia gum).\n\n- **Starch:**\n - **Biological Source:** Polysaccharide granules obtained from grains of maize (*Zea mays* L.), rice (*Oryza sativa* L.), wheat (*Triticum aestivum* L.) [Family Gramineae], or tubers of potato (*Solanum tuberosum* L.) [Family Solanaceae].\n - **Microscopic Diagnostic Features:**\n - **Rice Starch:** Polyhedral simple granules (2\text{--}12\,\mu\text{m}$) or ovoid compound granules ($12\text{--}30 \times 7\text{--}12\,\mu\text{m}$) containing$2\text{--}150 components.\n - **Wheat Starch:** Simple lenticular circular/oval granules (5\text{--}50\,\mu\text{m}) with central hilum and faint concentric striations.\n - **Maize Starch:** Polyhedral or rounded granules (5\text{--}31\,\mu\text{m}$) with a distinct central cavity or$2\text{--}5\text{-rayed} cleft.\n - **Potato Starch:** Simple irregularly ovoid/sub-spherical granules (30\text{--}100\,\mu\text{m}); eccentric hilum located at narrower end with well-marked concentric striations.\n - **Chemical Constituents:** Composed of two fraction types (1:2 ratio):\n - **Amylose (\beta\text{-amylose}):** Water-soluble linear polymer; yields a pure blue color with iodine.\n - **Amylopectin (\alpha\text{-amylose}):** Water-insoluble branched polymer; swells in water to form a gel; yields a bluish-black color with iodine.\n - **Uses:** Tablet binder/disintegrant, dusting powder, iodine poisoning antidote.\n\n# Introduction and Classification of Glycosides\n\n- **Chemical Definition and Structure:**\n - A glycoside is any compound containing a sugar moiety (glycone) bound through its anomeric carbon atom to a non-sugar organic moiety (aglycone or genin) via a glycosidic bond.\n - The glycosidic bond represents a condensation reaction between the hemiacetal hydroxyl group of the saccharide and an hydroxyl, thiol, amino, or carbon center of the aglycone.\n - Natural plant glycosides predominantly exist in the \beta\text{-isomeric} conformation.\n\n- **General Properties:**\n - Crystalline or amorphous solids, optically active, soluble in water and alcohols, but insoluble in organic solvents such as ether, benzene, or chloroform (whereas free aglycones are soluble in organic solvents).\n - Do not reduce Fehling's solution directly; however, free sugars generated following acid or enzymatic hydrolysis will reduce Fehling's solution to red cuprous oxide (Cu_2O).\n\n- **Classification Systems:**\n - **By Glycone Unit:** Glucoside (glucose), fructoside (fructose), glucuronide (glucuronic acid), rhamnoside (rhamnose), etc.\n - **By Glycosidic Linkage Type:**\n - **O-glycosides:** Sugar attached to phenolic or alcoholic hydroxyl group of aglycone (e.g., salicin, amygdalin, sennosides, cardenolides).\n - **N-glycosides:** Sugar attached to amino nitrogen of aglycone (e.g., nucleosides).\n - **S-glycosides:** Sugar attached to thiol group of aglycone (e.g., sinigrin).\n - **C-glycosides:** Sugar linked directly via C--C bond to anomeric carbon (e.g., aloin, barbaloin, cascarosides).\n - **By Aglycone Chemical Class:**\n - Anthraquinone glycosides (Senna, Aloe, Rhubarb, Cascara).\n - Cardiac/Sterol glycosides (Digitalis, Strophanthus, Squill, Thevetia).\n - Saponin glycosides (Dioscorea, Liquorice, Ginseng, Shatavari).\n - Cyanogenetic glycosides (Bitter Almond, Wild Cherry Bark).\n - Thiocyanate/Isothiocyanate glycosides (Black Mustard).\n - Flavone glycosides (Ginkgo).\n - Aldehyde glycosides (Vanilla).\n - Phenol glycosides (Bearberry).\n - Steroidal glycosides (Solanum).\n - Bitter and Miscellaneous glycosides (Gentian, Picrorhiza, Chirata, Quassia, Kalmegh).\n\n- **General Extraction Methodology (Stas-Otto Method):**\n - Finely powdered drug is extracted by continuous hot percolation in a Soxhlet apparatus using ethanol or methanol to deactivate plant hydrolytic enzymes.\n - Thermolabile glycosides are extracted below 45^\circ\text{C}.\n - The extract is treated with lead acetate solution to precipitate tannins and non-glycosidal impurities, followed by filtration.\n - Excess lead ions are precipitated as insoluble lead sulfide (PbS$) by bubbling hydrogen sulfide gas ($H_2S) through the filtrate.\n - The solution is filtered, concentrated, and purified using fractional crystallization, preparative TLC, or column chromatography.\n\n# Anthracene Glycosides\n\n- **General Chemistry & Chemical Tests:**\n - Aglycone moieties derived from anthraquinones, anthranols, anthrones, or dianthrones.\n - Reduced derivatives (anthrones, anthranols) are biologically more potent laxatives than oxidized anthraquinones.\n - **Borntrager's Test:** Sample boiled with dilute HCl$or$H_2SO_4$, filtered, extracted with benzene/chloroform/$CCl_4, and organic layer shaken with dilute ammonia. Pink to red color in the ammoniacal layer confirms anthraquinones.\n - **Modified Borntrager's Test:** Used for stable C-glycosides. Sample treated with dilute HCl$and$5\%$ferric chloride ($FeCl_3) solution, heated, extracted with organic solvent, and shaken with ammonia to produce a pink-to-red color.\n\n- **Senna Leaf:**\n - **Biological Source:** Dried leaflets of *Cassia acutifolia* Delile (Alexandrian senna) or *Cassia angustifolia* Vahl (Tinnevelly senna) [Family Leguminosae].\n - **Comparative Diagnostic Characters:**\n - **Tinnevelly Senna:** Leaflets 2.5\text{--}5.0\,\text{cm}$long,$7\text{--}9\,\text{mm}$wide; lanceolate; less acute apex; less asymmetric base; less pubescent; vein islet number$19\text{--}22.5$; stomatal index$14\text{--}20$; palisade ratio$4\text{--}12\n - **Alexandrian Senna:** Leaflets 2.0\text{--}4.0\,\text{cm}$long,$6\text{--}12\,\text{mm}$wide; ovate-lanceolate; acute apex with sharp spine; conspicuously asymmetric base; more pubescent; vein islet number$25\text{--}29.5$; stomatal index$10\text{--}15$; palisade ratio$4.5\text{--}18\n - **Microscopy:** Isobilateral leaf structure; single-layered palisade under both upper and lower epidermises (discontinued over midrib); non-lignified unicellular warty trichomes; paracytic stomata; vascular bundle surrounded by a crystal sheath of calcium oxalate prisms and lignified pericyclic fibers.\n - **Chemical Constituents:** Sennosides A and B (dianthrones of rhein), Sennosides C and D (heterodianthrones of aloe-emodin and rhein), free chrysophanol, emodin, aloe-emodin, rhein.\n - **Uses:** Stimulant cathartic/laxative.\n - **Adulterants:** Dog Senna (*Cassia obovata*), Palthe Senna (*Cassia auriculata*, turns red with 80\%$$H_2SO_4), *Coriaria myrtifolia* (toxic Mediterranean shrub).\n\n- **Aloe:**\n - **Biological Source:** Dried juice from leaf bases of *Aloe perryi* Baker (Socotrine/Zanzibar), *Aloe vera* L. / *A. barbadensis* Mill. (Curacao/Barbados), or *Aloe ferox* Mill. (Cape) [Family Liliaceae].\n - **Processing:** Exudate drains spontaneously from pericyclic mucilage cells upon leaf incision and is concentrated by boiling or air-evaporation.\n - **Chemical Constituents:** Barbaloin (C-glycoside), Isobarbaloin (present in Curacao aloe), \beta\text{-barbaloin}, aloe-emodin, resin, and aloesin.\n - **Varietal Chemical Tests:**\n - **Borax Test:** Sample + borax + heat \rightarrow green fluorescence (aloe-emodin anthranol).\n - **Bromine Test:** Sample + bromine solution \rightarrow bulky yellow precipitate (tetrabromaloin).\n - **Nitric Acid Test:** Curacao (deep reddish-brown); Socotrine (pale yellowish-brown); Zanzibar (yellowish-brown); Cape (brown turning green).\n - **Cupraloin Test:** Dilute solution + 1$drop$CuSO_4$+ saturated$NaCl$$\rightarrow deep purple color (positive in Curacao, faint in Cape, negative in Socotrine/Zanzibar).\n\n- **Rhubarb:**\n - **Biological Source:** Peeled dried rhizomes and roots of *Rheum palmatum* L., *Rheum emodi*, or *Rheum webbianum* (Family Polygonaceae).\n - **Chemical Constituents:** Free anthraquinones (chrysophanol, aloe-emodin, emodin, physcion, rhein), anthrones, dianthrones, heterodianthrones, rheotannic acid, gallic acid, calcium oxalate rosette aggregates.\n - **Test for Rhapontic Rhubarb Adulteration (*Rheum rhaponticum*):** Alcohol extract spot on filter paper examined under UV light displays intense blue fluorescence (due to stilbene glycoside rhaponticin), intensified by ammonia vapor.\n\n- **Cascara Bark:**\n - **Biological Source:** Dried bark of *Rhamnus purshiana* DC. (Family Rhamnaceae), aged for at least 1\,\text{year} prior to medicinal administration.\n - **Aging Requirement:** Fresh bark contains reduced anthranol derivatives causing severe emesis and griping. Ageing for 1\,\text{year} oxidizes anthranols into non-griping anthraquinone monomeric/dimeric C- and O-glycosides.\n - **Microscopy:** Stratified cork, sclereids/stone cell groups in cortex, phloem rays 1\text{--}5 cells wide, crystal fibers containing calcium oxalate prisms.\n - **Chemical Constituents:** Cascarosides A and B (primary C-10 isomers of barbaloin), Cascarosides C and D (primary C-10 isomers of chrysaloin), free emodin, aloe-emodin, chrysophanol.\n\n# Sterol and Cardiac Glycosides\n\n- **General Structure & Stereochemistry:**\n - Composed of a tetracyclic steroidal aglycone nucleus (3\beta,14\beta\text{-dihydroxy}$substituted) linked at position$C\text{-}3$via a$\beta\text{-glycosidic} bond to one to four sugar moieties (e.g., D-digitoxose, D-digitalose, L-rhamnose).\n - **Classification by C\text{-}17 Lactone Ring:**\n - **Cardenolides:** Possess a 5\text{-membered}$$\alpha,\beta\text{-unsaturated}$$\gamma\text{-lactone}$ring ($C_{23} steroid framework; found in Digitalis, Strophanthus).\n - **Bufadienolides:** Possess a 6\text{-membered}$doubly unsaturated$\delta\text{-lactone}$/ pyrone ring ($C_{24} steroid framework; found in Squill).\n\n- **Digitalis Leaves (Purple Foxglove):**\n - **Biological Source:** Dried leaves of *Digitalis purpurea* Linn. (Family Scrophulariaceae), dried rapidly below 60^\circ\text{C}$to a moisture content$\le 5\%.\n\n\n\n - **Microscopy:** Dorsiventral leaf; non-lignified uniseriate covering trichomes (3\text{--}4 cells long with collapsed cells and warty cuticle); short glandular trichomes with 1-celled stalk and 1- or 2-celled head; anomocytic/ranunculaceous stomata; absolute absence of calcium oxalate crystals.\n - **Chemical Constituents:** Primary glycosides (Purpurea glycosides A and B, glucogitoloxin). Hydrolysis by endogenous digipuridase enzyme yields secondary glycosides digitoxin, gitoxin, and gitaloxin. Deoxysugars D-digitoxose and D-digitalose give positive Keller-Kiliani tests.\n - **Chemical Identification Tests:**\n - **Baljet Test:** Section/extract + sodium picrate reagent \rightarrow yellow to orange-red color.\n - **Legal Test:** Extract in pyridine + sodium nitroprusside in alkali \rightarrow pink to red color.\n - **Keller-Kiliani Test:** Glacial acetic acid extract + FeCl_3$layered over conc.$H_2SO_4$$\rightarrow reddish-brown junction layer with upper acetic acid layer turning blue-green.\n - **Adulterants:** Mullein leaves (*Verbascum thapsus*, candelabra trichomes); Primrose leaves (*Primula vulgaris*, 8\text{--}9\text{-celled} simple trichomes); Comfrey leaves (*Symphytum officinale*, hooked trichomes).\n\n- **Digitalis Lanata (Grecian Foxglove):**\n - **Biological Source:** Dried leaves of *Digitalis lanata* Ehrh. (Family Scrophulariaceae).\n - **Constituents:** Lanatosides A, B, C, D, and E (acetyl derivatives). Primary commercial source of crystalline digoxin (derived from Lanatoside C).\n\n- **Thevetia (Yellow Oleander):**\n - **Biological Source:** Dried seeds/kernels of *Thevetia nerifolia* Juss. / *T. peruviana* (Family Apocynaceae).\n - **Chemical Constituents:** Cardenoactive glycosides including Thevetin A, Thevetin B, peruvoside, nerrifolin, and ruvoside.\n\n- **Squill (White and Red Squill):**\n - **Biological Source:** Dried sliced bulb scales of *Urginea maritima* (L.) Baker / *Drimia maritima* (Family Liliaceae).\n - **Chemical Constituents:** Bufadienolides: Scillaren A (crystalline) and Scillaren B (amorphous). Hydrolysis of Scillaren A yields proscillaridin A and scillarenin A.\n - **Diagnostic Tests:** Fails Baljet and Legal tests. Liebermann's sterol test is positive. Mesophyll cells contain long acicular calcium oxalate raphides embedded in mucilage.\n - **Red Squill Specificity:** Contains scilliroside; highly toxic to rodents (used as a selective rodenticide).\n\n- **Indian Squill:**\n - **Biological Source:** Slices of bulb of *Urginea indica* Kunth. Mucilage stains reddish-purple with iodine solution.\n\n- **Strophanthus:**\n - **Biological Source:** Dried ripe seeds of *Strophanthus kombe* Oliv. (Family Apocynaceae), deprived of awns.\n - **Chemical Constituents:** 8\text{--}10\%$$k\text{-strophanthin}$(mixture of cymarin,$k\text{-strophanthin-}\beta$, and$k\text{-strophanthoside}). Aglycone is strophanthidin; sugar is D-cymarose.\n\n- **Oleander:**\n - **Biological Source:** Dried leaves/seeds of *Nerium indicum* L. (Apocynaceae). Contains oleandrin.\n\n# Saponin Glycosides\n\n- **General Properties & Classification:**\n - Surface-active glycosides producing persistent frothing/foaming when shaken with water. Induce hemolysis of erythrocytes by complexing with membrane cholesterol.\n - Toxic to cold-blooded animals (fish poisons) but non-toxic to humans orally.\n - **Structural Classes:**\n - **Steroidal Saponins (Tetracyclic C_{27}):** Common in monocots (Solanaceae, Liliaceae, Dioscoreaceae).\n - **Triterpenoid Saponins (Pentacyclic C_{30}$):** Derived primarily from$\beta\text{-amyrin} framework. Common in dicots (Leguminosae, Polygalaceae, Rosaceae).\n\n- **Dioscorea (Yam):**\n - **Biological Source:** Dried rhizomes of *Dioscorea villosa*, *Dioscorea prazeri*, *Dioscorea deltoidea*, *Dioscorea floribunda* (Family Dioscoreaceae).\n - **Chemical Constituents:** Contains 4\text{--}6\% diosgenin (steroidal sapogenin) and smilagenin. Diosgenin is the premier industrial precursor for semi-synthesizing progesterone, cortisone, and oral contraceptive steroids.\n\n- **Liquorice (Glycyrrhiza):**\n - **Biological Source:** Peeled/unpeeled roots and stolons of *Glycyrrhiza glabra* L. (Family Leguminosae).\n - **Microscopy:** Radiating xylem vessels, phloem fiber groups with crystal sheaths of calcium oxalate prisms, distinct medullary rays, yellow parenchymatous phelloderm.\n - **Chemical Constituents:** Glycyrrhizin (6\text{--}8\%$; mixture of potassium and calcium salts of glycyrrhizic acid, a pentacyclic triterpenoid$50\text{-fold} sweeter than sucrose). Hydrolysis yields glycyrrhetic acid (glycyrrhetinic acid). Flavonoid liquiritin converts to chalcone isoliquiritin (yellow color).\n - **Identification Test:** Section/powder + 80\%$$H_2SO_4$$\rightarrow orange-yellow color.\n - **Uses:** Demulcent, expectorant, anti-ulcer, anti-inflammatory. Mineralocorticoid side effects (sodium retention, hypertension) on prolonged high dosing.\n\n- **Shatavari:**\n - **Biological Source:** Dried tuberous roots of *Asparagus racemosus* Willd. (Family Liliaceae). Contains steroidal saponins Shatavarin I--IV (aglycone: sarsasapogenin).\n\n- **Brahmi:**\n - **Biological Source:** Fresh or dried herb of *Centella asiatica* (L.) [Family Umbelliferae]. Contains triterpenoid saponins asiaticoside, madecassoside, brahmoside, and brahmic acid. Nootropic, memory enhancer, wound healing agent.\n\n- **Ginseng:**\n - **Biological Source:** Dried roots of *Panax ginseng* C.A. Mey. (Family Araliaceae). Contains triterpenoid saponin ginsenosides/panaxosides (dammarane types and oleanolic acid types). Adaptogen and immunostimulant.\n\n- **Senega:**\n - **Biological Source:** Dried rootstocks/roots of *Polygala senega* L. (Family Polygalaceae). Contains senegin (8\text{--}10\%), yielding presenegenin on hydrolysis. Displays a prominent projecting line/keel along its concave surface.\n\n- **Quillaia (Soap Bark):**\n - **Biological Source:** Dried inner bark of *Quillaia saponaria* Molina (Family Rosaceae). Contains \sim 10\% saponins yielding pentacyclic triterpenoid quillaic acid. Sternutatory.\n\n- **Gokhru:**\n - **Biological Source:** Dried ripe fruits of *Tribulus terrestris* Linn. (Family Zygophyllaceae). Globose spiny fruits containing 5 spiny woody cocci. Contains steroidal saponins terrestrosins A--E, tribulosin, and diosgenin. Diuretic and aphrodisiac.\n\n- **Sarsaparilla:**\n - **Biological Source:** Dried roots of *Smilax ornata* Hook. (Family Liliaceae). Contains sarsaponin (yielding sarsasapogenin).\n\n# Cyanogenic Glycosides\n\n- **General Chemistry & Chemical Tests:**\n - Glycosides yielding hydrocyanic acid (HCN), an aldehyde/ketone, and sugar upon enzymatic or acid hydrolysis.\n - **Sodium Picrate Test (Guignard Test):** Powdered sample moistened with water in a conical flask, filter paper strip impregnated with picric acid and sodium carbonate suspended over it. Volatile HCN converts yellow sodium picrate paper to brick-red.\n - **Mercurous Nitrate Test:** Sample treated with 3\%$aqueous mercurous nitrate solution$\rightarrow reduction to black metallic mercury.\n\n- **Bitter Almond:**\n - **Biological Source:** Expression/extraction of seeds of *Prunus amygdalus* Batsch var. *amara* (Family Rosaceae).\n - **Chemical Constituents:** Contains 2.5\text{--}4.0\%$cyanogenic glycoside amygdalin alongside emulsin enzyme complex. Hydrolysis yields benzaldehyde, hydrocyanic acid ($HCN), and glucose.\n\n- **Wild Cherry Bark (Virginian Prune):**\n - **Biological Source:** Dried bark of *Prunus serotina* Ehrh. (Family Rosaceae).\n - **Chemical Constituents:** Cyanogenic glycoside prunasin, hydrolyzed by endogenous prunase enzyme to benzaldehyde, HCN, and glucose. Contains scopoletin. Expectorant and sedative.\n\n# Isothiocyanate Glycosides\n\n- **General Chemistry & Specific Drug Profile:**\n - Glucosinolates yielding volatile, pungent isothiocyanates (\text{-NCS}) upon enzymatic cleavage by myrosin.\n - **Mustard:** Fixed oil/volatile oil obtained from seeds of *Brassica nigra* (L.) Koch (Black mustard) or *Brassica juncea* (Family Cruciferae/Brassicaceae). Black mustard contains glucosinolate sinigrin and enzyme myrosin. Enzymatic cleavage yields allyl isothiocyanate (CH_2=CH-CH_2-N=C=S).\n\n# Flavone Glycosides\n\n- **Ginkgo:**\n - **Biological Source:** Dried leaves of *Ginkgo biloba* L. (Family Ginkgoaceae).\n - **Chemical Constituents:** Diterpene trilactones (Ginkgolides A, B, C, J, M), sesquiterpene bilobalide, and flavonol glycosides (derivatives of kaempferol, quercetin, isorhamnetin, amentoflavone).\n - **Pharmacology:** Ginkgolides act as specific platelet-activating factor (PAF) receptor antagonists. Used for cerebral circulatory insufficiency, short-term memory loss, and vertigo.\n\n# Coumarin and Furanocoumarin Glycosides\n\n- **Visnaga:**\n - **Biological Source:** Ripe fruits of *Ammi visnaga* L. (Family Umbelliferae).\n - **Chemical Constituents:** \gamma\text{-Benzopyrone}$derivatives khellin ($1\text{--}2\%) and visnagin; pyranocoumarins visnadin and samidin. Smooth muscle relaxant, coronary vasodilator, antiasthmatic.\n\n- **Ammi:**\n - **Biological Source:** Ripe fruits of *Ammi majus* L. (Family Umbelliferae).\n - **Chemical Constituents:** Furanocoumarins xanthotoxin (methoxsalen), imperatorin, bergapten. Used topically/systemically to stimulate epidermal melanogenesis in vitiligo and psoriasis.\n\n- **Psoralea (Bavachi):**\n - **Biological Source:** Dried ripe fruits/seeds of *Psoralea corylifolia* L. (Family Leguminosae). Contains psoralen, isopsoralen, psoralidin, and bakuchiol. Used in leucoderma and vitiligo.\n\n# Aldehyde Glycosides\n\n- **Vanilla:**\n - **Biological Source:** Cured fully grown unripe fruits of *Vanilla fragrans* (Salisb.) Ames / *Vanilla planifolia* (Family Orchidaceae).\n - **Curing Enzymatic Process:** Green vanilla contains glucovanillin (vanilloside) and glucovanillic alcohol. Slow curing activates enzymes converting glucovanillic alcohol \rightarrow$vanillic alcohol$\rightarrow vanillin (vanillic aldehyde).\n\n# Phenol Glycosides\n\n- **Bearberry (Uva Ursi):**\n - **Biological Source:** Dried leaves of *Arctostaphylos uva-ursi* (L.) Spreng. (Family Ericaceae). Contains arbutin (hydroquinone \beta\text{-D-}glucopyranoside) and methylarbutin. Urinary antiseptic.\n\n# Steroidal Glycosides\n\n- **Solanum:**\n - **Biological Source:** Dried berries of *Solanum khasianum* C.B. Clarke (Family Solanaceae). Contains \sim 3\% steroidal glycoalkaloid solasodine, used as an industrial precursor for steroid synthesis.\n\n# Bitter and Miscellaneous Glycosides\n\n- **Gentian:**\n - **Biological Source:** Dried unfermented rhizomes and roots of *Gentiana lutea* L. (Family Gentianaceae).\n - **Chemical Constituents:** Secoiridoid bitter glycosides gentiopicrin (gentiopicroside), amarogentin (extremely bitter), gentiamarin, gentisin (xanthone pigment), and gentianose (trisaccharide).\n\n- **Picrorhiza:**\n - **Biological Source:** Dried rhizomes of *Picrorhiza kurroa* Royle ex Benth. (Family Scrophulariaceae). Contains iridoid glycosides kutkin, picroside I, picroside II, picroside III, and kutkoside. Hepatoprotective and bitter tonic.\n\n- **Chirata:**\n - **Biological Source:** Entire dried herb of *Swertia chirata* Buch.-Ham. (Family Gentianaceae). Contains amarogentin (phenol carboxylic acid ester of sweroside), ophelic acid, chiritin, gentianine.\n\n- **Quassia:**\n - **Biological Source:** Dried stem wood of *Aeschrion excelsa* (Sw.) Planch. [Jamaica Quassia] (Family Simarubaceae).\n - **Microscopy:** Lignified xylem vessels, multiseriate medullary rays (1\text{--}5 cells wide), starch, calcium oxalate prisms in parenchyma.\n - **Chemical Constituents:** Seco-triterpenoid bitter amaroids quassin, isoquassin (picrasmin), neoquassin. Pure bitter tonic, pediculicide.\n\n- **Kalmegh:**\n - **Biological Source:** Dried leaves or aerial parts of *Andrographis paniculata* Nees. (Family Acanthaceae).\n - **Chemical Constituents:** Bitter diterpene lactones andrographolide, 14\text{-deoxy-11-oxo-andrographolide}$$, neoandrographolide, andrograpanin. Hepatoprotective, febrifuge, immunostimulant.