BP105T Unit 5 – Plant Tissue Culture & Traditional Systems of Medicine
Unit 5 explores plant metabolic pathways (Photosynthesis, Shikimic Acid pathway, Mevalonic Acid pathway) and provides exhaustive coverage of Primary Metabolites (Carbohydrates: Agar, Acacia, Tragacanth; Lipids: Castor oil, Chaulmoogra oil, Beeswax; Proteins: Gelatin) and Secondary Metabolites (Alkaloids, Glycosides, Tannins, Resins, Volatile Oils) with diagnostic phytochemical color tests.
📋 Prescribed Syllabus Topics
📖 Detailed Lecture Notes & Solved Examples
11. Primary vs. Secondary Metabolites & Biosynthetic Pathways
Dedicated Webpage➔Plants synthesize two distinct classes of chemical compounds: (1) Primary Metabolites — ubiquitous, basic biochemical building blocks (Carbohydrates, Amino Acids, Lipids, Proteins, Nucleic Acids) essential for cellular survival, growth, respiration, and reproduction; and (2) Secondary Metabolites — chemically diverse, specialized organic molecules (Alkaloids, Glycosides, Tannins, Resins, Flavonoids, Volatile Oils) produced in specific plant families for ecological defense against herbivores, insects, microbial pathogens, UV radiation, and inter-plant competition (allelopathy). Secondary metabolites are synthesized from primary metabolic precursors through three major intersecting biosynthetic pathways: (1) The Shikimic Acid Pathway (generates aromatic amino acids Phenylalanine, Tyrosine, Tryptophan $\rightarrow$ Phenylpropanoids, Lignans, Alkaloids, Hydrolyzable Tannins), (2) The Mevalonic Acid / MEP Pathway (generates Isopentenyl pyrophosphate - IPP $\rightarrow$ Monoterpenes, Sesquiterpenes, Steroids, Cardiac Glycosides), and (3) The Acetate-Malonate / Polyketide Pathway (generates Fatty Acids, Anthraquinones, Polyketides).Primary metabolites (Carbohydrates, Lipids, Proteins) paudhe ke zinda rehne ke liye zaroori hain. Secondary metabolites (Alkaloids, Glycosides, Tannins) paudha apni suraksha ke liye banata hai jo hamare liye tez dawaiyan banti hain. Shikimic acid pathway se aromatic amino acids aur alkaloids bante hain, jabki Mevalonic acid pathway se Terpenes, Volatile oils aur Cardiac glycosides bante hain.
▶Biosynthetic Precursor Mapping for Therapeutic Secondary Metabolites
How basic cellular sugars transform into complex pharmaceuticals.
| Metabolic Class | Biological Role in Plants | Distribution | Pharmacological Examples in Humans |
|---|---|---|---|
| Primary Metabolites (Sugars, Lipids, Proteins) | Cellular growth, respiration, structural membrane components | Universal in all plant species | Agar (laxative), Acacia (emulsifier), Gelatin (capsule shell) |
| Secondary: Alkaloids (Basic Nitrogen) | Defense against herbivores and insect attack | Specific families (Solanaceae, Apocynaceae) | Morphine (analgesic), Quinine (antimalarial), Atropine (mydriatic) |
| Secondary: Glycosides (Sugar + Aglycone) | Chemical storage, detoxification of xenobiotics | Scrophulariaceae, Liliaceae | Digoxin (cardiotonic), Sennosides (purgative) |
| Secondary: Tannins (Polyphenols) | Astringent protection against rot, viral/fungal defense | Fabaceae, Combretaceae | Catechu (antidiarrheal), Arjuna (cardioprotective) |
| Secondary: Volatile Oils (Terpenoids) | Attract pollinators, repel predatory insects | Lamiaceae, Apiaceae, Rutaceae | Eugenol (dental analgesic), Menthol (carminative/cooling) |
- •Primary Metabolites: Universal in all plants, high physiological necessity, no specific therapeutic specialization.
- •Secondary Metabolites: Restricted to specific families/taxa, variable distribution, profound pharmacological activities in humans.
- •Shikimic Acid Pathway is absent in animals, making it an ideal target for non-toxic herbicides (Glyphosate).
22. Primary Metabolites in Pharmacy: Carbohydrates, Lipids & Proteins
Dedicated Webpage➔Pharmaceutical primary metabolites serve as essential excipients, gelling agents, binders, and active therapeutics. (1) Carbohydrates: Agar (dried gelatinous substance from red algae Gelidium amansii; acts as bulk laxative and microbiological culture media), Acacia Gum (dried gummy exudate from Acacia senegal; acts as suspending and emulsifying agent), Tragacanth (Astragalus gummifer; superior viscosity grade suspending agent). (2) Lipids: Castor Oil (fixed oil from Ricinus communis containing Ricinoleic acid; acts as stimulant cathartic), Chaulmoogra Oil (Hydnocarpus wightiana containing hydnocarpic acid; historically used for leprosy), Beeswax (Apis mellifera; ointment stiffener). (3) Proteins: Gelatin (collagen hydrolysis product; used for hard/soft capsule shells).Agar lal algae (Gelidium amansii) se milta hai jo culture media aur bulk laxative ka kaam karta hai. Acacia gum babbool ke ped se nikalta hai jo emulsion banane me emulgent banta hai. Castor oil me Ricinoleic acid hota hai jo pet saaf (purgative) karta hai. Gelatin se capsule shells banti hain.
▶Standard Chemical Identification Tests for Carbohydrates & Mucilage
Colorimetric reactions used in pharmacognostic screening.
- •Agar: Composed of Agarose (gelling fraction) and Agaropectin (viscous sulfate fraction).
- •Acacia Gum: Composed of Arabin (calcium, magnesium, potassium salt of arabic acid).
- •Tragacanth: Composed of Bassorin (60-70% water-insoluble swelling fraction) and Tragacanthin (water-soluble fraction).
- •Castor Oil Cathartic Mechanism: Pancreatic lipases hydrolyze castor oil in duodenum into Ricinoleic Acid, which irritates small intestinal mucosa, stimulating peristalsis.
33. Diagnostic Phytochemical Screening of Secondary Metabolites
Dedicated Webpage➔Secondary metabolites are detected through standardized chemical color and precipitation tests conducted on plant extracts. The major classes include Alkaloids (basic organic nitrogen-containing compounds), Glycosides (organic compounds yielding a sugar and non-sugar aglycone upon hydrolysis), Tannins (high molecular weight phenolic astringents that precipitate proteins), and Volatile Oils (steam-distillable aromatic terpenoids).Alkaloids ke 4 main tests hain (MDWH): Mayer (Cream color), Dragendorff (Orange-red precipitate), Wagner (Reddish-brown), aur Hager (Yellow). Senna ke liye Borntrager test me ammonia layer pink/red ho jati hai. Digitalis ke liye Keller-Kiliani test me green-blue layer aati hai. Saponins paani me hilane par 15 min tak jhaag (foam) banate hain.
▶Official Pharmacopoeial Colorimetric Screening Test Suite
Reagents and characteristic positive color reactions.
| Secondary Metabolite | Diagnostic Reagent / Test | Observation / Positive Reaction | Phytochemical Class |
|---|---|---|---|
| Alkaloids | Dragendorff's Reagent | Prominent Orange-Red Precipitate | Nitrogenous base (e.g. Quinine, Atropine) |
| Anthraquinones | Borntrager's Test | Cherry-Red color in upper Ammonia layer | Senna, Aloe, Rhubarb |
| Cardiac Glycosides | Keller-Kiliani Test | Greenish-Blue layer above Reddish-Brown ring | Digitalis purpurea (Digitoxose sugars) |
| Saponins | Froth / Foam Test | Persistent honeycomb foam (> 15 min) | Dioscorea, Glycyrrhiza, Senega |
| Flavonoids | Shinoda Test (Mg + HCl) | Crimson / Scarlet Red color | Rutin, Quercetin, Ginkgo biloba |
| Tannins | Goldbeater's Skin / Gelatin | Black staining / Gelatin precipitate | Catechu, Ashoka, Arjuna bark |
- •Mnemonic for Alkaloid Reagents: MDWH -> Mayer (Cream), Dragendorff (Orange-red), Wagner (Reddish-brown), Hager (Yellow).
- •Cardiac Glycosides: Aglycone (Steroid nucleus with unsaturated lactone ring) + Glycone (Digitoxose deoxy-sugar).
- •Hydrolyzable Tannins (Gallotannins/Ellagitannins) yield gallic acid upon heating with mineral acids; Condensed Tannins (Proanthocyanidins) polymerize into insoluble red Phlobaphenes.
- In a 10-mark question on Phytochemical Screening, list all 4 Alkaloid reagents (Mayer, Dragendorff, Wagner, Hager) and specific tests for Anthraquinones (Borntrager), Cardiac glycosides (Keller-Kiliani), Flavonoids (Shinoda), and Tannins (FeCl3, Gelatin).
- Explain the primary biosynthetic differences between the Shikimic Acid and Mevalonic Acid pathways.