Pharmacognosy
Natural Products, Medicinal Plants & Herbal Medicines
In This Section
1. Introduction to Pharmacognosy
Definition & Scope
Pharmacognosy (Greek: pharmakon = drug, gnosis = knowledge) is the study of medicines derived from natural sources—plants, animals, minerals, and microorganisms.
Areas of Study
- • Identification of crude drugs
- • Cultivation and collection
- • Isolation of active constituents
- • Structure elucidation
- • Biological activity evaluation
Importance
- • ~40% of drugs from natural origin
- • Source of lead compounds
- • Traditional medicine validation
- • Herbal supplement regulation
- • Biodiversity conservation
Classification of Natural Drugs
| Classification Basis | Categories | Examples |
|---|---|---|
| Alphabetical | A to Z listing | Acacia, Belladonna, Cinchona... |
| Morphological | Plant part used | Leaves, roots, bark, seeds, flowers |
| Taxonomic | Botanical families | Solanaceae, Rubiaceae, Papaveraceae |
| Chemical | Active constituent type | Alkaloids, glycosides, terpenes |
| Pharmacological | Therapeutic action | Cardiotonics, antihypertensives |
Drug Parts Terminology
Herba
Aerial parts (herb)
Folium
Leaf
Flos
Flower
Fructus
Fruit
Semen
Seed
Radix
Root
Rhizoma
Rhizome
Cortex
Bark
Lignum
Wood
2. Alkaloids
Definition & Properties
Nitrogen-containing organic compounds of plant origin with marked pharmacological activity. Usually basic (form salts), bitter taste, and often toxic in large doses.
General Properties
- • Basic nature (contain N)
- • Form salts with acids
- • Usually colorless, crystalline
- • Bitter taste
- • Potent pharmacological effects
Detection Tests
- Mayer's: Cream/white precipitate
- Dragendorff's: Orange-red precipitate
- Wagner's: Reddish-brown precipitate
- Hager's: Yellow precipitate
Classification by Chemical Structure
| Class | Examples | Source | Action |
|---|---|---|---|
| Tropane | Atropine, Scopolamine, Cocaine | Belladonna, Coca | Anticholinergic, Local anesthetic |
| Phenanthrene | Morphine, Codeine, Thebaine | Opium poppy | Analgesic, Antitussive |
| Quinoline | Quinine, Quinidine | Cinchona bark | Antimalarial, Antiarrhythmic |
| Isoquinoline | Papaverine, Berberine | Opium, Goldenseal | Vasodilator, Antimicrobial |
| Indole | Reserpine, Vincristine | Rauwolfia, Vinca | Antihypertensive, Antineoplastic |
| Purine | Caffeine, Theophylline | Coffee, Tea | CNS stimulant, Bronchodilator |
| Piperidine | Piperine, Lobeline | Black pepper, Lobelia | Bioenhancer, Respiratory stimulant |
Important Alkaloid-Containing Drugs
Opium (Papaver somniferum)
- Part used: Unripe capsule latex
- Morphine (10%): Narcotic analgesic
- Codeine (0.5%): Antitussive, mild analgesic
- Papaverine (1%): Smooth muscle relaxant
- Noscapine: Antitussive
Cinchona (Cinchona species)
- Part used: Stem bark
- Quinine (5-8%): Antimalarial, bitter tonic
- Quinidine: Antiarrhythmic (Class IA)
- Cinchonine: Antimalarial
- Totaquine: Mixed alkaloids
Belladonna (Atropa belladonna)
- Part used: Leaves, root
- Atropine (0.4%): Anticholinergic, mydriatic
- Scopolamine: Antiemetic, motion sickness
- Uses: Preoperative, ophthalmology
Rauwolfia (Rauwolfia serpentina)
- Part used: Root
- Reserpine: Antihypertensive (depletes catecholamines)
- Ajmaline: Antiarrhythmic
- Historical: First effective antihypertensive
3. Glycosides
Definition & Structure
Compounds containing a sugar moiety (glycone) linked to a non-sugar component (aglycone/genin) via a glycosidic bond. The aglycone determines pharmacological activity.
Glycoside = Sugar (Glycone) + Non-sugar (Aglycone)
Hydrolysis (acid/enzyme) breaks the glycosidic bond, releasing both components
Types of Glycosides
Cardiac Glycosides (Cardiotonics)
Aglycone = steroidal nucleus with lactone ring. Increase cardiac contractility (positive inotropic).
Digitalis (Foxglove)
- • D. purpurea → Digitoxin (lipophilic)
- • D. lanata → Digoxin (more polar)
- • Inhibit Na⁺/K⁺-ATPase
- • CHF, Atrial fibrillation
Other Sources
- • Strophanthus → Ouabain (g-strophanthin)
- • Convallaria → Convallatoxin
- • Thevetia → Thevetin
Anthraquinone Glycosides (Laxatives)
Stimulate peristalsis in large intestine. 8-12 hours onset—bedtime dosing.
Senna
Sennosides A & B
Cascara
Cascarosides
Aloe
Aloin (barbaloin)
Rhubarb
Rhein, emodin
Frangula
Frangulin
Saponin Glycosides
Form foam in water (surfactant properties). Hemolytic—not for parenteral use.
Steroidal Saponins
- • Diosgenin (Dioscorea) → steroid precursor
- • Sarsaparilla saponins
Triterpenoid Saponins
- • Glycyrrhizin (Licorice) → sweetener, anti-ulcer
- • Ginseng saponins (ginsenosides)
Cyanogenic Glycosides
Release HCN (hydrogen cyanide) on hydrolysis—toxic. Characteristic bitter almond smell.
- Amygdalin: Bitter almonds, apricot seeds
- Prunasin: Wild cherry bark (cough syrup flavoring)
- Linamarin: Cassava (requires proper processing)
Other Glycoside Types
Flavonoid Glycosides
- • Rutin (Buckwheat) → capillary fragility
- • Hesperidin (Citrus) → antioxidant
Coumarin Glycosides
- • Sweet clover → dicumarol (anticoagulant)
- • Warfarin derived from spoiled clover
4. Terpenes & Essential Oils
Terpenes Classification
Built from isoprene units (C₅H₈). Classification based on number of isoprene units.
| Type | Carbon Units | Examples | Activity |
|---|---|---|---|
| Monoterpenes | C₁₀ (2 units) | Menthol, Limonene, Camphor | Essential oil components |
| Sesquiterpenes | C₁₅ (3 units) | Artemisinin, Farnesol | Antimalarial |
| Diterpenes | C₂₀ (4 units) | Taxol, Vitamin A | Anticancer |
| Triterpenes | C₃₀ (6 units) | Squalene, Steroids | Various |
| Tetraterpenes | C₄₀ (8 units) | Carotenoids, β-carotene | Antioxidant, Vitamin A precursor |
Essential Oils (Volatile Oils)
Complex mixtures of volatile, aromatic compounds. Obtained by distillation or expression. Main components: monoterpenes, sesquiterpenes, and their oxygenated derivatives.
Extraction Methods
Steam Distillation
- • Most common method
- • Steam carries volatile oils
- • Condense and separate
- • Examples: Peppermint, Eucalyptus
Expression (Cold Press)
- • Mechanical pressing
- • Citrus peel oils
- • No heat damage
- • Lemon, Orange, Bergamot
Important Essential Oils
Peppermint Oil
Mentha piperita
Menthol (42-52%), carminative, counterirritant
Eucalyptus Oil
Eucalyptus globulus
Eucalyptol (1,8-cineole), expectorant
Clove Oil
Syzygium aromaticum
Eugenol (85-90%), dental analgesic
Tea Tree Oil
Melaleuca alternifolia
Terpinen-4-ol, antiseptic
Lavender Oil
Lavandula angustifolia
Linalool, anxiolytic, aromatherapy
Turpentine Oil
Pinus species
α-pinene, counterirritant
Notable Terpenoids
Artemisinin (Qinghaosu)
- Source: Artemisia annua (Sweet wormwood)
- Class: Sesquiterpene lactone with peroxide
- Use: Antimalarial (ACT therapy)
- MOA: Free radical generation in parasite
- Nobel Prize 2015: Tu Youyou
Paclitaxel (Taxol)
- Source: Taxus brevifolia (Pacific yew)
- Class: Diterpene (taxane)
- Use: Ovarian, breast, lung cancer
- MOA: Microtubule stabilization
- Now: Semi-synthetic from 10-DAB
5. Phenolic Compounds
Classification
Compounds containing one or more hydroxyl groups attached to aromatic ring. Common antioxidants with various pharmacological activities.
Tannins
Polyphenols that precipitate proteins. Astringent taste. Used in wound healing.
Hydrolyzable Tannins
- • Gallotannins (gallic acid esters)
- • Ellagitannins
- • Sources: Oak, Nutgall
Condensed Tannins
- • Proanthocyanidins
- • Not hydrolyzable
- • Sources: Catechu, Witch hazel
Flavonoids
C6-C3-C6 structure. Potent antioxidants, reduce capillary fragility.
Flavones
Apigenin, Luteolin
Flavonols
Quercetin, Kaempferol
Flavanones
Hesperidin, Naringenin
Isoflavones
Genistein, Daidzein (soy)
Anthocyanins
Red/blue pigments
Catechins
Green tea EGCG
Coumarins
Benzopyran-2-one derivatives. Some are anticoagulants.
- Dicumarol: Anticoagulant (vitamin K antagonist)
- Psoralen: Photochemotherapy (PUVA for psoriasis)
- Umbelliferone: Sunscreen ingredient
Important Phenolic Drugs
Ginkgo (Ginkgo biloba)
- Active: Flavonoids, ginkgolides, bilobalide
- Uses: Cognitive function, peripheral circulation
- MOA: PAF antagonist, antioxidant
- Caution: May increase bleeding risk
Milk Thistle (Silybum marianum)
- Active: Silymarin complex (silybin)
- Uses: Hepatoprotective, antioxidant
- MOA: Stabilizes hepatocyte membranes
- Indications: Alcoholic liver disease, cirrhosis
St. John's Wort (Hypericum)
- Active: Hypericin, hyperforin
- Uses: Mild-moderate depression
- Caution: CYP3A4 inducer—many interactions
- Photosensitivity: Common adverse effect
Green Tea (Camellia sinensis)
- Active: EGCG (epigallocatechin gallate)
- Uses: Antioxidant, weight loss
- Benefits: Cardiovascular, anticancer potential
- Contains: Caffeine (stimulant)
6. Philippine Medicinal Plants
DOH-Approved Herbal Medicines (10 Herbs)
The Philippine Department of Health has endorsed these 10 medicinal plants with clinically proven safety and efficacy for specific therapeutic uses.
1. Lagundi (Vitex negundo)
Five-leaved chaste tree
- Part used: Leaves
- Active: Chrysoplenol D, luteolin
- Uses: Cough, asthma, fever, pharyngitis
- Form: Decoction, syrup, tablet
2. Sambong (Blumea balsamifera)
Ngai camphor
- Part used: Leaves
- Active: L-borneol, cineole
- Uses: Diuretic, dissolves kidney stones
- Form: Decoction, tablet
3. Tsaang-gubat (Carmona retusa)
Wild tea
- Part used: Leaves
- Active: Rosmarinic acid
- Uses: Diarrhea, stomach pain, mouthwash
- Form: Decoction
4. Yerba Buena (Mentha cordifolia)
Peppermint
- Part used: Leaves
- Active: Menthol, pulegone
- Uses: Analgesic, headache, rheumatism
- Form: Decoction, poultice
5. Niyog-niyogan (Quisqualis indica)
Chinese honeysuckle
- Part used: Seeds
- Active: Quisqualic acid
- Uses: Anthelmintic (roundworms)
- Dose: 4-7 seeds (children), chewed
6. Bayabas (Psidium guajava)
Guava
- Part used: Leaves
- Active: Tannins, flavonoids
- Uses: Antiseptic wash for wounds, diarrhea
- Form: Decoction for washing
7. Akapulko (Cassia alata)
Ringworm bush
- Part used: Leaves
- Active: Chrysophanic acid
- Uses: Antifungal (ringworm, scabies)
- Form: Poultice, lotion
8. Ulasimang-bato (Peperomia pellucida)
Pansit-pansitan
- Part used: Whole plant
- Active: Flavonoids, phenolic acids
- Uses: Lowers uric acid, gout, arthritis
- Form: Decoction, salad
9. Bawang (Allium sativum)
Garlic
- Part used: Bulb
- Active: Allicin, ajoene
- Uses: Lower cholesterol, hypertension
- Dose: 1-2 cloves daily
10. Ampalaya (Momordica charantia)
Bitter melon
- Part used: Leaves, fruit
- Active: Charantin, momordicin
- Uses: Non-insulin dependent diabetes
- Form: Decoction, capsule, vegetable
Other Philippine Medicinal Plants
Banaba (Lagerstroemia speciosa)
Corosolic acid • Blood sugar control
Oregano (Origanum vulgare)
Carvacrol • Cough, sore throat
Luya (Zingiber officinale)
Gingerols • Antiemetic, anti-inflammatory
Tawa-tawa (Euphorbia hirta)
Flavonoids • Dengue (platelet booster)
Malunggay (Moringa oleifera)
Vitamins, minerals • Nutritive, galactagogue
Makabuhay (Tinospora rumphii)
Berberine • Fever, malaria
7. Quality Control of Crude Drugs
Evaluation Methods
| Method | Parameters | Purpose |
|---|---|---|
| Organoleptic | Color, odor, taste, texture | Initial identity check, crude detection of adulteration |
| Morphological | Size, shape, surface characteristics | Identify plant part, detect substitutes |
| Microscopic | Cells, tissues, trichomes, crystals | Species identification, powder analysis |
| Physical | Moisture, ash, extractive values | Purity assessment |
| Chemical | Assay of active constituents | Potency determination |
| Biological | Bioassays, animal tests | Activity comparison to standard |
Physical Constants
Moisture Content
- • Loss on drying (LOD)
- • Karl Fischer titration
- • Usually <10-14%
- • High moisture → microbial growth
Ash Values
- Total ash: All inorganic residue
- Acid-insoluble ash: Sand, silica (earthly matter)
- Water-soluble ash: Mineral oxides
- • Detects inorganic adulteration
Extractive Values
- • Water-soluble extractive
- • Alcohol-soluble extractive
- • Indicates constituent solubility
- • Detects exhausted drug
Foreign Matter
- • Other plant parts
- • Insects, mold
- • Soil, stones
- • Usually <2% allowed
Chromatographic Methods
TLC (Thin Layer)
- • Quick fingerprint analysis
- • Identity confirmation
- • Adulteration detection
- • Rf value comparison
HPLC/HPTLC
- • Quantitative analysis
- • Marker compound assay
- • Stability studies
- • Batch consistency
8. Biotechnology & Modern Applications
Plant Tissue Culture
In vitro propagation of plant cells/tissues under sterile conditions for mass production of secondary metabolites or conservation of rare medicinal plants.
Applications
- • Micropropagation of rare species
- • Production of secondary metabolites
- • Germplasm conservation
- • Disease-free plant production
Examples
- • Shikonin from Lithospermum
- • Paclitaxel from Taxus cells
- • Vincristine from Catharanthus
- • Berberine from Coptis
Genetic Engineering
- •Metabolic engineering: Modify biosynthetic pathways for enhanced production
- •Recombinant DNA: Express plant genes in microorganisms (artemisinin in yeast)
- •Hairy root culture: Agrobacterium-transformed roots for alkaloid production
- •Molecular pharming: Plants as bioreactors for therapeutic proteins
Modern Trends
Metabolomics
- • Comprehensive metabolite profiling
- • Quality control fingerprinting
- • Biomarker discovery
- • LC-MS, NMR techniques
Systems Biology
- • Network pharmacology
- • Multi-target drug effects
- • Synergistic interactions
- • Traditional medicine validation
Nanotechnology
- • Herbal nanoformulations
- • Enhanced bioavailability
- • Targeted delivery
- • Phytosome technology
Sustainable Sourcing
- • Good Agricultural Practices (GAP)
- • Conservation of endangered species
- • CITES regulations
- • Bioprospecting ethics
Key Takeaways
- ✓Alkaloids contain nitrogen, are basic, and detected by Mayer's/Dragendorff's reagents
- ✓Glycosides = sugar + aglycone; cardiac glycosides inhibit Na⁺/K⁺-ATPase
- ✓Terpenes built from isoprene (C₅); monoterpenes in essential oils
- ✓Artemisinin (Nobel 2015) and Paclitaxel are important terpenoid drugs
- ✓Know all 10 DOH-approved Philippine medicinal plants and their uses
- ✓Lagundi for cough, Sambong for kidney stones, Ampalaya for diabetes
- ✓Quality control: ash values detect inorganic adulteration
- ✓Biotechnology enables sustainable production of plant-derived medicines