Pharmacognosy questions are mostly recall: which plant, which family, which constituent, which use. These notes group the facts that appear most often.
How this book helps in the exam
- Biological source and family of a crude drug.
- The main active constituent and its chemical class.
- Chemical tests that identify a constituent.
- Therapeutic use or toxicity of a plant drug.
What the book covers
10 high-yield topics. Each has the points most often examined and links to practise them.
1Crude drug evaluation
- Evaluation is organoleptic, microscopic, physical, chemical and biological.
- Ash values detect earthy matter; acid-insoluble ash shows silica such as sand.
- Stomatal index and palisade ratio help identify leaf drugs.
- Adulteration includes substitution with inferior or exhausted material.
2Alkaloids
- Alkaloids are basic nitrogen-containing compounds detected with Dragendorff's and Mayer's reagents.
- Tropane alkaloids (atropine, hyoscine) come from belladonna and datura (Solanaceae).
- Opium (Papaver somniferum) gives morphine, codeine and papaverine.
- Cinchona gives quinine; vinca (Catharanthus) gives vincristine and vinblastine.
3Cardiac and other glycosides
- Digitalis purpurea and D. lanata give cardiac glycosides; Keller-Kiliani detects their deoxy sugars.
- Anthraquinone glycosides in senna, cascara and aloe are stimulant laxatives; Borntrager's test detects them.
- Saponins froth in water and haemolyse red cells; liquorice contains glycyrrhizin.
- Cyanogenic glycosides (amygdalin) release hydrogen cyanide.
4Volatile oils
- Volatile oils are mainly terpenes, extracted by steam distillation.
- Clove oil contains eugenol, used in dental pain.
- Peppermint gives menthol; eucalyptus gives cineole.
- Volatile oils evaporate without leaving a permanent stain, unlike fixed oils.
5Resins and balsams
- Balsams contain benzoic or cinnamic acid (benzoin, tolu, Peru).
- Oleo-gum-resins include myrrh and asafoetida.
- Colophony is the resin left after distilling turpentine.
- Podophyllum resin is used for warts and is toxic if swallowed.
6Tannins
- Tannins precipitate proteins and are astringent.
- Hydrolysable tannins give a blue-black colour with ferric chloride; condensed tannins give green-black.
- The goldbeater's skin test identifies tannins.
- Galls, catechu and myrobalan are tannin sources.
7Carbohydrates and gums
- Acacia and tragacanth are gums used as emulsifying and suspending agents.
- Agar comes from red algae and is used in culture media.
- Starch gives a blue colour with iodine.
- Ispaghula (psyllium) husk is a bulk-forming laxative.
8Lipids and fixed oils
- Castor oil contains ricinoleic acid and is a stimulant laxative.
- Iodine value measures unsaturation; saponification value relates to chain length.
- Drying oils such as linseed have high iodine values.
- Waxes are esters of long-chain fatty acids with long-chain alcohols.
9Plant drugs in modern medicine
- Paclitaxel comes from the yew (Taxus) and artemisinin from Artemisia annua.
- Ephedrine comes from Ephedra, reserpine from Rauwolfia.
- Colchicine comes from Colchicum (autumn crocus).
- Ergot alkaloids (ergometrine, ergotamine) come from a fungus on rye.
10Herbal safety and interactions
- St John's wort induces CYP3A4 and P-gp, lowering levels of many drugs.
- Ginkgo and garlic can increase bleeding risk with anticoagulants.
- Liquorice can cause low potassium and high blood pressure.
- Kava and some traditional preparations are linked to liver toxicity.
These are PharmaPrep's own notes on the knowledge this book teaches. No text, tables or figures are reproduced from it. Read the book for full explanations, and check doses and laws against current official sources.
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