Pharmacognosy and Phytochemistry: Sources, Tests and Standardisation
Pharmacognosy and Phytochemistry covers crude-drug sources, chemical classes, evaluation and standardisation - a scoring area because the facts are concrete and often repeated.
Core material
- Alkaloids: Atropa belladonna (tropane alkaloids), Papaver somniferum (morphine), Cinchona bark (quinine, quinidine), Rauwolfia serpentina root (reserpine), Catharanthus roseus (vincristine, vinblastine), Ephedra (ephedrine).
- Glycosides: Digitalis purpurea leaf (digitoxin, gitoxin), Digitalis lanata (digoxin), Strophanthus (ouabain), Glycyrrhiza (glycyrrhizin), Senna (sennosides).
- Others: clove (eugenol), peppermint (menthol), cinnamon (cinnamaldehyde), guggul (guggulsterones), Taxus (paclitaxel).
- Evaluation: organoleptic, microscopic (stomata, trichomes, calcium oxalate, starch), physical (ash value, extractive value, swelling index, foaming index), chemical and biological assays.
- Adulteration may be substitution, inferior material, exhausted drug or a synthetic adulterant; detect by morphology, microscopy and marker-based assays.
Worked example
A leaf sample gives a positive Keller–Kiliani test (reddish-brown colour at the interface) and a positive Baljet reaction, while the froth and Dragendorff tests are negative. Keller–Kiliani detects 2-deoxy sugars, characteristic of cardiac glycosides; the negative Dragendorff excludes alkaloids. The drug is therefore Digitalis, and identity is confirmed by comparing its TLC fingerprint with a standard.
Traps
Learn the part used (Cinchona bark, not root; Rauwolfia root); distinguish Digitalis purpurea (digitoxin) from D. lanata (digoxin); do not use a single colour test as identity proof; and remember that ash values measure inorganic residue, not alkaloid content.