JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Pharmacy IV Year QUALITY CONTROL AND STANDARDIZATION OF HERBALS Previous Question Paper (February-2022 - R17)

Phytochemical screening involves specific chemical tests to identify the presence of secondary metabolites in plant extracts:

1. Alkaloids: Dragendorff’s test involves adding potassium bismuth iodide to the extract; the formation of a reddish-brown precipitate indicates the presence of alkaloids. Mayer’s test uses potassium mercuric iodide, yielding a cream-colored precipitate.
2. Glycosides: Borntrager’s test is used for anthraquinone glycosides; adding dilute ammonia to the extract produces a pink-red color. Keller-Killiani test is used for cardiac glycosides (deoxy sugars), where glacial acetic acid and ferric chloride followed by concentrated sulfuric acid produce a reddish-brown ring at the junction.
3. Flavonoids: Shinoda test involves adding magnesium turnings and concentrated hydrochloric acid to the alcoholic extract; the appearance of a pink, crimson, or magenta color indicates the presence of flavonoids. Alkaline reagent test involves adding sodium hydroxide solution to the extract, which produces an intense yellow color that turns colorless upon the addition of dilute acid.

Quality evaluation of medicinal plants is performed through organoleptic, microscopic, physical, chemical, and biological parameters. Microscopic evaluation is essential for the identification of powdered drugs and crude plant materials by observing characteristic cellular structures.

Microscopic evaluation involves:

• Preparation: The sample is cleared with chloral hydrate to remove cell contents, stained with reagents like phloroglucinol and hydrochloric acid to detect lignified tissues (which turn red), or iodine solution to detect starch grains.
• Quantitative Microscopy: This includes determining the stomatal number, stomatal index, vein-islet number, vein-termination number, and palisade ratio, which are constant for specific species.
• Diagnostic Features: Observation of trichomes, calcium oxalate crystals (rosette, prism, or needle-shaped), starch grains, xylem vessels, and cork cells helps in authenticating the drug and detecting adulterants.