*6.3.6 Tests for flavonoids*

Flavonoids are present in hydrolyzed plant extracts. Its presence is maximum in parts of the leaves and they are highly soluble in methanol. The flavonoids are all derived structurally from the important substance called flavone. The flavonoids occur in the free form as well as bound to sugars as glycosides. Flavonoids are found maximum in herbal plants and have good phytopharmacological activities.

Preparation of test solution:

i. To 1 ml of extract, equal volume of 2 M HCl was added and heated in a test tube for 30 to 40 min. at 100°C.

	- Shinoda test: to 2 ml of extract, add 5 ml of 95% ethanol, 5 drops of concentrated HCl, and 0.5 g magnesium turnings. Pink color was observed. To small quantity of residue, acetate solution was added and observed for yellow colored precipitate. Addition of sodium hydroxide to the residue showed yellow coloration, which was decolorized after addition of dilute hydrochloric acid.
	- Ferric chloride test: to 2 ml of test solution, add few drops of ferric chloride solution, which shows intense green color.
	- Alkaline reagent test: 2 ml of test solution was treated with 2 ml of sodium hydroxide solution, which showed intense yellow color that became colorless on addition of few drops of dilute hydrochloric acid.
	- • Lead acetate solution test: 2 ml of test solution with few drops of lead acetate solution (10%) gives yellow precipitates.
