1. What is Phytochemical?
Phytochemicals are chemical compounds that occur naturally in plants (phyto means "plant" in Greek). Some are responsible for color and other organoleptic properties, such as the deep purple of blueberries and the smell of garlic.
2. What is Phytochemical Screening?
Phytochemical screening is a process of tracing plant constituents. For example you want to found out if a certain plant contains alkaloids (a plant constituent) then, you will be performing a phytochemical screening procedures for alkaloids (in this case mayer's and Wagner's test).
3. What are the different reagents used in phytochemical screening? How are these reagents are prepared?
A. For Alkaloids:
Mayer’s reagent - is freshly prepared by dissolving a mixture of mercuric chloride (1.36 g) and of potassium iodide (5.00 g) in water (100.0 ml).
B. For Carbohydrates:
Molisch's reagent- dissolve 25 g of α-naphthol in 95% ethanol and dilute it to 500 mL with ethanol.
C. For Glycosides:
Modified Borntrager’s Test- Extracts were treated with Ferric Chloride solution and immersed in boiling water for about 5 minutes. The mixture was cooled and extracted with equal volumes of benzene.
D. For Saponins:
Froth Test- Extracts were diluted with distilled water to 20ml and this was shaken in a graduated cylinder for 15 minutes. Formation of 1 cm layer of foam indicates the
presence of saponins.
E. For Phenols:
Ferric Chloride Test- Extracts were treated with 3-4 drops of ferric chloride solution.
F. For Tannins:
Ferric Chloride Test- Extracts were treated with 3-4 drops of ferric chloride solution.
G. For Anthocyanins:
Sodium Hydroxide Test- Extracts are added with colorless sodium hydroxide.
H. For Proteins:
Xanthoproteic Test- The extracts were treated with few drops of concentrated nitric acid.
I. For Flavonoids:
Alkaline Reagent Test- Extracts were treated with few drops of sodium hydroxide solution.
4. What are the indicators of the presence of each phytochemical?
A. Mayer's Reagent- to give a cream colored precipitate
B. Molisch's Reagent- a positive reaction is indicated by appearance of a purple ring at the interface between the acid and test layers.
C. Modified Borntrager’s Test- formation of rose-pink color in the ammonical layer indicates the presence of anthranol glycosides.
D. Froth Test- formation of 1 cm layer of foam indicates the presence of saponins.
E. Ferric Chloride Test- formation of bluish black color indicates the presence of phenols.
F. Ferric Chloride Test- formation of bluish black color indicates the presence of tannins.
G. Sodium Hydroxide Test- when there is a formation of blue or green precipitates. It indicates that anthocyanin Is present.
H. Xanthoproteic Test- formation of yellow color indicates the presence of proteins.
I. Alkaline Reagent Test- formation of intense yellow color, which becomes colourless on addition of dilute acid, indicates the presence of flavonoids.
