Phytochemical analysis for
plant’s crude extract
By…….
Ass. Lec. Farah J. Hashim
Ass. Lab. Sumaya S. Hashim
Alkaloids
Alkaloids generally include alkaline substances that have
nitrogen as part of a ring structure. More than 6500 alkaloids
are known and are the largest class of secondary compounds.
They are very common in certain plant families.
Detection of Alkaloids.
Mayer’s test:
Mayer’s reagent was prepared by:
1.Solution A: 1.358 g of Mercuric chloride was dissolved in 60 ml of
distilled water.
2.Solution B: 2.5g of potassium iodide was dissolved in 10 ml of
distilled water.
Both solution were mixed and the volume was completed to 100
ml with distilled water.
The test:
Few drops of freshly prepared Mayer’s reagent were added to 5 ml
of the sample, a white precipitate will appear if Alkaloids were present.
Wagner’s reagent:
Tow grams of potassium iodide was dissolved in 5 ml of distilled
water ,then 1.27 g of iodide was added and the volume was completed
to 100 ml with distilled water.
The test:
Few drops of freshly prepared Wagner’s reagent were added
to 1 ml of the sample, a brown precipitate were appear of alkaloids
were present.
Terpenoids
• Terpenoids are dimers and polymers of 5 carbon
precursors called isoprene units (C5 H8).
• Terpenoids often evaporate from plants and contribute
to the haze we see on hot sunny days. They are
expensive to make; they often take 2% of the carbon
fixed in photosynthesis; carbon that could otherwise be
used for sugars.
Detection of Terpenoids and Steroids:
Four milliliters of acetic acid anhydride and 1 ml of
concentrated sulfuric acid( H2SO4 ) added to 2ml of
chloroform then mixed with 1 ml of crude extract. The
appearance of pink color indicated the presence of
Terpens while formation of blue color after leaving the
sample for 1minute indicated the presence of Steroids.
Saponins
Saponins are a class of chemical compounds, one of many secondary
metabolites found in natural sources, with saponins found in particular
abundance in various plant species. More specifically, the
are amphipathic glycosides grouped, in terms of phenomenology, by the
soap-like foaming they produce when shaken in aqueous solutions, and,
in terms of structure, by their composition of one or
more hydrophilic glycoside moieties combined with a lipophilic
triterpene derivative.
Detection of Saponins:
Five milliliters of the sample were added to three ml of mercuric
chloride (1%) solution ,formation of white precipitate indicating
presence of saponins.
Phenols
• Compounds that contain a fully unsaturated six carbon ring
linked to an oxygen are called phenolics.
• Salicylic acid (basic part of aspirin) is a simple phenol.
Detection of Phenols:
Mix equal volumes of 1% ferric chloride solution and
alcoholic crude extract .The appearances of blue-green
color indicated the presence of Phenols.
Flavonoids
are complex phenolics . They are often sold in health food stores as
supplements to vitamin C. The most commonly available flavonoid
is rutin from buckwheat.
Detection of Flavonoids:
Four milliliters of 95% ethanol were added to 1 ml of the
sample and then placed in boiling water path for 25-30 minutes.
Then few drops of potassium hydroxide 0.5N were added to
5ml of the sample. The presence of flavonoids was indicated by the
formation of dark yellow color.
Tannin
Tannin is a naturally occurring polyphenol found in
plants, seeds, bark, wood, leaves and fruit skins. About 50% of
the dry weight of plant leaves are tannins. As a characteristic of
wine, tannin adds both bitterness and astringency as well as
complexity. Wine tannins are most commonly found in red wine,
although white wines have tannin from being aged in wooden
barrels.
Detection of Tannin:
Few drops of lead acetate (1%) were added to 1ml of the
sample, appearance of white gel precipitate indicating tannins
were present.
Resin
Resin is a natural or synthetic compound that begins in a
highly viscous state and hardens with treatment. Typically, it is
soluble in alcohol, but not in water. The compound is classified in a
number of different ways, depending on its exact chemical
composition and potential uses. It also has many applications,
ranging from art to polymer production, and many consumers
interact with products that contain it on a daily basis.
Detection of Resin:
Ten milliliters of the sample were added to 20 ml of
acidic distilled water with hydrochloric acid 4%,formation of
turbidity Indicates to positive test.
Glycoside
A compound formed by the reaction of a pyranose sugar with a
nonsugar molecule (an aliphatic or aromatic hydrocarbon) termed the
aglycone. The aglycone replaces the hydrogen in the hydroxyl group of
carbon atom one of the sugar ring. Glucose is the sugar component of
many glycosides, such compounds being called glucosides. Some rare
sugars are only found in glycosides, e.g. digilalose, which has only been
detected in certain Digitalis glycosides
Detection of Glycosides.
Kid's reagent:
Solution A: 1g of 3,5 di nitrate benzoic acid was dissolved
in 50 ml of 95% methanol.
Solution B: 1g of potassium hydroxide was dissolved in
50ml of 95% ethanol. Then mix 0.4 ml from solution A with
0.6 ml from solution B.
The test:
Add few drops of Kid's reagent to 5 ml of the sample,
the presence of Glycosides is the formation of violet ring
color.