What Are Phytochemicals?
Phytochemicals are substances produced mainly by plants that possess biological activity. In the pharmaceutical industry, plants represent the primary source for obtaining various active ingredients.
Phytochemicals include:
- Phenolic compounds
- Terpenoids
- Alkaloids
- Flavonoids
- Glycosides
- Lignins
- Saponins
- Sterols
- Tannins
- Anthraquinones
- Reducing agents
More than 500 individual dietary phytochemicals have been identified in plant foods — including fruits, vegetables, whole grains, legumes, and nuts — with varying content and composition.
What is Phytochemical Investigation?
Phytochemical investigation (also called phytochemical screening) is the process of confirming the presence of a large array of phytoconstituents in a plant material. In this method, aqueous and organic extracts are prepared from plant samples that serve as reservoirs of secondary metabolites — such as leaves, stems, roots, or bark.
Process of Phytochemical Investigation
Phytochemical investigation of plant material involves four key stages:
1. Procurement of Raw Material and Quality Control Collection and quality assessment of raw plant material before analysis begins.
2. Extraction, Purification, and Characterisation Isolation of constituents of pharmaceutical interest from the plant material, along with in-process quality control to ensure accuracy and consistency.
3. Investigation of Biosynthetic Pathways Study of the biosynthetic routes through which particular compounds are produced within the plant.
4. Quantitative Evaluation Determination of the concentration and quantity of phytoconstituents present.
Types of Phytochemical Tests
Phytochemical tests are broadly classified into two types:
1. Quantitative Chemical Tests Used to determine the purity or concentration of a constituent in the plant material.
2. Qualitative Chemical Tests Used to detect the presence of different types of phytoconstituents and to identify adulterants.
Qualitative Chemical Tests — Drug-wise
For Alkaloids
| Test | Reagent |
|---|---|
| Dragendroff’s Test | Potassium bismuth iodide |
| Mayer’s Test | Potassiomercuric iodide |
| Wagner’s Test | Iodine in potassium iodide |
| Hager’s Test | Saturated picric acid solution |
For Glycosides
a. Cardiac Glycosides
| Test | Purpose |
|---|---|
| Killer-Killani Test | Detects digitoxose sugar in cardiac glycosides |
| Baljet Test | Detects unsaturated lactone ring |
| Legal Test | Detects cyclopentanoperhydrophenanthrene nucleus |
| Raymond’s Test | Identifies cardiac glycosides |
b. Anthraquinone Glycosides
| Test | Purpose |
|---|---|
| Borntrager’s Test | Detects anthraquinone derivatives; positive result — pink/red colour in ammonia layer |
| Modified Borntrager’s Test | Enhanced sensitivity for anthraquinone glycosides |
c. Saponin Glycosides
| Test | Purpose |
|---|---|
| Foam Test | Persistent froth on shaking indicates saponins |
| Haemolysis Test | Rupture of RBCs on contact with saponin-containing drug |
d. Flavonoids
| Test | Purpose |
|---|---|
| Shinoda Test | Positive result — pink to red colour with magnesium and HCl |
| Ammonia Test | Yellow fluorescence under UV light |
For Carbohydrates
| Test | Identifies |
|---|---|
| Molisch Test | General test for carbohydrates — purple/violet ring |
| Fehling’s Test | Reducing sugars — brick-red precipitate |
| Benedict’s Test | Reducing sugars — colour change from blue to red/orange |
| Tollens’ Reagent (Silver Mirror Test) | Aldehyde sugars — silver mirror formation |
For Proteins
| Test | Identifies |
|---|---|
| Biuret Test | Peptide bonds — violet/purple colour |
| Millon’s Test | Tyrosine-containing proteins — red colour |
| Xanthoproteic Test | Aromatic amino acids — yellow colour turning orange with alkali |
For Amino Acids
| Test | Identifies |
|---|---|
| Ninhydrin Test | Free amino acids and proteins — purple/violet colour |
Summary
Phytochemical evaluation is a critical step in drug analysis and quality control. It helps confirm the identity and purity of crude drugs, detect adulteration, and quantify active constituents. The combination of qualitative and quantitative chemical tests provides a comprehensive profile of the phytoconstituents present in any plant-derived drug material.
D.Pharma 1st Year — All Subjects Notes
D.Pharma 2nd Year — All Subjects Notes