Practice

• Xanthoproteic Test


  Tests for the presence of aromatic amino acids (proteins containing aromatic rings)
• Indication of positive results in the Xanthoproteic Test is the formation of yellow color upon the addition of concentrated nitric acid
• Principle of the Xanthoproteic Test

  Nitration of aromatic rings in amino acids or proteins by concentrated nitric acid leads to the formation of yellow-colored nitro compounds, indicating the presence of aromatic amino acids or proteins
• Wagner's Test


  Tests for the presence of alkaloids
• Indication of positive results in Wagner's Test is the formation of a brownish-red precipitate
• Principle of Wagner's Test

  Wagner's reagent (iodine in potassium iodide) reacts with alkaloids to form insoluble iodine-alkaloid complexes, leading to the formation of the precipitate
• Concentrated Sulfuric Acid Test

  Tests for the presence of flavonoids
• Indication of positive results in the Concentrated Sulfuric Acid Test is the formation of various color changes (typically ranging from yellow to orange to red) depending on the specific flavonoid present
• Principle of the Concentrated Sulfuric Acid Test

  Flavonoids contain phenolic structures that can undergo dehydration and oxidation reactions when treated with concentrated sulfuric acid, leading to the formation of various colored compounds
• Gelatin Test


  Tests for the presence of tannins
• Indication of positive results in the Gelatin Test is the formation of a white precipitate
• Principle of the Gelatin Test


  Tannins can form insoluble complexes with proteins such as gelatin, resulting in the formation of a precipitate
• Sodium Hydroxide Test


  Tests for the presence of flavonoids
• Indication of positive results in the Sodium Hydroxide Test is the formation of yellow coloration
• Principle of the Sodium Hydroxide Test

  Flavonoids react with sodium hydroxide to produce yellow coloration due to the presence of conjugated double bonds in their structure
• Salkowski Test


  Tests for the presence of terpenoids or steroids
• Indication of positive results in the Salkowski Test is the development of a reddish-brown coloration
• Principle of the Salkowski Test


  The reaction involves the formation of a complex between the terpenoids/steroids and sulfuric acid, leading to the development of the characteristic color
• Keller-Killiani Test


  Tests for the presence of glycosides, particularly cardiac glycosides
• Indication of positive results in the Keller-Killiani Test is the formation of red color
• Principle of the Keller-Killiani Test


  The reagent (glacial acetic acid and concentrated sulfuric acid) reacts with cardiac glycosides to produce a red color due to the presence of sugar moieties in the glycoside molecule
• Frothing Test


  Tests for the presence of saponins
• Indication of positive results in the Frothing Test is the formation of froth upon shaking
• Principle of the Frothing Test


  Saponins can form stable foam when shaken vigorously due to their amphiphilic nature, which can allow them to interact with water and trap air bubbles