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Phytochemistry II (206) 2014/2015 Alkaloids Basic, organic, nitrogenous compounds of plant origin possessing a physiological activity. Hegnauer’s classification **True alkaloids **Proto alkaloids **Pseudo alkaloids Detection of alkaloids * Chromatographic techniques Spots in TLC corresponding to alkaloids: - Spraying with Dragendorff’s reagent - Expose to I2 vapor (not specific) * Chemical tests i. Alkaloid precipitants + alk soln amorphous or crystaline ppt ii. Alkaloid color reagent + alk residue or pd Characteristic color I. Alkaloid precipitants (Heavy metals) Mayer’s reagent Potassium-mercuric iodide soln Creamy white ppt Wagner’s reagent Soln of iodine in KI Reddish brown ppt Hager’s reagent Sat soln of picric acid in H2O Yellow ppt Dragendorff’s reagent Soln of potassium bismuth iodide Marme’s reagent Soln of potassium cadmium Yellow ppt iodide Orange to reddish brown ppt II. Alkaloid color reagents (H2SO4) Froehd’s reagent Ammonium molybdate/H2SO4 Mandalin’s reagent Ammonium vanadate/H2SO4 Marqui’s reagent HCHO / H2SO4 Erdmann’s reagent HNO3 / H2SO4 Modified Dragendorff’s reagent Potassium bismuth iodide Qualitative tests for identification of selected alkaloids • • • • • • • • • • Ephedrine Eserine Strychnine Atropine Papaverine Caffeine Quinine Brucine Morphine Pilocarpine First Lab 1-Eserine 1-Mayer’s test Indole alkaloid 0.5ml of alk soln 4 drops of Mayer's Reagent precipitate Special test (Rubreserine test) 1- 1ml alkaloid Shake solution 2- 2ml NaOH 3- 5ml H2O Red color 2.Ephedrine Phenylethylamine alkaloid OH NHCH3 1-Mayer’s test 0.5 ml alk soln + 4 dp Mayer’s reagent No ppt 2- Special test (Chen’s test) 1 ml alkaloid solution Purple + 2dps CuSO4 color +1ml CHCl3 + 1ml NaOH shake ???? ???? Purple color in CHCl3 layer 3.Strychnine Indole alkaloid 1-Mayer’s test 0.5 ml alk soln + 4 dp Mayer’s reagent precipitate 2- Conc. HNO3 test : A-Evaporate on BWB 1ml alkaloid till complete dryness solution B- Cooling C- 3dps Conc. HNO3 D- See color I E- Evaporate on BWB till complete dryness F-See color II of the residue Rapidly changes G- CooL H- 3 dps Alc KOH Brown color Violet color 3- Special test (H2SO4/K2Cr2O7 test) A-Evaporate on BWB 1ml alkaloid till complete dryness solution B- Cooling Few K2Cr2O7 Crystals + 2dps conc H2SO4 Violet streaks 4.Atropine H3C N H Tropane alkaloid CH2OH O O 1-Mayer’s test 0.5 ml alk soln + 4 dp Mayer’s reagent precipitate 2- Conc HNO3 test (Vitali’s test) : A-Evaporate on BWB 1ml alkaloid till complete dryness solution B- Cooling colorless C- 3dps conc HNO3 D- See color I E- Evaporate on BWB till complete dryness F-See color II of the residue G- CooL H- 3 dps alc KOH Violet color fades by time colorless 5-Papaverine 1-Mayer’s test 0.5ml of alk soln 4 drops of Mayer's Reagent Isoquinoline alkaloid precipitate 2- Conc HNO3 test A-Evaporate on BWB 1ml alkaloid till complete dryness solution B- Cooling C- 3 dps conc HNO3 D- See color I E- Evaporate on BWB till complete dryness F-See color II of the residue 3-Special test (Warren’s test) 1-Evaporate till dryness 1ml alkaloid solution 2-Cool 3- One crystal of KMnO4 4-Crush with end of test tube 5-2 dps of Marqui’s Bluish green Thanks for your Attention