Natural Product Chemistry: Extraction of eugenol from clove oil and identification by TLC.

Natural Product Chemistry: Extraction of eugenol from clove oil and identification by TLC.

Introduction:

Clove oil is essential oil extracted from clove. The main component of clove oil is eugenol. Because of the structural similarity of eugenol to aspirin, clove oil exhibits analgesic and anti-inflammatory activity and used primarily in dentistry for the remedy of toothache. This can be purchased in pharmacies over the counter. The analgesic and anti-inflammatory effects are due to the ability of eugenol to inhibit the enzyme cyclo-oxygenase.

Aims:

Extraction eugenol from clove oil and its identification

Equipment, chemicals and Materials:

Chemicals and solvents- Clove oil (10ml), Eugenol (100ul), DCM (50ml), Ethyl acetate (100 ml), Hexane (100ml), Ethanol (10ml), 1% Ferric Chloride, Anhydrous Na2SO4 or MgSO4 (100 gm), 5% KOH (50ml), 2.5 M HCl (50 ml) Materials- Large Beaker (250ml; X2), Round bottom flask (250ml, 100ml), Measuring Cylinder (50ml), Funnel, Bunsen, Separating funnel (125ml), stand, Pipette (200ul, 1ml, 5ml), Stirring rod, 125ml conical flask, TLC plate, Watch glass, litmus paper, UV lamp Equipments- Rotary evaporator, TLC tank (large)

Procedure:

Part 1: Extraction of eugenol

1. Transfer 2.5ml (pipette accurately) of clove oil in a conical flask containing 20ml of 5% KOH. Swirl occasionally for 3 min.
2. Transfer the content into a separating funnel to remove the immiscible part of the oil. Collect the aqueous part in a 100 mL beaker and add 2.5 M HCl until it becomes acidic. Use litmus paper to observe the change.
3. Transfer the content into the separation funnel and add 10ml of DCM. Shake carefully and collect the DCM layer in a 250 mL beaker.
4. Add anhydrous Na2SO4 to the collected DCM layers to remove any remaining water. Keep adding until the Na2SO4 moves freely when the beaker is swirled.
5. Using a Buchner filtration system, remove the Na2SO4 and collect the dried DCM layer 6. Transfer to a pre-weighed round bottom flask and evaporate the solvent by rotavapour. 2 7. Allow to cool the flask and re-weigh to calculate the amount of eugenol extracted.
6. Calculate percentage yield of eugenol in the clove oil.

Part 2: Identification of eugenol by TLC

1. Dissolve the a few drops of extract in 2ml of alcohol in a small vial.
2. Apply the reference solution and sample solution on a TLC plate, 1 cm above bottom edge. Draw another line at 2 cm below the top edge.
3. Add 10ml mobile phase (Hexane: Ethyl acetate= 8:2) in TLC tank. Always place a lid on the tank.
4. Apply the TLC plate into the tank and develop the chromatograph until it reaches the mark.
5. Remove the TLC plate and allow to dry in fumehood.
6. View the TLC plate under UV light (254nm).
7. Comment on your observation.

Reflective questions

1. Write down the botanical name of clove. What types of compounds are present in clove?
2. Draw the chemical structure of eugenol and outline its tentative IR bands for the key functional groups.