Question

Objective

To extract essential oils and other natural products from the leaves of mentha spicata L. .

Reactions

Not applicable

Procedure

1.  Weigh 1.0 g of leaves and place them in a glass mortar.  Grind the material until a more or less homogenous mass is obtained.  Transfer the ground material into a 100 mL beaker, add a stir bar and 10 mL of water and 10 mL of diethyl ether.

Cover the beaker with a watch glass and stir vigorously for 10 minutes at room temperature.  It might be necessary to clamp the beaker to prevent it from moving off the stir plate.

2.  After 10 minutes of vigorous stirring, separate the solids from the liquid layers by vacuum filtration, wash the filter cake with 10 mL of diethyl ether.  Transfer the filtrate into a separatory funnel.

3.  Once two distinct layers have formed, separate them and place them in two Erlenmeyer flasks. Wash the aqueous layer once more with 10 mL of diethyl ether and add that ethereal extract to the rest of the organic extract. Prepare four TLC plates, spot the aqueous layer on each of them and allow the spots to dry.  Dry the combined organic extracts with anhydrous magnesium sulfate.

4.  Filter the dried organic extract into a pre-weighed round bottom flask, use this filtered solution to make one spot on each TLC plate. Then remove the solvent from the round bottom flask under reduced pressure.

5.  Weigh the dried organic extract.

6.  Develop two of the TLC plates in a chamber with a high polarity eluent, the other two in a chamber with a low polarity eluent.

7.  After observing the plates under UV-light, stain one 'high polarity plate' and one 'low polarity plate' with anisaldehyde stain, the other two plates with ceric ammonium molybdate solution.  Report your results.

Post-Lab Questions

1.      What are terpenoids and how can they be visualized best on TLC-plates? Why?

2.      What are the highly polar components found in the leave extract? How are they visualized?

3.      What are chlorophylls and how can they be visualized best?

4.      Describe the use of one natural product in medicine.

Answer 1

1) Carbone terpenoid is present in Carbone and perillyl alcohol.

They can be separated by thin layer chromatin as they have long hydrocarbon chain a prenyl diphosphate which can be IONIZED

Thus varying lengths of the hydrocarbon and the modification of the Chian by acetylation or methylation can give them speficities.

In thin layer chromatography, the terpenoids which are separated is mostly hydrophobic because if their long hydrocarbon chains.

Larger terpenoids will be eluted last .

But cyclic terpenoids will be eluted faster because of their compact nature than the linear terpenoids .

Thank you