Jennifer Lagnado                                                                                        Return to Chemistry Menu

Lawrence High School, Long Island

Summer 2001

Extraction of Allicin:  The Active Ingredient in Garlic

Many drugs used by consumers for medicinal purposes are derived from plants.  Plants can be called the first chemists because they can synthesize large molecules for biological activity.  These compounds are used by plants as defense against plant eating insects and other are by-products of  growth processes of plants.  A number of these plant compounds have a property or chemical activity useful to humans. 

Part I.  Outside Research

Using outside sources, such as the library or Internet determine the scientific name of garlic and the structural formula for Allicin. 

Part II.  Laboratory Activity

1.     Using a mortar and pistle, crush a clove of garlic

2.     Place the crushed garlic and oil in a 50 ml beaker. 

3.     Soak the crushed garlic and oil in 20 ml. of ethanol.

4.     Cover the beaker with a watch glass and allow it to stand for half an hour.

5.     Pour 15 ml of hexane and 5 ml. of isopropanol in a beaker to produce a 3:1 hexane isopropanol solvent.

6.     Pour the solvent mixture into a TLC chamber.  No more than ¼ of an inch of solvent should be added to the chamber.

7.     Cut a piece of filter paper into a rectangle that fits into the TLC chamber.

8.     Using a pencil, draw a line approximately 3 cm. from the bottom of the filter paper.

9.     Using a capillary spotter, place one drop of the garlic/ethanol mixture on the penciled line of the filter paper.

10. Place the filter paper in the TLC chamber.

11. Allow it to stand until you see a clear colored band approximately half to three-fourths from the bottom of the paper.

Part III.  Conclusion Questions

1.     What chemical causes the strong smelling odor in garlic?

2.     Draw the structural formula of Allicin.

3.     How does thin layer chromatography work?

4.     Why do we use the 3:1 hexane isopropanol as the solvent in the thin layer chromatography chamber?

5.  What are the other benefits of the ingestion of garlic?

6.  What other compounds could you extract from plants?  Using the space below, design an experiment to extract a compound of your choice.  What kind of solvent would you use in the TLC chamber and why? 

New York State Standards

            The above lesson plan satisfies a number of New York State Learning Standards for mathematics, science, and technology. 

Standard 1:  Analysis, Inquiry, and Design

            Students will use mathematical analysis, scientific inquiry, and engineering design, as appropriate, to pose questions, seek answers, and develop solutions.

Standard 2:  Information Systems

            Students will access, generate, process, and transfer information using appropriate technologies.

Standard 4:  Science

            Students will understand and apply scientific concepts, principles, and theories pertaining to the physical setting and living environment and recognize the

            historical development of ideas in science.

References

National Research Council.  National Science Education Standards.  National Academy Press.  Washington, DC.  1996.

Wilbraham, A.C., Staley, D.D, Matia, M.S., & Waterman, E.L.  Chemistry.  Prentice Hall.  Palo Alto, California.  Fifth Edition.  2000.

            Zubrick, J.W.  The Organic Chemistry Lab Survival Manual:  A Student Guide To Techniques.  Fourth Edition.  Pg. 252-264.