Summer Research Program for Science Teachers

Eric Paul

Bergen Academies, New Jersey



Activity #3 Related to Natural Products

Activity 1: Operation of the Microwave Oven for Chemistry Experiments

Activity 2: Extraction of Caffeine from Tea Leaves

Introduction to Activity 3: Natural products are substances produced in living systems that may be useful to humankind, especially in the field of medicine. For example, taxol is a substance derived from Pacific yew trees that has been shown to be effective against certain types of cancer.   The extraction of such substances is necessary before their therapeutic value can be evaluated.

This action plan presents three activities related to natural products. One of these is the extraction of a natural product, caffeine, from tea leaves. This has been chosen since the starting ingredients are relatively easy to come by, and the student will still find a reasonable level of challenge. The microwave oven was chosen to provide energy for heating the tea bags, to emphasize the importance of the microwave oven in the field of organic chemistry. Microwave-assisted chemical reactions are increasingly important, especially for organic chemistry. Many chemical reactions that used to take hours now take minutes or seconds with the use of microwave techniques. A simple demonstration of the microwave is included in the action plan. A third activity is the growing of barley under controlled conditions, since it is often necessary to grow plants (or animals) to provide raw material from which natural products can be extracted. The growing of plants offers ample opportunity for open-ended activities


III.  Growing Barley and Detecting the Presence of Amino Acids

Barley is fairly easy to grow in a classroom.  It has even been grown in a windowless classroom under fluorescent light!  The teacher will designate a particular part of the plant, such as the roots or the shoots, as the target material, and students will try to grow this target material to the greatest extent possible for a given amount of starting materials.  Students will conduct experiments in which conditions will be varied from one setup to another to determine which conditions are most favorable to plant growth.  The plants grown will be judged not just on the sheer mass of the roots or shoots produced, but on how free of fungus they are (fungal growth is one of the major drawbacks when barley is grown in these conditions). 



                1.  To produce the greatest mass of plant material possible for 100 seeds of barley.

                2.  To detect amino acids in barley plant material.


Materials and Equipment


barley seeds (obtainable from grocers with food of India)

250-mL beakers                                     10-cm petri dishes

paper towels (various brands)               scissors (for separating target material)

distilled water                                         bleach (such as Clorox)

balance (preferably electronic)             autoclave

hairdryer                                               forceps or crucible tongs

Na2HPO4                                               ninhydrin

2-propanol                                              notebook and pen

graph paper                                           round marbles

goggles                                                  glass stirring rod

[Teaching Standard D- Make accessible science materials]


1.  Put on goggles.


2.  Every student will maintain a notebook for this activity which will include hypotheses to be tested, plans for testing hypotheses, data, and results.


3.  At the outset, 100 seeds of barley are counted out by a designated student, and these seeds are massed to establish the mass of 100 seeds.  By doing this, it will be unnecessary for every student to count out 100 seeds.  Instead, each student will use a mass of seeds equal to that of the original 100-seed batch.  In this way everyone will have approximately 100 seeds.


4.  Autoclave the beakers, petri dishes and marbles to be used for 15 minutes.


5.  Students are to plant seeds in a glass container (petri dish or a beaker), with nothing but paper towel, marbles (marbles may be omitted), and water present in the container with the seeds themselves.


6.  Students may water the plants as often as they wish, but all activities, including watering, must be recorded in the notebook. 


7.  Among the variables students may choose are the frequency of watering, the type of container to be used (beaker or petri dish), the amount of paper toweling to use, the number of marbles (if any) to be placed in the container, the way the paper towel is situated in the container, and the extent to which seeds are soaked in bleach before being planted (this may be varied from a condition of no soaking at all to overnight soaking).  [9-12 Content Standard A- Design and conduct a scientific investigation]


8.  Germination may be aided by soaking the barley seeds in water, usually overnight.  Students may modify this step as follows:

                (1) The step may be omitted entirely.

                (2) The duration of soaking may be extended or reduced.

                (3) The liquid in which the seeds are soaked may have a certain percentage of       bleach included, but if this is done, the seeds must be thoroughly rinsed before planting. 

                (4) Treatment with bleach and soaking in water may be accomplished in separate steps.  The seeds may for example be soaked for 5 minutes in 30% Clorox, then rinsed.  Then, the seeds may be soaked in ordinary distilled water for a predetermined duration.


9.  A committee of five students will set ground rules for the investigation.  For example, conditions for a control setup for the class will be specified,  and criteria for disqualifying plantings will be established.  The committee will decide criteria for excessive fungus, which will result in the “farmer” having to start over again, with a new harvest date specified by the committee.  (The committee may want to limit replantings to one time, to allow the class investigation to be completed on schedule.) [Teaching Standard E- Nurture collaboration among students]


10.  Seeds may be planted in various settings.  For example, the control planting may be set up close to a window, while one of the experimental plantings may be set up away from sunlight but under fluorescent light, to compare the effect of sunlight with that of artificial light on growth.


11.  Plants are harvested 10 school days from when they were planted, or earlier, if the student so chooses, and the target material is massed  to determine how well the student did. [Teaching Standard D- Structure time for extended investigations]  Each student has his or her own container.  The committee will have to establish some means of monitoring the growth of the plants; for example, students might measure and record the height of the tallest plant each day, and record this in a table.  A graph based on this table will be required of each student to show the progress of the plant growth as a function of time.  [9-12 Content Standard A- Use mathematics to improve scientific communication] Each student will prepare a computer spreadsheet of the table, and  computer-generated graphs will be made.  Each student will take a turn describing his or her results to the class, using charts and computer generated graphs to illustrate the presentation. [Teaching Standard D- Orchestrate scientific discourse]


12.  Students will take the harvested plants, separate the target material, and place this material in a solution of Na2HPO4 (10 grams per 100 mL of solution should be sufficient) to soak overnight and break up proteins into amino acids.


Note:  Ninhydrin is poisonous and the ninhydrin solution can cause skin to turn purple.  Be sure to wear gloves for this step.

13.  After putting on gloves, prepare a ninhydrin solution as follows:

                (1)  Mass 0.10 g of ninhydrin and place it in a test tube.

                (2) Add 10 mL of 2-propanol.

                (3) Seal the end of the test tube with Parafilm and shake.

                (4) Place in a test tube rack. Be sure to label this ninhydrin solution so that it may be saved for future use.


14.  Using a clean capillary tube, transfer a small amount of the liquid from the Na2HPO4 solution the barley has been soaking in, to a clean piece of filter paper.  Then use a stirring rod to transfer a small drop of ninhydrin solution to the same spot on the filter paper.  Wash and dry the stirring rod.


15.  While holding the filter paper with a forceps or crucible tongs, heat the spot with a hairdryer.  If amino acids are present, the spot will eventually turn purple.


16.  Clean up.  Save the ninhydrin solution for future experiments.


Students will report their results to the class.  Based on these results, students will make hypotheses predicting the heights of plants grown in a subsequent cycle, and will then grow plants again, to test the hypotheses.



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