Overall, the plant extraction process involves a few critical steps:
1. Processing of the crude drug (in this case, fresh plant material).
a. Bulk plant materials are separated by plant part (roots, stems, leaves, flowers, etc) and cut into small pieces.
b. Oftentimes, bulk plant materials are dried in the field in order to prevent spoilage before the extraction can be done.
c. The plant material may be further broken down into a fine powder (for dry samples) or a slurry (for fresh samples) prior to extraction.
a. In this case, we will be using water and another solvent (clear alcohol or white vinegar)
a. The solvent (organic solvent or water) is strain filtered to remove the plant material, leaving a colored liquid.
a. Organic solvents are removed from the extract with a rotary evaporator and then lyophilized (freeze-dried) to remove any remaining water. If done properly, the final product consists of crystals of mixed plant compounds. For the purposes of this lab, you will use a low heat source from your kitchen.
• Be familiar with the basic types of plant extraction methods
• Understand how to perform 3 types of extractions (decoction, maceration, and solvent extraction)
• Section 1 (pp. 21-54) of “Extraction Technologies for Medicinal and Aromatic Plants” (attached as pdf in module)
For this lab, you will explore 3 different extraction techniques using plant material of your choice and some common kitchen tools. At the end of this lab, you will write a comprehensive lab report describing your experiment. Here is an outline of the protocol that you will need to follow for the experiment:
1. Collect a voucher and bulk samples of a plant of your choice. I suggest using something that you know is safe and that you have easy access to. For example fresh food plants are a great choice (peppers, garlic, onion, citrus fruits, basil, mint, eggplant, carrots, celery, and so on). Choose a specific plant part or part(s) to extract (fruit, leaves, aerial parts, flowers, etc).You may either gather the plant from the wild or your garden, or you may purchase it at the store.
2. Chop up the plant materials – you should have at least ½ cup of materials for each extraction. You will be doing 3 types of plant extractions – so you will need at least 1 ½ cups of material. If you have access to a small scale, it would be good for you to accurately weigh the material to ensure that you have the same amount of material in each of the three groups. If you do not have access to a scale, you may measure based on volume (½ cup of material).
3. For each extraction, you will need to add at least double the plant volume of water or solvent (e.g. for ½ cup of chopped leaves, add 1 cup of water to your bowl). It is important that the plant material be completely immersed in the liquid. Also, to improve the surface to volume ratio of exposure for plant material to the solvent, you may wish to create a slurry for extraction. To do so, simply place the plant materials and solvent (or water) in a blender to make a slurry before moving to a bowl for the intended extraction period.
a. Decoction. You will boil the plant material for a defined amount of time. This process is useful for extracting water soluble, heat stable phytochemicals. You can do this in a small pot on a kitchen stove.
b. Maceration. You will soak the plant material in water at room temperature for a defined period of time with a defined amount of agitation. A mixing bowl with cover (or you may cover with aluminum foil) will suffice.
c. Solvent extraction. You will soak the plant material in an organic solvent at room temperature for a defined period of time with a defined amount of agitation. I recommend using a clear alcohol safe for human consumption (i.e. vodka, light rum, tequila, etc.). A mixing bowl with cover (or you may cover with aluminum foil) will suffice.
4. Following the extraction process, the plant material will need to be separated from the liquid extract. You may use something like a cheese cloth or paper coffee filter to do this. There should be no chunks of plant material in the liquid extract. Oftentimes, filtration is performed 2-3 times with new filters to ensure the removal of plant material.
5. Now that you have the liquid extract prepared, you can proceed to the final step of concentration. I suggest using a low heat source (place in a safe bowl on low in the oven, a toaster oven or stove top). Do NOT microwave the materials in any of the extraction steps.
Your lab report should consist of a detailed explanation of the extraction process and your findings. The aim of this project is to study the differences in the final product of these various extraction techniques.You should make observations throughout the different stages of the project in regards to the extract properties (e.g. color, density, smell, presence/absence of bubbles, and so on). Follow this format for your lab report:
Research question: create your own
Null hypothesis: create your own
Alternate hypothesis: create your own
I. Description of plant material. (3 points)
a. Describe the plant and its part(s) that you selected for your extraction study.
b. List the common and scientific name.
c. Collect a voucher and submit a photo or the voucher plus voucher tag with your report.
d. Answer the following questions in this section:
i. Where did you get the material (purchased or collected)?
ii. Why did you choose this plant?
iii. How is this plant used (medicine, food, no use known)
iv. What are some of the major known constituents (phytochemicals) found in this plant? List references at the end of your report and properly cite them.
II. Materials and methods for the extractions. (3 points)
a. In a very detailed fashion, describe the materials used for your 3 extraction experiments and methods employed.
i. List the volume or weight of plant materials extracted and volume of solvent used.
ii. List the amount of time for each extraction (e.g. – you may boil the material for 20 minutes in the decoction, but perform the maceration or solvent extraction for several days).
iii. How finely chopped up were the plant materials? Did you make a slurry?
iv. How often did you agitate (stir) the plant mixture during the extraction process?
v. How did you filter/separate the plant materials from the liquid extract?
vi. How long and at what temperature did you heat the final extract to remove the liquid?
III. Results and conclusions. (4 points)
a. In detail, describe your observations regarding the physical qualities (color, smell, consistency, taste – only if food plant used) of the extract at each of the different extraction stages. For example, did the color of the liquid extract change over time?
b. What does the final extract look like at the end of the drying process? Are there crystals? Is it goopy or like a syrup? Is it different for the different extraction techniques used?
c. Is the final yield different or the same for the 3 extracts? You may measure this in weight or volume.
d. Include at least one graph or table in the results section when reporting your data.
e. In conclusion, comment on the differences and similarities in product (extract) outcome when using different extraction techniques
f. Do your findings support your hypothesis? Why or why not
g. What effects would changes (such as time of extraction or heat) have on the final outcome of this project?
h. (Optional) Include photos in your lab report to help illustrate your findings