The Science of Aspirin
Aspirin is the common name for medical grade acetylsalicylic acid. It can be naturally processed from the bark of the White Willow. The bark from the willow tree has been used in human society as a pain reliever and anti-inflammatory for thousands of years. The ancient Egyptians used willow bark in many or their medicines. It was commonly boiled in water which and drank as a tea. This was first brought to light in 1862 with the discovery of medical papyrus written around 1500BC. White willow’s scientific name is Salix alba. Salix from the willow’s genus is from which scientists derive the name Salicin from after extracting it from the bark of the tree in crystal form. It is one of the main active compounds in the willow bark once it has been processed either naturally or in a lab. Today Aspirin is a common pain reliever and blood thinner. It’s commonly used by people with hypertension and those who are at risk for heart attacks, strokes, and blood clotting. It helps with thinning out the blood by affecting the platelets’ ability to bind to one another. It can also still be used as a quick remedy for headaches and other aches and pains. The compound Salicin is what is the active constituent in the willow bark. It can be used as is and the body will naturally metabolize it in the liver. It will break down into glucose and salicylic acid in the body. All three chemicals can be seen bellow in figure 1.
Figure 1
The Salicin can be processed with HCl in the stomach, and later in the liver. Salicin breaks into two separate compounds. This process can also be replicated in a lab by acid-catalyzed ester hydrolysis. Once Salicin is broken into D-glucose and salicyl alcohol, the alcohol goes through a process of oxidation and salicylic acid is produced. This breakdown can be seen below in figure 2. Salicylic acid in itself has many applications to the modern world. It is a great anti-inflammatory and is the main anti-inflammatory compound in Aspirin. It is commonly used in acne medication to reduce inflammation and unclog pores. It is a karyolitic meaning that it can help slough off dead skin. This not only helps with acne but other dry skin condition like psoriasis and eczema.
Figure 2
Once Salicylic acid has been produced it can be further processed into acetylsalicylic acid. The Acetylsalicylic acid is produced by synthesizing Salicylic acid with an acetic anhydride by acetylation. Heat is applied to a mixture of Salicylic acid and acetic anhydride in a liquid solution of . This process can be observed in figure 3. There are two products at the end of the acetylation process. The main wanted compound of acetylsalicylic acid and a byproduct of acetic acid. A main reason Salicylic acid is synthesized into this alternate compound is because it is easier for the human body to handle. The ingestion of Salicylic acid can be toxic to the human body and can cause internal burns to the mucus membranes, and damage stomach lining. By changing it into acetylsalicylic acid it is easier on the stomach and the liver can still process it into Salicylic acid and use it for its anti-inflammatory properties without causing internal damage. By using acetylsalicylic acid, the body also synthesizes the compound differently than it would when it would have received the Salicin from processing the bark of Salix alba.
Figure3
Aspirin has many benefits to the modern world and has been held in high esteem for thousands of years as a wonder drug in the form of its natural state found in the bark of Salix alba. Aspirin has also been studied to reduce the risk of several types of cancer, including breast and some types of throat cancers. In the modern world Salicylic acid is created in a lab using acid-catalyzed ester hydrolysis then salicyl alcohol is oxidized forming the compound of Salicylic acid. It can be used in many laboratory applications, but for human consumption it is formed into acetylsalicylic acid via acetylation. This is because though Salicylic acid can be a good inflammatory it can be hard on the stomach. So, by using the acetylation process and adding two carbons and a double bonded oxygen it is easier on the stomach and can be broken back down into salicylic acid in the liver where it can be used by the body. High levels of Aspirin can still have a negative effect on the body and can cause liver dysfunction. Acetylsalicylic acid has been used for over 100 years in modern pharmaceutical industry, it is a well-known and most used anti-inflammatory and fever reducer.
Sources
American Association of Health. “Salicylic Acid Topical: Medlineplus Drug Information.” MedlinePlus, U.S. National Library of Medicine, https://medlineplus.gov/druginfo/meds/a607072.html#:~:text=Topical%20salicylic%20acid%20treats%20acne,or%20can%20be%20removed%20easily.
Desborough, Michael. “From Willow to Wonder Drug .” DOI, https://doi.org/10.1111/bjh.14520.
“Personal Chemical Formulations.” ChemDraw JS Sample Page, https://chemdrawdirect.perkinelmer.cloud/js/sample/index.html.
PubChem. “Aspirin.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine, https://pubchem.ncbi.nlm.nih.gov/compound/Aspirin.
