To discover what a thing is good requires knowledge about relevant situations, which are often subtle and difficult. Lack of such knowledge partly explains why many chemicals sat on the shelf for decades before their therapeutic values were realized. This happened to aspirin’s rival Tylenol. Its active ingredient was synthesized in 1878, but had to wait until 1955 before being developed into a popular drug. Ever more revealing are the stories of antibacterial drugs. Sulfanilamide was synthesized in 1908, but it was the discovery of its therapeutic effectiveness in 1932 that won a Nobel Prize. Penicillin was discovered in 1928 and its therapeutic properties in 1939, and both discoveries were cited in the Nobel Prize. In Nobel Prizes such as these, the scientific community acknowledges the equal scientific importance of discovering and developing a drug. Unfortunately, this point is often overlooked in science studies, so that Hoffmann is often accorded with the credit for aspirin, to the neglect of Eichengrün and others in Bayer.
The dyes industry was also in the forefront in asserting intellectual property rights. Favorable patent laws play important roles in the pharmaceutical and life science industries; witness the recent scramble to patent human genes. However, they did not benefit aspirin. Bayer settled for registering a trademark for the name Aspirin. It did not patent acetylsalicylic acid, not because it would not but because it could not. The chemical was old stuff, synthesized by French chemist Charles Frederic Gerhardt back in 1853.
How does aspirin curb prostaglandin production? The many kinds of prostaglandin are synthesized by a host of complicated biochemical pathways. However, all pathways share a common stage facilitated by an enzyme called COX, whose action aspirin suppresses.
Aspirin's ability to suppress the production of prostaglandins and thromboxanes is due to its irreversible inactivation of the (PTGS) enzyme. Cyclooxygenase is required for prostaglandin and thromboxane synthesis. Aspirin acts as an acetylating agent where an group is covalently attached to a residue in the active site of the PTGS enzyme. This makes aspirin different from other NSAIDs (such as and ), which are reversible inhibitors.
Diaspirin [bis(2-carboxyphenyl) succinate; PN508]and fumaryl diaspirin [bis(2-carboxyphenyl) fumarate; PN517] wereprepared as previously described (). Aspirin is commercially available asacetylsalicylic acid, and the synthesis of the other compounds isas described in supplementary information (provided upon request).The compounds tested are shown in .
The synthesis of aspirin is classified as an reaction. is treated with , an acid derivative, causing a that turns salicylic acid's group into an group, (R-OH → R-OCOCH3). This process yields aspirin and , which is considered a of this reaction. Small amounts of (and occasionally ) are almost always used as a . This method is commonly employed in undergraduate teaching labs.
To understand the molecular basis for the antitumoureffects of aspirin and identify more effective alternatives, wepreviously synthesised a series of derivatives of the aspirinmolecule. These studies revealed that diaspirin (DiA) and fumaryldiaspirin (F-DiA) inhibit proliferation of CRC cell lines atsignificantly lower concentrations than aspirin (). To extend these studies and identifyfurther lead molecules, we synthesised an additional series ofaspirin derivatives ().Cytotoxicity (MTT) assays demonstrated that at 0.5 mM(pharmacologically relevant dose for aspirin), DiA (PN508) andF-DiA (PN517) and to an even greater extent, isopropylm-bromobenzoylsalicylate (PN529) reduced the viability of SW480 CRCcells (). To investigate thespecificity of compound toxicity in more detail, we tested thecapacity of DiA, F-DiA and PN529 to affect proliferation of anumber of established cell lines ( and ), controlling for any variabilitythat could arise from cell culture conditions through culturing allcells with DMEM as the basal medium. While we noted that culturingSW480 cells in their non-native medium (DMEM rather than L-15medium) reduced the sensitivity of the cells to the compoundstested, DiA and F-DiA in this assay system arguably showed amodicum of specificity towards the other CRC cell lines tested(HCT116 and LoVo), and given our finding that PN529 can inducenecrosis (), we focused ourattention on the anti-proliferative activity of DiA and F-DiA inmore detail and .
However, several of the new PTGS2 selective inhibitors, such as , have been withdrawn recently, after evidence emerged that PTGS2 inhibitors increase the risk of heart attack. It is proposed that endothelial cells lining the microvasculature in the body express PTGS2, and, by selectively inhibiting PTGS2, prostaglandin production (specifically PGI2; prostacyclin) is downregulated with respect to thromboxane levels, as PTGS1 in platelets is unaffected. Thus, the protective anti-coagulative effect of is removed, increasing the risk of thrombus and associated heart attacks and other circulatory problems. Since platelets have no DNA, they are unable to synthesize new PTGS once aspirin has irreversibly inhibited the enzyme, an important difference with reversible inhibitors.
Low-dose, long-term aspirin use irreversibly blocks the formation of in , producing an inhibitory effect on . This anticoagulant property makes aspirin useful for reducing the incidence of heart attacks. 40 mg of aspirin a day is able to inhibit a large proportion of maximum thromboxane A2 release provoked acutely, with the prostaglandin I2 synthesis being little affected; however, higher doses of aspirin are required to attain further inhibition.
In 1828, German pharmacologists isolated from willow bark a yellow bitter crystal, which they called salicin. Swiss pharmacologists isolated a similar substance from meadowsweet. Ten years later, French chemists synthesized salicylic acid. Physicians administered the two compounds to patients, whose symptoms they observed and whose urine they analyzed. They found that taking both compounds reduced rheumatic fever, and salicin was transformed in the body to salicylic acid. Based on the observations, they identified salicylic acid as the active medicinal ingredient responsible for willow bark’s efficacy in relieving pain and fever.
Six years later, in 1859, von Gilm obtained analytically pure acetylsalicylic acid (which he called "acetylierte Salicylsäure", acetylated salicylic acid) by a reaction of salicylic acid and acetyl chloride. In 1869 Schröder, Prinzhorn and Kraut repeated both Gerhardt's (from sodium salicylate) and von Gilm's (from salicylic acid) syntheses and concluded that both reactions gave the same compound—acetylsalicylic acid. They were first to assign to it the correct structure with the acetyl group connected to the phenolic oxygen.