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Cantharidin1 is a tricyclic molecule that contains anhydride and ether groups. It is a virulent toxin produced by blister beetles of the family Meloidae, mostly in the genus Epicauta.
An early mention of cantharidin in the chemical literature came in an 1878 article by British physician/chemist Alexander Wynter Blyth, who of some alkaloids and similar compounds. (Cantharidin sublimes at 110 掳C under 12-Torr pressure.) Twenty years later, physician Francis Whitaker Tunnicliffe at St. Bartholomew鈥檚 Hospital (London) (vesicant, or blister former) for treating tuberculosis and lupus.
It was not until 1953 that the presence of cantharidin in blister beetles was documented. Taiwanese chemist Hung-Yuan Hsu reported that the content of the molecule in the Formosan blister beetle (genus Maloe) was 0.97%. In a more complete analysis in 1967, Wilbert G. Walter and John F. Cole at the University of Mississippi (Oxford) described the of the North American blister beetle Epicauta pestifera and their determination that it was cantharidin.
Hundreds of articles in subsequent years described the toxic nature of cantharidin. It does, however, have a few medical uses, mainly as a topical treatment for warts, but also as an abortifacient (abortion inducer) and a veterinary diuretic. Notoriously, it is also the active ingredient in 鈥淪panish fly鈥� an ancient, risky, and not always effective aphrodisiac.
In 2001, Lisa Moed, Tor A. Shwayder, and Mary Wu Chang* at New York University School of Medicine (New York City) wrote an extensive review titled 鈥溾�. In their section on cantharidin鈥檚 history with the US Food and Drug Administration (FDA), they noted that the drug was first registered in the 1950s, when the agency did not require efficacy data. After a 1962 amendment to the original FDA act of 1938 required efficacy data , the agency took cantharidin off the market because no data had been submitted. (In July 2023, long after the review was published, FDA reinstated cantharidin as a topical for treating molluscum contagiosum [鈥渨ater warts鈥漖.)
Chang et al.鈥檚 2001 defense of cantharidin was that it is a safe drug when properly used. They cited a 1995 article by Stefan Herzig, Martin Tepel, and co-workers at University Hospital Eppendorf (Hamburg, Germany), who reported that the compound, a phosphatase inhibitor, (muscle strengthener) in guinea pigs and in vitro in human cardiac tissue. Based on these results, they conjectured that less toxic derivatives of cantharidin could be therapies for treating human cardiac failure.
1. Scifindern: 4,7-epoxyisobenzofuran-1,3-dione, hexahydro-3a,7a-dimethyl-, (3aR,4S,7R,7aS)-rel-.
Cantharidin听hazard information
| Hazard class* | GHS code and hazard statement | |
|---|---|---|
| Acute toxicity, oral, category 2 | H300鈥擣atal if swallowed |  |
| Skin corrosion/irritation, category 2 | H315鈥擟auses skin irritation |  |
| Serious eye damage/eye irritation, category 2A | H319鈥擟auses serious eye irritation | |
| Specific target organ toxicity, single exposure, respiratory tract irritation, category 3 | H335鈥擬ay cause respiratory irritation | |
*Globally Harmonized System (GHS) of Classification and Labeling of Chemicals.听.
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Cantharidin听fast facts
| CAS Reg. No. | 56-25-7 |
| Empirical formula | C10H12O4 |
| Molar mass | 196.20 g/mol |
| Appearance | White crystals or powdera |
| Melting point | 218 掳C |
| Water solubility | 31 mg/L (20 掳C) |
MOTW update
Lisdexamfetamine1 was the Molecule of the Week for March 4, 2008. It is a prodrug for treating attention deficit hyperactivity disorder (ADHD) that was approved by FDA in 2007. Under the trade name Vyvanse, it is an alternative to the more commonly used drug Adderall.
Whereas Adderall is a combination of salts of racemic amphetamine2 and its enantiomer D-amphetamine3, lisdexamfetamine is a single molecule consisting of dextroamphetamine coupled with L-lysine4. In a 2022 article, Richard Crabbe at Free by the Sea drug and alcohol recovery center (Ocean Park, WA) explained the 5.
Among the differences is that Vyvanse is significantly slower to be absorbed by the body than Adderall because it must first release D-amphetamine. Vyvanse鈥檚 slower absorption rate, however, leads to fewer side effects than Adderall.
In 2015, FDA approved Vyvanse for . Last August, FDA as an alternative to brand-name Vyvanse.
1. CAS Reg. No. 608137-32-2.
2. CAS Reg. No. 300-62-9.
3. CAS Reg. No. 51-64-9.
4. CAS Reg. No. 56-87-1.
5. Our thanks to a reader who sent this article to MOTW.
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