Potions and Poisons

In my non-majors class this semester, students will design a magical potion of their choice using chemical principles. This is a “theoretical” design because my class does not have a lab component, and I’m not sure I want them extracting and mixing a bunch of chemicals that vary in their hazard-ness. The students will write this up as part of a textbook chapter and work in small groups. The assignment makes up 20% of the course grade. For quality control purposes, and also to ease student anxiety about “out-of-the-box” assignments, my goal is to provide an example of what I’m looking for.

Over winter break, I mulled over the idea of choosing something whimsical that the students would not have thought of, and therefore unlikely to choose as their “potion of interest”. (I was planning to poll the students sometime in week 4 or 5 to gather a list of their potions of interest.) The first idea was a joke potion that would make your voice change at parties if someone slipped it into your drink. The active ingredient would be nitrous oxide (N₂O) but it would have to be appropriately “packaged” so that the chemical delivery happens at the right time – when the intended “victim” takes a beverage sip. A tiny capsule would be too obvious in a clear drink. But if you had a solid package or powder that dissolved too quickly, the N₂O would just bubble out of the beverage before the drink was consumed. I had a few ideas of some fancy liquid-soluble cavitands, but I would be making some complicated chemical leaps that may be rather challenging for the students.

So this weekend I started reading The Poisoner’s Handbook by Deborah Blum. Each chapter discusses a particular chemical substance used as a poison during the Jazz Age in New York. While there is some chemistry in the book, it is more interesting as a history and sign of the times. I learned many interesting factoids about how one sets up a toxicology lab and the types of analyses one could do a century ago, when we did not know as much chemistry as we do today. (There’s lots of trial and error. Not to mention court trials and errors in judgment!) A couple of days ago I read the chapter on wood alcohol, CH₃OH, sometimes called methyl alcohol (from the Greek words meaning wine and wood) or methanol (following IUPAC convention). With the backdrop of prohibition, wood alcohol was a popular cheap moonshine – even though it caused blindness, nausea, dizziness and death.

Grain alcohol, C₂H₅OH (ethanol), or ethyl alcohol is safer to consume because the biochemical pathways result in different chemical substances produced. In the case of methanol however, two of the problem-causing products in particular are formaldehyde (featured in my previous post!) and formic acid. I also read the chapter just in time for my General Chemistry class yesterday when we talked about fuels. After calculating the energy efficiency of hydrocarbons, we looked at compounds containing oxygen and nitrogen; methanol was one of the main examples used to illustrate the challenges in thinking about alternative fuels. (I worked on direct methanol fuel cells and partial methane oxidation many moons ago.) And I was able to appropriately warn my students not to consume methanol! (There was nervous laughter in class.)

Yesterday night I read the chapter on cyanides. Upon reading the symptoms of cyanide poisoning, I was immediately reminded of Harry Potter and the Half-Blood Prince where Ron gets temporarily poisoned when consuming a fine alcoholic beverage, ironically just after he has been given an antidote for a love potion gone awry. (I admit to having immediately cracking open Book 6 and reading the appropriate section to confirm the similarity in Ron’s symptoms.) Unlike a love potion that targets a specific individual, presumably through an ingredient that is pheromone-related, no “magic” ingredient was needed for the poison. One wonders if the poisoner knew something about chemistry to extract the appropriate cyanide compounds (there are many sources) and spike the drink. Professor Slughorn is too shocked to mix up an antidote, but quick-thinking Harry manages to save Ron with a bezoar. Given how fast cyanide acts, mixing up an antidote might have taken too long anyway.

Could one design a potion as an antidote for cyanide poisoning? Cyanide essentially acts by replacing oxygen in hemoglobin (the carrier of oxygen). So essentially you can’t “breathe”, your cells get deprived of oxygen, and then all sorts of nasty things happen metabolically. Hence, there are two general approaches to an antidote: (1) One could flush someone with a high dose of oxygen in an attempt to swamp out the cyanide. (2) One could add a substance that scavenges the cyanide away from hemoglobin, i.e., trapping the cyanide. Anything that you add must not cause more problems than it solves. A high dosage of oxygen can be potentially dangerous if not administered carefully. There are many other substances that can trap cyanide, but not many that you should consume. One possibility is hydroxocobalamin found in Vitamin B12. This molecule has some structural similarities to hemoglobin, notably the presence of a porphyrin ring surrounding a metal center. In hemoglobin, the metal is iron; in hydroxocobalamin it is cobalt. Cyanide binds to the metal ion.

I haven’t done the research to look at other possible substances, but it may be that a cocktail of substances mixed together could provide several ways to either displace cyanide from hogging the hemoglobin. Extracting these chemicals from natural sources (since that’s what Potions is about) both magical and non-magical and mixing them together in the right amounts could produce a suitable antidote potion. Vitamin B12 is found mainly in meat, eggs and dairy. Maybe there is a magical creature that has a related vitamin and therefore a slightly modified version of hydroxocobalamin that is particularly good at removing cyanide. (I also want my students to exercise some creativity and imagination.) The concoction might also contain some iron compounds that would form complexes with cyanide. For example, the “Prussian Blue” test to detect cyanide involves adding iron sulphate to a cyanide solution. Hopefully students would use chemical principles to think about how substances could be “modified” (creatively, of course) for the desired outcome.

Or maybe I could investigate the chemistry of a bezoar. Hmmm… so many interesting things to think about!