Sunday, March 9, 2014

Benjamin Franklin, Asparagus Pee and Thiols

English: Dimethyl disulfide 日本語: Dimethyl disu...
English: Dimethyl disulfide 日本語: Dimethyl disulfide(ジメチルスルフィド) (Photo credit: Wikipedia)
If you love asparagus as much as I do you probably are aware of its interesting byproduct: "smelly urine." Even Ben Franklin noted it in his letter to the Royal Academy of the Sciences in Brussels c 1781, " A few Stems of Asparagus eaten, shall give our urine a disagreeable odour..." 

So what is the cause of the odor? 


Answer: Thiols.


For the non-chemist reader a thiol is an organic molecule similar to an alcohol molecule except that sulfur takes the place of oxygen. Hence the smell. For the readers who are familiar with chemistry it is precisely the following:
  • dimethyl sulfide, dimethyl disulfide
  • dimethyl sulfoxide, bis-(methylthio)methane
  • S-methyl thioacrylate
  • S-methyl-3-(metyhylthio)thiopropionate 
  • dimethyl sulphone
Interestingly, thiols can contribute to pleasant smells such as roasted coffee, grapefruit and garlic.

This is a blog about pharmaceuticals. So here is where thiols tie-in. It appears that thiols are important parts of Active Pharmaceutical Ingredients (APIs). My first encounter with a  thiol was working with nizatidine. I often described it as smelling like a locker room and tasting like yak vomit. There are other commonly used drugs that contain thiol groups. Examples are:
Thiols are chelatng agents. They are often referred to as mercaptins. They have many industrial uses and laboratory uses. As therapy, Dimercaptosuccinic Acid is indicated for the treatment of lead poisoning in children with lead blood levels above 45 ug/dL.
 
So next time you eat asparagus, the smell of your normal body functions contains an important chemical group. I think even Ben Franklin thought something important was going on. I'm surprised he didn't add thiol discovery to his amazing list of achievements.
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Sunday, March 2, 2014

The Pharmaceutical Importance of Amines

Ball-and-stick model of the fluotracen molecul...
Ball-and-stick model of the fluotracen molecule, a tricyclic antidepressant and antipsychotic drug. Colour code (click to show) : Black: Carbon, C : White: Hydrogen, H : Blue: Nitrogen, N : Yellow-green: Fluorine, F (Photo credit: Wikipedia)
The role of amines in pharmaceuticals is immense and the science of using amines as pharmaceutical actives goes back at least a century. Amine drugs are designed to mimic or to interfere with the action of natural amine neurotransmitters. Amines have a wide range of functionality that includes stimulants, vasoconstrictors, decongestants, antihistamines and antidepressants. Here is a short list of amines used in pharmaceutical preparations from Wikipedia:

Cocoa butter based suppository formulation

This usually gets a chuckle when I talk about suppository dosage forms.  Most people are surprised to find how technical the processing and formulation issues are.  See below:
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