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 are probably aware of its interesting byproduct: "smelly urine." Even this countries favorite scientist 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? 

The short answer is: Thiols.

For the non-chemist reader a thiol is an organic molecule similar to an alcohol molecule R-O-H except that sulfur takes the place of oxygen R-S-H. Hence the bad smell. 
For the readers who are familiar with chemistry I offer the following compounds which precisely describe what is found in asparagus:
  • dimethyl sulfide, dimethyl disulfide
  • dimethyl sulfoxide, bis-(methylthio)methane
  • S-methyl thioacrylate
  • S-methyl-3-(metyhylthio)thiopropionate 
  • dimethyl sulphone
Thiols can also contribute to pleasant smells such as roasted coffee, grapefruit and garlic.

Now since this blog is about pharmaceuticals and formulation here is where thiols tie-in. Thiols are critical elements of prescribed drugs. Examples include:
My first encounter with a  thiol was working with nizatidine which treats heartburn. It is an older drug of class called an H2  inhibitor. I often described the compound as smelling like a old socks and tasting like yaks vomit. 

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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