Can nicotine be turned into niacin? There are those who declare there is no relationship between the two, that it is a mere accident of nomenclature. Well, let's see.

Here is the molecular structure of nicotine.
For those unfamiliar with the shorthand in these diagrams, every unlabelled 'corner' is a carbon atom and the single-hydrogen-atoms poking out all over the place are routinely omitted for clarity. Lines represent bonds, double lines represent double-bonds. Carbon makes four bonds so any corner with three bonds showing has a hydrogen tacked on the outside of the ring. Nitrogen makes three bonds, oxygen two, hydrogen one... oh hell, I'm not getting into lecture mode at this time of night!

Now, here is the molecular structure of nicotinic acid - niacin - vitamin B3:

Take the five-atom ring off nicotine by breaking just one bond and replace it with a COOH group and you're there. In biochemical terms, this is known as 'a piece of piss'.

The two molecules are not unrelated. A simple oxidation reaction is all you need to turn nicotine into nicotinic acid. It's not an accident of nomenclature at all.

Much as the Righteous would like to have us believe.