Retinol

Retinol, the most useful form of vitamin A, (along with retinal[?] and retinoic acid[?]) is a fat-soluble vitamin important in vision and bone growth. It is sometimes used in the treatment of severe acne. As can be seen from the structure, this is a compound synthesized from isoprene.

A deficiency of vitamin A is not only disease causing, it can kill. On the other hand, overdoses of vitamin A are also lethal. For example, the liver of the polar bear has enough vitamin A to kill a man.

External link:

• http://www.cc.nih.gov/ccc/supplements/vita