Is it a vitamin? I’ve seen it at the vitamin counter but I’m not sure what it’s used for.
http://www.supplementwatch.com/supatoz/supplement.asp?supplementId=91
Basically, it’s an antioxidant.
Coenzyme Q[sub]10[/sub] (ubiquinone) isn’t a vitamin as all animals, including humans, synthesize it from simpler compounds. Among other things, Co-Q is essential for setting up the proton gradient across the inner membrane of mitochondria which provides the driving force for ATP synthesis.
It also, as ultrafilter pointed out, serves as an antioxidant, and has several Being a faddish supplement, the web is loading with all sorts of wild claims about the uses and amazing properties of Coenzyme Q[sub]10[/sub]. Some might even be true. Here’s a bit of discussion of Co-Q at the Linus Pauling Institute that doesn’t drift too far from biochemical orthodoxy.