27 June 2008, at 15:42
Niacin, also known as nicotinic acid and vitamin
B3, is the organic compound with the formula
HO2CC5H4N. This water-soluble,
colourless solid is a derivative of pyridine, featuring a
carboxylic acid functional group at the 3-position. The designation
vitamin B3 also includes the corresponding amide
nicotinamide ("niacinamide"), wherein the CO2H
group has been replaced by a CONH2 group. Niacin is
converted to niacinamide in vivo, and though the two are
identical in their vitamin functions, niacinamide does not have the
same pharmacologic and toxic effects of niacin, which occur
incidental to niacin's conversion. Thus niacinamide does not reduce
cholesterol or cause flushing, although nicotinamide may be toxic
to the liver at doses exceeding 3 g/day for adults. Niacin is a
precursor to NADH, NAD, NAD+, and NADP, which play
essential metabolic roles in living cells. DNA repair, and the
production of steroid hormones in the adrenal gland.