Apart from choline inositol is a main component of lecithin. Insoitol is needed for the normal function of cell membranes and is important for transfer of signals between neurons. Together with choline it is also important for lipidic metabolism.
Inositol is considered to be a vitaminoid, a vitamin-like substance. It is found in plants (as phytic acid) and animals (as myo-inositol). In the human body high amounts of inositol are found in brain, liver, spleen and testicles.