Vitamin B12 is a cyanide ion substituted cobalamin derivative (cyanocobalamin) with the presence of cobalt mineral at 6 position. Vitamin B12 is the only vitamin which contains metal ion (trivalent cobalt). Cobalamin is sometimes defined as the synonym of Vitamin B12, although they are not same compound but closely related compounds to fulfill folic acid role. Vitamin B12 is typically any substituted cobalamin derivative having similar biological activity. Hydroxocobalamin (abbreviated OHCbl), a cobalamin derivative in which the substituent is a hydroxyl group, is called vitamin B12b.