HUMAN MEDICINES

   Vitamin B12, also known as cobalamin, is a polycyclic compound containing trivalent cobalt. Four reduced pyrrole rings are linked together to form one porphyrin macroring (similar to porphyrin), making it the only vitamin containing metallic elements. Vitamin B12 is a red crystalline powder, odorless and tasteless, soluble in water, insoluble in ethanol, insoluble in acetone, chloroform, and ether. It is most stable under weak acid conditions with a pH of 4.5-5.0 and can decompose in strong acids (pH<2) or alkaline solutions. It can be damaged to a certain extent when exposed to heat. Higher animals and plants cannot produce vitamin B12, which is synthesized by microorganisms in nature. Vitamin B12 is the only vitamin that requires the help of an endogenous factor secreted by gastric wall cells to be absorbed. It is involved in the production of bone marrow red blood cells, preventing pernicious anemia, and preventing damage to brain nerves.