MOLECULE

Glucosamine

Glucosamine, also known as chitosamine, belongs to the class of organic compounds known as hexoses. These are monosaccharides in which the sugar unit is a is a six-carbon containing moiety. Glucosamine is a moderately basic compound (based on its pKa). Glucosamine exists in all living organisms, ranging from bacteria to humans. It is naturally present in plants, the shells of shellfish, animal bones, bone marrow, and fungi. Glucosamine is produced commercially by the hydrolysis of shellfish exoskeletons or, less commonly, by fermentation of a grain such as corn or wheat. D-Glucosamine is made naturally in the form of glucosamine-6-phosphate and is the biochemical precursor of all nitrogen-containing sugars (PMID:11553646). In humans, glucosamine-6-phosphate is synthesized from fructose 6-phosphate and glutamine by glutamine-fructose-6-phosphate transaminase as the first step of the hexosamine biosynthesis pathway. The end-product of this pathway is uridine diphosphate N-acetylglucosamine (UDP-GlcNAc), which is then used for making glycosaminoglycans, proteoglycans, and glycolipids (PMID:11553646). In the United States, glucosamine is not approved by the Food and Drug Administration for medical use in humans. Since glucosamine is classified as a dietary supplement, evidence of safety and efficacy is not required as long as it is not advertised as a treatment for a medical condition. Nevertheless, glucosamine is a popular alternative medicine used by consumers for the treatment of osteoarthritis. Glucosamine is also extensively used in veterinary medicine as an unregulated but widely accepted supplement for the treatment of osteoarthritis in companion animals. Since glucosamine is a precursor for glycosaminoglycans, and glycosaminoglycans are a major component of joint cartilage, supplemental glucosamine may help to rebuild cartilage and treat arthritis. However, there is little evidence that any clinical effect of glucosamine works this way. Its use as a therapy for osteoarthritis appears safe but there is conflicting evidence as to its effectiveness.