L-Carnosine

L-Carnosine is the naturally occurring dipeptide β-alanyl-L-histidine, C9H14N4O3 at 226.23 g/mol, first identified in vertebrate skeletal muscle. Commercial material is a white to off-white odourless crystalline powder that melts with decomposition somewhere between 253 and 260 °C depending on heating rate. It dissolves freely in water — around 33 g in 100 mL at 25 °C — is only slightly soluble in ethanol and essentially insoluble in ether. The histidine residue contributes an unfused imidazole ring whose ionisation sits close to physiological pH, so the molecule buffers in that region, while the carboxyl pKa is about 2.6. Optical purity matters commercially: the L-histidine residue makes the dipeptide chiral, and food-grade specifications carry a specific rotation window of roughly +19° to +23° in water, with reported literature values clustering near +21°. Origin is the point buyers most often get wrong. Carnosine occurs in animal muscle and in no plant food, which leads purchasing teams to assume a meat extract and to write a bovine or porcine declaration they do not need. Commercial L-carnosine is not extracted from tissue; it is built by coupling β-alanine with L-histidine, chemically or enzymatically, with the histidine itself normally produced by microbial fermentation on a carbohydrate substrate. The resulting ingredient is non-animal and suitable for vegan and vegetarian positioning, with no milk, egg, soy, fish, crustacean, gluten, sesame or nut inputs. Because the natural occurrence is animal, however, take the manufacturer's written origin declaration for each batch rather than inferring it — a wrong statement in this box is a recall, not a correction. Keep L-carnosine separate from the articles it is routinely confused with. Anserine is β-alanyl-N-methyl-L-histidine, a methylated analogue. N-acetyl-L-carnosine is the acetylated derivative, sold mainly into topical and ophthalmic bases. Zinc L-carnosine, also called polaprezinc (CAS 107667-60-7, roughly 23 % zinc and 77 % carnosine by mass), is a coordination compound rather than a physical blend, is a prescription medicine in Japan and South Korea, and carries a regulatory position of its own — it is not a substitute and should never be quoted as one. On composition, carnosine is properly described as a buffering, metal-chelating dipeptide and a carbonyl scavenger; nothing beyond that belongs in label copy. Finished-product doses commonly sit around 500 mg per capsule, the powder is mildly bitter and needs masking in flavoured formats, and brands should confirm the ingredient's regulatory standing — including EU novel food status — in every destination market before committing artwork.