New sialic acid-containing sulfolipid: "ungulic acid".

Human epidermis, hair, nails, and kidney as well as bovine and horses' hooves were found to contain a lipid fraction, which on thin-layer chromatography migrated slightly ahead of the cerebroside sulfate esters and gave the color reaction specific for sialic acid. This fraction was isolated from horse hoof, in which it constituted nearly half of the total lipids. The purified fraction contained sulfur, but no phosphorus. The IR spectrum revealed the presence of a sulfate group, which was also determined by the benzidine method. Thin-layer and gas-liquid chromatography of the products of acid hydrolysis revealed the presence of sphingosine, galactose, galactosamine, and sialic acid. Fatty acid analysis showed that stearic acid was the major component, with minor amounts of palmitic and arachidic acids. The fraction isolated contained ceramide, sialic acid, galactose, galactosamine, and sulfate in equimolar amounts. We conclude that the new lipid is a ganglioside sulfate, which we have called "ungulic acid" because it was first separated and identified from a horse's hoof (Latin, ungula).