Neuramin-lactose, a new compound isolated from the mammary gland of rats.

Chromatographic analysis of the carbohydrates extracted from the mammary gland of rats showed, besides the spots of glucose and lactose, those of two other carbohydrate derivatives (1). Malpress and Morrison (2) and Reithel et al. (3) have found components of similar chromatographic behavior in the mammary gland of guinea pigs. Also, in the extracts of a lactose-requiring strain of Lactobacillus bulgaricus, Rutter and Hansen (4) reported a lactose derivative which they suggest may be related to those isolated from mammary gland. The compounds found in the extracts of rats are present in trace amounts, usually at concentrations 30 times less than lactose; the yields obtained are of the order of 1 PM per rat, as reckoned from the saccharide moiety they contain. This paper deals with the study of one of these compounds, to be named neuramin-lactose to account for the fact that the only two components so far detected are neuraminic (or sialic) acid and lactose. Neuraminic acid was isolated by Klenk (5) in 1941, from the ganglioside fraction of brain lipide. There is general agreement (6, 7) that it is identical with sialic acid isolated by Blix (8) in 1936 from submaxillary mucin and also with the prehemataminic acid obtained by Yamakawa and Suzuki ((9); see also Klenk and Wolter (10)) from the hematoside fraction of red cell stroma. The structure of this acid still remains unknown. Elementary analysis and equivalent determination of the acid isolated from the submaxillary mucin showed the composition CnHZ30sN (11). It is identified by the concurrence of several properties, among which of special importance are those of reacting with the Bial (giving purple color) and Ehrlich reagents, of forming humin compounds very readily in acid medium, and of evolving carbon dioxide on treatment with mineral acids.