SPECIES-SPECIFIC COMPOSITION PATTERN OF MILK RIBONUCLEOSIDES AND RIBONUCLEOTIDES - CHEMICAL AND PHYSIOLOGICAL-ASPECTS

The largest amounts of ribonucleosides and ribonucleotides were measur ed directly after parturition in the milk of humans and ruminants. Gen erally, the concentrations of most of the ribonucleos(t)ides tend to d ecrease gradually with nursing time or advancing lactation period. The species-specific pattern of these minor constituents in milk from dif ferent mammals is a remarkable property and confirms, at least, the sp ecific physiological impact of these minor compounds in early life. Di etary nucleos(t)ides are ingested mainly as nucleoproteins and are con verted in the course of intestinal digestion to monomeric compounds. N ucleosides and nucleobases are transported by specified translocation systems localized in intestinal and kidney epithelial cells. Thus, nuc leic acid-derived compounds are used by the body as exogenous trophoch emical sources and can be important for optimal functions. Nucleos(t)i des have been recognized, therefore, to be semiessential; up to 20 % o f the total daily need for a breast-fed infant was calculated to come from dietary nucleic acids and related compounds, the rest comes from de novo synthesis. Dietary nucleos(t)ides may affect the immune modula tion and contribute to iron absorption in the gut. Human milk has been suggested, therefore, as a factor in facilitating iron absorption and immune response in breast-fed infants. Dietary nucleos(t)ides are fou nd to influence desaturation and elongation rates in fatty acid synthe sis, in particular long-chain polyunsaturated fatty acids in early sta ges of life. The in vitro modulation of cell proliferation and apoptos is has been described by ribonucleosides, in particular, by modified c omponents using human cell culture models. Due to the bio-and trophoch emical properties of dietary nucleos(t)ides, the European Commission h as recently allowed the use of supplementation with specific ribonucle otides in the manufacture of infant and follow-on formulae. From the t echnochemical point of view, ribonucleosides are useful chemical indic ators to quantify adulterations of milk and milk products, e.g. heat t reatment of milk and identification of butter types.