Cytochemical model systems for the detection and characterization of potentially bioactive milk components

Various bioactive food-derived substances (genuine or generated) occur in f oods ready for consumption and exert regulative activities beyond basic nut rition. Accordingly, there is a need for analytical methods that help to as sess bioactive substances concerning their beneficial or potentially advers e effects. Cytochemical assays using human cell culture model systems repre sent an analytical tool for screening 'health claims' which must be proved in human studies. Well established cytochemical methods might also serve as a quality control tool within or after the production process to continuou sly monitor the desired effectivity and safety of a product (functional foo d, FOSHU). An overview is given on various cytochemical methods for detection and char acterization of milk-derived bioactive substances, especially peptides and ribonucleosides. Mainly the effects on cell viability (apoptosis, prolifera tion) and enterocytic cell differentiation (TEER, Transepithelial Electrica l Resistance; ALP, alkaline phosphatase activity) were investigated using H L-60 cells, Caco-2 cells, peripheral blood lymphocytes (PBL), B cells, and polymorphonuclear leukocytes (PML). It could be demonstrated that high quan tities of PML can be obtained in a safe and non-invasive way from the oral cavity. Various modulating effects on cell viability were found for the analyzed pe ptides and Gouda extract. In contrast to the isolated beta-casein-derived c aseinophosphopeptide (CPP) beta-CN (f1-25)4P and its dephosphorylated form beta-CN (f1-25)OP, the CPP enriched preparations from a tryptic casein hydr olystae had no modulating effect on cell viability or differentiation. Howe ver, higher immunoglobulin concentrations (culture supernatant) were found after the exposure of PBL to either of the two CPP preparations tested comp ared to cells stimulated with known mitogens. Among all 16 ribonucleosides tested, the modified adenine ribonucleosides i p6ado and m6,2ado showed the highest modulation activity in all the investi gated cell types, even in micromolar concentrations. Guo (1 mmol/l) initial ly prevented freshly plated Caco-2 cells from forming a normal monolayer st ructure. No adverse effects were detected when up to 1 mmol/l guo or ado wa s administered to a precultivated, partially differentiated Caco-2 cell mon olayer. In conclusion, cell chemical methods using human cell culture model systems represent new analytical tools for food scientists, thus enabling a substa nce-oriented research on an interdisciplinary basis.