Nuclei of tea flowers as targets for flavanols

The tea plant (Camellia sinensis L.) is famous for its flavanol-based constituents being valuable for human health. These flavanols associate with the nuclei of tea flowers, which is demonstrated histochemically by blue colouration using the selective staining reagent p-dimethylaminocinnamaldehyde (DMACA). Sepals, petals, stamens, pollen tubes, ovaries and ovules were studied. All these organs were shown to contain flavanols in vacuolar compartments, in nuclei and, exceptionally, also in the cytoplasm of pollen tubes. In all cells, even in those lacking vacuoles, the nuclei stained blue for flavanols. The extremely divergent development, shape and function of the diverse flower organs did not basically influence the nuclear flavanol association. Nevertheless, within the limits of this study, a few tissue-dependent differences in staining intensity were obvious. Interactions between epicatechin and nuclear histone proteins (histone sulphate) were studied by UV-VIS spectroscopic titration and by means of Mauser diagrams. The results show that the observed association equilibria are strongly dependent on pH (8.0 and 7.4) and on the buffer used (Tris, phosphate).