The order of the affinities of tea catechins for phospholipid membranes, cholic acid micelles, and antiviral activity was consistent with the order of the partition coefficients determined for the octanol/water system. The astringency, antiviral activity, and aggregation activity of cholic acid micelles caused by black teas were more potent than those caused by green tea. This suggests that theaflavins (TFs) and thearubigins (TRs), which are red, orange, or dark brown pigments, show stronger interactions with phospholipids than with catechins. The concentration of total theaflavins (TFs) in a black tea infusion is not sufficient to explain the activities of diluted black tea infusions. TRs are mixtures of myriad polyphenols formed by the oxidation and condensation of catechins and theaflavins. Authentic TRs prepared from black tea extracts showed aggregation activity, and the concentration-dependent curves matched those of black tea infusions. There is a possibility that TRs in black tea infusions interact with phospholipids of epithelial cells, viruses, bacteria, and cholic acid micelles. These interactions could result in astringency, antiviral activity, antibacterial activity, and aggregation of cholic acid micelles after the consumption of black teas.