The polyphenolic, flavonoid, and caffeine compositions of four commercial tea bag products (typical of those used in the UK, US, continental Europe, and the Middle East) and beverages prepared from them under a range of typical consumer use conditions have been studied. Leaf composition was determined by extraction with aqueous methanol: the absolute compositions of all four products were remarkably similar in terms of most phenolic compounds. The flavonoids comprised the major proportion (93-94%) of the total phenolics estimated by the Folin-Ciocalteu method. At brew times up to 2 min the composition of the brew solids was for each product practically independent of brew time, with flavonoids again comprising the major proportion (86-88%) of the total phenolics. The efficiency of extraction in brewing of total phenolics, total flavonoids, catechins, and theaflavins was up to 35-55% of the total available in the leaf, whereas the flavonol and flavone glycosides and caffeine were more efficiently extracted (up to 55-90%). The contribution of tea to the UK adult average total dietary intake of flavonols and flavones was calculated to be up to 80% depending on brewing conditions.

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The photoreactions of 9,10‐diphenylanthracene with two iodonium salts and a sulfonium salt in different solvents were investigated by fluorescence quenching, flash photolysis with UV/vis detection, measurements of the quantum yields of sensitizer decomposition, and photo‐CIDNP spectroscopy. Energy‐transfer sensitization is precluded by thermodynamics in these systems. In a solvent of lower polarity such as dimethoxyethane, the quenching rate constant is still about a third of the value in acetonitrile; the quantum yields of formation of radical cations and the quantum yields of sensitizer decomposition are decreased by about the same factor. In contrast, dramatic effects occur in the CIDNP spectra of the iodonium salts, which derive from two consecutive radicals pairs, the first containing the radical cation DPA± of the sensitizer and the radical On• of the onium salt, the second comprising DPA± and a phenyl radical produced by fragmentation of On•: In less polar solvents, the polarizations from the first pair are strongly reduced, and the polarizations from the second pair are larger by an order of magnitude. From a kinetic analysis, this effect was attributed to a higher rate of transformation of the first radical pair into the second in the less polar solvent. For the sulfonium salt, this transformation is faster than in the case of iodonium salts, so even in acetonitrile all polarizations stem from the second radical pair. S‐T±‐type CIDNP, which had been proposed in the literature for analogous chemical systems, could be excluded unambiguously, and all CIDNP effects could be explained by radical pair theory (S‐T0‐type CIDNP).