UV吸収スペクトルを用いた緑茶飲料中のガレート型カテキンの簡易定量

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UV absorption spectra of authentic tea catechins were measured in the pH range between 5.0-10.0. Gallated and non-gallated catechins exhibited quite different pH dependence to each other. On raising the pH from 5.0 to 8.7, the UV absorption maxima of gallated catechins typically shift from 274 nm to 322 nm with a distinct isosbestic point around 290 nm. On further raising the pH to 10, the absorption intensity at 322 nm became more intense with the spectra deviating from the isosbestic point. On the other hand, non-gallated catechins showed small spectral changes upon these pH changes. The content of gallated catechins contained in commercial tea beverages and tea extracts are determined on the basis of the UV absorption difference between gallated and non-gallated catechins. Results of the UV absorption method showed good correspondence with those by the HPLC method.
2008-01-10