Light Emission and the Formation of Radicals after Grinding Tea Leaves(Food & Nutrition)

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Light emission and the ESR spectra of tea leaves treated in various ways were studied. The fresh leaf showed a delayed light emission, which decreased exponentially with half times of 15 and 54 seconds. When the leaf was ground in water, the delayed light emission became small, because of destruction of the chloroplasts, and almost time-independent chemiluminescence was emitted. The chemiluminescence became very strong when the leaf was ground in an NaOH solution. ESR spectra of the tea leaf ground in water showed a singlet absorption attributable to an organic free radical, overlapping the six-line absorption due to the Mn^<2+> ion. The intensity of the radical became high when the leaf was treated with the NaOH solution and increased with time. In the case of the leaf ground in an NaCl solution, the singlet signal did not appear. These results suggest that the chemiluminescence and singlet absorption of the ESR spctra are attributable to oxidation of the catechins.
社団法人日本農芸化学会の論文