Binkoh Yoda

Antioxidative Activity of Amino Acids and Sulfur-containing Compounds to Superoxide : Measurement by Quenching the Chemiluminescence of a Cypridina Luciferin Analogue

Reaction rate constants between superoxide (O2(-)) and natural anti-oxidants, amino acids and some related sulfur-containing compounds were determined by quenching the chemiluminescence of a Cypridina luciferin analogue, 2-methyl-6-phenyl-3,7-dihydroimidazo[1,2-a]pyrazin-3-one (CLA) in pH 7.0 buffer solutions at 25°C as described in our previous report. The results are discussed in comparison with the literature data. We found that the present method can be applied to measured antioxidative activity of even a fairly unstable sample.

Antioxidative Activity Against Superoxide of Anticarcinogenic Tea-Leaf Catechins: Measurement by the Cypridina Chemiluminescence Method

The reaction constants between superoxide (O2 -) and tea-leaf catechins, whose anticarcinogenic activity to stomach cancer has been confirmed, were measured using the Cypridina chemiluminescence method for measuring rate constants between O2 - and antioxidants established in our previous report. The quenching experiments of chemiluminescence of a Cypridina luciferin analog, 2-methyl-6-phenyl-3,7-dihydroimidazo[1,2-a]pyrazin-3-one (CLA) in 25mM buffer solution (pH 7.0) at 25°C were used. Small amounts of antioxidants were needed for the measurement (<10mg). The activities are expressed in quenching constants so we can compare them quantitatively. Tea-leaf catechins showed reaction rate constants ranging from 104 to 106M-1s-1 (as large as ascorbic acid). Some teas showed reactivity to superoxide as well as peroxide values. The results were compared with the data in the literature. They prove that tea-leaf catechins have strong antioxidative activity against O2 - in aqueous solutions and suggest that superoxide can cause stomach cancer. We also found that the present measuring method is applicable to the measurement of reaction rate constants of antioxidative samples against superoxide even when the samples are fairly unstable.