Pyrroloquinoline quinone (PQQ) is reduced to pyrroloquinoline quinol (PQQH2) by vitamin C,and PQQH2 produced is recycled to PQQ by air oxidation in buffer solution at pH 7.4 |
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Authors: | Kazuo Mukai Aya Ouchi Shin-ichi Nagaoka Kazuto Ikemoto |
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Affiliation: | 1. Faculty of Science, Department of Chemistry, Ehime University , Matsuyama, Japan;2. Niigata Research Laboratory, Mitsubishi Gas Chemical Company, Inc. , Niigata, Japan |
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Abstract: | Measurements of the reaction of sodium salt of pyrroloquinoline quinone (PQQNa2) with vitamin C (Vit C) were performed in phosphate-buffered solution (pH 7.4) at 25 °C under nitrogen atmosphere, using UV–vis spectrophotometry. The absorption spectrum of PQQNa2 decreased in intensity due to the reaction with Vit C and was changed to that of pyrroloquinoline quinol (PQQH2, a reduced form of PQQ). One molecule of PQQ was reduced by two molecules of Vit C producing a molecule of PQQH2 in the buffer solution. PQQH2, thus produced, was recycled to PQQ due to air oxidation. PQQ and Vit C coexist in many biological systems, such as vegetables, fruits, as well as in human tissues. The results obtained suggest that PQQ is reduced by Vit C and functions as an antioxidant in biological systems, because it has been reported that PQQH2 shows very high free-radical scavenging and singlet-oxygen quenching activities in buffer solutions. |
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Keywords: | pyrroloquinoline quinone pyrroloquinoline quinol reaction rate UV–vis absorption spectrum vitamin C |
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