Wataru Sakamoto, Takashi Kanehira, Hirohisa Hongou, Akemi Matsuda, Masanori Mune and Kozo Asano
This study was performed to develop a novel colorimetric system using anthocyanins as a clinical pH indicator. Anthocyanins prepared from red wine and red currant extract were characterized by HPLC analysis, alcohol content, and pH. The stability of anthocyanins in aqueous solution and the solid phase was compared. Anthocyanin on a cotton swab was hardly affected by storage for 60 days at room temperature, but the anthocyanin strikingly decreased in aqueous solution. Cotton swabs in which anthocyanin was absorbed displayed a variety of color variations in the pH range from 5.5 to 8.0. Interestingly, it was shown that the color changes correlated with the color component of a* (redness), which was quantified using a chromometer. Measurements of pH in nasal secretions and saliva were reproducible for the visual color and color component of a*. These results show that the assay system can be used as a visual indicator for clinical measurement of pH.
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