University of North Florida
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Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Website: @unf

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Classification: Fruit -> banana

Citations 1

"Flow Injection Determination Of Polyphenols Using A Plant Juice Carrier"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 361-365
Shunichi Uchiyama* and Shuichi Suzuki

Abstract: Extracts (in 0.1 M phosphate buffer containing 0.3% of NaN3 as antioxidant) of banana pulp and spinach leaves, which contain catechol oxidase and catechol oxidase (dimerizing), respectively, were evaluated as carrier solution for the flow injection determination of polyphenols. The decrease in O content of the carrier solution due to enzymatic reaction was detected as a decrease in the reduction current at an O electrode. Although banana pulp extracts gave the larger current response, the baseline was unstable and decreased to zero after 3 to 4 days; the spinach solution gave a stable background current for at least 9 to 10 days, and could be used in the determination of, e.g., dopamine, (±)-adrenaline or catechol (rectilinear calibration range up to 6 mM or better). Although the method was not highly selective, glucose, L-ascorbic acid and uric acid gave no response. Banana pulp and spinach leaves exhibit enzyme activities of polyphenol oxidase and catechol oxidase (dimerizing), respectively, and the extd. solutions of these plants were employed as carriers for the flow injection amperometric determination of polyphenols. Spinach leaf juice was found to be superior to banana juice in terms of its long stability and broad linear range of the calibration graphs for dopamine (1 x 10^-4-6 x 10^-3 M), catechol (2 x 10^-4-8 x 10^-3 M) and dl-epinephrine (2 x 10^-4-6 x 10^-3 M). Each peak current returned to the original baseline completely within about 5 min when the flow-rate was 0.65 mL min-1. The enzyme activity of spinach leaf solution containing 0.3% of sodium azide did not vary for at least 7 days and it was found that this solution was useful as a carrier in a flow-
Phenols, poly Dopamine Adrenaline Catechol Electrode Amperometry Sample preparation