2
O2 when the brown scales were suspended in water. Brown components isolated from the brown scales also transformed molecular oxygen into H2O2. During the autooxidation process, absorbance in the visible region was increased. On acid hydrolysis of the brown fraction, 2,4,6-trihydroxyphenylglyoxylic acid, 3,4-dihydroxybenzoic acid and the quinone form of benzoic acid were detected. In addition, glucose was detected as a sugar. 3,4-Dihydroxybenzoic acid was preferentially oxidized during autooxidation of the brown fraction. One of the oxidation products was the quinone form. Stable electron spin resonance (ESR) signals were detected in the brown fraction. New ESR signals appeared on oxidation of the brown fraction by hexacyanoferrate (III). One of the newly formed radicals seemed to have a 3,4-dihydroxyphenyl group. Based on these results, possible structures, mechanism of H2O2 formation and biological significance of the brown components are discussed.
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Received 11 April 2001/ Accepted in revised form 3 August 2001
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Takahama, U., Oniki, T. & Hirota, S. Phenolic Components of Brown Scales of Onion Bulbs Produce Hydrogen Peroxide by Autooxidation. J Plant Res 114, 395–402 (2001). https://doi.org/10.1007/PL00014004
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DOI: https://doi.org/10.1007/PL00014004