Oxidation of phenolic compounds from Aloe barbadensis by peroxidase activity: Possible involvement in defence reactions

Sephadex LH-20 chromatography and reverse phase-high performance liquid chr omatography (RP-HPLC) have been combined to analyse different phenolics in Aloe barbadensis Mill. Among them, a new chromone peak was found. Whole phe nolics, and anthrone and chromone fractions were assayed as substrates of e ndogenous peroxidases (donor:hydrogen peroxide oxidoreductase; EC 1.11.1.7) and polyphenol oxidases (1,2-benzenediol:oxygen oxidoreductase; EC 1.10.3. 1) by following the disappearance of specific RP-HPLC peaks after appropria te incubations in the presence and in absence of H2O2. Chromones, but not a nthrones, were found to be good substrates of peroxidases. It is postulated that peroxidase oxidation of chromones may have a protective and sealing e ffect against infection after wounding. Polyphenol oxidases may have a seco ndary, if any, effect. (C) 2001 Editions scientifiques et medicales Elsevie r SAS.