Sephadex LH-20 chromatography and reverse phase-high performance liquid chromatography (RP-HPLC) have been combined to analyse different phenolics in Aloe barbadensis Mill. Among them, a new chromone peak was found. Whole phenolics, and anthrone and chromone fractions were assayed as substrates of endogenous 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 appropriate incubations in the presence and in absence of H 2 O 2 . Chromones, but not anthrones, were found to be good substrates of peroxidases. It is postulated that peroxidase oxidation of chromones may have a protective and sealing effect against infection after wounding. Polyphenol oxidases may have a secondary, if any, effect.