The effect of thermal treatment on the degradation of the polyphenolic compounds in plum extract was investigated in the range of 70-110 degrees C by means of fluorescence spectroscopy and spectrophotometric techniques. The fluorescence results suggested that plum extract represents a multicomponent system with different fluorescence species. The heating of plum extract resulted in structural changes that led to a significant decrease in fluorescence intensity at higher temperature when the solutions were excited at 300 nm, whereas, when excited at 410 nm, significant increase in fluorescence intensity was measured in the temperature range of 70 and 110 degrees C. Degradation rate constants were estimated using a first order kinetic model. Temperature dependence of the degradation rate constants were expressed according to the Arrhenius model. The total monomeric anthocyanins showed the highest degradation in comparison to other polyphenols, as well as to antioxidant activity. (C) 2015 Elsevier Ltd. All rights reserved.