Study concerning the involvement of guaiacol peroxidase-phenolic compounds relationship on assimilatory pigment degradation in Vitis vinifera L. leaves

Abstract

Previous research highlighted that chlorophyll and some carotenoids are bleached by the action of oxidative enzymes such as peroxidases in the presence of phenolic compounds. In the present investigation, leaves of 11 Vitis vinifera L. varieties (in blooming phenophase), were assayed for their chlorophyll (a+b) and carotenoid (x+c) concentration and their degradation after 30 days of cold (6°C) and dark storage. Peroxidase activity (EC 1.11.1.7) and total phenolic content (TP) of leaves were initially determined. We found an important linear correlation between peroxidase activity (PA) and the percentage of total chlorophyll (Chl) degraded (R2=0.9243; p<0.05), and also a positive statistically significant relationship between PA and TP concentration (R2=0.8389; p<0.05). Analyzing by fractions, the most important coefficient of determination was registered for the relationship PA – % of Chl a degraded (R2=0.8389; p<0.05), with a poor correlation for PA – % of Chl b degraded and PA – % of carotenoid degraded relationships. Experimental data obtained indicates that peroxidase might be involved in chlorophyll bleaching in the presence of phenolic compounds, and might mediate in a lesser extent leaf carotenoids degradation.