Quantitative TLC analysis of (+)-catechin and (-)-epicatechin from Fagus sylvatica L. with and without red heartwood

The aim of this study was to investigate the role of (+)-catechin and (-)-epicatechin in the molecular processes of formation of red heartwood, a structural and color anomaly of living beech which causes substantial economic loss. The causes of the formation of red heartwood and the molecular carriers and participants are unknown. It has been proven that the activity of phenol oxidizing enzymes (POD, PPO) increases at the color boundary, but the phenolic compounds participating in these reactions, and probably building up the red chromophores are unknown. Catechins play an important role in defense reactions against oxidative stress in plant tissues and are also major phenolic constituents of beech wood. A simple and readily applicable TLC method has been implemented to measure the radial distribution of the concentrations of the two epimers in healthy and discolored beech disks. The reactions at the color boundary could also be tracked by use of this technique. The results show unequivocally the role of the two catechins, and presumably the role of other flavan-3-ols also, in the formation of the red chromophores. By establishing the exact composition of the red chromophores the color stability of red-heartwood material and its industrial utilization could also be enhanced.