Quantitative Seasonal Changes in the Leaf Phenolic Content Related to the Alternate-Bearing Patterns of Olive ( Olea europaea L. cv. Gemlik)

Abstract

Using HPLC, the seasonal changes in the phenolic co mpound content of the leaves of the Gemlik olive cultivar ( Olea europaea L) has been investigated with respect to the effects on the alternate bearing of the cultivar. F or this purpose, the leaf concentrations of oleuropein, chlorogenic acid, caffeic acid, 3-hydro xycinnamic acid, scopolin and p- coumaric acid were analyzed at 10 day intervals aro und the years. The quantity and distribution of these phenolics in the leaves showe d significant differences in 2008 (off year) and 2009 (on year). In the “on” year, the lev els of chlorogenic and p-coumaric acids were high, whereas the abundance of other phenolic compounds was low. In contrast, during the “off” year, the chlorogenic and p-coumar ic acid levels were at low levels, whereas the levels of the other phenolics were high . We found a negative relationship between the chlorogenic acid and caffeic acid conce ntrations in the “on” and “off” years: the amount of caffeic acid in the leaves was high, and the chlorogenic acid level was low. The contents of chlorogenic acid, caffeic acid, 3-h ydroxycinnamic acid and p-coumaric acid were significantly different in the “on” and “ off” years. These findings indicated that these compounds and the other phenolics examined in this study were related to alternate bearing. Interestingly, the levels of all of the ph enolic compounds examined in this study were at their highest during the dormant season. Keywords: Caffeic acid, Chlorogenic acid, Oleuropein, Olive l eaves, P-coumaric acid, Scopolin, 3-hydroxycinnamic acid.