Factors affecting the contents of iridoid oleuropein in olive leaves (Olea europaea L.).

In this study, for the first time, the impact of the genetic factor on the contents of oleuropein in olive leaves was not only evaluated but the influence exerted by the color/age of leaves (green, green-yellowish, and yellow) and the collecting period (spring or autumn) was also evaluated. A repetitive high-resolution gas chromatographic quantitation method and an accurate high-performance liquid chromatographic method were developed. These analytical methods gave results showing a highly linear relationship.