Effect of Olive Leaves Drying on the Content of Oleuropein

Oleuropein content in olive leaves dried at ambient temperature, and at elevated temperature (50°C) from Palestinian olive trees collected from West Bank in the middle of November was determined by HPLC and compared to naturally dry olive leaves (collected dry from the tree). Results showed that higher concentration was obtained from olive leaves dried at room temperature (10.0 mg per gram of dry olive leaves), compared to those dried at 50°C (1.7 mg/g), and those that collected dry from the tree (2.5 mg/g). Oleuropein content of dried olive leaves was compared with leaves that chopped and extracted fresh, and results show that fresh leaves showed the lowest oleuropein content (<0.1 mg/g) denoting that drying of leaves is required for high oleuropein recovery.