Oleuropein, the major active compound in olive leaf, has been of considerable interest for its many health benefits. This work aims the determination of oleuropein in olive leaves from Turkey by a rapid and simple capillary electrophoretic method, and then to correlate the oleuropein amounts and the bioactivities of olive leaf extracts. The optimal separation medium was composed of 30 mmol/L borate (pH: 9.6), 25 mmol/L2-hydroxypropyl-beta-cyclodextrin (2-HP-beta-CD), 10% (v/v) methanol. Moreover, olive leaf extracts were examined for antioxidant, antidiabetic, and anti-inflammatory activities. The antioxidant activities were determined by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity. The antidiabetic activities were predicted using alpha-glucosidase inhibitory effects. For the anti-inflammatory activities of the extracts, their reduction power of pro-inflammatory tumor necrosis factor (TNF)-alpha were measured. Oleuropein concentration ranged between 11.7-106 mg/g dry leaf. Strong correlations were detected between each biological activity and the oleuropein content of olive leaves.