Olive leaves were extracted with homogenizer-assisted extraction (HAE). Box-Behnken (BBN) design was employed through response surface approach (RSA) to achieve the optimum conditions. Bioactivity of the extract was assessed by its oleuropein, total biophenol (TBC) and total flavonoid (TFC) content along with its antioxidant activity determined by DPPH and CUPRAC assays. A new nanocomposite was developed using reduced graphene oxide (rGO) modified with TiOx (Ti-rGO) for trace amount determination of oleuropein in olive leaf extract. Structural characterization of the electrode was clarified using atomic force microscopy (AFM) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) techniques. Cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques were performed to investigate electrochemical behavior of oleuropein using three electrode configurations. Results of CV and SWV showed that quasi-reversible reaction occurred on electrode/electrolyte interface and a linear concentration range of 5-30 nM was obtained with a detection limit of 0.57 nM for oleuropein.