Study of phenolic composition of olive fruits: validation of a simple and fast HPLC-UV method

A high-performance liquid chromatography (HPLC) method endowed with a gradient elution and a UV detection system was established and validated for the determination of phenolic acids, phenolic alcohols, hydroxycinnamic acid derivatives, flavonoids, secoiridoids and lignans during olive (Olea europaea L.) fruit development (green, purple and black olives). Within the test range, the calibration curves exposed a good linear regression (R 2>0.9995). Detection limits ranged between 0.63 and 13.43 mg/L for the detected phenolic compounds. The presented method yielded satisfactory repeatability in terms of retention times and average concentrations of phenolic compounds (RSD < 0.3%). Verbascoside was established as the major phenolic compound in black olives. Oleuropein was established as the dominating phenolic compound in green olives, and its level decreased during maturation. Additionally, this research is the first to experimentally evidence that the flavone luteolin-7-rutinoside is the predominant flavonoid glucoside in black olives, showing the most significant variation with fruit development. The above results validate the method for an easy and fast determination of different classes of phenolic compounds present in olive fruits.