Rapid determination of oleuropein in food supplements and in Olea europaea L. leaves extracts by a densitometric-HPTLC approach

A research aiming to a rapid HPTLC method for the screening and the determination of the oleuropein in acqueous and hydro-alcoholic olive leaves extracts and in commercial products claiming oleuropein as their major component is described. Oleuropein is a natural secoiridoid present especially in Olea europaea L.. Oleuropein and its derivatives exhibit several biological activities, e.g. anti-hypertensive, anti-inflammatory, free radical scavenging, antioxidant, prevention of neoplastic diseases and anti-platelet. The Olea europaea L. leaves are the main source of these compounds; therefore their extracts have been recently used to prepare affordable dietary supplements. A HPTLC-densitometric method, based on external standard approach combined with FeCl3 derivatization, was developed for routine analysis of oleuropein in olive leaves extracts. The separation has been carried out by reversed-phase wettable C 18 plates. The method was optimized and validated; the obtained results were comparable with those from a HPLC/DAD/MS method. Moreover the method was set up with the aim to obtain a simultaneous cross comparative evaluation of different Olea leaves extracts and extra virgin olive oils by the HPTLC fingerprint approach. It highlights the presence of four classes of compound: secoiridoids, polyphenols, lignans and hydroxycinnamic acids.