Preparative isolation of oleocanthal, tyrosol, and hydroxytyrosol from olive oil by HPCCC

• High performance countercurrent chromatography, a powerful tool to isolate olive oil phenolics.
• Options for large-scale isolation of olive oil phenolics.
• First spectroscopic proof of the equilibrium of (3S,4E)- and (3S,4Z)-oleocanthal in olive oil extracts.

For the provision of oleocanthal (OLC), a phenolic compound with very promising pharmacological properties, isolation from olive oil is a very important option. Due to the compound’s sensitivity to decomposition upon exposure to oxygen and light, a very gentle isolation method has been developed under use of high performance countercurrent chromatography (HPCCC). By partition of olive oil between hexane and methanol, an extract enriched in phenolics was prepared and subjected to a two-step HPCCC separation under use of heptane–EtOAc–MeOH–H2O mixtures in normal-phase and reverse phase mode, respectively. With this method, the isolation of tyrosol, hydroxytyrosol, and the mixture of (3S,4E)- and (3S,4Z)-OLC was achieved in approx. 70 min for each step. By one- and two-dimensional NMR-experiments and LC–MS, the equilibrium of (3S,4E)- and (3S,4Z)-OLC in such olive oil extracts has unambiguously been proven for the first time.