Phenolic profiling of various olive bark-types and leaves: HPLC-ESI/MS study

The complete phenolic composition of Olea europaea L. (olive) barks covered by periderm or rhytidome was determined for the first time. For the identification of compounds accurate molecular mass and formula, acquired by LC and electrospray ionization (ESI) with time-of-flight (TOF) MS and fragmentation pattern given by LC-ESI/MS/MS analyses were used. Quantitation of the compounds was performed by a validated LC MS method in MRM mode using external standard calibration method. Results were also compared qualitatively and quantitatively with the phenolic composition of olive leaves. Our analytical platform was able to characterize 41 different phenolics including 5 hydroxycoumarins, 16 secoiridoids, 3 cinnamic acid derivatives, 8 flavonoids and 9 low molecular weight phenols. 8 of the compounds were identified for the first time from olive tissues. Quantitative analyses show that the amounts of compounds are significantly different in the periderm, rhytidome and leaf samples. The old type, rhytidome bark contains large amounts of hydroxycoumarin esculetin (3.01%) while the young, periderm bark contains this in traces (0.34%). This compound cannot be detected in olive leaf extract at all. In contrast, the secoiridoid oleuropein is present in the highest concentration in the leaves (8.52%), followed by the periderm (4.98%) and rhytidome (1.89%). Our results clearly show that both types of O. europaea L. bark are inexpensive, easily available natural sources of phenolic compounds with pharmacologic and cosmetic perspectives. (C) 2015 Elsevier B.V. All rights reserved.