Abstract
Oleuropein (OE) is a secoiridoid glycoside, which occurs mostly in the Oleaceae family presenting several pharmacological properties, including antioxidant, cardio-protective, anti-atherogenic effects etc. Based on these findings OE is commercially available, as Herbal Medicinal Product (HMP), claimed for its antioxidant effects. As there are general provisions of the medicine regulating bodies e.g. European Medicines Agency, the quality of the HMP’s must always be demonstrated. Therefore, a novel LC-MS methodology was developed and validated for the simultaneous quantification of OE and its main degradation product, hydroxytyrosol (HT), for the relevant OE claimed HMP’s. The internal standard (IS) methodology was employed and separation of OE, HT and IS was achieved on a C18 Fused Core column with 3.1 min overall run time employing the SIM method for the analytical signal acquisition. The method was validated according to the International Conference on Harmonisation requirements and the results show adequate linearity (r2 > 0.99) over a wide concentration range [0.1–15 μg/mL (n=12)] and a LLOQ value of 0.1 μg/mL, for both OE and HT. Furthermore, as it would be beneficial to control the quality taking into account all the substances of the OE claimed HMP’s; a metabolomics-like approach has been developed and applied for the total quality control of the different preparations employing UHPLC-HRMS-multivariate analysis (MVA). Four OE-claimed commercial HMP’s have been randomly selected and MVA similarity-based measurements were performed. The results showed that the examined samples could also be differentiated as evidenced according to their scores plot. Batch to batch reproducibility between the samples of the same brand has also been determined and found to be acceptable. Overall, the developed combined methodology has been found to be an efficient tool for the monitoring of the HMP’s total quality. Only one OE HMP has been found to be consistent to its label claim.
Highlights
Oleuropein (OE) is a natural secoiridoid glycoside, occuring mainly in the Olea genous of the Oleaceae family and it is the most well studied phenolic compound in olive cultivars [1,2,3]
A second aim of the present study is to develop a metabolomics-like approach, combining UHPLC-(-ESI)-High Resolution Mass Spectrometry (HRMS) and multivariate analysis (MVA) for studying the “total quality” characteristics of the selected herbal medicinal products (HMP)’s in terms of their minor component uniformity with the aid to assess their batch to batch reproducibility
Their purity was found to be more than 98% (HPLC-UV) and their structures were identified by High Resolution Mass Spectrometry (HRMS) and 1 & 2D Nuclear Magnetic Resonance (NMR)
Summary
Oleuropein (OE) is a natural secoiridoid glycoside, occuring mainly in the Olea genous of the Oleaceae family and it is the most well studied phenolic compound in olive cultivars [1,2,3]. Its main degradation product, which is a natural occurring substance in olive products, is hydroxytyrosol (HT), which exhibits several interesting biological properties [17]. It should be noted that the quality control of HMP’s represents a demanding task, as they are usually complex mixtures, extracts or enriched extracts, often containing several hundreds of minor constituents that are impossible to be accurately quantified one by one, taking into account the current status of instrumental capabilities. On the other hand the measurement of the quality of HMP’s taking into account as many constituents as possible is crucial and at least the batch to batch reproducibility of such products should be demonstrated, as it ensures the same biological activity (due to both the main constituent and the synergistic effects) for the patients receiving the selected commercial formulation. In the current work the term “total quality” reflects the accurate quantitation of the main bioactive substance (OE) and the simultaneous evaluation of the total phytochemical profile of the investigated OE claimed HMP’s in each formulation
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