Analysis of flavonoids from propolis by on-line HPLC–electrospray mass spectrometry

In this paper, the qualitative and quantitative separation and determination of the polyphenolic component of propolis preparations in the form of ethanolic extract, usually used for commercial pharmaceutical preparations, has been investigated by means of on-line HPLC–ESI/MS technique. Propolis of different origin have been evaluated for their components and a specific fingerprint has been determined potentially useful for the quality control of extracts in pharmaceutical preparations.The ethanolic extracts of propolis from Argentina, Italy and Spain shows approximately the same total ion chromatogram (TIC) profile due to the presence of the same molecular species, identified by the negative ESI–MS. On the contrary, the samples from Azerbaijan, China, Ethiopia and Kenya show a very peculiar TIC profiles. By using many purified flavonoids and calibration curves over a wide concentration range, from 0.05 (5 μg/ml) to 5 μg (500 μg/ml), an accurate assessment of the contents of several bioactive compounds in extract samples was performed. The propolis from Argentina, Italy and Spain show a great amount of pinocembrin (approximately 49%, 48% and 39% of the total identified flavonoids, respectively) and variable but similar percentages of the other species. On the contrary, the propolis from China, Azerbaijan and Ethiopia have a great amount of pinocembrin (approximately 63%, 46% and 62%, respectively) but no presence of genistein, kaempferol, apigenin and chrysin for the sample from China, genistein, kaempferol, acacetin and chrysin for the propolis from Azerbaijan, and no kaempferol and acacetin for the sample from Ethiopia. The ethanolic extract from propolis of Kenya has no identified flavonoid species but just a peak possessing a m/z of 253.0. Finally, an evaluation of the presence of total flavonoids for the various propolis samples was performed, with extracts from Argentina, Italy and Spain more rich in polyphenols than those from Azerbaijan, China, Ethiopia and Kenya.The HPLC–ESI/MS under the experimental conditions illustrated represents a valuable method for the qualitative and quantitative assay of the most relevant components of propolis. On-line HPLC–ESI/MS analysis constitutes an alternative to obtain typical fingerprints of propolis and a reliable identification of a large number of propolis polyphenolic components.