Analysis of the polyphenolic fraction of propolis from different sources by liquid chromatography–tandem mass spectrometry

A reverse phase LC–DAD–MS method for quantification of phenolic acids and flavonoids in propolis raw materials was developed. The propolis samples from different geographical areas were extracted with ethanol for 2 h at 70 °C and the resulting solutions analyzed on a 5 μm C18 symmetry 250 mm × 4.6 mm column. The separation was performed by means of a linear gradient elution and DAD and MS data were acquired in the 200–450 nm and 100–1000 Da range, respectively. The identity of most of the compounds was assessed by comparing their chromatographic and UV behaviour with that of authentic standards. When the standards were not available, the identity was achieved by means of chromatographic and on-line UV data combined with mass spectrometry. European, Chinese and Argentinean propolis are characterized by the presence of phenolic acids and flavonoids and the most abundant were chrysin (2–4%), pinocembrin (2–4%), pinobanksin-acetate (1.6–3%) and galangin (1–2%). Some Brazilian propolis contains mainly artepillin C, different caffeoyl quinic acids and some flavonoids. When considering the total flavonoid content as quality index, we suggest that propolis with a content less than 11% should be considered of low quality, whereas propolis with a content of 11–14%, 14–17% or >17% should be classified as propolis of acceptable, good and high quality, respectively. The reported LC–DAD–MS analysis method may be applied for the phytochemical screening of raw propolis and its commercial formulations.