Evaluation of propolis polyphenols absorption in humans by liquid chromatography/tandem mass spectrometry

Propolis has various biological activities such as antibacterial, antiviral, antioxidant, immunostimulating and antiinflammatory, which are generally ascribed to the polyphenolic fraction. The aim of this study was to evaluate the absorption of the main polyphenols [caffeic acid (CA), pinobanksin-5methyl ether (P-5ME), pinobanksin (Pb), chrysin (C), pinocembrin (P), galangin (G), pinobanksin- 3-acetate, pinobanksin esters and caffeic acid phenylethyl ester (CAPE)] from a dewaxed and standardized extract of propolis (EPID1). Fifteen healthy volunteers consumed 5mL EPID1 in water, corresponding to 125mg of flavonoids. Blood samples were collected before, each hour for 8 h and 24 h after EPID1 intake. After deconjugation by beta- glucuronidase/sulfatase the plasma samples were analyzed by a selective liquid chromatography/tandem mass spectrometry (LC/MS/MS) method using morin as internal standard (I.S.). A kinetic profile characterized by two tmax, respectively at 1 h and about 5 h post-ingestion, was observed in all the subjects. The two peaks may be due to enterohepatic cycling. Among the various polyphenols ingested, only P-5ME, Pb, C, P and G were detected in plasma and Cmaxt1h were 65.7+/-13.3, 46.5+/-12.7, 79.5+/-18.6, 168.1+/-16.3 and 113.7+/-16.8 ng/mL, respectively. These levels decreased significantly after 8 h and were no longer detectable 24 h after EPID1 intake. The recovery of the extraction for CA, Pb, C, P, G and I.S. from spiked plasma was 95.2W3.1, 93.1+/-3.6, 91.0+/-2.5, 96.4+/-4.2, 93.4+/-2.4 and 85.5W2.4%, respectively. The results of this study evidence that flavonoids from EPID1 are absorbed, metabolized and Pb-5ME and G seem to have apparent absorption, measured as (AUC/dose), higher than C, P and Pb.