Evaluation of the contributions of polyphenols in Chinese propolis by on-line HPLC–ABTS method

Propolis, a well-known folk medicine in the world, has drawn growing attention due to the various bioactivities. An on-line method of coupling HPLC with 2,2′-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) cationic radical scavenging detection (HPLC–ABTS) was developed to screen the single polyphenol possessing ABTS cationic radical scavenging activity in ethanol extracts of Chinese propolis (EECP). Ten common polyphenols were selected from the active fingerprints of ten EECP samples obtained from different provinces of China by the on-line HPLC–ABTS method and quantified by Trolox equivalent. Their contributions to the antioxidant property of EECP were compared. Furthermore, Pearson’s correlation analysis was applied to determine whether there was a correlation between the antioxidant activity of individual polyphenol and total antioxidant activity of EECP. The results indicated that the composition of polyphenols in ten EECP samples obtained from China was similar. But the different polyphenols contributed in different way. Caffeic acid, kaempferol, and galangin simultaneously were the most prominent contributors to the antioxidant properties of ten EECP. The contributions of pinobanksin 3-acetate, caffeic acid phenethyl ester (CAPE), and caffeic acid cinnamyl ester varied largely with the different geographical regions. They, except galangin, significantly correlated with the antioxidant property of propolis. However, pinobanksin, pinocembrin, chrysin, p -coumaric acid, and ferulic acid rarely contributed to the antioxidant property of Chinese propolis. Therefore, the on-line HPLC–ABTS method was convenient, effective, and comprehensive to evaluate the contributions of polyphenols to the antioxidant property for Chinese propolis.