Antioxidant activity and phenolic constituents of red propolis from Shandong, China

Abstract

Propolis is a resinous substance collected by honeybees from various plant sources and whose composition depends on the area of collection. This study examined the antioxidant activity of red propolis from Shandong, China. Ethanol extracts of propolis (EEP) were prepared and evaluated for their antioxidant activities using four assays: 2,2-diphenyl-1-picrylhydrazyl free radical-scavenging, 2,2'-azinobis (3-ethylbenzothiazoline- 6-sulfonic acid) radical cation decolorization, ferric ion reducing antioxidant and oxygen radical absorbance capacity assays. Red propolis from Shandong, China showed strong antioxidant activity across all assay systems used. Furthermore, the major constituents in EEP from Shandong, China were identified by HPLC analysis using photodiode array detection, and each component was quantitatively analyzed. In total, 17 compounds were identified: 9 flavonoids, 5 aromatic carboxylic acids and 3 phenolic acid esters. Red propolis from Shandong, China contains a large amount of the antioxidant compounds galangin and phenethyl caffeate (101.6 and 32.7 mg/g of EEP, respectively).