Abstract: In order to explore the effect of season on the quality of propolis, propolis samples harvested in different seasons from temperate, subtropical and tropical regions in China were extracted with 60% aqueous ethanol, and the color intensity, total phenol content, total flavonoid content, flavonol content, flavanone content and specific absorbance constant of ethanol extract of propolis (EEP) obtained were spectrometrically determined. Meanwhile, the antioxidant activity and antibacterial activity of EEP were also evaluated. The results showed that harvest season had a significant effect on the chemical composition of EEP. The contents of total phenol, total flavonoids, flavonol and flavanone revealed the highest level in the propolis harvested in June and July and the lowest level in September, which suggested that the best quality of Chinese propolis is in August. Moreover, an obvious difference in the contents of total phenol and total flavonoids in EEP from different seasons was observed. The highest levels of total phenol and total flavonoids were( 243.87 ± 152.13) mg/g and (189.34 ± 107.51) mg/g, respectively; in contrast, the lowest levels of both components were (187.25 ± 146.45 ) mg/g and (122 ± 81.02 ) mg/g, respectively. Furthermore, propolis from temperate zones in China had the best antioxidant activity, which was followed by propolis from sub-tropical zones and tropical zones. An obvious correlation between specific absorbance constant and DPPH radical scavenging capacity, total phenol content or total flavonoid content was observed. Therefore, harvest season exhibits a great impact on the quality of propolis.

Key words: propolis, ethanol extract of propolis (EEP), season, chemical composition, biological activity