关键词: 荔枝, 多酚, 抗氧化, 动力学, 稳定性

Abstract: In this study, fresh litchi pulp was extracted with 70% aqueous ethanol twice by shaking for 6 h each time; afterward, the resulting extracts were pooled, condensed by rotary evaporation, defatted with n-hexane and reextracted with ethyl acetate/ethyl ether mixture (1:1, V/V); and finally, an organic phase and an aqueous phase both containing polyphenols were obtained. The antioxidant activity of litchi polyphenols in the two phases was evaluated by DPPH radical scavenging and ferric reducing antioxidant power (FRAP) assays. Meanwhile, the relationship between total phenol content (TPC) and antioxidant activity of the two phases were explored. The stability and antioxidant activity of litchi polyphenols showed a downward trend with increasing temperature (25－70 ℃), and prolonged exposure to sunlight (12－96 h) could also result in a gradual decrease in the stability and antioxidant activity of litchi polyphenols. TPC and antioxidant activities of both polyphenolic extracts were kept stable in the pH range of 8－9. Meanwhile, an obvious correlation between TPC and antioxidant activity was observed for both polyphenolic extracts (P＜0.05). Therefore, lower temperature and light-free environments are benefit for TPC and antioxidant activity of litchi polyphenols during storage and processing.

Key words: Litchi chinensis Sonn, polyphenols, antioxidant activity, kinetics, stability