Abstract: The contents of total phenolics, total flavonoids and proanthocyanidins in six different varieties of red raspberry leaves growing in northeast China were investigated by spectrophotometry. Their phenolic compositions were investigated by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). In addition, their antioxidant activity was evaluated by three different assays. The results showed that all cultivars were richer in total phenolics than total flavonoids and proanthocyanidins. The cultivar European red possessed the highest total phenol content (5.56 ± 0.06) mg/g and total flavonoid content (3.77 ± 0.06) mg/g. Heritage possessed the highest proanthocyanidins content (3.06 ± 0.04) mg/g. There was a significantly positive correlation between the 2,2’-azino-bis(3-ethylbenzthiazoline-6-sulphonic) acid (ABTS) cation radical scavenging capacity and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity of red raspberry leaf extracts, with a correlation coefficient of 0.992 (P < 0.01); ABTS cation and DPPH radical scavenging capacity showed significantly positive correlations with the total content of polyphenols with correlation coefficients of 0.886 and 0.891, respectively. Thirteen phenolic compounds, including six phenolic acids and seven flavonoids, were identified by UPLC-MS/MS from the red raspberry leaf extracts. Ellagic acid, chlorogenic acid, gallic acid were the dominant phenolic acids, and rutin, catechin, epicatechin, and hyperoside were the dominant flavonoids in the extracts.

Key words: red raspberry leaves, polyphenols, antioxidant activity, ultra performance liquid chromatography-tandem mass spectrometry