Rapid qualitative profiling and quantitative analysis of phenolics in Ribes meyeri leaves and their antioxidant and antidiabetic activities by HPLC-QTOF-MS/MS and UHPLC-MS/MS

Ribes meyeri leaves are used as traditional Kazakh medicine in China. However, no study on the characterization of the phenolic compounds in R. meyeri leaves has been reported, resulting in the lack of quality control measures and poor standardization. This study was conducted to identify the phenolic compounds in R. meyeri leaves and evaluate their antioxidant and antidiabetic activities. A total of 77 phenolics were tentatively identified by liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry. Ultra-high performance liquid chromatography coupled with triple quadrupole mass spectrometry was applied to simultaneously quantify 12 phenolics in R. meyeri leaves. Rutin, epigallocatechin, isoquercitrin, epicatechin, protocatechuic acid, and kaempferol-3-O-rutinoside were abundant in the R. meyeri leaves. The methanol extract and four different extracts enhanced the glucose uptake in 3T3-L1 adipocytes. The ethyl acetate extracts showed a total phenolic content of 966.89 +/- 3.59 mg gallic acid equivalents/g, a total flavonoid content of 263.58 +/- 17.09 mg catechin equivalents/g, and good protein-tyrosine phosphatase-1B inhibitory activities (IC50 : 0.60 +/- 0.03 mu g/mL). To our knowledge, this work is the first to identify and quantify the major phenolics in R. meyeri leaves.