UPLC/ESI-Q-TOF-MS analysis of (poly)phenols, tocols and amino acids in Chaenomeles leaves versus in vitro anti-enzyme activities

Abstract

The aim of this study was to investigate the content of phenolics, free amino acids, tocopherols, tocotrienols and in vitro biological activities (α-amylase, α-glucosidase, and pancreatic lipase inhibition activity) of 12 cultivars of Chaenomeles × superba, japonica and speciosa leaves. In the present work 39 phenolic compounds were tentatively identified, including polymeric procyanidins > flavan-3-ols > phenolic acids > flavonols > flavanones > flavones > ellagitannins. Chaenomeles leaves contained on average 16.8 g of phenolics per 100 g dry weight (dw), with C. × superba ˈNicolineˈ displaying the highest (27.5 g/100 g dw), and C. × superba ˈColour Trailˈ the lowest (7.7 g/100 g dw) total phenolic content. Chaenomeles leaves possess all eight tocol analogs (four tocopherols (TP), and four tocotrienols (TT)), ranked in decreasing content: α-TP > β-TP > γ-TP > δ-TP > α-TT > β-TT > δ-TT > γ-TT. The most active form (α-tocopherol) was present in amounts from 480.6 to 7201.1 µg/100 g dw. 23 amino acids were identified, including all nine essential amino acids. The highest amount of O-phospho-L-serine was found (average 249.2 mg/100 g dw). Leaves of C. japonica ˈRed Joyˈ displayed the highest total amino acid content (2735.2 mg/100 g dw). Chaenomeles leaves showed α-amylase (8.2–24.5 mg/mL), α-glucosidase (1.2-6.3 mg/mL), and pancreatic lipase (7.0-10.5 mg/mL) inhibition activity (expressed as half maximal inhibitory concentration, IC50). Chaenomeles leaves can be a good material for obtaining extracts rich in phenolics, vitamin E or amino acids, providing an alternative, natural source of these compounds to help meet the growing demand for nutraceuticals and supplements.