Identification of secondary metabolites in Averrhoa carambola L. bark by high-resolution mass spectrometry and evaluation for α-glucosidase, tyrosinase, elastase, and antioxidant potential

In this study, paper spray ionization (PSI) coupled to high-resolution mass spectrometry has been used to identify secondary metabolites from ethanol extracts of Averrhoa carambola L. bark (ABE). Various phytoconstituents including phenolic acids, flavonoids, xanthones and terpenoids were identified from the bark. ABE shows potential antioxidant activity as well as markedly inhibited alpha-glucosidase, elastase, and tyrosinase enzyme activities in a concentration-dependent fashion, respectively. ABE significantly inhibited alpha-glucosidase at lower concentration (IC50: 7.15 +/- 0.06 mu g/mL). Identified compounds were tested to understand the biological activity of ABE. Experimental results suggest that norathyriol, one of the identified compounds, has significant alpha-glucosidase (IC50: 0.81 +/- 0.01 mu g/mL) inhibition and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activities (IC50: 4.90 +/- 0.09 mu g/mL). At a dose of 100 mg/kg, ABE significantly decreased the postprandial blood glucose level in oral glucose tolerance test (OGTT). This study shows that carambola bark can be a potential source of bioactive compounds.