Phenolics from Eugenia jambolana seeds with advanced glycation endproduct formation and alpha-glucosidase inhibitory activities
Published data suggest that dietary-derived phenolics exert beneficial effects against hyperglycemia-mediated diseases, such as diabetes, through inhibiting the formation of advanced glycation endproducts (AGEs) and carbohydrate hydrolyzing enzyme activities. In the course of our investigation on the edible berry, Eugenia jambolana (known as Jamun), 21 phenolics (1–21) were isolated and identified from its seeds. Among these, one compound (1) is new and eleven compounds (3, 6, 9–13, 17, and 19–21) are being reported from E. jambolana for the first time. The anti-AGE activities of thirteen pure isolates (2–7, 9–12, 14, 15, and 20) were either comparable or superior to the synthetic anti-glycation agent, aminoguanidine, at three test concentrations (20, 50, and 100 μM) in the BSA–fructose assay. Most of these phenolics with anti-AGE activity exhibited potent free radical scavenging activity in the DPPH assay, and attenuated intracellular levels of LPS-induced reactive oxygen species in RAW264.7 macrophage. In addition, compounds 2–6, and 14 showed superior α-glucosidase inhibitory activity (IC50 = 5.0–21.2 μM) compared to the clinical α-glucosidase inhibitor, acarbose (IC50 = 289.9 μM). This is the first report of the anti-AGE effects of compounds 2–6 and 9–12, and α-glucosidase inhibitory activities of compounds 3–6, 9, 11 and 14. The current study supports the role of phenolics in the antidiabetic properties attributed to this edible berry, and warrants further animal studies to evaluate their potential as dietary agents for the prevention and/or therapy of hyperglycemia-mediated diseases.