Novel Caffeic Acid - Zinc Acetate Complex: Studies on Promising Antidiabetic and Antioxidative Synergism Through Complexation

The role of Zn(II) in storage, insulin secretion and function has been documented, while plant phenolics have antioxidant and other pharmacological credence.The study aimed at synthesizing a novel medicinal Zn(II) complex. The medicinal properties of zinc(II) and caffeic acid were considered in synthesizing a novel complex with promising and improved antioxidant and anti-hyperglycaemic attributes.Complex synthesis was done using a 1:2 molar ratio of zinc acetate and caffeic acid and structurally characterized using NMR, FT-IR, high resolution-mass spectroscopy and HPLC. Its cellular toxicity was assessed in Chang liver cells and L-myotubes. In vitro, cellular, and isolated tissue models were used to evaluate the antioxidant and anti-hyperglycaemic properties of the complex relative to its precursors. Molecular docking was used to investigate the interaction with insulin signalling target proteins: GLUT-4 and protein kinase B (Akt/PKB).Zinc(II) and caffeic acid interacted via Zn:O4 coordination, with the complex having one moiety of Zn(II) and 2 moieties of caffeic acid. The complex showed in vitro radical scavenging, α- glucosidase and α-amylase inhibitory activity up to 2.6 folds stronger than caffeic acid. The ability to inhibit lipid peroxidation (IC50 = 26.4 μM) and GSH depletion (IC50 = 16.8 μM) in hepatocytes was comparable to that of ascorbic acid (IC50 = 24.5 and 29.2 μM) and about 2 folds stronger than caffeic acid. Complexation improved glucose uptake activity of caffeic acid in L-6 myotubes (EC50 = 23.4 versus 169 μM) and isolated rat muscle tissues (EC50 = 339 versus 603 μM). Molecular docking showed better interaction with insulin signalling target proteins (GLUT-4 and Akt/PKB) than caffeic acid. The complex was not hepatotoxic or myotoxic.Data suggest a synergistic antioxidant and anti-hyperglycaemic potential between zinc and caffeic acid, which could be attributed to the Zn:O4 coordination. Thus, it may be of medicinal relevance.