Experimental and computational approach to develop Rosmarinic acid against insulin resistance in the treatment of diabetes mellitus via PPAR-γ agonism.

From past to the present, plants and trees have benefited humans in many ways. As technology advanced the biological properties of plants are much more explored especially by the pharma industry. Rosemary plant has gained attention as a phytoconstituent-rich herb that may help to manage diabetes mellitus (DM), however, exact mechanism of action is still unknown. Rosmarinic acid (RA), is a one of the important bioactive compounds found in rosemary. In this study, we have investigated RA and we synthesized its alkylated derivative (RAD) by blocking the free hydroxyl groups as a probe to investigate. RA was extracted, isolated, purified, and structurally characterized by IR, 1D & 2D NMR, DEPT 135°, LC-MS/MS, similarly, RAD. In silico molecular docking studies indicated that both RA and RAD bind to PPAR-γ (Peroxisome Proliferator-Activated Receptor) protein, however, RA showed superior binding affinity with free hydroxyl groups. MD simulation results demonstrated stability in terms of RMSD, RMSF and Protein-ligand interaction profiles. RA demonstrated promising antidiabetic activities via PPAR-γ agonism such as glucose uptake in cells (65 % for RA vs. 51 % for RAD) and enhanced lipid-lowering effects (71 % for RA vs. 48 % for RAD). The EC50 values of on target protein binding assays (via TR-FRET) also showed better results for RA (7.78 μM vs. 37.84 μM for RAD). The GLUT-4 expression assay demonstrated that anti-diabetic potential of RA in L6 cells, Standard pioglitazone and RA showed better GLUT-4 expression of 67.87 % & 74.85 % compared to 51.83 % by RAD. The in silico studies have validated the biological studies. Altogether, we strategically isolated and elucidated mechanism for RA as a potential therapeutic in the treatment of DM via PPAR-γ agonism.