Sterols from Centaurea pumilio L. with cell proliferative activity: In vitro and in silico studies

Numerous studies highlighted the impact of natural products, particularly phytosterols, in wound healing while providing less expensive alternatives to chemically synthesized drugs, with less side effects. Centaurea pumilio L. (family Asteraceae) is a rare and endangered species of genus Centaurea with few reports concerning its chemistry. Our phytochemical investigation for the non-polar fraction of its aerial parts led to the isolation and identification of the new compound (6) identified as stigmast-1,5-dien-3-O-beta-D-glucopyranoside along with five known sterols and triterpenes (1-5) identified as taraxasterol, beta-sitosterol, stigmasterol, beta-sitosterol glucoside, and stigmasterol-3-O-beta-D-glucopyranoside. Structures of the isolated compounds have been characterized using 1D, 2D NMR, and mass spectral analyses. The cell viability and proliferative activity of the isolated compounds were evaluated using an MTT assay on cultured human primary umbilical vein endothelial cells (HUVEC). None of the compounds exhibited any sign of cytotoxicity. Nonetheless, compounds 5 and 6 moderately enhanced the HUVEC cell growth by 14 and 16%, respectively, at the maximal tested dose (50 mu g/mL). As inhibition of glycogen synthase kinase 3-beta (GSK3-beta) enzyme is important to enhance the wound healing process; therefore, molecular docking was performed to understand the possible interactions between bioactive compounds 5 and 6 and GSK-3 beta binding pocket active amino acid residues. Both compounds were able to bind to the substrate-binding site of GSK-3 beta and potentially interact with the key active site residues, forming strong p and hydrogen interactions with the catalytic site residues, revealing lower binding energy (-7.185 and -6.303 kcal/mol, respectively) than that of indirubin-3-onooxime (-5.303 kcal/mol); thereby representing strong natural replacements candidates for GSK-3 beta inhibitors.