Endothelial-Protective Actions of Diethylether Extract from Gentiana kochiana and Xanthone Gentiacaulein Against Oxidized LDL-Induced Injury—In Vitro Evaluation

Endothelial dysfunction is an early pathophysiological event in atherosclerosis. The endothelial-protective abilities of diethylether extract (EE) from the <i>Gentiana kochiana</i> (Gentianaceae) herb and its main component, xanthone aglycone gentiacaulein (GC), were evaluated in an oxidized low-density lipoprotein (oxLDL)-treated EA.hy926 endothelial cell line. The EE and GC actions were assessed using cell viability assays, flow cytometry, immunoblot, DPPH, NBT, TBARS, conjugated diene formation, and Griess tests. Both EE and GC prevented oxLDL-induced apoptosis by reducing intracellular reactive oxygen species levels, mitochondrial depolarization, and caspase activation in EA.hy926 cells. EE and GC dose-dependently diminished oxLDL-induced cellular lipid peroxidation. In cell-free conditions, EE moderately scavenged superoxide anions and had no affinity toward DPPH radicals, GC did not interact with either of investigated free radicals, while both EE and GC effectively delayed Cu²⁺-induced LDL oxidation. EE and GC upregulated oxLDL-suppressed protective Akt/CREB/eNOS and ERK signals and restored oxLDL-reduced nitric oxide levels. Therefore, EE and GC effectively counteract oxLDL-induced endothelial apoptosis by reducing oxidative stress, promoting mitochondrial recovery, and enhancing the prosurvival Akt/CREB/eNOS axis and ERK activity. Our study is the first to demonstrate that xanthone-rich EE from aerial parts of <i>G. kochiana</i> and xanthone GC alleviate oxLDL-induced endothelial cell injury, underscoring their potential for cardiovascular protection.