Oleuropein exhibits dose-dependent hepatoprotection against D-galactosamine-induced hepatotoxicity in male rats: An <i>in vivo</i> and network pharmacology approach

This study examined the hepatoprotective effects of oleuropein, a secoiridoid glycoside from olive leaves, against D-galactosamine (D-GalN)-induced liver injury in male Sprague–Dawley rats. Hepatic injury was triggered by a single intraperitoneal injection of D-GalN (200 mg/kg body weight), and rats were randomly assigned to five groups (n = 10) receiving oleuropein orally at 5, 10, or 20 mg/kg. Physiological parameters, including daily food intake, body weight gain (BWG), and feed efficiency ratio (FER), were recorded. Serum lipid profile markers [total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and very low-density lipoprotein cholesterol (VLDL-C)], liver enzymes [alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate aminotransferase (AST)], metabolic enzymes [fatty acid synthase (FAS), glucose-6-phosphate dehydrogenase (G6PD)], and oxidative stress markers [malondialdehyde (MDA) MDA, glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), conjugated dienes (CD), lipid hydroperoxides (LOOH)] were evaluated. Histopathological changes in liver tissues were also examined. Oleuropein exerted dose-dependent hepatoprotective effects. At 20 mg/kg, it significantly (p &lt; 0.05) improved liver function, attenuated oxidative stress and inflammation, protected hepatocytes from structural damage and apoptosis, and normalized biochemical markers toward control values. A single intraperitoneal dose of 200 mg/kg was administered on day 0, followed by daily oleuropein for 28 days. Network pharmacology revealed nine potential molecular targets of oleuropein—tumor necrosis factor (TNF), SRC proto-oncogene, non-receptor tyrosine kinase (SRC), matrix metallopeptidase 9 (MMP9), prostaglandin-endoperoxide synthase 2 (PTGS2), phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA), matrix metallopeptidase 3 (MMP3), mitogen-activated protein kinase 1 (MAPK1), poly(ADP-Ribose) polymerase 1 (PARP1), and Matrix metallopeptidase 1 (MMP1). These targets are implicated in hepatoprotective mechanisms, including suppression of inflammation, inhibition of fibrosis, preservation of hepatocyte integrity, and enhancement of autophagy. Overall, findings highlight oleuropein as a promising natural therapeutic candidate for liver diseases associated with oxidative stress and inflammation.