<![CDATA[Cissus quadrangularis is widely recognized for its antioxidant and hepatoprotective properties; however, its dose-dependent biological effects remain unclear. In this study, the dose-dependent effects of C. quadrangularis stem extract on oxidative stress, liver function, and liver histopathology were evaluated in Sprague–Dawley rats subjected to bilateral ovariectomy to induce an estrogen-deficient state, followed by D-galactose administration to induce oxidative stress. Thirty female rats were randomly divided into five groups (n = 6): a normal control group, a negative control group, and three treatment groups that received 150, 300, or 600 mg/kg body weight of the extract for 28 days, with D-galactose administered daily by intraperitoneal injection. Qualitative phytochemical screening was performed, and flavonoids, polyphenols, and triterpenoids were detected. GC–MS analysis identified steroidal compounds as the predominant chemical group (74.52%), followed by carboxylic acid derivatives (9.81%) and triterpenoids (8.49%). Serum levels of superoxide dismutase (SOD), malondialdehyde (MDA), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) were measured, and liver tissues were examined histopathologically. In the group treated with 150 mg/kg body weight, ALT and AST activities were significantly altered, while liver degeneration, necrosis, and inflammatory cell infiltration were reduced compared with the negative control group. Conversely, at the higher doses (300 and 600 mg/kg body weight), decreased SOD activity, altered MDA levels, and severe liver lesions were observed. These findings indicate that C. quadrangularis exerts a dose-dependent hepatoprotective effect, with the greatest protection against oxidative liver damage observed at 150 mg/kg body weight, highlighting the importance of dose optimization for therapeutic applications.]]>
