Species of Cirsium (Asteraceae family) have been used in folk hepatoprotective medicine in Taiwan. We collected four Cirsium species—including the aerial part of Cirsium arisanense (CAH), the aerial part of Cirsium kawakamii (CKH), the flower part of Cirsium japonicum DC. var. australe (CJF), and Cirsii Herba (CH)—and then made extractions from them with 70% methanol. We compared the antioxidant contents and activities of these four Cirsium species extracts by a spectrophotometric method and high-performance liquid chromatography⁻photodiode array detector (HPLC-DAD). We further evaluated the hepatoprotective effects of these extracts on CCl₄-induced acute liver damage in C57BL/6 mice. The present study found CAH possesses the highest antioxidant activity among the four Cirsium species, and these antioxidant activities are closely related to phenylpropanoid glycoside (PPG) contents. The extracts decreased serum ALT and AST levels elevated by injection with 0.2% CCl₄. However, only CJF and CH decreased hepatic necrosis. Silibinin decreased serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels and hepatic necrosis caused by CCl₄. CJF and CH restored the activities of hepatic antioxidant enzymes and decreased hepatic malondialdehyde (MDA) levels. CJF further restored the expression of hepatic antioxidant enzymes including Cu/Zn-superoxide dismutase (Cu/Zn-SOD), Mn-superoxide dismutase (Mn-SOD), and glutathione S-transferase (GST) proteins. HPLC chromatogram indicated that CKH, CJF, and CH contained silibinin diastereomers (α and β). Only CJF contained diosmetin. Hence, the hepatoprotective mechanism of CJF against CCl₄-induced acute liver damage might be involved in restoring the activities and protein expression of the hepatic antioxidant defense system and inhibiting hepatic inflammation, and these hepatoprotective effects are related to the contents of silibinin diastereomers and diosmetin.
Keywords: CCl4; Cirsium species; antioxidant; inflammation; liver damage; phenylpropanoid glycosides.