Abstract
The objective of this study was the investigation of a potential influence of artichoke leaf extract (ALE) on the cell physiology and gene expression of phase I/II enzymes of human liver cells HepG2 and investigation on potential cell protective effects against ethanol-induced cell toxicity against HepG2 cells. Cell biological assays under in vitro conditions using HepG2 liver cells and investigation of mitochondrial activity (MTT test), proliferation assay (BrdU incorporation ELISA), LDH as toxicity marker, gene expression analysis by RT-PCR and enzyme activity of glutationtransferase. Artichocke extract, containing 27% caffeoylquinic acids and 7% flavonoids induced mitochondrial activity, proliferation and total protein content under in vitro conditions in human liver cells HepG2. These effects could not be correlated to the well-known artichoke secondary compounds cynarin, caffeic acid, chlorogenic acid, luteolin and luteolin-7-O-glucoside. The flavones luteolin and luteolin-7-O-glucoside had inhibitory effects at 100 µg/mL level on HepG2 cells, with luteolin being a significant stronger inhibitor compared to the respective glucoside. Artichoke leaf extract had minor stimulating effect on gene expression of CYP1A2, while CYP3A4, GGT, GPX2, GSR and GST were slightly inhibited. GST inhibition under in vitro conditions was also shown by quantification of GST enzyme activity. Induction of gene expression of CYP1A2 was shown to be supraadditive after simultaneous application of ethanol plus artichoke extract. Artichoke leaf extract exhibited cell protective effects against ethanol-induced toxicity within cotreatment under in vitro conditions. Also H2O2 damage was significantly inhibited by simultaneous artichoke incubation. Pre- and posttreatments did not exert protective effects. DMSO-induced toxicity was significantly reduced by pre-, post- and cotreatment with artichoke extract and especially with luteolin-7-O-glucoside, indicating a direct interaction with the toxifying agent and an induction of repair mechanisms.
Highlights
Cynara scolymus L. is an herbal medicinal product widely used in functional foods and phytotherapeutics for digestive complaints, adjuvant treatment of moderate hyperlipidaemia and hepato-biliary disorders in traditional European medicine
In vitro studies of hepatoprotective effects of artichoke extracts on cultured rat hepatocytes are shown against t-butylhydroperoxideinduced peroxidation of membrane lipids (Gebhard, 1997)
Cyanarin and caffeic acid were shown to reduce the carbontetrachloride-induced leakage of liver enzymes glutamic oxaloacetic transaminase and glutamic pyruvic transaminase (Adzet et al, 1987). These data correlate with our investigations, indicating artichoke extract to have a direct effect on liver cells
Summary
Cynara scolymus L. is an herbal medicinal product widely used in functional foods and phytotherapeutics for digestive complaints, adjuvant treatment of moderate hyperlipidaemia and hepato-biliary disorders in traditional European medicine. For review of established clinical use see (ESCOP Monograph, 2003). Hepatostimulating effects are described; for review see (Brand, 1992). Concerning the mode of action for treatment of hypercholesterinaemia (Brand, 1990) the reduction of elevated serum cholesterol levels by artichoke is due to an inhibition of incorporation of acetate into the nonsaponifiable lipid fraction and will reduce cholesterol biosynthesis (Gebhard, 1995; Gebhard, 1996). As assessed by a recent Cochrane review [5] the clinical effects published unto indicate a clear tendency towards lower serum cholesterol during artichoke therapy. Other benefits as lipid-lowering efficacy are reported, the evidence is not compelling
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