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Improvement of liver function is one of the most popular commercial health claims of functional foods in Asian countries, including Korea. After examining the potential of several traditional Korean wild vegetables for enhancing liver function, we found that Youngia denticulata Kitam. has strong hepatoprotective effects against oxidative stress induced by tert-butylhydroperoxide (t-BHP). We are the first to report that the extract and ethyl acetate fractions of Y. denticulata have radical scavenging activities and inhibit oxidative stress-induced cell death and DNA damage in HepG2 cells. The extract and ethyl acetate fractions significantly decreased cellular reactive oxygen species production and apoptosis induced by t-BHP in HepG2 cells. In addition, they prevented the depletion of cellular glutathione, which is an important defense molecule against oxidizing xenobiotics. Chlorogenic acid and 3,5-dicaffeoylquinic acid were found to be major active components responsible for the activity of Y. denticulata and could serve as marker compounds for standardization. These data suggest that Y. denticulata could be promoted as a potential antioxidative functional food candidate, particularly for hepatoprotection against oxidative stress.

The upregulation of phase II detoxification genes is believed to play an important role in cancer prevention. The molecular mechanism underlying the changes in gene expression that accompany cancer prevention involves activation of the transcription factor, NF-E2-related factor 2 (Nrf2). In traditional medicine, the fruit of Schisandra chinensis Baill is used as a tonic, an anti-tussive and an anti-aging drug. In the current study, nine lignans were isolated from S. chinensis and tested for their ability to induce quinone reductase (QR) activity in Hepa1c1c7 mouse hepatocarcinoma cells. Tigloylgomisin H (TGH) and angeloylgomisin H (AGH) significantly induced QR activity and exhibited a relatively high chemoprevention index (CI) (10.80 and 4.59, respectively) as compared to control. TGH also induced QR activity in BPrc1 mouse hepatocarcinoma cells as well, which are defective in aryl hydrocarbon nuclear translocator (Arnt). In HepG2 human hepatocarcinoma cells, TGH significantly activated gene expression mediated by the antioxidant response element (ARE), a key regulatory region in the promoters of detoxification enzymes, through the nuclear accumulation of Nrf2. The results of the current study suggest that TGH functions as a novel monofunctional inducer that specifically upregulates phase II enzymes through the Nrf2-ARE pathway. TGH thus represents a potential liver cancer prevention agent.