Inhibition of TNF-α-mediated NF-κB Transcriptional Activity in HepG2 Cells by Dammarane-type Saponins from Panax ginseng Leaves

Panax ginseng (PG) is a globally utilized medicinal herb. The medicinal effects of PG are primarily attributable to ginsenosides located in the root and leaf. The leaves of PG are known to be rich in various bioactive ginsenosides, and the therapeutic effects of ginseng extract and ginsenosides have been associated with immunomodulatory and anti-inflammatory activities. We examined the effect of PG leaf extract and the isolated ginsenosides, on nuclear factor (NF)-${\kappa}B$transcriptional activity and target gene expression by applying a luciferase assay and reverse transcription polymerase chain reaction in tumor necrosis factor (TNF)-${\alpha}$-treated hepatocarcinoma HepG2 cells. Air-dried PG leaf extract inhibited TNF-${\alpha}$-induced NF-${\kappa}B$transcription activity and NF-${\kappa}B$-dependent cyclooxygenase (COX)-2 and inducible nitric oxide synthase (iNOS) gene expression more efficiently than the steamed extract. Of the 10 ginsenosides isolated from PG leaves, Rd and Km most significantly inhibited activity in a dose-dependent manner, with $IC_{50}$ values of $12.05{\pm}0.82$ and $8.84{\pm}0.99\;{\mu}M$, respectively. Furthermore, the ginsenosides Rd and Km inhibited the TNF-${\alpha}$-induced expression levels of the COX-2 and iNOS gene in HepG2 cells. Air-dried leaf extracts and their chemical components, ginsenoside Rd and Km, are involved in the suppression of TNF-${\alpha}$-induced NF-${\kappa}B$ activation and NF-${\kappa}B$-dependent iNOS and COX-2 gene expression. Consequently, air-dried leaf extract from PG, and the purified ginsenosides, have therapeutic potential as anti-inflammatory.