Nuclear Factor Erythroid 2-Related Factor 2 Activating Triterpenoid Saponins from Camellia japonica Roots.

Oxidative stress due to the presence of excess reactive oxygen species may cause cancers, aging, and many other conditions. Nuclear factor erythroid 2-related factor 2 (Nrf2) may control abnormal oxidative stress as a transcription factor by inducing antioxidant-related genes via antioxidant response elements (AREs) in the gene promoters. The 11 triterpenoid saponins (1-11) isolated from Camellia japonica roots were tested for ARE-luciferase activity and Nrf2 accumulation in human keratinocytes (HaCaT cells). The ARE-luciferase activity was significantly increased by compounds 1-11 (25 μM) as a result of nuclear Nrf2 accumulation in the cells. Thus, these compounds may contribute to the induction of Nrf2 activity against oxidative damage in cells.