Protective effects of Cambodian medicinal plants on tert-butyl hydroperoxide-induced hepatotoxicity via Nrf2-mediated heme oxygenase-1

Liver diseases are considered to be primary contributors to morbidity and mortality rates in humans. Oxidative stress is critical in liver injury, and oxidant-induced liver injury may be caused by toxins, including tert-butyl hydroperoxide (t-BHP). The present study investigated the hepatoprotective activities of 64 crude ethanol extracts of Cambodian medicinal plants against t-BHP-induced cytotoxicity in human liver-derived HepG2 cells, and assessed their cytoprotective mechanism pertaining to the expression of heme oxygenase (HO)-1 and nuclear factor E2-related factor 2 (Nrf2). Protective effects in HepG2 cells were determined by MTT assay. Protein expression levels of HO-1 and Nrf2 were determined by western blotting and mRNA expression levels were determined by reverse transcription-quantitative polymerase chain reaction. Of the 64 extracts, 19 extracts exhibited high hepatoprotective activities: Ampelocissus martini, Bauhinia bracteata, Bombax ceiba, Borassus flabellifer, Cardiospermum halicacabum, Cayratia trifolia, Cinnamomurn caryophyllus, Cyperus rotundus, Dasymaschalon lomentaceum, Ficus benjamina, Mangifera duperreana, Morinda citrifolia, Pandanus humilis, Peliosanthes weberi, Phyllanthus emblica, Quisqualis indica, Smilax glabra, Tinospora crispa and Willughbeia cochinchinensis, with half maximal effective concentrations ranging between 59.23 and 157.80 mu g/ml. Further investigations revealed that, of these 19 extracts, HO-1 and Nrf2 were expressed in P. weberi and T. crispa expressed in a dose-dependent manner. In addition, the activities of reactive oxygen species were suppressed following treatment of these