Protective effect of sweet and unshiu mikan oranges and mini tomato on t-BHP-induced oxidative stress in HepG2 cells

Abstract

The fruits of orange species and mini tomato originated from south East Asia, but are consumed all over the world as healthy foods, and contain bioactive key components. Epidemiological studies indicate that an increase in the consumption of fruits and vegetables associated with a decrease in the incidence of cardiovascular, chronic and degenerative, inflammatory, liver diseases. The aim of this study was to investigate the protective effect of juice powders from sweet orange (Citrus sinensis), unshui mikan orange (Citrus unshiu), mini tomato (Solanum lycopersicum) juice powders and their combinations as well as their major flavonoids such as hesperidin, narirutin and rutin on tert-butyl hydroperoxide (t-BHP)-induced oxidative stress on HepG2 cells. The cell viability of juice powders and their combinations as well as their flavonoids were measured by MTT assay. Hepatoprotective effect of juice powders against oxidative stress induced by t-BHP on HepG2 cells were investigated through the measurement of cytoprotective effect, intracellular ROS, GSH and the up-regulation of phase-ІІ protein such as heme oxygenase-1 (HO-1) expression through western blot analysis. HPLC was used to analyze the major flavonoids of juice powders. In the current study, juice powders and their combinations were evaluated for total phenolic and vitamin C content determination. According to HPLC analysis, hesperidin and narirutin are dominantly present in two orange species and rutin in tomato species. The increased ROS and decreased glutathione levels observed in t-BHP-treated HepG2 cells were ameliorated by juice powders pretreatment, indicating that the hepatoprotective effects of juice powders, their combinations and the major flavonoids are mediated by the induction of cellular defense action against oxidative stress. The protective effects of juice powders, their combinations and the major flavonoids significantly inhibited the cytotoxic effect induced by 200 µM t-BHP on HepG2 cells and also may be associated with positive regulation of GSH levels and decrease in ROS production, thereby preventing cellular damage and the resultant increase in HO-1 expression. These results suggest that the fruit juice powders and their combinations as well as their major flavonoids displayed a significant cytoprotective effect against oxidative stress which may be most likely because of the flavonoids-related bioactive compounds existing therein leading to the normal redox status of cells. Therefore these fruit juice powders and their specific combinations could be advantageous as a bioactive source for the prevention of oxidative injury in hepatoma cells.