Effect of Anoectochilus roxburghii flavonoids extract on H2O2 - Induced oxidative stress in LO2 cells and D-gal induced aging mice model

Anoectochilus roxburghii (A. roxburghii) is a popular folk medicine in many Asian countries, which has been used traditionally for treatment of some diseases such as diabetes, tumors, hyperlipemia, and hepatitis. The ethanol extract from A. roxburghii was recently shown to exert better ability to scavenge free radicals in vitro and possess antioxidant on natural aging mice in vivo. This study is to characterize the chemical composition, and investigate the protective effect of the A. roxburghii flavonoids extract (ARF) against hydrogen peroxide (H2O2)-induced oxidative stress in LO2 cells in vitro and D-galactose (D-gal)-induced aging mice model in vivo, and explore the underlying mechanisms. The chemical components of the flavonoids extract from A. roxburghii were detected by ultraperformance lipid chromatography coupled with quadrupole-time-of-flight mass spectrometry (UPLC-QTOF-MS/MS). H2O2 was used to establish an oxidative stress model in LO2 cells. Cytotoxic and protective effects of ARF on the LO2 cells were determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method. Moreover, the levels of superoxide dismutase (SOD), glutathione peroxidase (GSH-PX), and malondialdehyde (MDA) in cell supernatants were measured by commercial reagent kits. Kun-Ming mice were induced to aging with D-gal (400 mg/kg, BW) by subcutaneous injection for 58 days. From the 28th day to the 58th day of D-gal treatment, ARF (122.5, 245 and 490 mg/kg, BW) and vitamin E (100 mg/kg, BW) were orally administrated to aging mice once a day for consecutive 30 days. After 25 days of the treatment with ARF, learning and memory were assessed using Morris Water Maze (MWM). At the end of the test period, the animals were euthanized by cervical dislocation, and the levels of SOD, GSH-PX, and MDA in serum, liver homogenates and brain homogenates were measured. The levels of monoamine oxidase (MAO) and acetylcholinesterase (AchE) were determined in brain homogenates. Skin and liver histopathological morphology were observed by H&E staining. Furthermore, antioxidant-related gene expression levels in the liver were carried out by quantitative real-time polymerase chain reaction (qRT-PCR). Nine flavonoids were identified in the extracts of A. roxburghii. In vitro assay, a high concentration of ARF (>612.5 μg/ml) reduced the survival rate and had toxic effects on LO2 cells. In addition, ARF (245 μg/ml, 490 μg/ml) and Vitamin C (200 μg/ml) markedly inhibited generations of MDA and increased activities of SOD, GSH-PX in H2O2-induced LO2 cells supernatants. In vivo assay, ARF (122.5 mg/kg, 245 mg/kg and 490 mg/kg) and Vitamin E (100 mg/kg) not only ameliorated learning and memory ability but also improved skin and liver pathological alterations. Strikingly, ARF significantly decreased MDA and MAO levels, markedly enhanced antioxidant enzyme (SOD and GSH-PX) activities. Further, compared to the D-gal group, ARF could obviously up-regulate glutathione peroxidase-1 (GPx-1) and glutathione peroxidase-4 (GPx-4) mRNA levels. These findings suggested that ARF protects LO2 cells against H2O2-induced oxidative stress and exerts the potent anti-aging effects in D-gal aging mice model, which may be related to the inhibition of oxidative stress. Flavonoid compounds may contribute to the anti-oxidative capability and modulating aging.