Nonalcoholic fatty liver disease (NAFLD) is one of the most common liver diseases which lacks ideal treatment options. Kaempferol and kaempferide, two natural flavonol compounds isolated from Hippophae rhamnoides L., were reported to exhibit a strong regulatory effect on lipid metabolism, for which the mechanism is largely unknown. In the present study, we investigated the effects of kaempferol and kaempferide on oleic acid (OA)-treated HepG2 cells, a widely used in vitro model of NAFLD. The results indicated an increased accumulation of lipid droplets and triacylglycerol (TG) by OA, which was attenuated by kaempferol and kaempferide (5, 10 and 20 μM). Western blot analysis demonstrated that kaempferol and kaempferide reduced expression of lipogenesis-related proteins, including sterol regulatory element-binding protein 1 (SREBP1), fatty acid synthase (FAS) and stearoyl-CoA desaturase 1 (SCD-1). Expression of peroxisome proliferator-activated receptor γ (PPARγ) and CCAAT enhancer binding proteins β (C/EBPβ), two adipogenic transcription factors, was also decreased by kaempferol and kaempferide treatment. In addition, western blot analysis also demonstrated that kaempferol and kaempferide reduced expression of heme oxygenase-1 (HO-1) and nuclear transcription factor-erythroid 2-related factor 2 (Nrf2). Molecular docking was performed to identify the direct molecular targets of kaempferol and kaempferide, and their binding to SCD-1, a critical regulator in lipid metabolism, was revealed. Taken together, our findings demonstrate that kaempferol and kaempferide could attenuate OA-induced lipid accumulation and oxidative stress in HepG2 cells, which might benefit the treatment of NAFLD.

The high incidence of diabetes mellitus has caused widespread concern around the world, and has quickly become one of the most prevalent and costly chronic diseases. Alpha-glucosidase has been considered as the main target enzyme in the prevention and treatment of type 2 diabetes, and the inhibition of alpha-glucosidase activity can control postprandial blood glucose levels of diabetics and keep blood glucose levels normal. However, most of the current antidiabetic drugs in the clinic have many side effects. Recently, the screening of alpha-glucosidase inhibitors, from natural products, with excellent activity and less side effects has been successfully achieved, which also proposes more requirements and challenges for the approaches of alpha-glucosidase inhibitor (AGI) screening because of the trace level of active compounds in natural products, large-scale sample screening, and complex matrix of natural products. In this review, we comprehensively summarized the available strategies for the assay of alpha-glucosidase activity and AGI screening for the first time, including classic strategies such as high throughput screening methods (e.g. capillary electrophoresis strategies, HPLC/LC-MS strategies), emerging sensing strategies (e.g. colorimetric sensing, fluorescence sensing, electrochemical sensing, and surface plasmon resonance sensing) and other strategies. Finally, future opportunities and challenges in future research are tentatively proposed.

Porous CoFe₂O₄ was prepared via a simple and controllable method to develop a low-cost, high-efficiency, and good-stability nanozyme. The morphology and microstructure of the obtained CoFe₂O₄ was investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), specific surface area and pore analysis, and Raman spectroscopy. The results show that the annealing temperature has an important effect on the crystallinity, grain size, and specific surface area of CoFe₂O₄. CoFe₂O₄ obtained at 300 °C (CF300) exhibits the largest surface area (up to 204.1 m² g⁻¹) and the smallest grain size. The peroxidase-like activity of CoFe₂O₄ was further verified based on the oxidation of peroxidase substrate 3,3’,5,5’-tetramethylbenzidine (TMB) in the presence of H₂O₂. The best peroxidase-like activity for CF300 should be ascribed to its largest surface area and smallest grain size. On this basis, an effective method of colorimetric detection H₂O₂ was established. In addition, the porous CoFe₂O₄ was also used for the catalytic oxidation of methylene blue (MB), indicating potential applications in pollutant removal and water treatment.