Limonin, the main bioactive phytochemical constituent of limonoids with multi-functions, is enriched in citrus fruits and often found at a high concentration in citrus seeds. The present study was attempted to introduce a new and efficient extraction method to isolate limonoids from pummelo seeds, and to evaluate the antioxidant property of the main constituent limonin in Hep G2 cells. Three key single factors were identified for the extraction of limonoids from pummelo seeds using the Box-Behnken experiment design of response surface methodology(RSM), and the optimized extraction parameters were treatment with 89.68 m L of anhydrous acetone for 4.62 h at 78.94C, while the yield of limonoids was 11.52 mg/g. The structure of isolated main constituent of the limonoids was further identified as limonin by Fourier transform infrared(FT-IR) spectrometer and nuclear magnetic resonance(NMR)spectrum. Moreover, the molecular data in Hep G2 cells revealed that limonin exerted its anti-oxidant property mainly by the activation of nuclear factor(erythroid-2)-like 2(Nrf2)/kelch-like ECHassociated protein 1(Keap1)-antioxidant response element(ARE) pathway in the form of transcriptional regulation of Nrf2 m RNA and posttranscriptional regulation of Nrf2/Keap1 system. These results demonstrate that pummelo seeds are an ideal source of limonoids, and limonin is proved to exert its anti-oxidant property by the activation of Nrf2/Keap1 pathway.
Si QinChenghao LvQingshan WangZhibing ZhengXi SunMinyi TangFangming Deng
Reactive oxygen species （ROS） can be caused by mechanical, thermal, infectious, and chemical stimuli, and their negative effects on the health of humans and other animals are of considerable concern. The nuclear factor （erythroid-derived 2）-like 2/Kelch-like ECH-associated protein 1 （Nrf2/Keap1） system plays a major role in maintaining the balance between the production and elimination of ROS via the regulation of a series of detoxifying and antioxidant enzyme gene expressions by means of the antioxidant response element （ARE）. Dietary phytochemicals, which are generally found in vegetables, fruits, grains, and herbs, have been reported to have health benefits and to improve the growth performance and meat quality of farm animals through the regulation of Nrf2-mediated phase II enzymes in a variety of ways. However, the enormous quantity of somewhat chaotic data that is available on the effects of phytochemicals needs to be properly classified according to the functions or mechanisms of phytochemicals, in this review, we first introduce the antioxidant properties of phytochemicals and their relation to the Nrf2/Keap1 system. We then summarize the effects of phytochemicals on the growth performance, meat quality, and intestinal microbiota of farm animals via targeting the Nrf2/Keap1 system. These exhaustive data contribute to better illuminate the underlying biofunctional properties of phytochemicals in farm animals.
