| Majia pomelo is a characteristic fruit in Shangrao City,Jiangxi Province.It is widely cultivated and consumed because of its sweet taste,rich aroma,juicy and meaty,and rich in dietary fiber,vitamins,carotenoids and other nutrients.Majia pomelo seed is one of the by-products produced in the deep processing of Majia pomelo.At present,there is no literature report on Majia pomelo seed,leading to insufficient reference information for the development and utilization of Majia pomelo seed.Therefore,in this study,Majia pomelo seed as raw material to extract Majia pomelo seed oil by pressing method,organic solvent extraction method and water enzyme method.By comparing its composition and physical and chemical properties,the oil preparation method suitable for Majia pomelo seed oil was selected.Finally,the effect and potential mechanism of alleviating oxidative stress and lipid accumulation of Majia pomelo seed oil were studied by using high-fat HepG2 cell model in vitro,in order to provide theoretical basis for the application of Majia pomelo seed oil in human health.The main contents and results of the study are as follows:（1）The effects of three oil preparation technologies on lipid composition（fatty acids and triglycerides）and lipid concomitants（phytosterols,squalene,total phenols and tocopherols）of Majia pomelo seeds were systematically compared.The results showed that the seeds were rich in oil（39.32%）,carbohydrate（36.27%）and protein（12.51%）.The oil yield by solvent extraction method（36.31%）was significantly higher than that by hot pressing method（28.74%）and hydroenzymatic method（27.06%）.Majia pomelo seed oil is rich in unsaturated fatty acids（65.01-65.60%）,mainly linoleic acid（40.16-40.79%）,oleic acid（19.22-20.24%）and linolenic acid（4.62-4.72%）.Majia pomelo seed oil is mainly composed of myricide dioleate（24.21-25.00%）,glycerin dioleate palmitate（19.65-20.16%）and glycerin palmitate linoleate stearate（18.20-18.78%）.Lipid composition and chemical structure of Majia pomelo seed oil were not changed by oil preparation process.In addition,the contents of phytosterol（2350.55mg/kg）,tocopherol（111.30 mg/kg）and total phenol（496.97 mg GAE/kg）in Majia pomelo seed oil were significantly increased by hot pressing method.（2）The effects of three oil preparation processes on acid value,peroxide value,antioxidant activity,thermodynamic properties and cytotoxicity of Majia pomelo seeds were systematically compared.The results showed that the acid value of Majia pomelo seed oil was 1.00-3.52 mg KOH/g,and the peroxide value was 1.82-5.93 mEq O2/kg.Hot pressing oils had the lowest peroxide value.In addition,the oxidation stability（OSI=7.75h）and antioxidant capacity（DPPH=712μmol TE/kg,CAA=483.70μmol QE/100 g）of Majia pomelo seed oil were improved by hot pressing method,and the endothermic transition temperature was the lowest（7.72℃）.The cytotoxic IC50values of LO2 were 16.31-28.8 mg/mL,and oils by solvent extraction had the lowest cytotoxic IC50（16.31 mg/mL）.（3）Based on the compositional properties of Majia pomelo seed oil,the hot-pressed oils were selected as raw material to efficacy studies.The effects and mechanisms of the oil in reducing lipid accumulation and oxidative stress were investigated in an oleic acid-induced hyperlipidemic HepG2 cell model.The results showed that the treatment effectively alleviated lipid accumulation in high-fat HepG2cells,significantly reduced the levels of triglycerides,total cholesterol,LDL-cholesterol and increased HDL-cholesterol,and significantly reduced the levels of reactive oxygen species and malondialdehyde,and enhanced superoxide dismutase activity.Majia pomelo seed oil could serve to alleviate lipid accumulation and oxidative damage in high-fat cells by activating AMPK（down-regulating the relative m RNA expression and protein expression levels of ACC,SREBP-1c and PPAR-γgenes）and Nrf2（up-regulating the relative m RNA expression and protein expression levels of HO-1,γ-GCS and Nrf2 genes）signaling pathways,respectively. |
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