This study investigated the direct citric acid hydrolysis extraction method to optimize phytosterols extraction from hickory husk. Single factor experiments followed by a three-level three-factor Box-Behnken experiments were performed. The optimal extraction parameters were determined as: pH of 2.0, liquid-to-solid ratio of 17.12: 1 mL/g, and temperature of 55.81 °C. Practical experiments were carried out in triplicate, and subsequently yielded phytosterols of 912.452 ± 17.452 μg/g DW, in good consistence with the predicted extraction yield of 902.874 μg/g DW. The conductivity of the extract was also found to play effective role under direct citric acid hydrolysis and recorded 36.30 ± 1.08 μs/cm at optimum extraction condition. β-Sitosterol stigmasterol, campsterol, ergosterol and lupeol were detected as main PSs and triterpenoids in hickory husk using UPLC-Triple-TOF/MS. Finally, the comparison between direct hydrolysis extraction and traditional solvent extraction showed that this new method was more effective and eco-friendlier to extract both free and conjugated phytosterols.

中文翻译：

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用绿色直接柠檬酸水解提取方法从山核桃（山核桃）壳中提取植物甾醇。

本研究研究了柠檬酸直接水解提取方法，以优化山核桃皮中植物甾醇的提取。进行了单因素实验，然后进行了三级三因素Box-Behnken实验。确定最佳提取参数为：pH为2.0，液固比为17.12：1 mL / g，温度为55.81°C。一式三份地进行了实际实验，随后产生了912.452±17.452μg/ g DW的植物甾醇，与预计的902.874μg/ g DW的提取率非常一致。还发现提取物的电导率在直接柠檬酸水解下起有效作用，在最佳提取条件下记录的电导率为36.30±1.08μs/ cm。β-谷固醇豆甾醇，菜油甾醇，使用UPLC-Triple-TOF / MS将麦角固醇和羽扇豆酚检测为山核桃皮中的主要PS和三萜类化合物。最后，直接水解提取法与传统溶剂提取法的比较表明，该新方法提取游离和共轭植物甾醇都更有效，更环保。