Citrus sinensis (orange) by-products represent one of the most abundant citric residues from orange juice industrial production, and are a promising source of health-promoting compounds like terpenes. In this work, different extraction solvents have been employed to increase terpene extraction yield and selectivity from this orange juice by-product. A set of bioactivity assays including enzymatic (acetylcholinesterase (AChE), butylcholinesterase (BChE) and lipoxygenase (LOX)) as well as antioxidant (ABTS, reactive oxygen species (ROS) and reactive nitrogen species (RNS)) activity tests have been applied to investigate the neuroprotective potential of these compounds. New fluorescence-based methodologies were developed for AChE and BChE assays to overcome the drawbacks of these tests when used in vitro to determine the anticholinergic activity of colored extracts. Comprehensive phytochemical profiling based on gas chromatography coupled to quadrupole time of flight mass spectrometry (GC-qTOF-MS) analysis showed ahigh content of mono- and sesquiterpenes in the extracts obtained with ethyl acetate, whereas n-heptane extracts exhibited a large amount of triterpenes and carotenoids. From a neuroprotective activity point of view, ethyl acetate extract is the most promising due to its anticholinergic activity and antioxidant capacity. Finally, a multivariate data analysis revealed a good correlation between some monoterpenes (e.g. nerol or limonene) and the antioxidant capacity of the natural extract, while a group of sesquiterpenes (e.g. δ-Cadinene or nootkatone) showed correlation with the observed AChE, BChE and LOX inhibition capacity. Hydrocarbons mono- and sesquiterpenoids reveal high capacity in vitro to cross the blood–brain barrier (BBB).

中文翻译：

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工业橙汁副产物中萜烯的体外神经保护潜力

柑桔（橙色）副产物代表了橙汁工业生产中柠檬酸的最丰富残留之一，并且是萜烯等促进健康的化合物的有希望的来源。在这项工作中，已经采用了不同的萃取溶剂来提高萜烯从这种橙汁副产物中的萃取产率和选择性。一套生物活性测定方法已应用于酶法（乙酰胆碱酯酶（AChE），丁基胆碱酯酶（BChE）和脂氧合酶（LOX））以及抗氧化剂（ABTS，活性氧（ROS）和活性氮（RNS））活性测试。研究这些化合物的神经保护潜力。针对AChE和BChE分析开发了新的基于荧光的方法，以克服体外使用时这些测试的缺点以确定有色提取物的抗胆碱能活性。基于气相色谱和四极杆飞行时间质谱（GC-qTOF-MS）分析的综合植物化学谱分析显示，乙酸乙酯萃取物中的单萜和倍半萜含量高，而正庚烷萃取物中则显示出大量的三萜和类胡萝卜素。从神经保护活性的观点来看，乙酸乙酯提取物由于其抗胆碱能活性和抗氧化能力而最有前途。最后，多变量数据分析显示，某些单萜类化合物（例如，神经醇或柠檬烯）与天然提取物的抗氧化能力之间具有良好的相关性，而一组倍半萜类化合物（例如，δ-Cadinene或Nootkatone）与观察到的AChE，BChE和LOX抑制能力相关。碳氢化合物单倍半萜和倍半萜在体外具有很高的穿越血脑屏障（BBB）的能力。