Anti-acetylcholinesterase activity and antioxidant properties of extracts and fractions of Carpolobia lutea

Context: There is an unmet need to discover new treatments for Alzheimer’s disease. This study determined the anti-acetylcholinesterase (AChE) activity, DPPH free radical scavenging and antioxidant properties of Carpolobia lutea G. Don (Polygalaceae). Objective: The objective of this study is to quantify C. lutea anti-AChE, DPPH free radical scavenging, and antioxidant activities and cell cytotoxicity. Materials and methods: Plant stem, leaves and roots were subjected to sequential solvent extractions, and screened for anti-AChE activity across a concentration range of 0.02–200 μg/mL. Plant DPPH radical scavenging activity, reducing power, and total phenolic and flavonoid contents were determined, and cytotoxicity evaluated using human hepatocytes. Results:Carpolobia lutea exhibited concentration-dependent anti-AChE activity. The most potent inhibitory activity for the stem was the crude ethanol extract and hexane stem fraction oil (IC50 = 140 μg/mL); for the leaves, the chloroform leaf fraction (IC50 = 60 μg/mL); and for roots, the methanol, ethyl acetate and aqueous root fractions (IC50 = 0.3–3 μg/mL). Dose-dependent free radical scavenging activity and reducing power were observed with increasing stem, leaf or root concentration. Total phenolic contents were the highest in the stem: ∼632 mg gallic acid equivalents/g for a hexane stem fraction oil. Total flavonoid content was the highest in the leaves: ∼297 mg quercetin equivalents/g for a chloroform leaf fraction. At 1 μg/mL, only the crude ethanol extract oil was significantly cytotoxic to hepatocytes. Discussion and conclusions:Carpolobia lutea possesses anti-AChE activity and beneficial antioxidant capacity indicative of its potential development as a treatment of Alzheimer’s and other diseases characterized by a cholinergic deficit.上下文：目前阿尔茨海默病（Alzheimer’s disease）仍存在未被满足的治疗需求，亟需发掘全新的治疗手段。本研究探究了Carpolobia lutea G. Don（远志科（Polygalaceae））的抗乙酰胆碱酯酶（anti-acetylcholinesterase, AChE）活性、DPPH自由基清除能力与抗氧化特性。 研究目的：本研究旨在定量测定C. lutea的抗AChE活性、DPPH自由基清除活性、抗氧化活性以及细胞毒性。 材料与方法：对该植物的茎、叶及根进行连续溶剂萃取，并在0.02–200 μg/mL的浓度范围内筛选其抗AChE活性。同时测定了植物提取物的DPPH自由基清除活性、还原能力，以及总酚与总黄酮含量，并采用人肝细胞评估其细胞毒性。 结果：Carpolobia lutea表现出浓度依赖性的抗AChE活性。其中各部位活性最强的提取物分别为：茎的粗乙醇提取物与正己烷茎馏分油（半数抑制浓度（IC50）=140 μg/mL）；叶的氯仿叶馏分（IC50=60 μg/mL）；根的甲醇、乙酸乙酯与水相根馏分（IC50=0.3–3 μg/mL）。随着茎、叶或根提取物浓度升高，可观察到剂量依赖性的自由基清除活性与还原能力。总酚含量以茎部最高，正己烷茎馏分油约为632 mg没食子酸当量/克。总黄酮含量以叶片最高，氯仿叶馏分约为297 mg槲皮素当量/克。在1 μg/mL浓度下，仅粗乙醇提取物油对肝细胞具有显著细胞毒性。 讨论与结论：Carpolobia lutea具备抗AChE活性与有益的抗氧化能力，表明其有望开发为阿尔茨海默病及其他以胆碱能系统缺陷为特征的疾病的治疗候选药物。