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.