Phytochemical Constituents and Cholinesterase Inhibitory Activities of Millingtonia hortensis

Abstract

Acetylcholine (ACh) is an important neurotransmitter in the human brain and nervous system. Acetylcholinesterase inhibitors (AChEIs) are commonly used to improve cognitive function and exist in many plants, including Millingtonia hortensis. M. hortensis, a Thai medicinal plant, has been used as a smoke delivered bronchodilator. The aims of this study were to identify phytochemical constituents and evaluate the cholinesterase inhibitory activity of M. hortensis leaves and flower extracts. The phytochemical identifications were performed by gas chromatography-mass spectrometry. The inhibitory activities of acetylcholinesterase (AChE), and butyrylcholinesterase (BChE) were measured through kinetic enzyme analysis by Ellman’s method. The results showed that all the extracts exhibited specific AChEIs less than 30 % inhibition. While only the chloroform leaf extract inhibited BChE below 30 % inhibitory activities at 5.0 mg/mL. The GC-MS fingerprints revealed 15 main phytochemical constituents in the crude extracts. Additionally, all plant extracts showed antioxidant activity. The leaf extracts were non-poisonous when AChE activity is decreased by 20 - 30 % compared to normal AChE activity.