Bioassay-guided isolation of acetylcholinesterase and butyrylcholinesterase inhibitors from Horsfieldia tomentosa fruits (Myristicaceae)

Abstract

Alzheimer's disease (AD) is the most common form of dementia associated with the accumulation of abnormal protein deposits in the brain, including beta-amyloid plaques and tau tangles, as well as oxidative stress. The limited effectiveness of current medications in temporarily treating symptoms has driven interest in natural products for their diverse biological activities. This study investigates the bioactive potential of various extracts obtained from the fruits of Horsfieldia tomentosa, focusing on their antioxidant and anticholinesterase properties. Total phenolic and flavonoid contents were quantified, antioxidant and anticholinesterase activities were evaluated. The ethyl acetate extract exhibited the highest bioactivity, with total flavonoid content (361.11 ± 26.24 mg QE/g), total phenolic content (1601.46 ± 1.23 mg GAE/g), antioxidant activity (1.81 ± 0.06 µg/L), and significant anticholinesterase activities (AChE = 6.0 ± 0.30 µg/mL; BuChE = 32.1 µg/mL). Three previously undescribed phenolic compounds along with four known compounds were purified from this extract. The assayed isolated compounds exhibit selective cholinesterase inhibition, with compound 2 showing the strongest activity (IC₅₀ value of 3.9 µM against AChE), while compound 1 was more effective against butyrylcholinesterase (IC₅₀ value of 7.8 µM). Molecular docking supported the in vitro findings, revealing binding energies of - 9.0 ± 0.5, - 8.5 ± 0.1, and - 8.3 ± 0.1 kcal mol⁻¹ for compounds 1, 2 and 5, respectively, against butyrylcholine protease (6ESY). Compound 1 also showed significant binding energy (- 8.0 ± 0.1 kcal mol⁻¹⁾ against acetylcholine protease (4MOE). In these results, compound 2 acts as a dual inhibitor, while compounds 1 and 5 primarily inhibit butyrylcholinesterase. These results underscore the therapeutic potential of Horsfieldia tomentosa in treating Alzheimer’s disease.