Abstract:

Inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) is one of the important targets in reducing β-amyloid accumulation in the brain and increasing acetylcholine utilization in the treatment of Alzheimer's disease (AD). Damage to neurons and metal accumulation in the brain by free radicals caused by oxidative stress is directly related to the pathogenesis of AD. Galantamine, which is contained by members of the Amaryllidaceae family (Galanthus, Leucojum, etc.), is one of the AChE inhibitors used in the treatment of senile dementia. In this study, the total phenolic substance and polyphenol contents of the methanol: chloroform (1:1 (v:v)) extracts of narcissus (Narcissus L.) cultivar bulbs', which the genus belongs to the mentioned family, were determined. Also, the investigation of the relationship between in vitro antioxidant activities, AChE, and BChE inhibitions of the extracts and Alzheimer's treatment was aimed. The total phenolic content of the extracts was determined between 20.78 ± 0.25 and 57.97 ± 0.49 mg gallic acid equivalent (GAE)/g extract, and it was observed that 'Golden Ducat' had the richest one for total phenolic contentDetermined phenolic acids by High-Pressure Liquid Chromatography-Diode Array Detector (DDD) for 'Golden Ducat' cultivar were gallic acid and protocatechuic acid; for 'Golden Harvest' cultivar was para-hydroxybenzoic acid; for 'Carlton' cultivar was chlorogenic acid; for 'Cheerfulnes' cultivar was para-coumaric acid and for 'Einstein' cultivar was ferulic acid. In terms of DPPH• radical scavenging activity, the inhibition value of the cultivar 'Einstein' was 23.65 ± 0.73 (at 9.6 × 10-4 concentration), the inhibition value of the cultivar 'Cheerfulnes' was 26.69 ± 1.04 (at 1.8 × 10-3 concentration) and 28.51 ± 0.1 (3.6 × 10-3 concentration). The extract obtained from the cultivar 'Carlton' showed the highest metal-chelating antioxidant activity with 14.61% at 0.2 mg/mL concentration (Ethylenediamine tetraacetic acid (EDTA): 77.84). The extract of 'Strong Gold' variety showed higher activity on reducing power measurement with a 50% Effective Concentration (EC50) value of 1.19 (mg/mL) compared to other species (50% Effective Concentration of Butylated Hydroxytoluene (BHT) (EC50): 0.21), ascorbic acid EC50: 0.094). The inhibitory activity of AChE was found to be 53.36% (donepezil 92.077% at the same concentration) in the cultivar 'Tête-à-Tête' at 200 µg/mL concentration. For the BChE inhibitory activity, the cultivar 'Tête-à-Tête' was showed 30.25% inhibition at 200 µg/mL and 26.8% inhibition at 100 µg/mL.