Chemical profile, acetylcholinesterase, butyrylcholinesterase, and prolyl oligopeptidase inhibitory activity of Glaucium corniculatum subsp. refractum

Abstract Papaveraceae is one of the prominent alkaloid-containing families, and plants of the genus Glaucium (Papaveraceae) are known for their bioactive alkaloids. Glaucium species have been used in traditional medicine in Turkey as an analgesic, narcotic, sedative, and antitussive. In this study, it was planned to evaluate the inhibitory activity of an alkaloidal extract of Glaucium corniculatum subsp. refractum on acetylcholinesterase (AChE), butyrylcholinesterase (BuChE) and prolyl oligopeptidase (POP), as well as exploring the chemical profile of the plant by using Gas Chromatography-Mass Spectrometry (GC-MS). The AChE, BuChE and POP inhibition activities of the alkaloidal extract of G. corniculatum subsp. refractum were determined spectrophotometrically. A rapid GC-MS method was used to identify alkaloids that could be responsible for these inhibition activities. In total, eleven alkaloids were identified in the alkaloid extract of the plant by GC-MS. Allocyptopine (52.92%) and protopine (25.38%) were found as the major constituents. The alkaloidal extract of G. corniculatum subsp. refractum showed potent AChE inhibitory activity (IC50:1.25 µg/mL) and BuChE inhibitory activity (IC50: 7.02 µg/mL). The extract also showed a remarkable inhibitory effect on POP with an IC50 value of 123.69 µg/mL. This study presents the first GC-MS investigation and POP inhibitory activity of G. corniculatum subsp. refractum.

Ocotea daphnifolia: phytochemical investigation, in vitro dual cholinesterase inhibition, and molecular docking studies

This study aimed to evaluate the anticholinesterase activities of extracts and fractions of Ocotea daphnifolia in vitro and characterize its constituents. The effects of hexane, ethyl acetate, and ethanolic extracts on acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) activity were determined with a spectrophotometry assay. All extracts inhibited cholinesterase activity, and the ethanolic extract (2 mg/mL) exhibited the highest inhibition of both enzymes (99.7% for BuChE and 82.4% for AChE). The ethanolic extract was fractionated by column chromatography resulting in 14 fractions that were also screened for their anticholinesterase effects. Fraction 9 (2 mg/mL) showed the highest activity, inhibiting AChE and BuChE by 71.8% and 90.2%, respectively. This fraction was analyzed by high-performance liquid chromatography high-resolution mass spectrometry which allowed the characterization of seven glycosylated flavonoids (containing kaempferol and quercetin nucleus) and one alkaloid (reticuline). In order to better understand the enzyme-inhibitor interaction of the reticuline toward cholinesterase, molecular modeling studies were performed. Reticuline targeted the catalytic activity site of the enzymes. Ocotea daphnifolia exhibits a dual cholinesterase inhibitory activity and displays the same pattern of intermolecular interactions as described in the literature. The alkaloid reticuline can be considered as an important bioactive constituent of this plant.