Neuropharmacological Effects of the Dichloromethane Extract from the Stems of Argemone ochroleuca Sweet (Papaveraceae) and Its Active Compound Dihydrosanguinarine

Abstract

Argemone ochroleuca Sweet (Papaveraceae) is used in folk medicine as a sedative and hypnotic agent. This study aimed to evaluate the anxiolytic-like, sedative, antidepressant-like, and anticonvulsant activities of a dichloromethane extract of A. ochroleuca stems (AOE), chemically standardized using gas chromatography-mass spectrometry (GC-MS), and its active compound dihydrosanguinarine (DHS). The anxiolytic-like, sedative, antidepressant-like, and anticonvulsant activities of the AOE (0.1-50 mg/kg p.o.) and DHS (0.1-10 mg/kg p.o.) were evaluated using murine models. A possible mechanism for the neurological actions induced by the AOE or DHS was assessed using inhibitors of neurotransmission pathways and molecular docking. Effective dose 50 (ED₅₀) values were calculated by a linear regression analysis. The AOE showed anxiolytic-like activity in the cylinder exploratory test (ED₅₀ = 33 mg/kg), and antidepressant-like effects in the forced swimming test (ED₅₀ = 3 mg/kg) and the tail suspension test (ED₅₀ = 23 mg/kg), whereas DHS showed anxiolytic-like activity (ED₅₀ = 2 mg/kg) in the hole board test. The AOE (1-50 mg/kg) showed no locomotive affectations or sedation in mice. A docking study revealed the affinity of DHS for α2-adrenoreceptors and GABA_A receptors. The anxiolytic-like and anticonvulsant effects of the AOE are due to GABAergic participation, whereas the antidepressant-like effects of the AOE are due to the noradrenergic system. The noradrenergic and GABAergic systems are involved in the anxiolytic-like actions of DHS.

Keywords: Argemone ochroleuca Sweet; anticonvulsant; antidepressant; anxiolytic.

Figure 1

Chemical structures (2D and 3D) of dihydrosanguinarine.

Figure 2

The chromatogram obtained during GC–MS analysis of AOE indicated the peaks registered at 330 ± 16 nm, under analytical conditions.

Figure 3

Anxiolytic-like effects of AOE measured by the number of head dippings (A) and the number of rearings (B) during 5 min of exposure. A possible mechanism of the anxiolytic-like effects of AOE was evaluated in the cylinder exploratory test (C). Clonazepam (CNZ) was the reference drug. Data are presented as mean ± standard error of the mean (n = 7 per group), ** p < 0.05 vs. the vehicle group, and ** p < 0.05 vs. the AOE 33 mg/kg p.o. group.

Figure 4

Anxiolytic-like effects of DHS (0.1–10 mg/kg p.o.) measured by the number of head dippings (A) during 5 min of exposure. A possible mechanism of the anxiolytic-like effects of DHS was evaluated in the hole board test (B). Clonazepam (CNZ) was the reference drug. Data are presented as mean ± standard error of the mean (n = 7 per group) and ** p < 0.05 vs. the vehicle group.

Figure 5

Antidepressant-like actions of AOE (0.1–50 mg/kg p.o.) in the tail suspension test (A) and the forced swimming test (B). The possible mechanism of action of AOE was evaluated in the forced swimming test (C). Fluoxetine (FLX) was the reference drug. Data are presented as mean ± standard error of the mean (n = 7 per group), ** p < 0.05 vs. the vehicle group.

Figure 6

Antidepressant-like actions of DHS (0.1–10 mg/kg p.o.) in the tail suspension test. Fluoxetine (FLX) was the reference drug. Data are presented as mean ± standard error of the mean (n = 7 per group) and ** p < 0.05 vs. the vehicle group.

Figure 7

Effects of AOE on sedation and locomotor coordination. The pentobarbital-induced sleeping test measured the sedative effects of AOE on the onset of sleep (A) and the duration of sleep (B). The rotarod test assessed motor coordination (C). Clonazepam (CNZ) was the reference drug. Data are presented as mean ± standard error of the mean (n = 7 per group) and ** p < 0.05 vs. the vehicle group.

Figure 8

The docking complex of (A) dihydrosanguinarine (deep salmon color) with GABAA receptor and (B) 2D representations of molecular interactions. (C) Interactions of FYP (co-crystal ligand; green color) with GABAA receptor and (D) overlay of the co-crystallized pose (green) and the re-docked pose (blue) from validation (RMSD = 0.914 Å).

Figure 9

The docking complex of (A) dihydrosanguinarine (deep salmon color) with α_2A-adrenergic receptor and (B) 2D representations of molecular interactions. (C) Interactions of E3F (co-crystal ligand; yellow color) with α_2A-adrenergic receptor and (D) overlay of the co-crystallized pose (yellow) and the re-docked pose (green) from validation (RMSD = 1.398 Å).