Neuroprotective Evaluation of Murraya Carbazoles: In Vitro and Docking Insights into Their Anti-AChE and Anti-Aβ Activities

Abstract

The present study investigated the neuroprotective potential of the Murraya carbazole derivatives murrayanol, mahanimbine, murrayafoline A, and 9-methyl-9H-carbazole-2-carbaldehyde using in silico and in vitro assays. The pharmacokinetic properties and potential toxicity (ADME/T) of the carbazole derivatives were assessed to evaluate their prospects as up-and-coming drug candidates. Molecular docking was used to investigate the interactions of the compounds with Aβ (PDB: 1IYT, 2BEG, and 8EZE) and AChE receptors (PDB: 4EY7 and 1C2B). The results from the in vitro assays were used to validate and support the findings from the in silico assays. The compounds demonstrated significant inhibition of acetylcholinesterase (AChE), a key target in neurodegenerative disorders. Murrayanol and mahanimbine presented superior inhibitory activity (IC₅₀ ~0.2 μg/mL), outperforming the reference drug, galantamine. The inhibition mechanisms were competitive (murrayanol, murrayafoline A, and 9-methyl-9H-carbazole-2-carbaldehyde) and non-competitive (mahanimbine), supported by low Ki values and strong docking affinities. The compounds also proved effective in reducing Aβ fibrillization (murrayanol: 40.83 ± 0.30%; murrayafoline A: 33.60 ± 0.55%, mahanimbine: 27.68 ± 2.71%). These findings highlight Murraya carbazoles as promising scaffolds for multifunctional agents in AD therapy. Further optimization and mechanistic studies are warranted to advance their development into clinically relevant neuroprotective agents.

Keywords: ADME/T properties; acetylcholinesterase; anti-Aβ fibrilization; carbazole; molecular docking; neuroprotection.

Figure 1

Structures of some Murraya carbazole derivatives.

Figure 2

Visual representation of the interactions between ligands and receptor molecule (4EY7). Two-dimensional visualization of the binding interactions of (A) murrayanol (dark blue), (B) mahanimbine (sky blue), (C) murrayafoline A (orange), and (D) 9-methyl-9H-carbazole-2-carbaldehyde (pink). (E) The marked black zone indicates the binding sites of the ligands in the 3D structure of the protein.

Figure 3

Visual representation of the interaction between ligands and receptor molecule (1C2B). Two-dimensional visualization of the binding interactions of (A) murrayanol (dark blue), (B) mahanimbine (sky blue), (C) murrayafoline A (orange), and (D) 9-methyl-9H-carbazole-2-carbaldehyde (pink). (E) The marked black zone indicates the binding sites of the ligands in the 3D structure of the protein.

Figure 4

Visual representation of the interaction between ligands and receptor molecule (1IYT). Two-dimensional visualization of the binding interactions of (A) murrayanol (dark blue), (B) mahanimbine (sky blue), (C) murrayafoline A (orange), and (D) 9-methyl-9H-carbazole-2-carbaldehyde (pink). (E) Binding sites of the ligands in the 3D structure of the protein.

Figure 5

Visual representation of the interaction between ligands and receptor molecule (2BEG). Two-dimensional visualization of the binding interactions of (A) murrayanol (dark blue), (B) mahanimbine (sky blue), (C) murrayafoline A (orange), and (D) 9-methyl-9H-carbazole-2-carbaldehyde (pink). (E) Binding sites of the ligands in the 3D structure of the protein.

Figure 6

Visual representation of the interaction between ligands and receptor molecule (8EZE). Two-dimensional visualization of the binding interactions of (A) murrayanol (dark blue), (B) mahanimbine (sky blue), (C) murrayafoline A (orange), and (D) 9-methyl-9H-carbazole-2-carbaldehyde (pink). (E) Binding sites of the ligands in the 3D structure of the protein.

Figure 7

IC₅₀ curves for murrayanol, mahanimbine, murrayafoline A, and 9-methyl-9H-carbazole-2-carbaldehyde against Electrophorus electricus AChE. Galantamine was used as a positive control. The IC₅₀ values were calculated using GraphPad Prism 10.3. The values were determined as the mean from three experiments ± SD.

Figure 8

Inhibition plots (Lineweaver–Burk plots) for (A) murrayafoline A; (B) murrayanol; (C) mahanimbine; and (D) 9-methyl-9H-carbazole-2-carbaldehyde.

Figure 9

Aβ fibrillization inhibition by Murraya carbazole derivatives at 500 μg/mL. Phenol red (50 μM) was used as a positive control. All data are expressed as mean ± SD (n = 3). A significant difference *** (p < 0.001) using one-way ANOVA followed by Dunnett’s post hoc was observed in the percent oligomerization reduction vs. that of the negative control (buffer + Aβ).