Alkaloids of Abuta panurensis Eichler: In silico and in vitro study of acetylcholinesterase inhibition, cytotoxic and immunomodulatory activities

Abstract

Natural products obtained from species of the genus Abuta (Menispermaceae) are known as ethnobotanicals that are attracting increasing attention due to a wide range of their pharmacological properties. In this study, the alkaloids stepharine and 5-N-methylmaytenine were first isolated from branches of Abuta panurensis Eichler, an endemic species from the Amazonian rainforest. Structure of the compounds was elucidated by a combination of 1D and 2D NMR spectroscopic and MS and HRMS spectrometric techniques. Interaction of the above-mentioned alkaloids with acetylcholinesterase enzyme and interleukins IL-6 and IL-8 was investigated in silico by molecular docking. The molecules under investigation were able to bind effectively with the active sites of the AChE enzyme, IL-6, and IL-8 showing affinity towards the proteins. Along with the theoretical study, acetylcholinesterase enzyme inhibition, cytotoxic, and immunomodulatory activity of the compounds were assessed by in vitro assays. The data obtained in silico corroborate the results of AChE enzyme inhibition, the IC 50 values of 61.24μM for stepharine and 19.55μM for 5-N-methylmaytenine were found. The compounds showed cytotoxic activity against two tumor cell lines (K562 and U937) with IC 50 values ranging from 11.77 μM to 28.48 μM. The in vitro assays revealed that both alkaloids were non-toxic to Vero and human PBMC cells. As for the immunomodulatory activity, both compounds inhibited the production of IL-6 at similar levels. Stepharine inhibited considerably the production of IL-8 in comparison to 5-N-methylmaytenine, which showed a dose dependent action (inhibitory at the IC 50 dose, and stimulatory at the twofold IC 50 one). Such a behavior may possibly be explained by different binding modes of the alkaloids to the interleukin structural fragments. Occurrence of the polyamine alkaloid

In Vitro and In Silico Evaluation of Cholinesterase Inhibition by Alkaloids Obtained from Branches of Abuta panurensis Eichler

“…All compounds were first isolated by us from A. panurensis either previously ( 2 , 4 ) [ 10 ] or in the present work ( 1 , 3 , 5 ). They were identified by a comparison of the obtained spectral results with the data reported in the literature.…”

“…In the present study, we isolated the lindoldhamine isomer 1 , palmatine 3 and the N - trans -feruloyltyramine 5 for the first time from A. panurensis , while the other two alkaloids (stepharine 2 and 5- N -methylmaytenine 4 ) were isolated by us earlier [ 10 ]. This is also the first report on the occurrence of 1 and 5 in the Abuta genus.…”

“…There are only a few phytochemical investigations regarding the alkaloid content on A. panurensis published so far. Namely, the isolation of bisbenzylisoquinoline alkaloids panurensine and norpanurensine was reported in mid-1970s [ 9 ], and recently we described the isolation of stepharine and 5- N -methylmaytenine, proaporphine and polyamine alkaloids, respectively [ 10 ]. Those alkaloids reveal a wide range of pharmacological properties including the inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes [ 11 , 12 , 13 , 14 , 15 , 16 ], cytotoxic [ 17 , 18 , 19 , 20 ], and immunomodulatory activity [ 10 , 21 ].…”

Recent Developments in New Therapeutic Agents against Alzheimer and Parkinson Diseases: In-Silico Approaches

“…Currently, researchers are focused in molecules that can occupy both binding sites and inhibit acetylcholine hydrolysis [17]. Grafov et al studied the affinity of several naturally occurring alkaloids for both binding sites of AChE (PDB#6H12) using neostigmine, a known AChE inhibitor, as positive control [18]. The molecular docking results demonstrated that the alkaloid 5-N- Many researchers took advantage of the available 3D human AChE structures deposited in the PDB database and the information regarding the interactions with several ligands to carry out in silico methodologies to design potential inhibitors [17].…”

“…Grafov et al studied the affinity of several naturally occurring alkaloids for both binding sites of AChE (PDB#6H12) using neostigmine, a known AChE inhibitor, as positive control [18]. The molecular docking results demonstrated that the alkaloid 5-N-methylmaytenine (Figure 2) could simultaneously bind to both binding sites, mainly by hydrophobic interactions, and therefore, could have a high pharmacological potential towards the design of novel AChE inhibitors [18]. A similar analysis was carried out by Ortiz and his research group for other alkaloid compounds extracted from plants of the Hieronymiella genus, but employing an additional step of molecular dynamic simulations to evaluate the binding modes to better understand in vitro results [19].…”