Curare Alkaloids: Constituents of a Matis Dart Poison

Nicotinic acetylcholine receptors in cancer: Limitations and prospects

Nicotinic acetylcholine receptors (nAChRs) have long been considered to solely mediate neurotransmission. However, their widespread distribution in the human body suggests a more diverse physiological role. Additionally, the expression of nAChRs is increased in certain cancers, such as lung cancer, and has been associated with cell proliferation, epithelial-to-mesenchymal cell transition, angiogenesis and apoptosis prevention. Several compounds that interact with these receptors have been identified as potential therapeutic agents. They have been tested as drugs for treating nicotine addiction, alcoholism, depression, pain and Alzheimer's disease. This review focuses on nAChR-mediated signalling in cancer, presenting opportunities for the development of innovative nAChR-based anticancer drugs. It displays the differences in expression of each nAChR subunit between normal and cancer cells for selected cancer types, highlighting their possible involvement in specific cases. Antagonists of nAChRs that could complement existing cancer therapies are summarised and critically discussed. We hope that this review will stimulate further research on the role of nAChRs in cancer potentially leading to innovative cancer therapies.

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

Alkaloids are natural products known as ethnobotanicals that have attracted increasing attention due to a wide range of their pharmacological properties. In this study, cholinesterase inhibitors were obtained from branches of Abuta panurensis Eichler (Menispermaceae), an endemic species from the Amazonian rainforest. Five alkaloids were isolated, and their structure was elucidated by a combination of 1D and 2D 1H and 13C NMR spectroscopy, HPLC-MS, and high-resolution MS: Lindoldhamine isomer m/z 569.2674 (1), stepharine m/z 298.1461 (2), palmatine m/z 352.1616 (3), 5-N-methylmaytenine m/z 420.2669 (4) and the N-trans-feruloyltyramine m/z 314.1404 (5). The compounds 1, 3, and 5 were isolated from A. panurensis for the first time. Interaction of the above-mentioned alkaloids with acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes was investigated in silico by molecular docking and molecular dynamics. The molecules under investigation were able to bind effectively with the active sites of the AChE and BChE enzymes. The compounds 1–4 demonstrated in vitro an inhibitory effect on acetylcholinesterase with IC50 values in the range of 19.55 µM to 61.24 µM. The data obtained in silico corroborate the results of AChE enzyme inhibition.

Owners' Knowledge and Approaches to Colic in Working Equids in Honduras

In Honduras, many families are reliant on working equids in their daily life. The aim of this study was to evaluate knowledge about, and approaches to colic used by owners of working equids in Choluteca, Honduras using a phenomenological approach. Semi-structured, verbal questionnaires were conducted with ninety-three owners from eleven different communities in the Choluteca region on equid horse owners' knowledge of colic and treatments. Additional context was gained through observations and verbal questionnaires with three veterinary practitioners and eight agricultural pharmacy (agrovet) store owners. Working equids were commonly used for firewood collection 31% (40/126), transportation 24% (30/126), and carrying crops 13% (17/126). Thirty-eight percent of owners (35/92) said they did not know what colic was, 27% (24/89) could not name any clinical signs, and 46% (42/92) could not name any causes. Most owners with previous experience of colic had treated it themselves 79% (53/67), typically using herbal remedies. Colic was a major concern for owners of working equids who had prior experience or knowledge of the condition. Knowledge and understanding of colic varied, and access to evidence-based treatments was very limited. The findings will be used to inform the development of educational resources on colic in working equids.

Amide-Iminoate Isomerism in Antineuroinflammatory Isoquinoline Alkaloids from Stephania cepharantha

Six new (1-6) and two known (7, 8) alkaloids that were chemically inseparable geometrical isomers (two isomers present in a 1:1 ratio for 1-4 and 6 and a 1:3 ratio for 5, 7, and 8) were identified from Stephania cepharantha. Their structures and absolute configurations were determined by spectroscopic data analyses and comparison of their experimental and calculated ECD spectra. Moreover, using NOE correlations and DFT-based calculations, the NMR data of each geometrical isomer of 1-6 were assigned. The biological evaluation of 1-8 showed that 5 and 6 have stronger inhibitory effects (IC₅₀ values, 12.0 and 12.6 μM, respectively) than minocycline (IC₅₀ value, 17.5 μM) against NO production in overactivated BV2 cells, suggesting they have great potential in the development of neuroinflammatory therapeutics for treating neurodegenerative diseases.

Curare alkaloids from Matis Dart Poison: Comparison with d-tubocurarine in interactions with nicotinic, 5-HT3 serotonin and GABAA receptors

Several novel bisbenzylisoquinoline alkaloids (BBIQAs) have recently been isolated from a Matis tribe arrow poison and shown by two-electrode voltage-clamp to inhibit mouse muscle nicotinic acetylcholine receptors (nAChR). Here, using radioligand assay with Aplysia californica AChBP and radioiodinated α-bungarotoxin ([125I]-αBgt), we show that BBIQA1, BBIQA2, and d-tubocurarine (d-TC) have similar affinities to nAChR orthosteric site. However, a competition with [125I]-αBgt for binding to the Torpedo californica muscle-type nAChR revealed that BBIQAs1, 2, and 3 are less potent (IC50s = 26.3, 8.75, and 17.0 μM) than d-TC (IC50 = 0.39 μM), while with α7 nAChR in GH4C1 cells, BBIQA1 was less potent that d-TC (IC50s = 162 μM and 7.77 μM, respectively), but BBIQA2 was similar (IC50 = 5.52 μM). In inhibiting the Ca2+ responses induced by acetylcholine in Neuro2a cells expressing the mouse adult α1β1εδ nAChR or human α7 nAChR, BBIQAs1 and 2 had similar potencies to d-TC (IC50s in the range 0.75-3.08 μM). Our data suggest that BBIQA1 and BBIQA2 can inhibit adult muscle α1β1εδ nAChR by both competitive and noncompetitive mechanisms. Further experiments on neuronal α3β2, α4β2, and α9α10 nAChRs, expressed in Xenopus laevis oocytes, showed that similar potencies for BBIQAs1, 2, and d-TC. With α3β2γ2 GABAAR currents were almost completely inhibited by d-TC at a high (100 μM) concentration, but BBIQAs1 and 2 were less potent (only 40-50% inhibition), whereas in competition with Alexa Fluor 546-α-cobratoxin for binding to α1β3γ2 GABAAR in Neuro2a cells, d-TC and these analogs had comparable affinities. Especially interesting effects of BBIQAs1 and 2 in comparison with d-TC were observed for 5-HT3AR: BBIQA1 and BBIQA2 were 5- and 87-fold less potent than d-TC (IC50 = 22.63 nM). Thus, our results reveal that these BBIQAs differ from d-TC in their potencies towards certain Cys-loop receptors, and we suggest that understanding the reasons behind this might be useful for future drug design.

New Alkaloid and Aromatic Glucoside from the Flowers of Cymbidium Lunagrad Eternal Green

In this paper, we investigated the chemical components of the flowers of Cymbidium Lunagrad Eternal Green for the first time. In the whole post-fertilization, a new alkaloid, named Lunagrad A (1), and a new aromatic glucoside, named Lunagrad B (2), were isolated from the MeOH extract of the flowers of Cymbidium Lunagrad Eternal Green, along with other six known aromatic compounds (3–8) and three flavone glucosides (9–11). These structures were determined on the basis of NMR experiments, as well as chemical evidence.

Drugs Interfering with Muscarinic Acetylcholine Receptors and Their Effects on Place Navigation

Muscarinic acetylcholine receptors (mAChRs) have been found to regulate many diverse functions, ranging from motivation and feeding to spatial navigation, an important and widely studied type of cognitive behavior. Systemic administration of non-selective antagonists of mAChRs, such as scopolamine or atropine, have been found to have adverse effects on a vast majority of place navigation tasks. However, many of these results may be potentially confounded by disruptions of functions other than spatial learning and memory. Although studies with selective antimuscarinics point to mutually opposite effects of M1 and M2 receptors, their particular contribution to spatial cognition is still poorly understood, partly due to a lack of truly selective agents. Furthermore, constitutive knock-outs do not always support results from selective antagonists. For modeling impaired spatial cognition, the scopolamine-induced amnesia model still maintains some limited validity, but there is an apparent need for more targeted approaches such as local intracerebral administration of antagonists, as well as novel techniques such as optogenetics focused on cholinergic neurons and chemogenetics aimed at cells expressing metabotropic mAChRs.

Recent developments in multicomponent synthesis of structurally diversified tetrahydropyridines

Tetrahydropyridines (THPDs) have recognized as a major constituent of naturally occurring alkaloids and exhibits various biological and pharmacological profiles. For their synthesis, MCRs are employed as an excellent tool to generate vast libraries.