Exploring the antileishmanial activity of dicentrine from Ocotea puberula (Lauraceae) using biomembrane models.

This study aimed to assess the antiprotozoal efficacy of dicentrine, an aporphine alkaloid isolated from Ocotea puberula, against amastigote forms of Leishmania (L.) infantum. Our findings reveal that dicentrine demonstrated a notable EC50 value of 10.3 µM, comparable to the positive control miltefosine (EC50 of 10.4 µM), while maintaining moderate toxicity to macrophages (CC50 of 51.9 µM). Utilizing an in silico methodology, dicentrine exhibited commendable adherence to various parameters, encompassing lipophilicity, water solubility, molecule size, polarity, and flexibility. Subsequently, we conducted additional investigations to unravel the mechanism of action, employing Langmuir monolayers as models for protozoan cell membranes. Tensiometry analyses unveiled that dicentrine disrupts the thermodynamic and mechanical properties of the monolayer by expanding it to higher areas and increasing the fluidity of the film. The molecular disorder was further corroborated through dilatational rheology and infrared spectroscopy. These results contribute insights into the role of dicentrine as a potential antiprotozoal drug in its interactions with cellular membranes. Beyond elucidating the mechanism of action at the plasma membrane's external surface, our study sheds light on drug-lipid interface interactions, offering implications for drug delivery and other pharmaceutical applications.

A semi-quantitative histochemical method for assessment of biochemical responses to osmotic stress in Coffea arabica leaf disks.

A simple method set for assessing biochemical changes associated with osmotic stress responses was developed using coffee (Coffea arabica L.) leaf disks. Stress was induced by polyethylene glycol (PEG) exposure. Quantitative evaluation of tissue physiological stress parameters was carried out using analytical methods to validate the conversion of classic qualitative histochemical tests for localizing lipid peroxidation, hydrogen peroxide, and total xanthine alkaloids into semi-quantitative assays. Relative electrolyte leakage (EL%) and chlorophyll content (SPAD index) were also recorded. EL% levels of treated disks were higher than those of control ones, whereas SPAD indexes were comparable. Histochemical localization indicated that levels of lipid peroxidation, H2O2, and total xanthines were also higher under osmotic stress than in control conditions. Semi-quantitative data obtained by image processing of histochemical staining consistently matched quantitative evaluations. Chromatographic analyses revealed that theophylline and caffeine concentrations increased in the presence of PEG, whereas theobromine remained constant in relation to the control. The methods herein described can be useful to rapidly acquire initial data regarding biochemical osmotic stress responses in coffee tissues based on simple staining and imaging steps. Moreover, it is likely that the same method may be applicable to other types of stresses and plant species upon minor adjustments.

Novel anti-inflammatory diketopiperazine alkaloids from the marine-derived fungus Penicillium brasilianum.

Diketopiperazine alkaloids have proven the most abundant heterocyclic alkaloids up to now, which usually process diverse scaffolds and rich biological activities. In our search for bioactive diketopiperazine alkaloids from marine-derived fungi, two novel diketopiperazine alkaloids, penipiperazine A (1) and its biogenetically related new metabolite (2), together with a known analogue neofipiperzine C (3), were obtained from the strain Penicillium brasilianum. Their planar structures and absolute configurations were elucidated by extensive spectroscopic analyses, 13C NMR calculation, Marfey's, ECD, and ORD methods. Compound 1 featured a unique 6/5/6/6/5 indole-pyrazino-pyrazino-pyrrolo system, and its plausible biogenetic pathway was also proposed. Additionally, compounds 1-3 have been tested for their inflammatory activities. 1 and 2 significantly inhibited the release of NO and the expression of related pro-inflammatory cytokines on LPS-stimulated RAW264.7 cells, suggesting they could be attracting candidate for further development as anti-inflammatory agent. KEY POINTS: • A novel diketopiperazine alkaloid featuring a unique 6/5/6/6/5 indole-pyrazino-pyrazino-pyrrolo system was isolated from the marine fungus Penicillium brasilianum. • The structure of 1 was elucidated by detailed analysis of 2D NMR data, 13C NMR calculation, Marfey's, ECD, and ORD methods. • Compounds 1 and 2 significantly inhibited the release of NO and the expression of related pro-inflammatory cytokines on LPS-stimulated RAW264.7 cells.

Exploring the antileishmanial activity of dicentrine from Ocotea puberula (Lauraceae) using biomembrane models

This study aimed to assess the antiprotozoal efficacy of dicentrine, an aporphine alkaloid isolated from Ocotea puberula, against amastigote forms of Leishmania (L.) infantum. Our findings reveal that dicentrine demonstrated a notable EC50 value of 10.3 μM, comparable to the positive control miltefosine (EC50 of 10.4 μM), while maintaining moderate toxicity to macrophages (CC50 of 51.9 μM). Utilizing an in silico methodology, dicentrine exhibited commendable adherence to various parameters, encompassing lipophilicity, water solubility, molecule size, polarity, and flexibility. Subsequently, we conducted additional investigations to unravel the mechanism of action, employing Langmuir monolayers as models for protozoan cell membranes. Tensiometry analyses unveiled that dicentrine disrupts the thermodynamic and mechanical properties of the monolayer by expanding it to higher areas and increasing the fluidity of the film. The molecular disorder was further corroborated through dilatational rheology and infrared spectroscopy. These results contribute insights into the role of dicentrine as a potential antiprotozoal drug in its interactions with cellular membranes. Beyond elucidating the mechanism of action at the plasma membrane's external surface, our study sheds light on drug-lipid interface interactions, offering implications for drug delivery and other pharmaceutical applications.

Antibacterial and immunological properties of piperine evidenced by preclinical studies: a systematic review.

Aim: To review in vitro, in vivo, and in silico studies examining the antibacterial and immunomodulatory properties of piperine (PPN). Methods: This systematic review followed PRISMA guidelines, and five databases were searched. Results: A total of 40 articles were included in this study. Six aspects of PPN activity were identified, including antibacterial spectrum, association with antibiotics, efflux pump inhibition, biofilm effects, protein target binding, and modulation of immune functions/virulence factors. Most studies focused on Mycobacterium spp. and Staphylococcus aureus. Cell lineages and in vivo models were employed to study PPN antibacterial effects. Conclusion: We highlight PPN as a potential adjuvant in the treatment of bacterial infections. PPN possesses several antibacterial properties that need further exploration to determine the mechanisms behind its pharmacological activity.

The Antitumor Activity of Piplartine: A Review.

Cancer is a worldwide health problem with high mortality in children and adults, making searching for novel bioactive compounds with potential use in cancer treatment essential. Piplartine, also known as piperlongumine, is an alkamide isolated from Piper longum Linn, with relevant therapeutic potential. Therefore, this review covered research on the antitumor activity of piplartine, and the studies reported herein confirm the antitumor properties of piplartine and highlight its possible application as an anticancer agent against various types of tumors. The evidence found serves as a reference for advancing mechanistic research on this metabolite and preparing synthetic derivatives or analogs with better antitumor activity in order to develop new drug candidates.

Chemical and Biological Aspects of Different Species of the Genus Clinanthus Herb. (Amaryllidaceae) from South America.

The genus Clinanthus Herb. is found in the Andes Region (South America), mainly in Peru, Ecuador, and Bolivia. These plants belong to the Amaryllidaceae family, specifically the Amaryllidoideae subfamily, which presents an exclusive group of alkaloids known as Amaryllidaceae alkaloids that show important structural diversity and pharmacological properties. It is possible to find some publications in the literature regarding the botanical aspects of Clinanthus species, although there is little information available about their chemical and biological activities. The aim of this work was to obtain the alkaloid profile and the anti-cholinesterase activity of four different samples of Clinanthus collected in South America: Clinanthus sp., Clinanthus incarnatus, and Clinanthus variegatus. The alkaloid extract of each sample was analyzed by gas chromatography coupled with mass spectrometry (GC-MS), and their potential against the enzymes acetyl- and butyrylcholinesterase were evaluated. Thirteen alkaloids have been identified among these species, while six unidentified structures have also been detected in these plants. The alkaloid extract of the C. variegatus samples showed the highest structural diversity as well as the best activity against AChE, which was likely due to the presence of the alkaloid sanguinine. The results suggest this genus as a possible interesting new source of Amaryllidaceae alkaloids, which could contribute to the development of new medicines.

Alkaloid from Geissospermum sericeum Benth. & Hook.f. ex Miers (Apocynaceae) Induce Apoptosis by Caspase Pathway in Human Gastric Cancer Cells.

Gastric cancer is among the major causes of death from neoplasia leading causes of death worldwide, with high incidence rates and problems related to its treatment. Here, we outline how Geissospermum sericeum exerts antitumor activity on the ACP02 cell line (human gastric adenocarcinoma) and the mechanism of cell death. The ethanol extract and fractions, neutral fraction and alkaloid fraction, were characterized by thin-layer chromatography and HPLC-DAD, yielding an alkaloid (geissoschizoline N4-methylchlorine) identified by NMR. The cytotoxicity activity of the samples (ethanol extract, neutral fraction, alkaloid fraction, and geissoschizoline N4-methylchlorine) in HepG2 and VERO cells was determined by MTT. The ACP02 cell line was used to assess the anticancer potential. Cell death was quantified with the fluorescent dyes Hoechst 33342, propidium iodide, and fluorescein diacetate. The geissoschizoline N4-methylchlorine was evaluated in silico against caspase 3 and 8. In the antitumor evaluation, there was observed a more significant inhibitory effect of the alkaloid fraction (IC50 18.29 µg/mL) and the geissoschizoline N4-methylchlorine (IC50 12.06 µg/mL). However, geissoschizoline N4-methylchlorine showed lower cytotoxicity in the VERO (CC50 476.0 µg/mL) and HepG2 (CC50 503.5 µg/mL) cell lines, with high selectivity against ACP02 cells (SI 39.47 and 41.75, respectively). The alkaloid fraction showed more significant apoptosis and necrosis in 24 h and 48 h, with increased necrosis in higher concentrations and increased exposure time. For the alkaloid, apoptosis and necrosis were concentration- and time-dependent, with a lower necrosis rate. Molecular modeling studies demonstrated that geissoschizoline N4-methylchlorine could occupy the active site of caspases 3 and 8 energetically favorably. The results showed that fractionation contributed to the activity with pronounced selectivity for ACP02 cells, and geissoschizoline N4-methylchlor is a promising candidate for caspase inhibitors of apoptosis in gastric cancer. Thus, this study provides a scientific basis for the biological functions of Geissospermum sericeum, as well as demonstrates the potential of the geissoschizoline N4-methylchlorine in the treatment of gastric cancer.

Molecular Modeling and In Vitro Evaluation of Piplartine Analogs against Oral Squamous Cell Carcinoma.

Cancer is a principal cause of death in the world, and providing a better quality of life and reducing mortality through effective pharmacological treatment remains a challenge. Among malignant tumor types, squamous cell carcinoma-esophageal cancer (EC) is usually located in the mouth, with approximately 90% located mainly on the tongue and floor of the mouth. Piplartine is an alkamide found in certain species of the genus Piper and presents many pharmacological properties including antitumor activity. In the present study, the cytotoxic potential of a collection of piplartine analogs against human oral SCC9 carcinoma cells was evaluated. The analogs were prepared via Fischer esterification reactions, alkyl and aryl halide esterification, and a coupling reaction with PyBOP using the natural compound 3,4,5-trimethoxybenzoic acid as a starting material. The products were structurally characterized using 1H and 13C nuclear magnetic resonance, infrared spectroscopy, and high-resolution mass spectrometry for the unpublished compounds. The compound 4-methoxy-benzyl 3,4,5-trimethoxybenzoate (9) presented an IC50 of 46.21 µM, high selectively (SI > 16), and caused apoptosis in SCC9 cancer cells. The molecular modeling study suggested a multi-target mechanism of action for the antitumor activity of compound 9 with CRM1 as the main target receptor.

Antihypertensive Activity of the Alkaloid Aspidocarpine in Normotensive Wistar Rats.

The alkaloid Aspidocarpine was isolated from the bark of Aspidosperma desmanthum. Its structure was elucidated by the spectral data of 1H and 13C-NMR (1D and 2D) and high-resolution mass spectrometry (HRESIMS). The antihypertensive activity was investigated by intravenous infusion in Wistar rats. This alkaloid significantly reduced (p < 0.05) the systolic, median, and diastolic blood pressures of rodents, without causing motor incoordination and imbalance in the rotarod test. The results indicate that the alkaloid Aspidocarpine exerts its antihypertensive activity without causing sedation or the impairment of motor functions.

Anonaine from Annona crassiflora inhibits glutathione S-transferase and improves cypermethrin activity on Rhipicephalus (Boophilus) microplus (Canestrini, 1887).

Rhipicephalus (Boophilus) microplus (Canestrini, 1887) is one of the most important ectoparasites of cattle, causing severe economic losses in tropical and subtropical regions of the world. The selection of resistance to the most commonly used commercial acaricides has stimulated the search for new products for tick control. The identification and development of drugs that inhibit key tick enzymes, such as glutathione S-transferase (GST), is a rational approach that has already been applied to other parasites than ticks. In this context, alkaloids such as anonaine display several biological activities, including an acaricidal effect. This study aimed to assess the specific inhibition of the R. microplus GST by anonaine, and analyze the effect on ticks when anonaine is combined with cypermethrin. For this purpose, a molecular docking analysis was performed using an R. microplus GST three-dimensional structure model with anonaine and compared with a human GST-anonaine complex. The absorption, distribution, metabolism, excretion, and toxicity properties of anonaine were also predicted. Then, for in vitro analyses, anonaine was isolated from Annona crassiflora (Martius, 1841) leaves. The inhibition of purified recombinant R. microplus GST (rRmGST) by anonaine and the effect of this alkaloid on cypermethrin efficacy towards R. microplus were assessed. Anonaine has a higher affinity to the tick enzyme than to the human enzyme in silico and has moderate toxicity, being able to inhibit, in vitro, rRmGST up to 37.5% in a dose-dependent manner. Although anonaine alone has no activity against R. microplus, it increased the cypermethrin effect on larvae, reducing the LC50 from 44 to 22 µg/mL. In conclusion, anonaine is a natural compound that can increase the effect of cypermethrin against R. microplus.

Indole-diterpenes alkaloid profiles of native grasses involved in tremorgenic syndromes in the Argentine Patagonia.

One of the main intoxications to livestock in the Patagonia region of Argentina is the tremorgenic disease "Mal de Huecú", attributed to the consumption of the native grasses Poa huecu and/or Festuca argentina. In this report, five outbreaks of spontaneous intoxications were investigated. Several indole-diterpene alkaloids were identified in Poa huecu and Festuca argentina including the known tremorgen terpendole C and are likely the cause of "Mal de Huecú" disease.

The short-term effects of berberine in the liver: Narrow margins between benefits and toxicity.

Berberine is a plant alkaloid to which antihyperglycemic properties have been attributed. It is also known as an inhibitor of mitochondrial functions. In this work short-term translation of the latter effects on hepatic metabolism were investigated using the isolated perfused rat liver. Once-through perfusion with a buffered saline solution was done. At low portal concentrations berberine modified several metabolic pathways. It inhibited hepatic gluconeogenesis, increased glycolysis, inhibited ammonia detoxification, increased the cytosolic NADH/NAD+ ratio and diminished the ATP levels. Respiration of intact mitochondria was impaired as well as the mitochondrial pyruvate carboxylation activity. These results can be regarded as evidence that the direct inhibitory effects of berberine on gluconeogenesis, mediated by both energy metabolism and pyruvate carboxylation inhibition, represent most likely a significant contribution to its clinical efficacy as an antihyperglycemic agent. However, safety concerns also arise because all effects occur at similar concentrations and there is a narrow margin between the expected benefits and toxicity. Even mild inhibition of gluconeogenesis is accompanied by diminutions in oxygen uptake and ammonia detoxification and increases in the NADH/NAD+ ratio. All combined, desired and undesired effects could well in the end represent a deleterious combination of events leading to disruption of cellular homeostasis.

The Natural Alkaloid Tryptanthrin Induces Apoptosis-like Death in Leishmania spp.

Leishmaniasis is a vector-borne disease against which there are no approved vaccines, and the treatment is based on highly toxic drugs. The alkaloids consist of a chemical class of natural nitrogen-containing substances with a long history of antileishmanial activity. The present study aimed at determining the antileishmanial activity and in silico pharmacokinetic and toxicological potentials of tryptanthrin alkaloid. The anti-Leishmania amazonensis and anti-L. infantum assays were performed against both promastigotes and intracellular amastigotes. Cellular viability was determined by parasites' ability to grow (promastigotes) or differentiate (amastigotes) after incubation with tryptanthrin. The mechanisms of action were explored by mitochondrion dysfunction and apoptosis-like death evaluation. For the computational pharmacokinetics and toxicological analysis (ADMET), tryptanthrin was submitted to the PreADMET webserver. The alkaloid displayed anti-promastigote activity against L. amazonensis and L. infantum (IC50 = 11 and 8.0 µM, respectively). Tryptanthrin was active against intracellular amastigotes with IC50 values of 75 and 115 µM, respectively. Mitochondrial membrane depolarization was observed in tryptanthrin-treated promastigotes. In addition, parasites undergoing apoptosis-like death were detected after 18 h of exposure. In silico ADMET predictions revealed that tryptanthrin has pharmacokinetic and toxicological properties similar to miltefosine. The results presented herein demonstrate that tryptanthrin is an interesting drug candidate against leishmaniasis.

Lycorine Alkaloid and Crinum americanum L. (Amaryllidaceae) Extracts Display Antifungal Activity on Clinically Relevant Candida Species.

Candida species are the main fungal agents causing infectious conditions in hospital patients. The development of new drugs with antifungal potential, increased efficacy, and reduced toxicity is essential to face the challenge of fungal resistance to standard treatments. The aim of this study is to evaluate the in vitro antifungal effects of two crude extracts of Crinum americanum L., a rich alkaloid fraction and lycorine alkaloid, on the Candida species. As such, we used a disk diffusion susceptibility test, determined the minimum inhibitory concentration (MIC), and characterized the components of the extracts using Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (ESI FT-ICR MS). The extracts were found to have antifungal activity against various Candida species. The chemical characterization of the extracts indicated the presence of alkaloids such as lycorine and crinine. The Amaryllidaceae family has a promising antifungal potential. Furthermore, it was found that the alkaloid lycorine directly contributes to the effects that were observed for the extracts and fraction of C. americanum.

Betalains and their applications in food: The current state of processing, stability and future opportunities in the industry.

Betalains are water-soluble nitrogenous pigments with coloring properties and antioxidant activities, which is why they have been incorporated into several foods. However, their use is limited by their instability in response to different factors, such as, pH, oxygen, water activity, light, metals, among others. In this work, a review of up-to-date and relevant information is presented on the primary natural sources of betalains. Additionally, the advantages and disadvantages of the primary betalain extraction techniques are discussed and compared. The results of these studies were focused on the stability of betalains when incorporated into foods, either in pure or encapsulated form, and they are discussed through different technologies. Lastly, the most relevant information related to their stability and a projection of their promising future applications within the food industry is presented.

GlucoMedix®, an extract of Stevia rebaudiana and Uncaria tomentosa, reduces hyperglycemia, hyperlipidemia, and hypertension in rat models without toxicity: a treatment for metabolic syndrome.

BACKGROUND: The objective of this in vivo study is to evaluate in five rat models the pharmacologic effects and toxicity of a commercial hydro-alcoholic extract, GlucoMedix®, derived from Stevia rebaudiana and the pentacyclic chemotype of Uncaria Tomentosa (Willd.) DC, for use as a treatment for metabolic syndrome. The extract contains phytochemicals of Stevia (e.g., steviol glycosides) and Uncaria (e.g., pentacyclic oxindole alkaloids, but lacks tetracyclic oxindole alkaloids). METHODS: The pharmacologic assessments in three rat models include reductions in chemically induced hyperglycemia, hyperlipidemia (cholesterol and triglycerides), and hypertension, all of which are comorbidities of metabolic syndrome. Acute toxicity and 28-day subacute toxicity were assessed in rat models at doses higher than those used in the efficacy models. RESULTS: The acute oral toxicity was evaluated in Holtzman rats and the extract did not produce acute toxic effects or lethality, with the LD50 > 5000 mg/kg (extract wet weight). Furthermore, subacute oral toxicity was evaluated in rats for 28 days at daily doses as high as 2000 mg/kg without toxicity or abnormal clinical chemistry or hematological effects. Daily oral doses of 250 - 1000 mg/kg were used to evaluate the treatment effects in hyperglycemic (alloxan-induced and glibenclamide-controlled), hyperlipidemic (cholesterol-induced and atorvastatin-controlled), and hypertensive (L-NAME-induced and enalapril-controlled) rat models. Alloxan-induced hyperglycemia was reduced in a dose-dependent manner within 28 days or less. Cholesterol-induced hyperlipidemic rats exhibited dose-dependent reductions in cholesterol and triglycerides at 21 days. Furthermore, GlucoMedix® produced a dose-dependent decrease in systolic and diastolic arterial blood pressure in L-NAME-induced hypertensive rats at 28 days. CONCLUSIONS: The five in vivo rat models revealed that the all-natural phytotherapy GlucoMedix® is a safe and effective treatment for hyperglycemia, hyperlipidemia, and hypertension. This extract is expected to affect multiple comorbidities of metabolic syndrome, without any acute or subacute oral toxicity in humans. Although multiple prescription drugs are well known for the treatment of individual comorbidities of metabolic syndrome, no drug monotherapy concurrently treats all three comorbidities.

Evaluación de la susceptibilidad in vitro a esparteína, en cuatro cepas de Mycobacterium tuberculosis / Evaluation of in vitro susceptibility to sparteine in four strains of Mycobacterium tuberculosis

RESUMEN La esparteína es un alcaloide con actividad bacteriostática sobre el género Mycobacterium. El objetivo de este trabajo fue evaluar la acción antimicrobiana de la esparteína en el crecimiento de cuatro cepas ATCC de Mycobacterium tuberculosis (susceptible, resistente a isoniazida, resistente a rifampicina y multidrogorresistente) in vitro. La evaluación de la actividad bactericida del sulfato de esparteína se realizó a través de una adaptación del método de ensayo de cultivo y susceptibilidad a medicamentos antituberculosos mediante observación microscópica (MODS, por sus siglas en inglés), según el protocolo descrito en el manual técnico elaborado por el Instituto Nacional de Salud. Los resultados demuestran que a concentraciones de 25; 50 y 100 mM de sulfato de esparteína, no se desarrollan unidades formadoras de colonia en las cuatro cepas evaluadas de Mycobacterium tuberculosis. Los resultados demuestran el potencial efecto antimicrobiano in vitro de la esparteína en la tuberculosis multidrogorresistente.

ABSTRACT Sparteine is an alkaloid with bacteriostatic activity on the genus Mycobacterium. The aim of this study was to evaluate the antimicrobial activity of sparteine on the growth of 4 ATCC strains of Mycobacterium tuberculosis (susceptible, resistant to isoniazid, resistant to rifampicin and multidrug-resistant) in vitro. Validation of bactericidal activity of sparteine sulfate was carried out through an adaptation of the Microscopic-Observation Drug-Susceptibility (MODS) method according to the guidelines of the Peruvian National Health Institute. The results demonstrate that at concentrations of 25; 50 and 100 Mm of sparteine sulfate, there is no development of colony-forming units in any of the 4 evaluated strains. Our results demonstrate the potential in vitro antimicrobial effect of sparteine on multidrug-resistant tuberculosis.

Iboga Inspired N-Indolylethyl-Substituted Isoquinuclidines as a Bioactive Scaffold: Chemoenzymatic Synthesis and Characterization as GDNF Releasers and Antitrypanosoma Agents.

The first stage of the drug discovery process involves the identification of small compounds with biological activity. Iboga alkaloids are monoterpene indole alkaloids (MIAs) containing a fused isoquinuclidine-tetrahydroazepine ring. Both the natural products and the iboga-inspired synthetic analogs have shown a wide variety of biological activities. Herein, we describe the chemoenzymatic preparation of a small library of novel N-indolylethyl-substituted isoquinuclidines as iboga-inspired compounds, using toluene as a starting material and an imine Diels-Alder reaction as the key step in the synthesis. The new iboga series was investigated for its potential to promote the release of glial cell line-derived neurotrophic factor (GDNF) by C6 glioma cells, and to inhibit the growth of infective trypanosomes. GDNF is a neurotrophic factor widely recognized by its crucial role in development, survival, maintenance, and protection of dopaminergic neuronal circuitries affected in several neurological and psychiatric pathologies. Four compounds of the series showed promising activity as GDNF releasers, and a leading structure (compound 11) was identified for further studies. The same four compounds impaired the growth of bloodstream Trypanosoma brucei brucei (EC50 1-8 µM) and two of them (compounds 6 and 14) showed a good selectivity index.

Modulation of GABAA receptors and of GABAergic synapses by the natural alkaloid gelsemine.

The Gelsemium elegans plant preparations have shown beneficial activity against common diseases, including chronic pain and anxiety. Nevertheless, their clinical uses are limited by their toxicity. Gelsemine, one of the most abundant alkaloids in the Gelsemium plants, have replicated these therapeutic and toxic actions in experimental behavioral models. However, the molecular targets underlying these biological effects remain unclear. The behavioral activity profile of gelsemine suggests the involvement of GABAA receptors (GABAARs), which are the main biological targets of benzodiazepines (BDZs), a group of drugs with anxiolytic, hypnotic, and analgesic properties. Here, we aim to define the modulation of GABAARs by gelsemine, with a special focus on the subtypes involved in the BDZ actions. The gelsemine actions were determined by electrophysiological recordings of recombinant GABAARs expressed in HEK293 cells, and of native receptors in cortical neurons. Gelsemine inhibited the agonist-evoked currents of recombinant and native receptors. The functional inhibition was not associated with the BDZ binding site. We determined in addition that gelsemine diminished the frequency of GABAergic synaptic events, likely through a presynaptic modulation. Our findings establish gelsemine as a negative modulator of GABAARs and of GABAergic synaptic function. These pharmacological features discard direct anxiolytic or analgesic actions of gelsemine through GABAARs but support a role of GABAARs on the alkaloid induced toxicity. On the other hand, the presynaptic effects of the alkaloid provide an additional mechanism to explain their beneficial effects. Collectively, our results contribute novel information to improve understanding of gelsemine actions in the mammalian nervous system.