Nicotine alkaloids as antioxidant and potential protective agents against in vitro oxidative haemolysis

Recent synthetic strategies for N-arylation of pyrrolidines: a potential template for biologically active molecules

The chemistry of nitrogen-containing heterocyclic compounds has been a multifaceted area of research for an extended period due to their varied therapeutic and biological significance. N-Aryl pyrrolidine formed by condensation of aryl group with nitrogen atom of pyrrolidine is present in a wide array of compounds. Various significant activities shown by N-arylated pyrrolidine include anti-Alzheimer, antihypoxic, anticancer, plant activator, analgesic effect, and hepatitis C inhibitor. This review summarizes different synthetic approaches, e.g., transition-metal catalyzed and transition-metal-free synthesis, decarboxylation reaction, reductive amination, nucleophilic cyclization, Ullmann-Goldberg amidation, Buchwald-Hartwig reaction, Chan-Evans-Lam coupling, addition to benzyne, multistep reaction, green synthesis, rearrangement reaction, and multicomponent reaction, to afford the derivatives of N-aryl pyrrolidine. It encompasses synthetic strategies documented from 2015 to 2023.

Recent insights about pyrrolidine core skeletons in pharmacology

To overcome numerous health disorders, heterocyclic structures of synthetic or natural origin are utilized, and notably, the emergence of various side effects of existing drugs used for treatment or the resistance of disease-causing microorganisms renders drugs ineffective. Therefore, the discovery of potential therapeutic agents that utilize different modes of action is of utmost significance to circumvent these constraints. Pyrrolidines, pyrrolidine-alkaloids, and pyrrolidine-based hybrid molecules are present in many natural products and pharmacologically important agents. Their key roles in pharmacotherapy make them a versatile scaffold for designing and developing novel biologically active compounds and drug candidates. This review aims to provide an overview of recent advancements (especially during 2015-2023) in the exploration of pyrrolidine derivatives, emphasizing their significance as fundamental components of the skeletal structure. In contrast to previous reviews that have predominantly focused on a singular biological activity associated with these molecules, this review consolidates findings from various investigations encompassing a wide range of important activities (antimicrobial, antiviral, anticancer, anti-inflammatory, anticonvulsant, cholinesterase inhibition, and carbonic anhydrase inhibition) exhibited by pyrrolidine derivatives. This study is also anticipated to serve as a valuable resource for drug research and development endeavors, offering significant insights and guidance.

Natural-product-inspired bioactive alkaloids agglomerated with potential antioxidant activity: Recent advancements on structure-activity relationship studies and future perspectives

Alkaloids derived from natural sources have been shown to have substantial antioxidant activity, suggesting that these natural-product-inspired bioactive entities may have major beneficial influence on human health and food processing sector. The primary process intricates in the etiology of several disorders such as neurodegenerative, inflammatory cardiovascular, and other chronic diseases appear to be either oxidative injury or a cellular damage caused by reactive oxygen species (ROS) or free-radicals. The alkaloid class of bio-heterocycles have been divided into numerous groups based on their biosynthetic precursor and heterocyclic ring systems i.e., piperidine, imidazole, purine, pyrrolizidine, indole, quinolozidine, isoquinoline, tropane, and pyrrolidine alkaloids. Distinct biological properties have been attributed to various compounds belonging to this chemical groups, including antirheumatic, cardiovascular, antispasmodic, anti-ulcer, anti-inflammatory, antibacterial, antinociceptive etc. For many years, natural products and their analogs have been recognized as a possible source of medicinal agents. Recently, research has been concentrated on the synthesis, separation/purification, and identification of new alkaloids derived from a variety of natural sources. This book chapter aims to summarize on the latest developments on the current knowledge on the relationship between the structural features of promising class of bioactive alkaloids with their antioxidant activities.

Neuroprotective Effects of Palmatine via the Enhancement of Antioxidant Defense and Small Heat Shock Protein Expression in Aβ-Transgenic Caenorhabditis elegans

Palmatine is a naturally occurring isoquinoline alkaloid that has been reported to display neuroprotective effects against amyloid-β- (Aβ-) induced neurotoxicity. However, the mechanisms underlying the neuroprotective activities of palmatine remain poorly characterized in vivo. We employed transgenic Caenorhabditis elegans models containing human Aβ_1-42 to investigate the effects and possible mechanisms of palmatine-mediated neuroprotection. Treatment with palmatine significantly delayed the paralytic process and reduced the elevated reactive oxygen species levels in Aβ-transgenic C. elegans. In addition, it increased oxidative stress resistance without affecting the lifespan of wild-type C. elegans. Pathway analysis suggested that the differentially expressed genes were related mainly to aging, detoxification, and lipid metabolism. Real-time PCR indicated that resistance-related genes such as sod-3 and shsp were significantly upregulated, while the lipid metabolism-related gene fat-5 was downregulated. Further studies demonstrated that the inhibitory effects of palmatine on Aβ toxicity were attributable to the free radical-scavenging capacity and that the upregulated expression of resistance-related genes, especially shsp, whose expression was regulated by HSF-1, played crucial roles in protecting cells from Aβ-induced toxicity. The research showed that there were significantly fewer Aβ deposits in transgenic CL2006 nematodes treated with palmatine than in control nematodes. In addition, our study found that Aβ-induced toxicity was accompanied by dysregulation of lipid metabolism, leading to excessive fat accumulation in Aβ-transgenic CL4176 nematodes. The alleviation of lipid disorder by palmatine should be attributed not only to the reduction in fat synthesis but also to the inhibition of Aβ aggregation and toxicity, which jointly maintained metabolic homeostasis. This study provides new insights into the in vivo neuroprotective effects of palmatine against Aβ aggregation and toxicity and provides valuable targets for the prevention and treatment of AD.

Synthesis, antioxidant and cytoprotective activity evaluation of C-3 substituted indole derivatives

A series of fifteen indole derivatives substituted at the C-3 position were synthesized and characterized. The antioxidant activity of all derivatives was investigated by three in vitro antioxidant assays, and the derivative with pyrrolidinedithiocarbamate moiety was the most active as a radical scavenger and Fe³⁺-Fe²⁺ reducer. It can be stated that possible hydrogen and electron transfer mechanism is suggested for the quenching of the free radical. Moreover, the indolyl radical stabilization and the presence of unsubstituted indole nitrogen atom are mandatory for the observed antioxidant activity, which strongly depends on the type of the substituent directly connected to the methylene group at the C-3 position. Human red blood cells (RBC) have been used as a cell model to study derivatives interaction with the cell membrane. Haemolytic activity and RBC shape transformation were observed for certain derivatives in a concentration-dependent manner. However, most of the derivatives at sublytic concentration showed high cytoprotective activity against oxidative haemolysis induced by 2,2′-azobis(2-methylpropionamidine) dihydrochloride (AAPH). The cytoprotective properties of derivatives can be explained mostly due to their interactions with the RBC membrane components. Taking together, theoretical estimations and experimental data confirm the beneficial interactions between the selected C-3 substituted indole derivatives and the RBC membrane under oxidative stress conditions. These results encourage us to further structural optimization of C-3 substituted indole derivatives as potent antioxidant compounds.

New triazole-bearing gramine derivatives - synthesis, structural analysis and protective effect against oxidative haemolysis

The new series of triazole-bearing gramine derivatives were synthesized through a CuAAC procedure. The structures of all newly obtained compounds were confirmed by spectroscopic analysis and DFT methods. The obtained derivatives were screened for their protective potency against oxidative haemolysis induced by free radicals generated from 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AAPH). Our work demonstrates that derivatives with propyl or octyl linker and phthalimide group associated with indole-triazole moiety, which have a folded structure, effectively protect human erythrocytes against oxidative stress-induced haemolysis.

Impact of Atomizer Age and Flavor on In Vitro Toxicity of Aerosols from a Third-Generation Electronic Cigarette against Human Oral Cells

Electronic cigarettes (ECs) are categorized into generations which differ in terms of design, aerosol production, and customizability. Current and former smokers prefer third-generation devices that satisfy tobacco cravings more effectively than older generations. Recent studies indicate that EC aerosols from first- and second-generation devices contain reactive carbonyls and free radicals and can cause in vitro cytotoxicity. Third-generation ECs have not been adequately studied. Further, previous studies have focused on cells from the respiratory tract, whereas those of the oral cavity, which is exposed to high levels of EC aerosols, have been understudied. We quantified the production of reactive carbonyls and free radicals by a third-generation EC and investigated the induction of cytotoxicity and oxidative stress in normal and cancerous human oral cell lines using a panel of eight commercial EC liquids. We found that EC aerosols produced using a new atomizer contained formaldehyde, acetaldehyde, and acrolein, but did not contain detectable levels of free radicals. We found that EC aerosols generated from only one of the eight liquids tested using a new atomizer induced cytotoxicity against two human oral cells in vitro. Treatment of oral cells with the cytotoxic EC aerosol caused a concomitant increase in intracellular oxidative stress. As atomizer age increased with repeated use of the same atomizer, carbonyl production, radical emissions, and cytotoxicity increased. Overall, our results suggest that third-generation ECs may cause adverse effects in the oral cavity and normal EC use, which involves repeated use of the same atomizer to generate aerosol, may enhance the potential toxic effects of third-generation ECs.

Effect of the Solvent on Propolis Phenolic Profile and its Antifungal, Antioxidant, and In Vitro Cytoprotective Activity in Human Erythrocytes Under Oxidative Stress

Propolis is a natural bee product with various beneficial biological effects. The health-promoting properties of propolis depend on its chemical composition, particularly the presence of phenolic compounds. The aim of this study was to evaluate the relationship between extraction solvent (acetone 100%, ethanol 70% and 96%) and the antifungal, antioxidant, and cytoprotective activity of the extracts obtained from propolis. Concentrations of flavonoids and phenolic acids in the propolis extracts were determined using ultrahigh-performance liquid chromatography. The antioxidant potential of different extracts was assessed on the basis of 2,2-diphenyl-1-picrylhydrazyl (DPPH·) free-radical-scavenging activity, Fe³⁺-reducing power, and ferrous ion (Fe²⁺)-chelating activity assays. The ability of the extracts to protect human red blood cell membranes against free-radical-induced damage and their antifungal activity was also determined. The results showed that the concentration of flavonoids in the propolis extracts was dependent on the solvent used in the extraction process and pinocembrin, chrysin, galangin, and coumaric acid were the most abundant phenols. All extracts exhibited high antioxidant potential and significantly protected human erythrocytes against oxidative damage. On the other hand, the antifungal activity of the propolis extracts depended on the solvent used in extraction and the fungal strains tested. It needs to be stressed that, to the best of our knowledge, there is no study relating the effect of solvent used for extraction of Polish propolis to its phenolic profile, and its antifungal, antioxidant, and cytoprotective activity.

Surface Modification of Luminescent LnIII Fluoride Core-Shell Nanoparticles with Acetylsalicylic acid (Aspirin): Synthesis, Spectroscopic and in Vitro Hemocompatibility Studies

Luminescent lanthanide fluoride core-shell (LaF₃ :Tb³⁺ ,Ce³⁺ @SiO₂ -NH₂ ) nanoparticles, with acetylsalicylic acid (aspirin) coated on the surface have been obtained. The synthesized products, which combine the potential located in the silica shell with the luminescent activity of the core, were characterized in detail with the use of luminescence spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and transmission electron microscopy (TEM) methods. The in vitro effects of the modified luminescent nanoparticles on human red blood cell (RBC) membrane permeability, RBC shape, and sedimentation rate were investigated to assess the hemocompatibility of the obtained compounds. This study demonstrates that LaF₃ : Tb³⁺ 5 %, Ce³⁺ 10 %@SiO₂ -NH₂ nanoparticles with acetylsalicylic acid (aspirin) coated on the surface are very good precursors for multifunctional drug-delivery systems or bio-imaging probes that can be used safely in potential biomedical applications.

Association between vitiligo and smoking: A nationwide population-based study in Korea

No study has examined the associations between vitiligo and smoking. The purpose of this study was to investigate the incidence of vitiligo according to smoking status. We used clinical data from individuals aged over 20 years who received a health examination in the National Insurance Program between 2009 and 2012 (n = 23,503,807). We excluded individuals with pre-existing vitiligo who had ever been diagnosed with vitiligo before the index year (n = 35,710) or who were diagnosed with vitiligo within a year of the index year (n = 46,476). Newly diagnosed vitiligo was identified using claims data from baseline to date of diagnosis or December 31, 2016 (n = 22,811). The development of vitiligo was compared according to self-reported smoking status by a health examination survey. The hazard ratio of vitiligo in current smokers was 0.69 (95% confidence interval; 0.65-0.72) with a reference of never-smokers after adjustment for age, sex, regular exercise, drinking status, body mass index, diabetes mellitus, hypertension, dyslipidemia, history of stroke, and history of ischemic heart diseases. The decreased risk of vitiligo in current smokers persisted after subgroup analysis of sex and age groups. The results suggested there are suppressive effects of smoking on the development of vitiligo. Further studies are needed to evaluate the mechanism of smoking on the development of vitiligo.

Non-cytotoxic hydroxyl-functionalized exfoliated boron nitride nanoflakes impair the immunological function of insect haemocytes in vivo

To induce the water solubility of hexagonal boron nitride (h-BN), we exfoliated and functionalized bulk h-BN with hydroxyl groups (h-BN-OH-n). Short-term studies showed that h-BN-OH-n induced low cytotoxicity in different models: insect haemocytes (in vivo), human erythrocytes and mouse fibroblasts (in vitro). We also demonstrated that Alexa Fluor 647-h-BN-OH-n administered topically to the insects passed through the cuticle barrier and was phagocytosed by haemocytes. Nanoflakes did not affect the haemocyte cell membrane and did not interfere with the phagocytosis of latex beads. Long-term immunoassays showed that h-BN-OH-n, despite not inducing haemocytotoxicity, impaired nodulation, the most important cellular immune response in insects. The haemocytes exposed to h-BN-OH-n and then to bacteria differed in morphology and adhesiveness from the haemocytes exposed only to bacteria and exhibited the same morphology and adhesiveness as the control haemocytes. The h-BN-OH-n-induced decrease in nodulation can therefore result from the reduced ability of haemocytes to recognize bacteria, migrate to them or form microaggregates around them, which can lead to dysfunction of the immune system during pathogen infection. Long-term in vivo studies with animal models are still necessary to unambiguously confirm that h-BN is biocompatible and useful for application as a platform for drug delivery or for bioimaging.

Phenolic Profile and Antioxidant Activity of Propolis Extracts From Poland

Propolis is a natural material collected by honeybees, containing bioactive compounds that exhibit biological activity. The aim of this study was to assess the chemical composition of Polish propolis extracted with two different concentrations of ethanol, namely 70% and 96%, and to evaluate their antioxidant activity depending on extraction conditions. Samples of Polish propolis were extracted with 70% and 96% ethanol in order to obtain the ethanolic propolis extracts EEP70 and EEP96, respectively. Concentrations of 10 flavonoids and 6 phenolic acids were determined using the UPLC-PDA-TQD system. The antioxidant properties were determined based on the DPPH· free radical scavenging activity, Fe3+ reducing power assay, and ferrous ions (Fe2+) chelating activity assays. Moreover, the effects of the propolis extracts on human red blood cell morphology , the selective permeability of their membrane, as well as on free radicals-induced hemolysis were also assessed. Qualitative and quantitative analyses of both propolis extracts indicated that 70% ethanolic extract contained higher amounts of phenolic compounds than 96% ethanolic extract. The levels of antioxidant activity indicated that both Polish propolis extracts exhibited a high and comparable antioxidant power. The concentration of ethanol used for extraction had no effect on the antioxidant potential of propolis. The presented results indicate that the extracts of Polish propolis are rich in phenolic compounds and are very effective as antioxidant agents. Therefore, they may be applied as a constituent of products used in phytotherapy regardless of the concentration of ethanol used in propolis extraction.

New Indices for Ethnotoxicological Assessment of Medicinal Plants: Example of Tafilalet Region, Morocco

Background:

Several botanical species are poisonous and are used for medicinal purposes in traditional medicine. In fact, a relationship between toxicity and phytotherapeutic potential of medicinal plants exists.

Objective:

Until now, there is no ethnopharmacological indices evaluating mathematically the toxic property of any medicinal plant used traditionally. Consequently, it is important to find this link through the establishment and development of novel indices that put into consideration the relationship between toxicity and phytotherapy. Two essential objectives were targeted in the present investigation: firstly, we aimed to establish novel indices which permit researchers to evaluate data obtained in any ethnobotanical survey targeting toxic plants. Secondly, we aimed also to collect data and information about toxic species, mainly those used traditionally for therapeutic purposes in the region of Tafilalet (southeast of Morocco).

Methods:

The total informant interviewed in our study was 1616 (where 1500 were simple local inhabitants and 116 were herbalists). This inquiry was carried out through semi-structured and structured interviews and the sampling technique used was the stratified sample (9 stratums). Data obtained was analyzed using 3 new indices: Degree of Taxonomic Toxicity (DT), Degree of Botanical Families Toxicity (DFT) and Relative Link of Toxicity (RLT).

Results:

47 toxic species belonging to 38 botanical families were quoted in our survey. The highest value of DT was observed for Atractylis gummifera L. (DT=24.67). According to the calculated value of DFT, the most toxic plant family in the region of Tafilalet was Asteraceae (DFT=143.90). Nervous system disorders are the main ailment caused by the toxicity of poisonous species used in the traditional medicine in Tafilalet (RLT=1.44).

Conclusion:

Novel indices established in this investigation (DT, DFT and RLT) have been demonstrated to be useful for interpreting data collected in Tafilalet region and could serve for other ethnopharmacological surveys of toxic medicinal plants.

Structural characterization of a complex triterpenoid saponin from Albizia lebbeck and investigation of its permeability property and supramolecular interactions with membrane constituents

As part of the ongoing efforts in discovering potentially bioactive natural products from medicinal plants, the present study was conducted to isolate a new complex triterpenoid saponin from the barks of Albizia lebbeck. It was isolated by using chromatographic methods and its structural elucidation was performed using detailed analyses of ¹H and ¹³C NMR spectra including 2D-NMR (COSY, TOCSY, HSQC and HMBC) spectroscopic techniques, high-resolution electrospray ionization mass spectrometry (HRESIMS) analysis and chemical conversions. Its structure was established as 21-[[(2E,6S)-6-[6-deoxy-4-O-[(2E,6S)-6-hydroxy-2-(hydroxymethyl)-6-methyl-1-oxo-2,7-octadienyl]-[(β-d-glucopyranosyl)oxy]-2-(hydroxymethyl)-6-methyl-1-oxo-2,7-octadienyl]-[(β-d-glucopyranosyl)oxy]-2,6-dimethyl-1-oxo-2,7-octadienyl]oxy]-16-hydroxy-3-[[O-β-d-xylopyranosyl-(1 → 2)-O-α-l-arabinopyranosyl-(1 → 6)-2-(acetylamino)-2-deoxy-β-d-glucopyranosyl]oxy]-(3β,16α,21β)-olean-12-en-28-oic acid O-α-l-arabinofuranosyl-(1 → 4)-O-[β-d-glucopyranosyl-(1 → 3)]-O-6-deoxy-α-l-mannopyranosyl-(1 → 2)-β-d-glucopyranosyl ester (1). Additionally, this study aimed to investigate the permeability property of 1, its activity on membrane integrity and supramolecular interactions with cellular constituents using in vitro experimental models.

Reactive oxygen species in organ-specific autoimmunity

Reactive oxygen species (ROS) have been extensively studied in the induction of inflammation and tissue damage, especially as it relates to aging. In more recent years, ROS have been implicated in the pathogenesis of autoimmune diseases. Here, ROS accumulation leads to apoptosis and autoantigen structural changes that result in novel specificities. ROS have been implicated not only in the initiation of the autoimmune response but also in its amplification and spreading to novel epitopes, through the unmasking of cryptic determinants. This review will examine the contribution of ROS to the pathogenesis of four organ specific autoimmune diseases (Hashimoto thyroiditis, inflammatory bowel disease, multiple sclerosis, and vitiligo), and compare it to that of a better characterized systemic autoimmune disease (rheumatoid arthritis). It will also discuss tobacco smoking as an environmental factor endowed with both pro-oxidant and anti-oxidant properties, thus capable of differentially modulating the autoimmune response.