Isoquinoline alkaloids isolated from Glaucium corniculatum var. corniculatum and Glaucium grandiflorum subsp. refractum var. torquatum with bioactivity studies

CONTEXT

The genus Glaucium Mill., one of the important Papaveraceae family plants, is rich in isoquinoline alkaloids and distributed worldwide.

OBJECTIVE

Isolation and identification of bioactive alkaloids from Glaucium grandiflorum Boiss. & Huet. subsp. refractum (Nabelek) Mory var. torquatum (Cullen) Mory and G. corniculatum (L.) Rudolph var. corniculatum (Aslan 2012), and investigation of their antioxidant and anticholinesterase activities.

MATERIALS AND METHODS

The aerial parts of each plant were dried, powdered, and percolated with methanol, then each extract was fractionated between 50% aqueous acetic acid and petroleum. Their aqueous acidic layer was adjusted to pH 7-8 with NH₄OH and extracted with chloroform, the extract was subjected to CC separation and isolation. Structures of the isolated alkaloids were elucidated by 1D and 2D-NMR and mass spectral analyses. The alkaloid extracts and their pure alkaloids were tested for anti-cholinesterase (AChE and BuChE) and antioxidant (ABTS, CUPRAC, β-carotene linoleic acid tests) activities in vitro.

RESULTS

Methanol extracts of Glaucium grandiflorum subsp. refractum var. torquatum and G. corniculatum var. corniculatum afforded a novel compound glauciumoline and seven known isoquinoline alkaloids three of which have an aporphine-type and the other five have a protopine-type skeleton. Among them, trans-protopinium (7) and cis-protopinium (8) were isolated from a Glaucium species for the first time. Tertiary amine extracts (TAEs) of both plants showed very strong acetylcholinesterase inhibitory activity. The TAE of the plants also showed strong antioxidant activity while the isolated alkaloids showed no meaningful activity in the anticholinesterase and antioxidant tests.

DISCUSSION AND CONCLUSIONS

Glaucium species are considered promising therapeutic agents in the treatment of Alzheimer's disease.

Molecular Mechanism Analysis of Protopine Against Triple Negative Breast Cancer

In this study, we utilized a pharmacological network and bioinformatics approach to investigate the molecular mechanism underlying the resistance of Protopine (PRO) against Triple Negative Breast Cancer (TNBC). To uncover the underlying mechanism of PRO, we employed network pharmacology analysis. We collected and enriched targets using various databases such as TCMSP, SwissTargetPrediction, PubChem, Genecards, and DAVID. Furthermore, we constructed Potential targets network and components-disease-core targets network by STRING 11.5 and Cytoscape 3.7.1 to investigate the association of targets of PRO with disease targets of TNBC. The results of the network pharmacology approach indicated that PRO may play a key role in protein phosphorylation, protein autophosphorylation, Progesterone-mediated oocyte maturation signaling pathway, PI3K-Akt signaling pathway, and acting as targets such as PRKACA, JAK2, CDK2, LRRK2, CCNE1, KDR, JAK1. Our findings suggest that PRO exerts its effects against TNBC through multi-channel and multi-target mechanisms. Therefore, this study provides a basis for further research on the mechanism of action of PRO.

Protopine Alleviates Dextran Sodium Sulfate-Induced Ulcerative Colitis by Improving Intestinal Barrier Function and Regulating Intestinal Microbiota

Ulcerative colitis (UC) is an inflammatory bowel disease (IBD), and its pathogenesis is related to intestinal mucosal barrier damage and gut microbiota imbalance. Protopine (PRO), an isoquinoline alkaloid, is one of the main anti-inflammatory ingredients of traditional Chinese medicine Macleaya cordata(Willd.) R. Br. This study investigated the effects of PRO on the intestinal mucosal barrier and gut microbiota in dextran sodium sulfate (DSS)-induced colitis mice. C57BL/6J mice were treated with 3% DSS in drinking water to induce acute colitis, while PRO was administered orally once daily for 7 days. The results showed that PRO administration significantly alleviated the symptoms of DSS-induced colitis in mice and inhibited the expression of inflammation-related genes. In addition, PRO restored the integrity of the intestinal barrier in colitis mice by restoring colonic mucin secretion and promoting the expression of tight junction proteins. Furthermore, PRO alleviated the DSS-induced gut microbiota dysbiosis by decreasing the abundance of Proteobacteria, Escherichia-Shigella and Enterococcus, as well as enhancing the abundance of beneficial bacteria, such as Firmicutes and Akkermansia. These findings suggested that PRO effectively alleviated DSS-induced ulcerative colitis by suppressing the expression of inflammation-related genes, maintaining the intestinal mucosal barrier and regulating the intestinal microbiota.

Computational Evaluation of N-Based Transannular Interactions in Some Model Fused Medium-Sized Heterocyclic Systems and Implications for Drug Design

As part of a project on fused medium-sized ring systems as potential drugs, we have previously demonstrated the usefulness of Density Functional Theory (DFT) to evaluate amine nitrogen-based transannular interactions across the central 10-membered ring in the bioactive dibenzazecine alkaloid, protopine. A range of related hypothetical systems have been investigated, together with transannular interactions involving ring-embedded imino or azo group nitrogens and atoms or groups (Y) across the ring. Electrostatic potential energies mapped onto electron density surfaces in the different ring conformations were evaluated in order to characterise these conformations. Unexpectedly, the presence of sp² hybridised nitrogen atoms in the medium-sized rings did not influence the conformations appreciably. The strength and type of the N^…Y interactions are determined primarily by the nature of Y. This is also the case when the substituent on the interacting nitrogen is varied from CH₃ (protopine) to H or OH. With Y = BOH, very strong interactions were observed in protopine analogues, as well as in rings incorporating imino or azo groups. Strong to moderate interactions were observed with Y = CS, CO and SO in all ring systems. Weaker interactions were observed with Y = S, O and weaker ones again with an sp³ hybridised carbon (Y = CH₂). The transannular interactions can influence conformational preferencing and shape and change electron distributions at key sites, which theoretically could modify properties of the molecules while providing new or enhanced sites for biological target interactions, such as the H or OH substituent. The prediction of new strong transannular interaction types such as with Y = BOH and CS should be helpful in informing priorities for synthesis and other experimental studies.

Placental Passage of Protopine in an Ex Vivo Human Perfusion System

The placental passage of protopine was investigated with a human ex vivo placental perfusion model. The model was first validated with diazepam and citalopram, 2 compounds known to cross the placental barrier, and antipyrine as a positive control. All compounds were quantified by partially validated U(H)PLC-MS/MS bioanalytical methods. Protopine was transferred from the maternal to the fetal circuit, with a steady-state reached after 90 min. The study compound did not affect placental viability or functionality, as glucose consumption, lactate production, and beta-human chorionic gonadotropin, and leptin release remained constant. Histopathological evaluation of all placental specimens showed unremarkable, age-appropriate parenchymal maturation with no pathologic findings.

Protopine alleviates lipopolysaccharide-triggered intestinal epithelial cell injury through retarding the NLRP3 and NF-κB signaling pathways to reduce inflammation and oxidative stress

BACKGROUND

Inflammatory bowel disease (IBD) is a common chronic intestinal disease. Protopine isolated from different plants has been investigated to understand its special functions on varied diseases. However, the regulatory effects of protopine on the progression of IBD remain unclear. Our study is aimed to explore the effects of protopine on the progression of IBD and its underlying regulatory mechanism of action.

METHODS

The cell viability was assessed through MTT colorimetric assay. The protein expressions of genes were examined by Western blot analysis. The cell apoptosis and reactive oxygen species level were measured using flow cytometry. The levels of inflammation and oxidative stress-related proteins were tested through enzyme-linked-immunosorbent serologic assay. The intracellular Ca²⁺ concentration and mitochondrial membrane potential were measured through immunofluorescence assay.

RESULTS

First, different concentrations of lipopolysaccharide (LPS) were treated with NCM460 cells to establish IBD cell model, and 5-μg/mL LPS was chosen for followed experiments. In this study, we discovered that protopine relieved the LPS-induced inhibited intestinal epithelial cell viability and enhanced cell apoptosis. Moreover, protopine attenuated LPS-stimulated inflammation activation and oxidative stress. Further experiments illustrated that the increased intracellular Ca²⁺ concentration and decreased mitochondrial membrane potential stimulated by LPS were reversed by protopine treatment. Finally, through Western blot analysis, it was demonstrated that protopine retarded the activated NLR family pyrin domain containing 3 (NLRP3) and nuclear factor kappa B (NF-κB) signaling pathways mediated by LPS.

CONCLUSION

Protopine alleviated LPS-triggered intestinal epithelial cell injury by inhibiting NLRP3 and NF-κB signaling pathways to reduce inflammation and oxidative stress. This discovery may provide a useful drug for treating IBD.

Effectiveness of Volatile Natural Deep Eutectic Solvents (VNADESs) for the Green Extraction of Chelidonium majus Isoquinoline Alkaloids

The Chelidonium majus plant is rich in biologically active isoquinoline alkaloids. These alkaline polar compounds are isolated from raw materials with the use of acidified water or methanol; next, after alkalisation of the extract, they are extracted using chloroform or dichloromethane. This procedure requires the use of toxic solvents. The present study assessed the possibility of using volatile natural deep eutectic solvents (VNADESs) for the efficient and environmentally friendly extraction of Chelidonium alkaloids. The roots and herb of the plant were subjected three times to extraction with various menthol, thymol, and camphor mixtures and with water and methanol (acidified and nonacidified). It has been shown that alkaloids can be efficiently isolated using menthol–camphor and menthol–thymol mixtures. In comparison with the extraction with acidified methanol, the use of appropriate VNADESs formulations yielded higher amounts of protopine (by 16%), chelidonine (35%), berberine (76%), chelerythrine (12%), and coptisine (180%). Sanguinarine extraction efficiency was at the same level. Additionally, the values of the contact angles of the raw materials treated with the tested solvents were assessed, and higher wetting dynamics were observed in the case of VNADESs when compared with water. These results suggest that VNADESs can be used for the efficient and environmentally friendly extraction of Chelidonium alkaloids.

Identification and Quantification, Metabolism and Pharmacokinetics, Pharmacological Activities, and Botanical Preparations of Protopine: A Review

Through pharmacological activity research, an increasing number of natural products and their derivatives are being recognized for their therapeutic value. In recent years, studies have been conducted on Corydalis yanhusuo W.T. Wang, a valuable medicinal herb listed in the Chinese Pharmacopoeia. Protopine, one of its components, has also become a research hotspot. To illustrate the identification, metabolism, and broad pharmacological activity of protopine and the botanical preparations containing it for further scientific studies and clinical applications, an in-depth and detailed review of protopine is required. We collected data on the identification and quantification, metabolism and pharmacokinetics, pharmacological activities, and botanical preparations of protopine from 1986 to 2021 from the PubMed database using “protopine” as a keyword. It has been shown that protopine as an active ingredient of many botanical preparations can be rapidly screened and quantified by a large number of methods (such as the LC-ESI-MS/MS and the TLC/GC-MS), and the possible metabolic pathways of protopine in vivo have been proposed. In addition, protopine possesses a wide range of pharmacological activities such as anti-inflammatory, anti-platelet aggregation, anti-cancer, analgesic, vasodilatory, anticholinesterase, anti-addictive, anticonvulsant, antipathogenic, antioxidant, hepatoprotective, neuroprotective, and cytotoxic and anti-proliferative activities. In this paper, the identification and quantification, metabolism and pharmacokinetics, pharmacological activities, and botanical preparations of protopine are reviewed in detail to lay a foundation for further scientific research and clinical applications of protopine.

Br.-A Bioactivity Guided Approach

Macleaya cordata (Willd.) R. Br. (M. cordata) is a perennial herb known for its chemotherapeutic properties, strong feeding additive, and potential antidiarrheal drug. Despite its therapeutic potentials, its clinical applications are hindered by an apparent lack of toxicity data. In this study, the toxic ingredients of this plant were investigated using a bioactivity-guided approach. Two compounds, protopine and allocryptopine, were purified and elucidated by LC-MS, ¹H-NMR, and ¹³C-NMR. Protopine, a primary component in M. cordata, had an LD₅₀ of 313.10 mg/kg i.e., which was considered toxic. An autopsy was performed on protopine-administered mice, and the histopathology of the kidney, liver, brain, heart, lung, and spleen was determined. Autopsy findings included hemorrhage in the respiratory system, lung congestion, and hemorrhage and edema in the parenchymatous organs (heart, liver, kidney, and brain). Histopathology confirmed the pathological changes in the brain, liver, and kidney. Protopine is one of the principal bioactive constituents of many phytopreparations used in veterinary and human medicine, such as Sangrovit and Iberogast. Our findings indicated that phytopreparations containing protopine might pose a serious health threat to humans and animals.

Screening Papaveraceae as Novel Antibiofilm Natural-Based Agents

The antimicrobial properties of herbs from Papaveraceae have been used in medicine for centuries. Nevertheless, mutual relationships between the individual bioactive substances contained in these plants remain poorly elucidated. In this work, phytochemical composition of extracts from the aerial and underground parts of five Papaveraceae species (Chelidonium majus L., Corydalis cava (L.) Schweigg. and Körte, C. cheilanthifolia Hemsl., C. pumila (Host) Rchb., and Fumaria vaillantii Loisel.) were examined using LC-ESI-MS/MS with a triple quadrupole analyzer. Large differences in the quality and quantity of all analyzed compounds were observed between species of different genera and also within one genus. Two groups of metabolites predominated in the phytochemical profiles. These were isoquinoline alkaloids and, in smaller amounts, non-phenolic carboxylic acids and phenolic compounds. In aerial and underground parts, 22 and 20 compounds were detected, respectively. These included: seven isoquinoline alkaloids: protopine, allocryptopine, coptisine, berberine, chelidonine, sanguinarine, and chelerythrine; five of their derivatives as well as non-alkaloids: malic acid, trans-aconitic acid, quinic acid, salicylic acid, trans-caffeic acid, p-coumaric acid, chlorogenic acid, quercetin, and kaempferol; and vanillin. The aerial parts were much richer in phenolic compounds regardless of the plant species. Characterized extracts were studied for their antimicrobial potential against planktonic and biofilm-producing cells of S. aureus, P. aeruginosa, and C. albicans. The impact of the extracts on cellular metabolic activity and biofilm biomass production was evaluated. Moreover, the antimicrobial activity of the extracts introduced to the polymeric carrier made of bacterial cellulose was assessed. Extracts of C. cheilanthifolia were found to be the most effective against all tested human pathogens. Multiple regression tests indicated a high antimicrobial impact of quercetin in extracts of aerial parts against planktonic cells of S. aureus, P. aeruginosa, and C. albicans, and no direct correlation between the composition of other bioactive substances and the results of antimicrobial activity were found. Conclusively, further investigations are required to identify the relations between recognized and unrecognized compounds within extracts and their biological properties.

Protopine/Gemcitabine Combination Induces Cytotoxic or Cytoprotective Effects in Cell Type-Specific and Dose-Dependent Manner on Human Cancer and Normal Cells

The natural alkaloid protopine (PRO) exhibits pharmacological properties including anticancer activity. We investigated the effects of PRO, alone and in combination with the chemotherapeutic gemcitabine (GEM), on human tumor cell lines and non-tumor human dermal fibroblasts (HDFs). We found that treatments with different PRO/GEM combinations were cytotoxic or cytoprotective, depending on concentration and cell type. PRO/GEM decreased viability in pancreatic cancer MIA PaCa-2 and PANC-1 cells, while it rescued the GEM-induced viability decline in HDFs and in tumor MCF-7 cells. Moreover, PRO/GEM decreased G1, S and G2/M phases, concomitantly with an increase of subG1 phase in MIA PaCa-2 and PANC-1 cells. Differently, PRO/GEM restored the normal progression of the cell cycle, altered by GEM, and decreased cell death in HDFs. PRO alone increased mitochondrial reactive oxygen species (ROS) in MIA PaCa-2, PANC-1 cells and HDFs, while PRO/GEM increased both intracellular and mitochondrial ROS in the three cell lines. These results indicate that specific combinations of PRO/GEM may be used to induce cytotoxic effects in pancreatic tumor MIA PaCa-2 and PANC-1 cells, but have cytoprotective or no effects in HDFs.

Phytochemical Composition and Antimicrobial Activity of Corydalis solida and Pseudofumaria lutea

Corydalis and Pseudofumaria are two closely related genera from the Papaveraceae subfamily Fumarioideae with Corydalis solida (C. solida) and Pseudofumaria lutea (P. lutea) as two representative species. Phytochemical analysis revealed significant differences in the quality and quantity of isoquinoline alkaloids, phenolic compounds and non-phenolic carboxylic acids between aerial and underground parts of both species. Using the Liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) technique, 21 compounds were identified: five protoberberine derivatives, three protopine derivatives, four phenanthridine derivatives, as well as three carboxylic acids, two hydroxycinnamic acids, one chlorogenic acid, one phenolic aldehyde, and two flavonoids. Moroever, significant differences in the content of individual compounds were observed between the two studied species. The phytochemical profile of C. solida showed a higher variety of compounds that were present in lower amounts, whereas P. lutea extracts contained fewer compounds but in larger quantities. Protopine was one of the most abundant constituents in C. solida (440-1125 µg/g d.w.) and in P. lutea (1036-1934 µg/g d.w.). Moreover, considerable amounts of coptisine (1526 µg/g) and quercetin (3247 µg/g) were detected in the aerial parts of P. lutea. Extracts from aerial and underground parts of both species were also examined for the antimicrobial potential against S. aureus, P. aeruginosa and C. albicans. P. lutea herb extract was the most effective (MIC at 0.39 mg/L) against all three pathogens.

Protopine Protects Mice against LPS-Induced Acute Kidney Injury by Inhibiting Apoptosis and Inflammation via the TLR4 Signaling Pathway

Corydalis humosa Migo is a traditional Chinese medicine that clears away damp heat, relieves sore. Protopine (PRO) is an alkaloid component isolated from C. humosa Migo. However, the role of protopine in acute kidney injury (AKI) has not yet been reported. This study aims to investigate the effect and mechanism of protopine isolated from C. humosa Migo on lipopolysaccharide (LPS)-induced AKI in mice. Inflammation accumulation was assessed by small animal living imaging. The blood urea nitrogen (BUN), and serum creatinine (Scr) were measured to assess the effects of protopine on renal function in LPS-induced AKI. The levels of tumor necrosis factor (TNF), interleukin-2 (IL-2), interferon-γ (IFN-γ), and (interleukin-10) IL-10 in serum were detected by cytometric bead array. Flow cytometry was used to detect the levels of reactive oxygen species (ROS) in primary kidney cells. The proportions of granulocytes, neutrophils, and macrophages in peripheral blood were examined to evaluate the effect of protopine on immune cells in mice with AKI. Toll-like receptor (TLR4) and apoptotic signaling pathway were detected by Western blot analysis. The results showed that protopine markedly improved the renal function, relieve inflammation, reversed inflammatory cytokines, transformed apoptosis markers, and regulated the TLR4 signaling pathway in mice with AKI induced by LPS. The protopine isolated from C.humosa Migo protected mice against LPS-induced AKI by inhibiting apoptosis and inflammation via the TLR4 signaling pathway, thus providing a molecular basis for a novel medical treatment of AKI.

Protopine isolated from Nandina domestica induces apoptosis and autophagy in colon cancer cells by stabilizing p53

The tumor suppressor p53 plays essential roles in cellular protection mechanisms against a variety of stress stimuli and its activation induces apoptosis or autophagy in certain cancer cells. Here, we identified protopine, an isoquinoline alkaloid isolated from Nandina domestica, as an activator of the p53 pathway from cell-based natural compound screening based on p53-responsive transcription. Protopine increased the p53-mediated transcriptional activity and promoted p53 phosphorylation at the Ser15 residue, resulting in stabilization of p53 protein. Moreover, protopine up-regulated the expression of p21^WAF1/CIP1 and BAX, downstream genes of p53, and inhibited the proliferation of HCT116 colon cancer cells. Apoptosis was elicited by protopine as indicated by caspase-3/7 activation, poly ADP ribose polymerase cleavage, and increased population of Annexin V-FITC-positive cells. Furthermore, protopine induced the formation of microtubule-associated protein 1 light chain 3 (LC3) puncta and LC3-II turnover, typical biochemical markers of autophagy, in HCT116 cells. Our findings suggest that protopine exerts its antiproliferative activity by stimulating the p53 pathway and may have potential as a chemopreventive agent for human colon cancer.

Confirming therapeutic target of protopine using immobilized β2 -adrenoceptor coupled with site-directed molecular docking and the target-drug interaction by frontal analysis and injection amount-dependent method

Drug-protein interaction analysis is pregnant in designing new leads during drug discovery. We prepared the stationary phase containing immobilized β₂ -adrenoceptor (β₂ -AR) by linkage of the receptor on macroporous silica gel surface through N,N'-carbonyldiimidazole method. The stationary phase was applied in identifying antiasthmatic target of protopine guided by the prediction of site-directed molecular docking. Subsequent application of immobilized β₂ -AR in exploring the binding of protopine to the receptor was realized by frontal analysis and injection amount-dependent method. The association constants of protopine to β₂ -AR by the 2 methods were (1.00 ± 0.06) × 10⁵ M^-1 and (1.52 ± 0.14) × 10⁴ M^-1 . The numbers of binding sites were (1.23 ± 0.07) × 10^-7 M and (9.09 ± 0.06) × 10^-7 M, respectively. These results indicated that β₂ -AR is the specific target for therapeutic action of protopine in vivo. The target-drug binding occurred on Ser¹⁶⁹ in crystal structure of the receptor. Compared with frontal analysis, injection amount-dependent method is advantageous to drug saving, improvement of sampling efficiency, and performing speed. It has grave potential in high-throughput drug-receptor interaction analysis.

Intestinal anti-inflammatory effects of total alkaloid extract from Fumaria capreolata in the DNBS model of mice colitis and intestinal epithelial CMT93 cells

BACKGROUND

Fumaria capreolata L. (Papaveraceae) is a botanical drug used in North Africa for its gastro-intestinal and anti-inflammatory properties. It is characterized for the presence of several alkaloids that could be responsible for some of its effects, including an immunomodulatory activity.

PURPOSE

To test in vivo the intestinal anti-inflammatory properties of the total alkaloid fraction extracted from the aerial parts of F. capreolata (AFC), and to evaluate its effects on an intestinal epithelial cell line.

STUDY DESIGN AND METHODS

AFC was chemically characterized by liquid chromatography coupled to diode array detection and high resolution mass spectrometry. Different doses of AFC (25, 50 and 100mg/kg) were assayed in the DNBS model of experimental colitis in mice, and the colonic damage was evaluated both histologically and biochemically. In addition, in vitro experiments were performed with this alkaloid fraction on the mouse intestinal epithelial cell line CMT93 stimulated with LPS.

RESULTS

The chemical analysis of AFC revealed the presence of 23 alkaloids, being the most abundants stylopine, protopine and coptisine. Oral administration of AFC produced a significant inhibition of the release and the expression of IL-6 and TNF-α in the colonic tissue. It also suppressed in vivo the transcription of other pro-inflammatory mediators such as IL-1β, iNOS, IL-12 and IL-17. Furthermore, AFC showed an immunomodulatory effect in vitro since it was able to inhibit the mRNA expression of IL-6, TNF-α and ICAM-1. Moreover, the beneficial effect of AFC in the colitic mice could also be associated with the normalization of the expression of MUC-2 and ZO-1, which are important for the intestinal epithelial integrity.

CONCLUSION

The present study suggests that AFC, containing 1.3% of stylopine and 0.9% of protopine, significantly exerted intestinal anti-inflammatory effects in an experimental model of mouse colitis. This fact could be related to a modulation of the intestinal immune response and a restoration of the intestinal epithelial function.

The Interference of Selected Cytotoxic Alkaloids with the Cytoskeleton: An Insight into Their Modes of Action

Alkaloids, the largest group among the nitrogen-containing secondary metabolites of plants, usually interact with several molecular targets. In this study, we provide evidence that six cytotoxic alkaloids (sanguinarine, chelerythrine, chelidonine, noscapine, protopine, homoharringtonine), which are known to affect neuroreceptors, protein biosynthesis and nucleic acids, also interact with the cellular cytoskeleton, such as microtubules and actin filaments, as well. Sanguinarine, chelerythrine and chelidonine depolymerized the microtubule network in living cancer cells (Hela cells and human osteosarcoma U2OS cells) and inhibited tubulin polymerization in vitro with IC50 values of 48.41 ± 3.73, 206.39 ± 4.20 and 34.51 ± 9.47 μM, respectively. However, sanguinarine and chelerythrine did not arrest the cell cycle while 2.5 μM chelidonine arrested the cell cycle in the G₂/M phase with 88.27% ± 0.99% of the cells in this phase. Noscapine and protopine apparently affected microtubule structures in living cells without affecting tubulin polymerization in vitro, which led to cell cycle arrest in the G2/M phase, promoting this cell population to 73.42% ± 8.31% and 54.35% ± 11.26% at a concentration of 80 μM and 250.9 μM, respectively. Homoharringtonine did not show any effects on microtubules and cell cycle, while the known microtubule-stabilizing agent paclitaxel was found to inhibit tubulin polymerization in the presence of MAPs in vitro with an IC50 value of 38.19 ± 3.33 μM. Concerning actin filaments, sanguinarine, chelerythrine and chelidonine exhibited a certain effect on the cellular actin filament network by reducing the mass of actin filaments. The interactions of these cytotoxic alkaloids with microtubules and actin filaments present new insights into their molecular modes of action.

In Vivo Anticonvulsant Activity of Extracts and Protopine from the Fumaria schleicheri Herb

The present study aimed to investigate the role of several biologically active compounds from Fumaria schleicheri Soy.-Will. in anticonvulsant models. The flavonoid fraction, alkaloid fraction, individual alkaloid protopine, and polysaccharide-protein complex were isolated from the Fumaria schleicheri herb and studied along with Fumaria schleicheri dry extract in mice with pentylenetetrazole-induced seizures. According to empirical results, the expressed anticonvulsant effect of Fumaria schleicheri dry extract depends on the synergism of biologically active compounds in herbal medicine, although some individual substances (mostly protopine and the protein-polysaccharide fraction) have shown moderate anti-seizure activity.

Electrophysiological effects of protopine in cardiac myocytes: inhibition of multiple cation channel currents

Protopine (Pro) from Corydalis tubers has been shown to have multiple actions on cardiovascular system, including anti-arrhythmic, anti-hypertensive and negative inotropic effects. Although it was thought that Pro exerts its actions through blocking Ca(2+) currents, the electrophysiological profile of Pro is unclear. The aim of this study is to elucidate the ionic mechanisms of Pro effects in the heart. In single isolated ventricular myocytes from guinea-pig, extracellular application of Pro markedly and reversibly abbreviates action potential duration, and decreases the rate of upstroke (dV/dt)(max), amplitude and overshoot of action potential in a dose-dependent manner. Additionally, it produces a slight, but significant hyperpolarization of the resting membrane potential. Pro at 25, 50 and 100 microM reduces L-type Ca(2+) current (I(Ca,L)) amplitude to 89.1, 61.9 and 45.8% of control, respectively, and significantly slows the decay kinetics of I(Ca,L) at higher concentration. The steady state inactivation of I(Ca,L) is shifted negatively by 5.9 - 7.0 mV (at 50 - 100 microM Pro), whereas the voltage-dependent activation of I(Ca,L) remains unchanged. In contrast, Pro at 100 microM has no evident effects on T-type Ca(2+) current (I(Ca,T)). In the presence of Pro, both the inward rectifier (I(K1)) and delayed rectifier (I(K)) potassium currents are variably inhibited, depending on Pro concentrations. Sodium current (I(Na)), recorded in low [Na(+)](o) (40 mM) solution, is more potently suppressed by Pro. At 25 microM, Pro significantly attenuated I(Na) at most of the test voltages (-60 approximately +40 mV, with a 53% reduction at -30 mV. Thus, Pro is not a selective Ca(2+) channel antagonist. Rather, it acts as a promiscuous inhibitor of cation channel currents including I(Ca,L), I(K), I(K1) as well as I(Na). These findings may provide some mechanistic explanations for the therapeutic actions of Pro in the heart.