Biological activities of nitidine, a potential anti-malarial lead compound

Modulation of hypoxia-inducible factor-1 signaling pathways in cancer angiogenesis, invasion, and metastasis by natural compounds: a comprehensive and critical review

Tumor cells employ multiple signaling mediators to escape the hypoxic condition and trigger angiogenesis and metastasis. As a critical orchestrate of tumorigenic conditions, hypoxia-inducible factor-1 (HIF-1) is responsible for stimulating several target genes and dysregulated pathways in tumor invasion and migration. Therefore, targeting HIF-1 pathway and cross-talked mediators seems to be a novel strategy in cancer prevention and treatment. In recent decades, tremendous efforts have been made to develop multi-targeted therapies to modulate several dysregulated pathways in cancer angiogenesis, invasion, and metastasis. In this line, natural compounds have shown a bright future in combating angiogenic and metastatic conditions. Among the natural secondary metabolites, we have evaluated the critical potential of phenolic compounds, terpenes/terpenoids, alkaloids, sulfur compounds, marine- and microbe-derived agents in the attenuation of HIF-1, and interconnected pathways in fighting tumor-associated angiogenesis and invasion. This is the first comprehensive review on natural constituents as potential regulators of HIF-1 and interconnected pathways against cancer angiogenesis and metastasis. This review aims to reshape the previous strategies in cancer prevention and treatment.

Oplodiol and nitidine as potential inhibitors of Plasmodium falciparum dihydrofolate reductase: insights from a computational study

Many natural products have been shown to possess antiplasmodial activities, but their protein targets are unknown. This work employed molecular docking and molecular dynamics simulations to explore the inhibitory activity of some antiplasmodial natural products against wild-type and mutant strains of Plasmodium falciparum dihydrofolate reductase (PfDHFR). From the molecular docking study, 6 ligands preferentially bind at the active site of the DHFR domain with binding energies ranging from -6.4 to -9.5 kcal/mol. Interactions of compounds with MET55 and PHE58 were mostly observed in the molecular docking study. From the molecular dynamics study, the binding of 2 of the ligands-nitidine and oplodiol-was observed to be stable against all tested strains of PfDHFR. The average binding free energy of oplodiol in complex with the various PfDHFR strains was -93.701 kJ/mol whereas that of nitidine was -106.206 kJ/mol. The impressive in silico activities of the 2 compounds suggest they could be considered for development as potential antifolate agents.Communicated by Ramaswamy H. Sarma.

Activity of the genus Zanthoxylum against diseases caused by protozoa: A systematic review

Neglected diseases (NDs) are treated with a less varied range of drugs, with high cost and toxicity, which makes the search for therapeutic alternatives important. In this context, plants, such as those from the genus Zanthoxylum, can be promising due to active substances in their composition. This study evaluates the potential of species from this genus to treat NDs. Initially, a protocol was developed to carry out a systematic review approved by Prospero (CRD42020200438). The databases PubMed, BVS, Scopus, Science Direct, and Web of Science were used with the following keywords: "zanthoxylum," "xanthoxylums," "fagaras," "leishmaniasis," "chagas disease," "malaria," and "African trypanosomiasis." Two independent evaluators analyzed the title and abstract of 166 articles, and 122 were excluded due to duplicity or for not meeting the inclusion criteria. From the 44 selected articles, results of in vitro/in vivo tests were extracted. In vitro studies showed that Z. rhoifolium, through the alkaloid nitidine, was active against Plasmodium (IC50 <1 μg/ml) and Leishmania (IC50 <8 μg/ml), and selective for both (>10 and >30, respectively). For Chagas disease, the promising species (IC50 <2 μg/ml) were Z. naranjillo and Z. minutiflorum, and for sleeping sickness, the species Z. zanthoxyloides (IC50 <4 μg/ml) stood out. In the in vivo analysis, the most promising species were Z. rhoifolium and Z. chiloperone. In summary, the species Z. rhoifolium, Z. naranjillo, Z. minutiflorum, Z. zanthoxyloides, and Z. chiloperone are promising sources of active molecules for the treatment of NDs.

Nitidine chloride, a benzophenanthridine alkaloid from Zanthoxylum nitidum (Roxb.) DC., exerts multiple beneficial properties, especially in tumors and inflammation-related diseases

Plant-derived alkaloids are a kind of very important natural organic compounds. Nitidine chloride is one of the main active ingredients in Zanthoxylum nitidum (Roxb.) DC. which is a frequently-used Chinese herbal medicine. Z. nitidum has many kinds of efficacy, such as activating blood circulation and removing stasis, promoting qi circulation and relieving pain, and detoxication and detumescence. In China, Z. nitidum is usually used for the treatment of gastrointestinal diseases, toothache, and traumatic injury. At present, there are numerous studies of nitidine chloride with regard to its pharmacology, pharmacokinetics, toxicology, etc. However, a systematic, cutting-edge review of nitidine-related studies is extremely lacking. The present paper aimed at comprehensively summarizing the information on the extraction, separation and purification, pharmacology, pharmacokinetics, toxicology and formulation of nitidine chloride. The knowledge included in the present study were searched from the following academic databases involving Web of Science, PubMed, Google scholar, Elsevier, CNKI and Wanfang Data, till July 2022. In terms of nitidine chloride extraction, enzymatic method and ultrasonic method are recommended. Resin adsorption and chromatography were usually used for the separation and purification of nitidine chloride. Nitidine chloride possesses diversified therapeutical effects, such as anti-tumor, anti-inflammation, anti-colitis, anti-malaria, anti-osteoporosis, anti-rheumatoid and so on. According to pharmacokinetics, the intestinal absorption of nitidine chloride is passive diffusion, and it is rarely excreted with urine and feces in the form of prototype drug. Nitidine chloride has a moderate binding to plasma protein, which is independent of the drug concentration. As to toxicology, nitidine chloride showed certain toxicity on liver, kidney and heart. Certain new formulations, such as nanoparticle, microsphere and nano-micelle, could increase the therapeutic effect and decrease the toxicity of nitidine chloride. Despite limitations such as poor solubility, low bioavailability and certain toxicity, nitidine chloride is still a promising natural alkaloid for drug candidates. Extensive and intensive exploration on nitidine chloride is essential to promote the usage of nitidine-based drugs in the clinic practice.

Potential Focal Adhesion Kinase Inhibitors in Management of Cancer: Therapeutic Opportunities from Herbal Medicine

Focal adhesion kinase (FAK) is a multifunctional protein involved in cellular communication, integrating and transducing extracellular signals from cell-surface membrane receptors. It plays a central role intracellularly and extracellularly within the tumor microenvironment. Perturbations in FAK signaling promote tumor occurrence and development, and studies have revealed its biological behavior in tumor cell proliferation, migration, and adhesion. Herein we provide an overview of the complex biology of the FAK family members and their context-dependent nature. Next, with a focus on cancer, we highlight the activities of FAK signaling in different types of cancer and how knowledge of them is being used for screening natural compounds used in herbal medicine to fight tumor development.

A Review on Synthetic Approaches of Phenanthridine

Abstract:

The phenanthridine family is widely found in medicinal chemistry and material science because of the biological activity and its presence in a variety of significant natural products and synthetic dye stuffs. The phenanthridine has many clinical applications, for e.g., being used as an anticancer agent, possessing antibacterial, antiprotozoal, pharmaceutical, and optoelectronic properties. Many methods have been reported for the synthesis of phenanthridine and phenanthridine alkaloids, such as Pd catalyzed C-C bond formation, a reaction involving C-H activation, radical, microwave-assisted, transition metal-catalyzed, one-pot cascade, benzyne mediated, photochemical, hypervalent iodine promoted methods, etc. Here, we have summarized the literature data from 2014 to the present concerning novel or improved synthetic approaches.

Genus Zanthoxylum as Sources of Drugs for Treatment of Tropical Parasitic Diseases

The tropical parasitic infections account to more than 2 billion infections and cause substantial morbidity and mortality, and accounts to several million deaths every year. Majorly parasitic infections in humans and animals are caused by protozoa and helminths. Chronic infections in host can cause retardation, impairment of cognitive skills, development in young children and weaken the immune system. The burden is felt to a greater extent in developing countries due to poverty, inaccessibility to medicines and resistance observed to drugs. Thus, human health continues to be severely harmed by parasitic infections. Medicinal plants have received much attention as alternative sources of drugs. Zanthoxylum genus has been used ethnobotanically as an antiparasitic agent and the phytoconstituents in Zanthoxylum, show wide variety of chemical substances with proven pharmacological actions such as alkaloids (isoquinolines and quinolines responsible for antitumor activity, antimalarial, antioxidant and antimicrobial actions), lignans, coumarins (antibacterial, antitumour, vasodilatory and anticoagulant activities), alkamide (strong insecticidal properties, anthelminthic, antitussive and analgesic anti antimalarial property). Therefore, this article is an attempt to review the existing literature that emphasizes on potential of genus Zanthoxylum as source of lead compounds for treatment of parasitic diseases.

Biology of quinoline and quinazoline alkaloids

Quinoline and quinazoline alkaloids, two important classes of N-based heterocyclic compounds, have attracted scientific and popular interest worldwide since the 19th century. More than 600 compounds have been isolated from nature to date. To build on our two prior reviews, we reexamined the promising molecules described in previous reports and provided updated literature on novel quinoline and quinazoline alkaloids isolated over the past 5 years. This chapter reviews and discusses 205 molecules with a broad range of bioactivities, including antiparasitic and insecticidal, antibacterial and antifungal, cardioprotective, antiviral, anti-inflammatory, and other effects. This survey should provide new clues or possibilities for the discovery of new and better drugs from the original naturally occurring quinoline and quinazoline alkaloids.

Antimalarial Natural Products

Natural products have made a crucial and unique contribution to human health, and this is especially true in the case of malaria, where the natural products quinine and artemisinin and their derivatives and analogues, have saved millions of lives. The need for new drugs to treat malaria is still urgent, since the most dangerous malaria parasite, Plasmodium falciparum, has become resistant to quinine and most of its derivatives and is becoming resistant to artemisinin and its derivatives. This volume begins with a short history of malaria and follows this with a summary of its biology. It then traces the fascinating history of the discovery of quinine for malaria treatment and then describes quinine's biosynthesis, its mechanism of action, and its clinical use, concluding with a discussion of synthetic antimalarial agents based on quinine's structure. The volume then covers the discovery of artemisinin and its development as the source of the most effective current antimalarial drug, including summaries of its synthesis and biosynthesis, its mechanism of action, and its clinical use and resistance. A short discussion of other clinically used antimalarial natural products leads to a detailed treatment of other natural products with significant antiplasmodial activity, classified by compound type. Although the search for new antimalarial natural products from Nature's combinatorial library is challenging, it is very likely to yield new antimalarial drugs. The chapter thus ends by identifying over ten natural products with development potential as clinical antimalarial agents.

Update and New Insights on Future Cancer Drug Candidates From Plant-Based Alkaloids

Cancer is a complex multifactorial disease that results from alterations in many physiological and biochemical functions. Over the last few decades, it has become clear that cancer cells can acquire multidrug resistance to conventional anticancer drugs, resulting in tumor relapse. Thus, there is a continuous need to discover new and effective anticancer drugs. Natural products from plants have served as a primary source of cancer drugs and continue to provide new plant-derived anticancer drugs. The present review describes plant-based alkaloids, which have been reported as active or potentially active in cancer treatment within the past 4 years (2017-2020), both in preclinical research and/or in clinical trials. In addition, recent insights into the possible molecular mechanism of action of alkaloid prodrugs naturally present in plants are also highlighted.

Synthetic and Naturally Occurring Heterocyclic Anticancer Compounds with Multiple Biological Targets

Cancer is a complex group of diseases initiated by abnormal cell division with the potential of spreading to other parts of the body. The advancement in the discoveries of omics and bio- and cheminformatics has led to the identification of drugs inhibiting putative targets including vascular endothelial growth factor (VEGF) family receptors, fibroblast growth factors (FGF), platelet derived growth factors (PDGF), epidermal growth factor (EGF), thymidine phosphorylase (TP), and neuropeptide Y4 (NY4), amongst others. Drug resistance, systemic toxicity, and drug ineffectiveness for various cancer chemo-treatments are widespread. Due to this, efficient therapeutic agents targeting two or more of the putative targets in different cancer cells are proposed as cutting edge treatments. Heterocyclic compounds, both synthetic and natural products, have, however, contributed immensely to chemotherapeutics for treatments of various diseases, but little is known about such compounds and their multimodal anticancer properties. A compendium of heterocyclic synthetic and natural product multitarget anticancer compounds, their IC50, and biological targets of inhibition are therefore presented in this review.

Natural products targeting cancer cell dependency

Precision cancer medicine is a tailored treatment approach for individual cancer patients with different genomic characteristics. Mutated or hyperactive oncogenes have served as main drug targets in current precision cancer medicine, while defective or inactivated tumor suppressors in general have not been considered as druggable targets. Synthetic lethality is one of very few approaches that enable to target defective tumor suppressors with pharmacological agents. Synthetic lethality exploits cancer cell dependency on a protein or pathway, which arises when the function of a tumor suppressor is defective. This approach has been proven to be effective in clinical settings since the successful clinical introduction of BRCA-PARP synthetic lethality for the treatment of breast and ovarian cancer with defective BRCA. Subsequently, large-scale screenings with RNAi, CRISPR/Cas9-sgRNAs, and chemical libraries have been applied to identify synthetic lethal partners of tumor suppressors. Natural products are an important source for the discovery of pharmacologically active small molecules. However, little effort has been made in the discovery of synthetic lethal small molecules from natural products. This review introduces recent advances in the discovery of natural products targeting cancer cell dependency and discusses potentials of natural products in the precision cancer medicine.

Bio-Guided Fractionation of Stem Bark Extracts from Phyllanthus muellarianus: Identification of Phytocomponents with Anti-Cholinesterase Activity

A combination of flash chromatography, solid phase extraction, high-performance liquid chromatography, and in vitro bioassays was used to isolate phytocomponents endowed with anticholinesterase activity in extract from Phyllanthus muellarianus. Phytocomponents responsible for the anti-cholinesterase activity of subfractions PMF1 and PMF4 were identified and re-assayed to confirm their activity. Magnoflorine was identified as an active phytocomponent from PMF1 while nitidine was isolated from PMF4. Magnoflorine was shown to be a selective inhibitor of human butyrylcholinesterase—hBChE (IC₅₀ = 131 ± 9 μM and IC₅₀ = 1120 ± 83 μM, for hBuChE and human acetylcholinesterase—hAChE, respectively), while nitidine showed comparable inhibitory potencies against both enzymes (IC₅₀ = 6.68 ± 0.13 μM and IC₅₀ = 5.31 ± 0.50 μM, for hBChE and hAChE, respectively). When compared with the commercial anti-Alzheimer drug galanthamine, nitidine was as potent as galanthamine against hAChE and one order of magnitude more potent against hBuChE. Furthermore, nitidine also showed significant, although weak, antiaggregating activity towards amyloid-β self-aggregation.

Photocatalytic xanthate-based radical addition/cyclization reaction sequence toward 2-biphenyl isocyanides: synthesis of 6-alkylated phenanthridines

A photocatalytic xanthate-based radical addition/cyclization reaction cascade toward 2-biphenylisocyanides is described as a practical and modular approach to 6-alkylated phenanthridines. The use of xanthates as radical precursors allowed the synthesis of diversely 6-substituted phenanthridines. Electrophilic radicals derived from nitriles, aromatic and aliphatic ketones, malonates, and amide derivatives, as well as radicals derived from phthalimidomethyl and benzylic derivatives were successfully introduced. The reaction proceeds under mild conditions without a stoichiometric amount of oxidant. Thirty novel phenanthridine scaffolds were synthesized with yields ranging from 24 to 76%.

Targeting X chromosome-linked inhibitor of apoptosis protein in mucoepidermoid carcinoma of the head and neck: A novel therapeutic strategy using nitidine chloride

Nitidine chloride (NC) was recently reported to exhibit a wide range of pharmacological properties for several diseases, including cancer. Here we report for the first time that NC is a potential therapeutic agent for mucoepidermoid carcinoma (MEC) occurring in the head and neck because it suppresses X chromosome-linked inhibitor of apoptosis protein (XIAP) in human MEC in vitro and in vivo. The antitumor effects of NC were evaluated by trypan blue exclusion assay, western blotting, live/dead assay, 4',6-diamidino-2-phenylindole (DAPI) staining, human apoptosis antibody array, immunofluorescence staining, immunohistochemistry, small interfering RNA assay, transient transfection of XIAP overexpression vector, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, and histopathological examination of organs. NC inhibited cell viability and induced caspase-dependent apoptosis in vitro. A human apoptosis antibody array assay showed that XIAP is suppressed by NC treatment. XIAP was overexpressed in oral squamous cell carcinoma (OSCC) tissues that arose from the head and neck, and high XIAP expression was correlated with poor prognosis in OSCC patients. XIAP depletion significantly increased apoptosis, and ectopic XIAP overexpression attenuated the apoptosis induced by NC treatment. NC suppressed tumor growth in vivo at a dosage of 5 mg/kg/day. The number of TUNEL-positive cells increased and the protein expression of XIAP was consistently downregulated in NC-treated tumor tissues. In addition, NC caused no histopathological changes in the liver or kidney. These findings provide new insights into the mechanism of action underlying the anticancer effects of NC and demonstrate that NC is a promising therapeutic agent for the treatment of human MEC of the head and neck. KEY MESSAGES: • Nitidine chloride induces caspase-dependent apoptosis in MEC of the head and neck. • High XIAP expression correlates with poor prognosis of OSCC patients. • Nitidine chloride suppresses tumor growth in vivo without any systemic toxicities. • Targeting XIAP is a novel chemotherapeutic strategy for MEC of the head and neck.

Photocatalyzed syntheses of phenanthrenes and their aza-analogues. A review

Phenanthrenes and their aza-analogues have important applications in materials science and in medicine. Aim of this review is to collect recent reports describing their synthesis, which make use of radical cyclizations promoted by a visible light-triggered photocatalytic process.

Antitumor functions and mechanisms of nitidine chloride in human cancers

Nitidine chloride (NC), a quaternary ammonium alkaloid, exhibits multiple biological activities, including antimalarial, antifungal, and antiangiogenesis. Recently, NC has been characterized to perform antitumor activity in a variety of malignancies. NC has been identified to suppress cell proliferation, stimulate apoptosis, and induce cell cycle arrest, retard migration, invasion and metastasis. Moreover, NC is reported to sensitize cancer cells to chemotherapeutic drugs. In this review article, we describe the functions of NC in human cancers and discuss the molecular insight into NC-involved antitumor feature. This review article will stimulate the deeper investigation for using NC as a potent agent for the management of cancer patients.

Antiplasmodial natural products: an update

Background

Malaria remains a significant public health challenge in regions of the world where it is endemic. An unprecedented decline in malaria incidences was recorded during the last decade due to the availability of effective control interventions, such as the deployment of artemisinin-based combination therapy and insecticide-treated nets. However, according to the World Health Organization, malaria is staging a comeback, in part due to the development of drug resistance. Therefore, there is an urgent need to discover new anti-malarial drugs. This article reviews the literature on natural products with antiplasmodial activity that was reported between 2010 and 2017.

Methods

Relevant literature was sourced by searching the major scientific databases, including Web of Science, ScienceDirect, Scopus, SciFinder, Pubmed, and Google Scholar, using appropriate keyword combinations.

Results and Discussion

A total of 1524 compounds from 397 relevant references, assayed against at least one strain of Plasmodium, were reported in the period under review. Out of these, 39% were described as new natural products, and 29% of the compounds had IC₅₀ ≤ 3.0 µM against at least one strain of Plasmodium. Several of these compounds have the potential to be developed into viable anti-malarial drugs. Also, some of these compounds could play a role in malaria eradication by targeting gametocytes. However, the research into natural products with potential for blocking the transmission of malaria is still in its infancy stage and needs to be vigorously pursued.

Natural Plants Compounds as Modulators of Epithelial-to-Mesenchymal Transition

Epithelial-to-mesenchymal transition (EMT) is a self-regulated physiological process required for tissue repair that, in non-controled conditions may lead to fibrosis, angiogenesis, loss of normal organ function or cancer. Although several molecular pathways involved in EMT regulation have been described, this process does not have any specific treatment. This article introduces a systematic review of effective natural plant compounds and their extract that modulates the pathological EMT or its deleterious effects, through acting on different cellular signal transduction pathways both in vivo and in vitro. Thereby, cryptotanshinone, resveratrol, oxymatrine, ligustrazine, osthole, codonolactone, betanin, tannic acid, gentiopicroside, curcumin, genistein, paeoniflorin, gambogic acid and Cinnamomum cassia extracts inhibit EMT acting on transforming growth factor-β (TGF-β)/Smads signaling pathways. Gedunin, carnosol, celastrol, black rice anthocyanins, Duchesnea indica, cordycepin and Celastrus orbiculatus extract downregulate vimectin, fibronectin and N-cadherin. Sulforaphane, luteolin, celastrol, curcumin, arctigenin inhibit β-catenin signaling pathways. Salvianolic acid-A and plumbagin block oxidative stress, while honokiol, gallic acid, piperlongumine, brusatol and paeoniflorin inhibit EMT transcription factors such as SNAIL, TWIST and ZEB. Plectranthoic acid, resveratrol, genistein, baicalin, polyphyllin I, cairicoside E, luteolin, berberine, nimbolide, curcumin, withaferin-A, jatrophone, ginsenoside-Rb1, honokiol, parthenolide, phoyunnanin-E, epicatechin-3-gallate, gigantol, eupatolide, baicalin and baicalein and nitidine chloride inhibit EMT acting on other signaling pathways (SIRT1, p38 MAPK, NFAT1, SMAD, IL-6, STAT3, AQP5, notch 1, PI3K/Akt, Wnt/β-catenin, NF-κB, FAK/AKT, Hh). Despite the huge amount of preclinical data regarding EMT modulation by the natural compounds of plant, clinical translation is poor. Additionally, this review highlights some relevant examples of clinical trials using natural plant compounds to modulate EMT and its deleterious effects. Overall, this opens up new therapeutic alternatives in cancer, inflammatory and fibrosing diseases through the control of EMT process.

Structurally Simple Phenanthridine Analogues Based on Nitidine and Their Antitumor Activities

A series of novel structurally simple analogues based on nitidine was designed and synthesized in search of potent anticancer agents. The antitumor activity against human cancer cell lines (HepG2, A549, NCI-H460, and CNE1) was performed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay in vitro. The results showed that some of them had good anticancer activities, especially derivatives with a [(dimethylamino)ethyl]amino side chain in the C-6 position. Planar conjugated compounds 15a, 15b, and 15c, with IC₅₀ values of 1.20 μM, 1.87 μM, and 1.19 μM against CNE1 cells, respectively, were more active than nitidine chloride. Compound 15b and compound 15c with IC₅₀ values of 1.19 μM and 1.37 μM against HepG2 cells and A549 cells demonstrated superior activities to nitidine. Besides, compound 5e which had a phenanthridinone core displayed extraordinary cytotoxicity against all test cells, particularly against CNE1 cells with the IC₅₀ value of 1.13 μM.

A ruthenium-catalyzed free amine directed (5+1) annulation of anilines with olefins: diverse synthesis of phenanthridine derivatives

A ruthenium(ii)-catalyzed cross-ring (5+1) annulation between 2-aminobiphenyls and activated olefins is disclosed for succinct synthesis of valuable phenanthridine scaffolds.

Nitidine Chloride Is a Mechanism-Based Inactivator of CYP2D6

Nitidine chloride (NC) is a benzophenanthridine alkaloid isolated from the roots of Zanthoxylum nitidum (Roxb.) DC, a widely used traditional herbal medicine. Several reports have revealed NC's multiple pharmacologic properties. The inhibitory effects of NC on human cytochrome P450 enzymes were investigated in the present study. We found that NC caused time- and concentration-dependent inhibition of CYP2D6, and more than 50% of CYP2D6 activity was suppressed after a 15-minute incubation with NC at 100 μM in the primary incubation mixtures, with K_I of 4.36 μM, k_inact of 0.052 minute^-1, and a partition ratio of approximately 290. Moreover, the loss of CYP2D6 activity required the presence of NADPH. Superoxide dismutase/catalase and glutathione showed minor protection against the NC-induced enzyme inhibition. Quinidine as a competitive inhibitor of CYP2D6 slowed down the inactivation by NC. Trapping experiments using N-acetylcysteine demonstrated that quinone and/or carbene intermediate(s) were/was generated in human liver microsomal incubations with NC. In addition, potassium ferricyanide prevented the enzyme from the inactivation mediated by NC, which provided evidence that inhibition of CYP2D6 resulted from heme destruction by the formation of a carbene-iron complex. CYP1A2 was found to be the major enzyme involved in the generation of NC quinone metabolites. In conclusion, NC is a mechanism-based inactivator of CYP2D6. The generation of a carbene intermediate might be mainly responsible for the enzyme inactivation.

The effects of nitidine chloride and camptothecin on the growth of Babesia and Theileria parasites

The treatment of bovine and equine piroplasmosis is limited to diminazene aceturate (DA) and imidocarb dipropionate. To address this challenge, we need to explore novel drug compounds and targets. Topoisomerases are potential drug targets because they play a vital role in solving topological errors of DNA strands during replication. This study documented the effectiveness of topoisomerase inhibitors, nitidine chloride (NC) and camptothecin (Cpt), on the growth of Babesia and Theileria parasites. The half maximal inhibitory concentrations (IC₅₀s) against B. bovis, B. bigemina, B. caballi, and T. equi were 1.01 ± 0.2, 5.34 ± 1.0, 0.11 ± 0.03, and 2.05 ± 0.4 μM for NC and 11.67 ± 1.6, 4.00 ± 1.0, 2.07 ± 0.6, and 0.33 ± 0.02 μM for Cpt, respectively. The viability experiment revealed that 4, 10, and 4 μM treatments of NC or 48, 8, and 8 μM treatments of Cpt were sufficient to stop the in vitro regrowth of B. bovis, B. bigemina, and B. caballi, respectively. However, T. equi regrew in all of the concentrations used. Moreover, increasing the concentration of NC and Cpt to 16 μM and 1.2 μM (8 × IC₅₀) did not eliminate T. equi. The micrographs of B. bigemina and B. caballi taken at 24 h and 72 h showed deformed merozoites and remnants of parasites within the red blood cell (RBC), respectively. The treatments of 25 mg/kg DA and 20 mg/kg NC administered intraperitoneally and 20 mg/kg NC given orally showed 93.7, 90.7, and 83.6% inhibition against Babesia microti (B. microti), respectively, compared to the untreated group on day 8. In summary, NC and Cpt were effective against Babesia and Theileria parasites in vitro. Moreover, 20 mg/kg NC administered intraperitoneally was as effective as 25 mg/kg DA against B. microti in mice and showed no toxic symptoms in mice. The results indicate that NC may, after further evaluations, prove to be an alternative drug against bovine and equine piroplasmoses.

Medicinal foods and beverages among Maasai agro-pastoralists in northern Tanzania

ETHNOPHARMACOLOGICAL RELEVANCE

Pastoralist Maasai populations of east Africa use several different wild plants as dietary and medicinal additives in beverages (soups and teas), yet little is known about how the plants used and the rationales for use compare and contrast across different Maasai beverages, including how gender specific dietary and health concerns structure patterns of intake.

AIM OF THE STUDY

We investigated three Maasai beverages: almajani (tea or herbal infusion); motorí (traditional soup); and okiti (psychoactive herbal tea). In order to build knowledge about the cultural functions of these Maasai food-medicines and their incidence of use we also investigated use rationales and self-reported frequencies of use. We conclude by examining gender differences and the possible pharmacological antimicrobial activity of the most frequently used plants.

MATERIALS AND METHODS

Research was conducted in 2015, with a population of semi-nomadic agropastoralist Maasai residing in northern Tanzania. Data were collected using key informant interviews, plant collections, n = 32 structured surveys, and n = 40 freelist interviews followed by a literature review to determine the known antimicrobial activity of the most used plants.

RESULTS

We identified 20 plants that Maasai add to soup, 11 in tea, and 11 in the psychoactive tea, for a total of 24 herbal additives. Seven plant species were used in all three Maasai beverages, and these clustered with 10 common ailments. Based on self-reports, women use the beverages less frequently and in smaller amounts than men. There were also several gender differences in the plants that Maasai add to motorí and their associated use rationales.

CONCLUSIONS

There are several intersections concerning the plant species used and their associated rationales for use in almajani, motori, and okiti. Moving outward, Maasai beverages and their additives increasingly involve gender specific concerns. Female use of food-medicines, relative to men, is structured by concerns over pregnancy, birth, and lactation. The frequent consumption of herbal additives, many of which contain antimicrobial compounds, potentially helps modulate infections, but could have other unintentional effects as well.

Biologically active quinoline and quinazoline alkaloids part II

To follow-up on our prior Part I review, this Part II review summarizes and provides updated literature on novel quinoline and quinazoline alkaloids isolated during the period of 2009-2016, together with the biological activity and the mechanisms of action of these classes of natural products. Over 200 molecules with a broad range of biological activities, including antitumor, antiparasitic and insecticidal, antibacterial and antifungal, cardioprotective, antiviral, anti-inflammatory, hepatoprotective, antioxidant, anti-asthma, antitussive, and other activities, are discussed. This survey should provide new clues or possibilities for the discovery of new and better drugs from the original naturally occurring quinoline and quinazoline alkaloids.

Exploring the scope of new arylamino alcohol derivatives: Synthesis, antimalarial evaluation, toxicological studies, and target exploration

Synthesis of new 1-aryl-3-substituted propanol derivatives followed by structure-activity relationship, in silico drug-likeness, cytotoxicity, genotoxicity, in silico metabolism, in silico pharmacophore modeling, and in vivo studies led to the identification of compounds 22 and 23 with significant in vitro antiplasmodial activity against drug sensitive (D6 IC₅₀ ≤ 0.19 μM) and multidrug resistant (FCR-3 IC₅₀ ≤ 0.40 μM and C235 IC₅₀ ≤ 0.28 μM) strains of Plasmodium falciparum. Adequate selectivity index and absence of genotoxicity was also observed. Notably, compound 22 displays excellent parasitemia reduction (98 ± 1%), and complete cure with all treated mice surviving through the entire period with no signs of toxicity. One important factor is the agreement between in vitro potency and in vivo studies. Target exploration was performed; this chemotype series exhibits an alternative antimalarial mechanism.

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New aryl-substituted propanol derivatives (APD) show promising antimalarial activity.

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γ-amino alcohol moiety is significant antimalarial chemotype.

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Compound 22 displays excellent in vivo parasitemia reduction (98%) and complete cure.

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APD are active against drug sensitive and multidrug resistant strains.

Natural products from Zanthoxylum heitzii with potent activity against the malaria parasite

Background

Zanthoxylum heitzii (Rutaceae) (olon) is used in traditional medicine in Central and West Africa to treat malaria. To identify novel compounds with anti-parasitic activity and validate medicinal usage, extracts and compounds isolated from this tree were tested against the erythrocytic stages of the human malaria parasite Plasmodium falciparum and for inhibition of transmission in rodent malaria parasite Plasmodium berghei.

Results

Hexane bark extract showed activity against P. falciparum (IC₅₀ 0.050 μg/ml), while leaf and seed extracts were inactive. Fractionation of the hexane bark extract led to the identification of three active constituents; dihydronitidine, pellitories and heitziquinone. Dihydronitidine was the most active compound with an IC₅₀ value of 0.0089 µg/ml (25 nM). This compound was slow acting, requiring 50 % longer exposure time than standard anti-malarials to reach full efficacy. Heitziquinone and pellitorine were less potent, with IC₅₀ values of 3.55 μg/ml and 1.96 µg/ml, but were fast-acting. Plasmodium berghei ookinete conversion was also inhibited by the hexane extract (IC₅₀ 1.75 µg/ml), dihydronitidine (0.59 µg/ml) and heitziquinone (6.2 µg/ml). Water extracts of Z. heitzii bark contain only low levels of dihydronitidine and show modest anti-parasitic activity.

Conclusions

Three compounds with anti-parasitic activity were identified in Z. heitzii bark extract. The alkaloid dihydronitidine is the most effective of these, accounting for the bulk of activity in both erythrocytic and transmission-blocking assays. These compounds may present good leads for development of novel anti-malarials and add to the understanding of the chemical basis of the anti-parasitic activity in these classes of natural product.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-016-1533-x) contains supplementary material, which is available to authorized users.

Hedgehog pathway is involved in nitidine chloride induced inhibition of epithelial-mesenchymal transition and cancer stem cells-like properties in breast cancer cells

Background

The complications of clinical metastatic disease are responsible for the majority of breast cancer related deaths, and fewer therapies substantially prolong survival. Nitidine chloride (NC), a natural polyphenolic compound, has been shown to exhibit potent anticancer effects in many cancer types, including breast cancer. The epithelial-mesenchymal transition (EMT) and the acquisition of cancer stem cells (CSCs)-like properties emerge as critical steps in the metastasis of human cancers. However, the effects of NC on the EMT and the CSCs-like properties in breast cancer cells, and the underlying molecular mechanisms are not fully understood.

Results

In the present study, MDA-MB-468 and MCF-7 cancer cells were treated with NC. Scratch and Transwell assays were performed to determine whether NC could attenuate the migratory and invasive capability of cancer cells; Mammosphere formation and flow cytometry analysis were performed to confirm that NC decreased CSCs-like phenotype; RT-PCR and western blot analysis were used to examine the expression level of EMT and CSC related markers in both cells. Mechanistically, NC could inhibit the components of Hedgehog pathway (smoothened, patched, Gli1 and Gli2), subsequently inhibited the expression of Snail, Slug and Zeb1, which were correlated with the significant changes of the expression of EMT related markers (N-cadherin, E-cadherin, and Vimentin) to reverse EMT. On the other hand, NC could also inhibit the expression of CSCs related factors such as Nanog, Nestin, Oct-4 and CD44 via Hedgehog pathway. Furthermore, transforming growth factor-β1 (TGF-β1)-induced increment of EMT and CSCs properties could be reversed by NC.

Conclusions

Taken together, these data indicated that NC suppressed breast cancer EMT and CSCs-like properties through inhibiting Hedgehog signaling pathway. Our study suggested that NC may be a potential anticancer agent for breast cancer.

Skeleton selectivity in complexation of chelerythrine and chelerythrine-like natural plant alkaloids with the G-quadruplex formed at the promoter of c-MYC oncogene: in silico exploration

Chelerythrine binds at the 5′ end and arrests the G-quadruplex formed in the promoter region ofc-MYConcogene thus restrict thec-MYCexpression. Position of methoxy group over the core skeleton of chelerythrine determines the binding pattern of ligand.

Neuroprotective effects of nitidine in Parkinson's disease models through inhibiting microglia activation: role of the Jak2–Stat3 pathway

In this work we found that nitidine could significantly suppress microglial activationviathe Jak2–Stat3 pathway and obviously improve behavioural function in Parkinson's disease (PD) animal models, which sheds light on PD treatment.

Novel agent nitidine chloride induces erythroid differentiation and apoptosis in CML cells through c-Myc-miRNAs axis

The proto-oncogene c-Myc plays critical roles in human malignancies including chronic myeloid leukemia (CML), suggesting that the discovery of specific agents targeting c-Myc would be extremely valuable for CML treatment. Nitidine Chloride (NC), a natural bioactive alkaloid, is suggested to possess anti-tumor effects. However, the function of NC in leukemia and the underlying molecular mechanisms have not been established. In this study, we found that NC induced erythroid differentiation, accompanied by increased expression of erythroid differentiation markers, e. g. α-, ε-, γ-globin, CD235a, CD71 and α-hemoglobin stabilizing protein (AHSP) in CML cells. We also observed that NC induced apoptosis and upregulated cleaved caspase-3 and Parp-1 in K562 cells. These effects were associated with concomitant attenuation of c-Myc. Our study showed that NC treatment in CML cells enhanced phosphorylation of Thr58 residue and subsequently accelerated degradation of c-Myc. A specific group of miRNAs, which had been reported to be activated by c-Myc, mediated biological functions of c-Myc. We found that most of these miRNAs, especially miR-17 and miR-20a showed strong decrement after NC treatment or c-Myc interference. Furthermore, overexpression of c-Myc or miR-17/20a alleviated NC induced differentiation and apoptosis in K562 cells. More importantly, NC enhanced the effects of imatinib in K562 and primary CML cells. We further found that even imatinib resistant CML cell line (K562/G01) and CML primary cells exhibited high sensitivity to NC, which showed potential possibility to overcome imatinib resistance. Taken together, our results clearly suggested that NC promoted erythroid differentiation and apoptosis through c-Myc-miRNAs regulatory axis, providing potential possibility to overcome imatinib resistance.

Protease activated receptor-2 (PAR2): possible target of phytochemicals

The use of phytochemicals either singly or in combination with other anticancer drugs comes with an advantage of less toxicity and minimal side effects. Signaling pathways play central role in cell cycle, cell growth, metabolism, etc. Thus, the identification of phytochemicals with promising antagonistic effect on the receptor/s playing key role in single transduction may have better therapeutic application. With this background, phytochemicals were screened against protease-activated receptor 2 (PAR2). PAR2 belongs to the superfamily of GPCRs and is an important target for breast cancer. Using in silico methods, this study was able to identify the phytochemicals with promising binding affinity suggesting their therapeutic potential in the treatment of breast cancer. The findings from this study acquires importance as the information on the possible agonists and antagonists of PAR2 is limited due its unique mechanism of activation.

Nitidine chloride induces apoptosis, cell cycle arrest, and synergistic cytotoxicity with doxorubicin in breast cancer cells

Medicinal plant extracts have been widely used for cancer treatment. Nitidine chloride (NC) is a natural bioactive alkaloid that has recently been reported to have diverse anticancer properties. We aimed to investigate the cytotoxic effects of NC and the effectiveness of combinatorial treatment including NC and doxorubicin in breast cancer cells. Using MTT and flowcytometry assays, we found that NC induced cell growth inhibition and G2/M cell cycle arrest in a time- and dose-dependent manner both in MCF-7 and MDA-MB-231 breast cancer cell lines. Cancer cell growth inhibition was associated with increased levels of the p53 and p21 proteins. Apoptosis induction by NC treatment was confirmed by JC-1 mitochondrial membrane potential, annexin V-positive cell, and TUNEL staining. Using western blot analysis, we found that NC upregulated the pro-apoptotic proteins Bax, cleaved caspase-9 and -3 and cleaved PARP and that it downregulated the anti-apoptotic proteins Bcl-2 and PARP. By using the PI3K/Akt inhibitor LY294002, we further demonstrated that NC-induced apoptosis might be Akt-specific or dependent. In addition, NC exhibited a synergistic effect with doxorubicin on the growth inhibition of the human breast cancer cell lines MCF-7 and MDA-MB-231. Our study demonstrated the anticancer effect of NC on breast cancer and highlighted the potential clinical application of NC.