Quinoline Alkaloids Research Articles

Synthesis and characterization of chloroquine-modified albumin-binding siRNA-lipid conjugates for improved intracellular delivery and gene silencing in cancer cells.

siRNA therapeutics have considerable potential as molecularly-targeted therapeutics in malignant disease, but identification of effective delivery strategies that mediate rapid intracellular delivery while minimizing toxicity has been challenging. Our group recently developed and optimized an siRNA conjugate platform termed "siRNA-L 2 ," which harnesses non-covalent association with endogenous circulating albumin to extend circulation half-life and achieve tumor-selective delivery without the use of traditional cationic lipids or polymers for transfection. To improve intracellular delivery and particularly the endosomal escape properties of siRNA-L 2 towards more efficient gene silencing, we report synthesis of siRNA-CQ-L 2 conjugates, in which chloroquine (CQ), an endosomolytic quinoline alkaloid, is covalently incorporated into the branching lipid tail structure. We accomplished this via synthesis of a novel CQ phosphoramidite, which can be incorporated into a modular siRNA-L 2 backbone using on-column solid-phase synthesis through use of asymmetric branchers with levulinyl-protected hydroxide groups that allow covalent addition of pendant CQ repeats. We demonstrate that siRNA-CQ-L 2 maintains the ability to non-covalently bind albumin, and with multiple copies of CQ, siRNA-CQ-L 2 mediates higher endosomal disruption, cellular uptake/retention, and reporter gene knockdown in cancer cells. Further, in mice, the addition of CQ did not significantly affect circulation kinetics nor organ biodistribution and did not produce hematologic or organ-level toxicity. Thus, controlled, multivalent conjugation of albumin-binding siRNA-L 2 to endosomolytic small molecule compounds holds promise in improving siRNA-L 2 knockdown potency while maintaining albumin-binding properties and overall safety.

Antimicrobial and anti-acetylcholinesterase activities of secondary metabolites isolated from Aspergillus fumigatus MNY-14

A systematic investigation of the secondary metabolites of Aspergillus fumigatus MNY-14, which was isolated from the ripe leaves of Achyranthes longifolia, led to the isolation of eighteen compounds, including twelve indole diketopiperazine alkaloids (1–12), an α-pyrone meroterpenoid (13), a nortriterpenoid (14), two benzophenones (15–16), and two quinoline alkaloids (17–18). Among them, compounds 8, 17 and 18 were isolated for the first time from A. fumigatus. The chemotaxonomic significance of the secondary metabolites was discussed. Some of the isolates (6, 10, 11, 10, 15 and 16) could be used as chemical markers for strain identification of this fungus. In addition, some of the isolates showed certain antimicrobial and acetylcholinesterase inhibitory activities.

Exploring the Antibacterial and Antibiofilm Efficacy of Psammogeton biternatum Edgew and Identification of a Novel Quinoline Alkaloid using X-ray Crystallography.

The prevalence of resistance to harmful human pathogens is steadily rising, emphasizing the urgent need to identify novel antimicrobial compounds. For this purpose, plants stand out as a significant source of bioactives worthy of exploration. Among these, alkaloids, a vast and structurally diverse category of plant secondary metabolites, have emerged as a foundation for crucial antibacterial medications such as metronidazole and the quinolones. In the current work, the crude methanol leaf extract of Psammogeton biternatum Edgew collected from District Bannu, Pakistan, was subjected to TLC (indirect) bioautography and X-ray crystallography for the isolation of potential antibacterial agents. From the crude extract, a novel quinoline alkaloid called quinoline dione ((3R,3aS,5aR)-3,5a,9-trimethyl-3a,4,5,5a-tetrahydro-2H-isoxazolo[2,3-a] quinoline-2,8(3H)-dione (C14H17NO3)) was isolated. The crystal information (M = 247.296 g/mol) is as follows: orthorhombic, P212121, a = 7.7339(14) Å, b = 10.7254(19) Å, c = 15.730(2) Å, V = 1304.8(4) Å3, Z = 4, T = 296 K, μ(Mo Kα) = 0.088 mm-1, ρ calc = 1.259 g/cm3, 13928 reflections measured (5.86° ≤ 2Θ ≤ 51.98°), 2478 unique (R int = 0.1613, R σ = 0.1335). The final R 1 was 0.1098 (I ≥ 2u(I)), and wR 2 was 0.2183. The antibacterial activity for both crude extract of leaves and quinoline dione was determined by a well diffusion method. The quinoline dione alkaloid demonstrated excellent inhibition zones against methicillin-resistant Staphylococcus aureus (18 mm), Bacillus subtills (17 mm), Escherichia coli (20 mm), and Pseudomonas aeruginosa (23 mm) compared to the crude extract. The antibiofilm potential was recorded against Pseudomonas aeruginosa by the 96-well microtiter plate method. A dose-dependent biofilm inhibition response was recorded, which increased with the increase in concentration. Moreover, quinoline dione showed a greater antibiofilm effect as compared to the crude extract, which may be linked to the presence of a particular active functional group positioned on the compound isolated in its pure form. Through in silico studies, i.e., molecular docking, quinoline dione shows strong binding energies with the LasR transcriptional regulator (6MVN) at -9.3 and LasR transcriptional activator (3IX4) at -9.2 kcal/mol, as well as moderate affinities with other targets such as AHL synthase LasI (PDB ID 1RO5) and OprM channel (PDB ID 3D5K), indicating its potential as a quorum sensing inhibitor. Thus, the antibacterial and antibiofilm potential of quinoline dione was confirmed.

Two-Dimensional Correlation Spectroscopy (2D-COS) Tracking of the Formation of Selected Transition Metal Compounds Cu(II) and Cd(II) With Cinchonine and Their Impact on Model Components of Erythrocytes.

Cinchonine is a quinoline alkaloid known for its antimalarial properties. Due to the advantages of using compounds of metal ions with alkaloids, a copper(II) compound with cinchonine was synthesized, and, for comparative purposes, a cadmium(II) compound with cinchonine. During the synthesis, the emerging interactions between the metal ion and cinchonine were studied. After crystallization, it was examined how the obtained compounds would interact with the model blood component, hematoporphyrin IX. Ultraviolet-visible (UV-Vis) spectroscopy, Raman spectroscopy, and attenuated total reflection Fourier transform infrared spectroscopy (ATR FT-IR) were used in the study. In the case of monitoring the synthesis, the best method turned out to be UV-Vis spectroscopy, combined with the possibility of two-dimensional correlation spectroscopy (2D-COS), which enabled the identification of peaks characteristic of the interactions of the cinchonine quinoline ring with metal ions. In turn, the obtained Raman spectra showed shifts of individual bands and changes in their intensity, and 2D-COS showed the sequence of formation of individual interactions, which confirmed the formation of cinchonine compounds with metals. ATR FT-IR also allowed us to compare the spectra of the substrates used in the synthesis with the crystallized compounds and thus confirm the formation of the expected compounds. Bands characteristic of π-π-stacking interactions between the quinoline ring and the tetrapyrrole ring of hematoporphyrin IX were also observed. Observed interaction with a model blood component may be important when designing drugs for antimalarial therapy.

Stereoisomeric separation and chiral recognition mechanism study of star cyclodextrin polymer as the chiral stationary phase

BackgroundAs the derivatives of cyclodextrin (CD), cyclodextrin polymers (CDPs) effectively increase the concentration of CD units and construct supramolecular structures with unique stereoselectivity by the structure design. CDPs have shown significant potential in chiral separation, however, the process of stereoselective interactions on chiral stationary phases (CSPs) and the specific contribution of intermolecular forces are still a challenge issue. A comprehensive understanding of the chiral recognition mechanism of CDPs will help to optimize chiral separation conditions and design new CSPs. ResultsThe star CDP with a supermolecular structure was synthesized by grafting β-CD onto the external 6-position hydroxyl groups using β-CD as the parent nucleus. The enhanced host-guest recognition ability of CD supramolecular polymer structure provided better inclusion interaction and increased chiral recognition of the isomers. The Star-CD CSP with star CDP as a chiral ligand performed satisfactory stereoisomer separation ability with the separation factor (α) up to 2.0 for various quinoline alkaloid isomers and 1.89 for catechins. To elucidate its chiral separation mechanism, molecular docking was used to construct the three-dimensional visual models of the binding sites and the contribution of non-covalent interactions between Star-CD CSP and quinoline alkaloid isomers. In addition, the formation sites of non-covalent interactions on the CD monomers of the polymer side chains were confirmed from the actual geometric structure by analyzing the NMR chemical shift changes before and after the formation of complexes between Star-CD polymers and isomers. Combined with the mutual evidence of molecular simulation and chiral NMR, the specific recognition mechanism of selector-selectand complexes was comprehensively expounded. SignificanceThe multi-mode CSP based on cyclodextrin supramolecular structure provides new ideas for the stereoisomeric separation of complex chiral components with multiple chiral centers in natural products. Not limited to the macroscopic performance of the chromatographic separation, molecular docking explored the theoretical model of chiral recognition from the molecular level. The chiral NMR analysis confirmed the credibility of the model from the geometry structure, and then the recognition mechanism of multi-mode CSP was fully elaborated combining the above three aspects.

Oxidation of Quinoline Alkaloids Bucharaine, Foliosidine, Evoxine, and Dubinidine by Periodic Acid

Oxidation of Quinoline Alkaloids Bucharaine, Foliosidine, Evoxine, and Dubinidine by Periodic Acid

Pharmacokinetics and Enterohepatic Circulation of 2-(Quinoline-8-carboxamido)benzoic Acid (2-QBA) in Mice.

The quinoline alkaloid 2-(quinoline-8-carboxamido)benzoic acid (2-QBA), which is isolated from Aspergillus sp. SCSIO06786, a deep sea-derived fungus, has been suggested as a therapeutic candidate for the treatment of Parkinson's disease. We developed an analytical method for 2-QBA using a liquid chromatography-tandem mass spectrometry (LC-MS/MS) in mouse plasma, in which a protein precipitation method for the sample preparation of 2-QBA in mouse plasma was used due to its simplicity and good extraction recovery rates (80.49-97.56%). The linearity of the calibration standard sample, inter- and intraday precision and accuracy, and stability of three quality control samples were suitable based on the assessment criteria and the lower limit of quantification (LLOQ) of the 2-QBA was 1 ng/mL. A pharmacokinetic study of 2-QBA was performed in mice divided into oral (2.0, 5.0, and 15 mg/kg) and intravenous (0.5 and 1.0 mg/kg) administration groups. The absolute oral bioavailability (BA) range of 2-QBA was calculated as 68.3-83.7%. Secondary peaks were observed at approximately 4-8 h after the oral administration of 2-QBA at all doses. The elimination half-life of the orally administered 2-QBA was significantly longer than that of the intravenous 2-QBA. In addition, glucuronide metabolites of 2-QBA were identified. They were transformed into 2-QBA using the β-glucuronidase treatment. Furthermore, the 2-QBA was readily absorbed from the jejunum to lower ileum. Taken together, the secondary peaks could be explained by the enterohepatic circulation of 2-QBA. In conclusion, the reabsorption of orally administered 2-QBA could contribute to the high oral BA of 2-QBA and could be beneficial for the efficacy of 2-QBA. Moreover, the simple and validated analytical method for 2-QBA using LC-MS/MS was applied to the pharmacokinetic study and BA assessments of 2-QBA in mice and would be helpful for subsequent pharmacokinetic studies, as well as for evaluations of the toxicokinetics and pharmacokinetic-pharmacodynamic correlation of 2-QBA to assess its potential as a drug.

Harnessing the power of natural alkaloids: the emergent role in epilepsy therapy.

The quest for effective epilepsy treatments has spotlighted natural alkaloids due to their broad neuropharmacological effects. This review provides a comprehensive analysis of the antiseizure properties of various natural compounds, with an emphasis on their mechanisms of action and potential therapeutic benefits. Our findings reveal that bioactive substances such as indole, quinoline, terpenoid, and pyridine alkaloids confer medicinal benefits by modulating synaptic interactions, restoring neuronal balance, and mitigating neuroinflammation-key factors in managing epileptic seizures. Notably, these compounds enhance GABAergic neurotransmission, diminish excitatory glutamatergic activities, particularly at NMDA receptors, and suppress proinflammatory pathways. A significant focus is placed on the strategic use of nanoparticle delivery systems to improve the solubility, stability, and bioavailability of these alkaloids, which helps overcome the challenges associated with crossing the blood-brain barrier (BBB). The review concludes with a prospective outlook on integrating these bioactive substances into epilepsy treatment regimes, advocating for extensive research to confirm their efficacy and safety. Advancing the bioavailability of alkaloids and rigorously assessing their toxicological profiles are essential to fully leverage the therapeutic potential of these compounds in clinical settings.

Integrated metabolomic and transcriptomic analysis reveals the regulatory mechanisms of flavonoid and alkaloid biosynthesis in the new and old leaves of Murraya tetramera Huang

BackgroundMurraya tetramera Huang is a traditional Chinese woody medicine. Its leaves contain flavonoids, alkaloids, and other active compounds, which have anti-inflammatory and analgesic effects, as well as hypoglycemic and lipid-lowering effects, and anti-tumor effects. There are significant differences in the content of flavonoids and alkaloids in leaves during different growth cycles, but the synthesis mechanism is still unclear.ResultsIn April 2021, new leaves (one month old) and old leaves (one and a half years old) of M. tetramera were used as experimental materials to systematically analyze the changes in differentially expressed genes (DEGs) and differentially accumulated metabolites (DAMs) with transcriptomics and metabolomics technology. This was done to identify the signaling pathways of flavonoid and alkaloid synthesis. The results showed that the contents of total alkaloids and flavonoids in old leaves were significantly higher than those in new leaves. Thirteen flavonoid compounds, three isoflavone compounds, and nineteen alkaloid compounds were identified, and 125 and 48 DEGs related to flavonoid and alkaloid synthesis were found, respectively. By constructing the KEGG (Kyoto Encyclopedia of Genes and Genomes) network of DEGs and DAMs, it was shown that the molecular mechanism of flavonoid biosynthesis in M. tetramera mainly focuses on the “flavonoid biosynthetic pathway” and the “flavonoid and flavonol biosynthetic pathway”. Among them, p-Coumaryl alcohol, Sinapyl alcohol, Phloretin, and Isoquercitrin were significantly accumulated in old leaves, the up-regulated expression of CCR (cinnamoyl-CoA reductase) might promote the accumulation of p-Coumaryl alcohol, upregulation of F5H (ferulate-5-hydroxylase) might promote Sinapyl alcohol accumulation. Alkaloids, including indole alkaloids, pyridine alkaloids, imidazole alkaloids, and quinoline alkaloids, were significantly accumulated in old leaves, and a total of 29 genes were associated with these substances.ConclusionsThese data are helpful to better understand the biosynthesis of flavonoids and alkaloids in M. tetramera and provide a scientific basis for the development of medicinal components in M. tetramera.

Correction to “QSAR studies of quinoline alkaloids camptothecin derivatives for prediction anticancer activity using linear and nonlinear methods”

Correction to “<scp>QSAR</scp> studies of quinoline alkaloids camptothecin derivatives for prediction anticancer activity using linear and nonlinear methods”

Room Temperature Phosphorescence from Natural, Organic Emitters and Their Application in Industrially Compostable Programmable Luminescent Tags.

Organic semiconductors provide the potential of biodegradable technologies, but prototypes do only rarely exist. Transparent, ultrathin programmable luminescent tags (PLTs) are presented for minimalistic yet efficient information storage that are fully made from biodegradable or at least industrially compostable, ready-to-use materials (bioPLTs). As natural emitters, the quinoline alkaloids show sufficient room temperature phosphorescence when being embedded in polymer matrices with cinchonine exhibiting superior performance. Polylactic acid provides a solution for both the matrix material and the flexible substrate. Room temperature phosphorescence can be locally controlled by the oxygen concentration in the film by using Exceval as additional oxygen blocking layers. These bioPLTs exhibit all function-defining characteristics also found in their regular nonenvironmentally degradable analogs and, additionally, provide a simplified, high-contrast readout under continuous-wave illumination as a consequence of the unique luminescence properties of the natural emitter cinchonine. Limitations for flexible devices arise from limited thermal stability of the polylactic acid foil used as substrate allowing only for one writing cycle and preventing an annealing step during fabrication. Few-cycle reprogramming is possible when using the architecture of the bioPLTs on regular quartz substrates. This work realizes the versatile platform of PLTs with less harmful materials offering more sustainable use in future.

Structurally Diverse Alkaloids with Anti-Renal-Fibrosis Activity from the Centipede Scolopendra subspinipes mutilans.

Twelve new alkaloids, scolopenolines A-L (1-7, 9-11, 13, 14), along with six known analogues, were isolated from Scolopendra subspinipes mutilans, identified by analysis of spectroscopic data and quantum chemical and computational methods. Scolopenoline A (1), a unique guanidyl-containing C14 quinoline alkaloid, features a 6/6/5 ring backbone. Scolopenoline B (2) is a novel sulfonyl-containing heterodimer comprising quinoline and tyramine moieties. Scolopenoline G (7) presents a rare C12 quinoline skeleton with a 6/6/5 ring system. Alkaloids 1, 8, 10, and 15-18 display anti-inflammatory activity, while 10 and 16-18 also exhibit anti-renal-fibrosis activity. Drug affinity responsive target stability and RNA-interference assays show that Lamp2 might be a potentially important target protein of 16 for anti-renal-fibrosis activity.

A novel polycyclic quinazoline and three quinolines alkaloids from marine-derived fungus trichoderma longibrachiatum QD01 with anti-bacterial and anti-quorum sensing activities

A novel polycyclic quinazoline alkaloid (1) along with one new natural quinoline alkaloid (2) and two known quinoline alkaloids (3,4) were isolated from the marine-derived fungus Trichoderma longibrachiatum QD01. Structural determinations of those isolates were established by comprehensive spectroscopic analyses and literature comparison. Single-crystal X-ray diffraction analysis of novel compound verified its structure and stereochemistry, representing the first characterised crystal structure of a trimeric-type of tetrahydroquinazoline. Compound 4 exhibited potential antibacterial and anti-quorum sensing activity against C. violaceum and C. violaceum CV026. The sub-MIC of 4 observably decreased the violacein production in C. violaceum CV026 by 55% on 15 μg/mL. Furthermore, molecular docking results revealed that 4 has stronger binding interactions with CviR receptor than ligand C6-HSL with lower binding energy of −8.68 kcal/mol. Hydrogen bond and π–π interactions formed by Trp84, Tyr88, Trp111, and Phe126 were predicted to play an important role in the inhibition against C. violaceum CV026.

Two new quinoline alkaloid with neuroprotective activities from Xylaria longipes

Two new quinoline alkaloids with an α, β-unsaturated amide side chain, xylarinines A and B (1 and 2), were isolated from the ethyl acetate extracts of Xylaria longipes solid fermentation. The structures of these were primarily determined though NMR and HRESIMS data analysis. The absolute configuration of compound 1 was assigned using experimental and calculated ECD data. The neuroprotective effects of compounds 1 and 2 against glutamate-induced damage in PC12 cells were evaluated in vitro bioassay. The results demonstrated that both compounds significantly improved cell viability, inhibited apoptosis, decreased malondialdehyde (MDA) levels, increased superoxide dismutase (SOD) and glutathione (GSH) levels, and reduced intracellular reactive oxygen species (ROS) accumulation. These findings suggested that these mechanisms contribute to the neuroprotective effects of the compounds.

A Candidate for Health Promotion, Disease Prevention and Treatment: Common Rue (Ruta graveolens L.), an Important Medicinal Plant in Traditional Medicine.

Ruta graveolens L. belongs to Rutaceae; it is a semi-wood perennial or a small evergreen sub-shrub, which is native to Southern Europe, West Asia and Northern Africa. The goal of this manuscript was to outline the most notable traditional and modern advantages and pharmaceutical benefits of common rue. The manuscript covers review articles, randomized control experiments, analytical studies and observations, which have been gathered from different sources, such as Google Scholar, Scopus, Science Direct and PubMed. A review of the literature was carried out using the keywords rutin, Ruta graveolens L., rue, common rune, coumarin, natural products and pharmaceutical benefits. Rue contains quinoline alkaloids, such as graveoline and graveolinine, acridone alkaloids, such as furacridone and gravacridone, furanoquinoline dictamnine, coumarins, such as gravelliferone, isorutarin, rutacultin, rutaretin, and suberenone, and the furanocoumarins 5-methoxypsoralen (bergapten) and 8-methoxypsoralen (xanthotoxine). Most of its aromatic and medicinal properties are due to the presence of rutin and its essential oil. It has been used in folk medicine as a stimulant, for its antiinflammatory and analgesic properties, anti-androgenic activity, anti-hyperglycemic effects, antihyperlipidemic effects, xanthine oxidase inhibition activity, and anticancer properties. According to pharmacological and phytochemical advantages, pennyroyal shows its importance as a medicinal plant in both modern medicinal science and traditional medicine.

Network pharmacology and invitro experiments reveal sophoridine-induced apoptosis and G1 phase arrest via ROS-dependent PI3K/Akt/FoxO3a pathway activation in human bladder cancer cells.

Bladder cancer (BLCA), a common primary malignancy, exhibits resistance to conventional chemotherapeutic agents. Sophoridine (SR) is a quinoline alkaloid derived from the traditional Chinese herb Sophora alopecuroides L., which belongs to the legume family Sophoraceae. SR is reported to exert growth-inhibitory effects against several cancers. However, the mechanisms underlying the growth-inhibitory effects of SR on BLCA have not been elucidated. This study performed molecular and cellular experiments to verify the growth-inhibitory effects of SR on BLCA and the underlying mechanisms. SR inhibited cell proliferation and promoted apoptosis and G1-phase arrest through the PI3K/AKT/FoxO3a signaling pathway. More interestingly, the effects of SR can be attributed to the accumulation of reactive oxygen species (ROS) invivo. ROS may be the upstream factor of this pathway. Additionally, SR inhibited the migration and invasion of BLCA cells in a concentration-dependent or time-dependent manner. This is the first study to demonstrate the ROS-dependent PI3K/AKT/FoxO3a pathway-mediated anticancer effect of SR and the anticancer mechanism of SR in BLCA. The correlation between SR-induced ROS-dependent cell proliferation inhibition, apoptosis, cell cycle arrest, and PI3K/AKT/FoxO3a suggests that SR is a promising novel therapeutic for BLCA.

Quinoline, Indole, and Isogranatanine Alkaloids from Malayan Leuconotis eugeniifolia.

Nine new alkaloids, eugeniinalines A-H (1-8) and (+)-eburnamenine N-oxide (9), comprising one quinoline, six indole, and two isogranatanine alkaloids, were isolated from the stem-bark extract of the Malayan Leuconotis eugeniifolia. The structures and absolute configurations of these alkaloids were established based on the analysis of the spectroscopic data, GIAO NMR calculations, DP4+ probability analysis, TDDFT-ECD method, and X-ray diffraction analysis. Eugeniinaline A (1) represents a new pentacyclic quinoline alkaloid with a 6/6/5/6/7 ring system. Eugeniinaline G (7) and its seco-derivative, eugeniinaline H (8), were the first isogranatanine alkaloids isolated as natural products. The known alkaloids leucolusine (10) and melokhanine A (11) were found to be the same compound, based on comparison of the spectroscopic data of both compounds, with the absolute configuration of (7R, 20R, 21S). Eugeniinalines A and G (1 and 7) showed cytotoxic activity against the HT-29 cancer cell line with IC50 values of 7.1 and 7.2 μM, respectively.

Two new alkaloids isolated from Dictamnus dasycarpus Turcz

Two new quinoline alkaloids (1–2) together with twenty-two known alkaloids (3–24) were isolated and identified from Dictamnus dasycarpus Turcz. Compounds 6–7, 9, 11, 15–16, 19 and 24 were isolated from D. dasycarpus for the first time. The structures of all compounds were characterised by spectroscopic methods (1D, 2D NMR and HRESIMS). The anti-proliferative activity was mediated by the arrest of three human cancer cell lines (SW982, HepG2 and A549) of all the compounds that were evaluated by CCK-8 assay.

Isolation of Bacterial Endophytes Associated with Cinchona ledgeriana Moens. and Their Potential in Plant-growth Promotion, Antifungal and Quinoline Alkaloids Production.

For centuries, quinoline alkaloids from the tree bark of Cinchona ledgeriana (C. ledgeriana) have been used in the treatment of malaria. However, unsustainable harvesting and poor growth conditions greatly limit its use as raw materials. Since plant endophytes are known to contribute to the physiology of the host and its metabolism for survival, this study showed the potential of endophytes isolated from C. ledgeriana roots in promoting the germination of Catharathus roseus (C. roseus) seedlings and the biosynthesis of quinoline alkaloid. In this present study, we found that the Enterobacteriaceae family comprised the majority of the bacterial community, with Klebsiella pneumoniae being the most abundant species at the C. ledgeriana roots. Characterization of culturable bacterial endophytes from the C. ledgeriana roots showed that all the isolates displayed plant growth-promoting factors and antifungal activities. Interestingly, chromatographic analyses led to the identification of the quinoline alkaloids producing Achromobacter xylosoxidans (A. xylosoxidans) A1. Moreover, the co-cultures of A. xylosoxidans A1, Cytobacillus solani (C. solani) A3, and Klebsiella aerogenes A6 increased the fresh and dry weight of the C. roseus seedlings. These results suggest that these bacterial endophytes may enhance quinine and quinidine production as well as the growth of the plant host.

Nature-derived Alkaloids as a Promising Bioactive Compound in Drug Discovery to Meet Global Leishmania Needs

Background: Natural products have been important resources for potential drug development. Among the many classes of natural products, alkaloids have the most therapeutic applications. Treatment of leishmaniasis by chemical drugs remains a challenge because of toxic side effects, limited efficacy, and drug resistance. This review focuses to embrace all researches on leishmanicidal alkaloids over a specific range of time, with special consideration the molecular mechanism of action, and structure-related activity. Methods: All publications (in English) from Web of Science, PubMed, Science Direct, Scopus, and Google Scholar from 2000-2021 using a variety of keywords such as natural alkaloids, herbal alkaloids, marine alkaloids along with leishmaniasis were included in the present study. In this summary, the focus is mainly on natural alkaloids of plant, mineral, marine origin, etc., which have empirically demonstrated the antileishmanial effect. Results: Fourteen categories of alkaloids with anti-leishmaniasis activity were extracted from the articles. The highest number of alkaloids belonged to isoquinoline, indole, and quinoline alkaloids (21.78%, 20.67%, and 16.48% respectively). This review indicated that the mentioned alkaloids are able to inhibit the proliferation of parasites, the respiratory chain and protein synthesis, arrest the cell cycle, disrupt the mitochondrial membrane integrity, inhibit leishmanial topoisomerase, induce mitochondrial dysfunction, and changes in the parasite morphology. Discussion: The present study highlighted antileishmanial alkaloids that are active against different species of Leishmania in vitro and some of them are also active in visceral and cutaneous leishmaniasis models. However, more clinical studies are needed to clarify the anti-leishmanial activity of alkaloids against leishmania in detail. Conclusion: Among the reported compounds, two main classes of alkaloids including isoquinoline and indole alkaloids cover a wider range of anti-parasitic compounds, and structure-activity relationships (SAR) studies of these molecular skeletons may be good lead compounds and afford the structural clues to develop novel medicines with more selective therapeutic profiles.