Lunacridine from Lunasia amara is a DNA intercalating topoisomerase II inhibitor

Quinoline Derivatives as Promising Scaffolds for Antitubercular Activity: A Comprehensive Review

BACKGROUND

Heterocyclic compounds and their derivatives play a significant role in the design and development of novel quinoline drugs. Among the various pharmacologically active heterocyclic compounds, quinolines stand out as the most significant rings due to their broad pharmacological roles, specifically antitubercular activity, and their presence in plant-based compounds. Quinoline is also known as benzpyridine, benzopyridine, and 1-azanaphthalene. It has a benzene ring fused with a pyridine ring, and both rings share two carbon atoms. The importance of quinoline lies in its incorporation as a key component in various natural compounds found in medicinal plant families like Fumariaceae, Berberidaceae, Rutaceae, Papavaraceae, and others.

OBJECTIVE

This article is expected to have a significant impact on the advancement of effective antitubercular drugs. Through harnessing the potent activity of quinoline derivatives, the research aims to make valuable contributions to combating tuberculosis more efficiently and ultimately reducing the global burden of this infectious disease.

METHODS

Numerous nitrogen-containing heterocyclic compounds exhibit significant potential as antitubercular agents. These chemicals have fused aromatic nitrogen-heterocyclic nuclei that can change the number of electrons they have, which can change their chemical, physical, and biological properties. This versatility comes from their ability to bind with the receptors in multiple modes, a critical aspect of drug pharmacological screening. Among these compounds, quinoline stands out as it incorporates a stable fusion of a benzene ring with a pyridine nucleus. Quinolines have demonstrated a diverse range of pharmacological activities, including but not limited to anti-tubercular, anti-tumor, anticoagulant, anti-inflammatory, antioxidant, antiviral, antimalarial, anti-HIV, and antimicrobial effects.

RESULTS

Some molecules, such as lone-paired nitrogen species, include pyrrole, pyrazole, and quinoline. These molecules contain nitrogen and take part in metabolic reactions with other molecules inside the cell. However, an excessive accumulation of reactive nitrogen species can lead to cytotoxicity, resulting in damage to essential biological macromolecules. Among these compounds, quinoline stands out as the oldest and most effective one, exhibiting a wide range of significant properties such as antitubercular, antimicrobial, anti-inflammatory, antioxidant, analgesic, and anticonvulsant activities. Notably, naturally occurring quinoline compounds, such as quinine, have proven to be potent antimalarial drugs.

CONCLUSION

This review highlights quinoline derivatives' antitubercular potential, emphasizing recent research advancements. Utilizing IC50 values, the study emphasizes the efficacy of various quinoline substitutions, hybrids, and electron-withdrawing groups against MTB H37Rv. Continued research is essential for developing potent, low-toxicity quinoline derivatives to combat tuberculosis.

Coumarin hybrid derivatives as promising leads to treat tuberculosis: Recent developments and critical aspects of structural design to exhibit anti-tubercular activity

Tuberculosis (TB) is a highly contagious airborne disease with nearly 25% of the world's population infected with it. Challenges such as multi drug resistant TB (MDR-TB), extensive drug resistant TB (XDR-TB) and in rare cases totally drug resistant TB (TDR-TB) emphasizes the critical and urgent need in developing novel TB drugs. Moreover, the prolonged and multi drug treatment regime suffers a major drawback due to high toxicity and vulnerability in TB patients. This calls for intensified research efforts in identifying novel molecular scaffolds which can combat these issues with minimal side effects. In this pursuit, researchers have screened many bio-active molecules among which coumarin have been identified as promising candidates for TB drug discovery and development. Coumarins are naturally occurring compounds known for their low toxicity and varied biological activity. The biological spectrum of coumarin has intrigued medicinal researchers to investigate coumarin scaffolds for their relevance as anti-TB drugs. In this review we focus on the recent developments of coumarin and its critical aspects of structural design required to exhibit anti-tubercular (anti-TB) activity. The information provided will help medicinal chemists to design and identify newer molecular analogs for TB treatment and also broadens the scope of exploring future generation potent yet safer coumarin based anti-TB agents.

Analysis of plant-derived phytochemicals as anti-cancer agents targeting cyclin dependent kinase-2, human topoisomerase IIa and vascular endothelial growth factor receptor-2

Cancer is caused by a variety of pathways, involving numerous types of enzymes. Among them three enzymes i.e. Cyclin-dependent kinase-2 (CDK-2), Human topoisomerase IIα, and Vascular Endothelial Growth Factor Receptor-2 (VEGFR-2) are three of the most common enzymes that are involved in the cancer development. Although many chemical drugs are already available in the market for cancer treatment, plant sources are known to contain a wide variety of agents that are proved to possess potential anticancer activity. In this experiment, total thirty phytochemicals were analyzed against the mentioned three enzymes using different tools of bioinformatics and in silico biology like molecular docking study, drug likeness property experiment, ADME/T test, PASS prediction, and P450 site of metabolism prediction as well as DFT calculation to determine the three best ligands among them that have the capability to inhibit the mentioned enzymes. From the experiment, Epigallocatechin gallate was found to be the best ligand to inhibit CDK-2, Daidzein showed the best inhibitory activities towards the Human topoisomerase IIα, and Quercetin was predicted to be the best agent against VEGFR-2. They were also predicted to be quite safe and effective agents to treat cancer. However, more in vivo and in vitro analyses are required to finally confirm their safety and efficacy in this regard.

Competitive DNA binding of Ru(bpy)2dppz2+ enantiomers studied with isothermal titration calorimetry (ITC) using a direct and general binding isotherm algorithm

While isothermal titration calorimetry (ITC) is widely used and sometimes referred to as the "gold standard" for quantitative measurements of biomolecular interactions, its usage has so far been limited to the analysis of the binding to isolated, non-cooperative binding sites. Studies on more complicated systems, where the binding sites interact, causing either cooperativity or anti-cooperativity between neighboring bound ligands, are rare, probably due to the complexity of the methods currently available. Here we have developed a simple algorithm not limited by the complexity of a binding system, meaning that it can be implemented by anyone, from analyzing systems of simple, isolated binding sites to complicated interactive multiple-site systems. We demonstrate here that even complicated competitive binding calorimetric isotherms can be properly analyzed, provided that ligand-ligand interactions are taken into account. As a practical example, the competitive binding interactions between the two enantiomers of Ru(bpy)₂dppz²⁺ (Ru-bpy) and poly(dAdT)₂ (AT-DNA) are analyzed using our new algorithm, which provided an excellent global fit for the ITC experimental data.

Synthesis, identification and in vitro biological evaluation of some novel quinoline incorporated 1,3-thiazinan-4-one derivatives

The present study describes the synthesis of two new series of 3-hydroxy-N-(4-oxo-2-phenyl-1,3-thiazinan-3-yl)-8-(trifluoromethyl)quinoline-2-carboxamide derivatives (4a-j) and 3-((7-chloroquinolin-4-ylamino)methyl)-2-phenyl-1,3-thiazinan-4-one derivatives (5a-7j). All the compounds were synthesized in moderate to good yield by one-pot three component cyclo-condensation reaction. The newly synthesized compounds were characterized by FT-IR, ¹H, ¹³C NMR and elemental analysis. The compounds were screened for their in vitro antibacterial activity against a panel of pathogenic bacterial strains, antitubercular activity against Mycobacterium tuberculosis H₃₇Rv and also for their in vitro antimalarial activity against Plasmodium falciparum. Among the synthesized compounds two of them (4f and 5f) showed excellent antibacterial activity against C. tetani at 15.6μg/mL. Some of them exhibited excellent antitubercular (4f &5f) and good antimalarial (4f, 5f &6f) activity compared with the first line drugs.

DMPPQA, a novel angiogenesis inhibitor, induces apoptosis in human colon cancer HCT-116 cells and HUVECs

Cytotoxic activity of 5,7-dimethoxy-2-phenyl-N-propylquinolin-4-amine (DMPPQA) was investigated in human colon cancer cells HCT-116 and umbilical vein endothelial cell line HUVEC. The IC(50) of DMPPQA on HCT-116 and HUVEC cells were respectively 1.26 and 7.43 µM after 72 h treatment. DMPPQA inhibited the growth of HCT-116 and HUVEC cells in concentration- and time-dependent manners. Typical morphological changes of apoptotic body formation were seen after DMPPQA with Hoechst 33258 staining. FCM analysis showed that DMPPQA induced apoptosis, mitochondrial membrane potential loss (ΔΨm) and increase in the production of intracellular reactive oxygen species (ROS) of HCT-116 cells. After treating with DMPPQA, apoptosis-related protein expression of Bax, cytochrome c, caspase-9, caspase-3, PARP-1 and P53 increased and Bcl-2 protein expression decreased. DMPPQA treatment of HUVECs reduced cell migration and microcapillary tube formation in a Matrigel matrix. It also decreased VEGF protein expression. Thus DMPPQA acts as an angiogenesis inhibitor and induces cell apoptosis by a caspase-dependent mitochondrial pathway.

Mechanism-based CYP2D6 inactivation by acridone alkaloids of Indonesian medicinal plant Lunasia amara

Fourteen acridone alkaloids isolated from Lunasia amara Blanco were tested for their mechanism-based inhibition on human liver microsomal dextromethorphan O-demethylation activity, a prototype marker for cytochrome P450 2D6 (CYP2D6). Among the 14 compounds, 5-hydroxygraveroline (1), 8-methoxyifflaiamine (2), lunamarine (3), and lunine (12) increased their inhibitory activity with increasing preincubation time. Then, we further examined the possibility of mechanism-based inhibition on 5-hydroxygraveroline (1) and lunamarine (3), which showed the potent inhibition. Further investigations on 1 and 3 showed that the characteristic time- and concentration-dependent inhibition, which required a catalytic step with NADPH, was not protected by nucleophiles, and was decreased by the presence of a competitive inhibitor. Thus, 1 and 3 were concluded as mechanism-based inactivators of CYP2D6.

Comparative ethnobotany and in-the-field antibacterial testing of medicinal plants used by the Bulu and inland Kaulong of Papua New Guinea

ETHNOPHARMACOLOGICAL RELEVANCE

The island of New Britain in Papua New Guinea is an area of great floristic and cultural diversity that has received little attention from ethnobotanists. Here we present the results of a comparative medicinal ethnobotanical survey of the Bulu and inland Kaulong; two distinct people groups inhabiting lowland rainforest on different sides of the island. A high proportion of species are used in the treatment of bacterial infections and plants with antibacterial activity were identified in the field using a specially developed antibacterial assay kit. Follow up testing with human pathogens was used to evaluate active plant material in more detail.

MATERIALS AND METHODS

Rapid appraisal techniques were used to survey both people groups with all data corroborated by three or more separate sources. Plants from both groups were tested in-the-field with a portable antibacterial test kit based on the agar diffusion assay, using a pressure cooker to sterilise glassware and media. Follow up laboratory based tests were carried out using standardised agar dilution protocols for drug resistant and drug sensitive strains of Staphylococcus aureus and Streptococcus pneumoniae.

RESULTS

We find surprisingly little overlap in the plant species used by the two people groups with only 1 out of 70 species used for the same purpose. There is also a difference in emphasis in the conditions treated with 53% of Kaulong medicinal plants dedicated to treating tropical ulcers compared with only 8% of in the Bulu group. In-the-field testing identified Garcinia dulcis bark (a Kaulong tropical ulcer treatment) to have antibacterial activity and follow up tests against a drug resistant strain of Staphylococcus aureus (a pathogen implicated in tropical ulcer pathogenesis) revealed the crude bark extract to be potently active with an MIC of just 1 mg/ml.

CONCLUSIONS

The results demonstrate extreme differences in medicinal plant use between two people groups living a mere 100 km apart and suggests the two medicinal plant systems have developed in isolation from one another. In-the-field antibacterial testing of plant extracts was found to be a valuable technique that enabled early identification of active plant material.

Secondary metabolites as DNA topoisomerase inhibitors: A new era towards designing of anticancer drugs

A large number of secondary metabolites like alkaloids, terpenoids, polyphenols and quinones are produced by the plants. These metabolites can be utilized as natural medicines for the reason that they inhibit the activity of DNA topoisomerase which are the clinical targets for anticancer drugs. DNA topoisomerases are the cellular enzymes that change the topological state of DNA through the breaking and rejoining of DNA strands. Synthetic drugs as inhibitors of topoisomerases have been developed and used in the clinical trials but severe side effects are a serious problem for them therefore, there is a need for the development of novel plant-derived natural drugs and their analogs which may serve as appropriate inhibitors with respect to drug designing. The theme for this review is how secondary metabolites or natural products inactivate the action of DNA topoisomerases and open new avenues towards isolation and characterization of compounds for the development of novel drugs with anticancer potential.

Quinoline alkaloids as intercalative topoisomerase inhibitors

Quinoline alkaloids are abundant in the Rutaceae, and many have exhibited cytotoxic activity. Because structurally related antitumor alkaloids such as camptothecin and fagaronine are known to function as intercalative topoisomerase poisons, it is hypothesized that cytotoxic Stauranthus alkaloids may also serve as intercalative topoisomerase inhibitors. To test this hypothesis theoretically, ten Stauranthus quinoline alkaloids were examined for potential intercalation into DNA using a molecular docking approach. Four of the alkaloids (stauranthine, skimmianine, 3',6'-dihydroxy-3',6'-dihydrostauranthine, and trans-3',4'-dihydroxy-3',4'-dihydrostauranthine) were able to intercalatively dock consistently into DNA. In order to probe the intermolecular interactions that may be responsible for intercalation of these quinoline alkaloids, density functional calculations have been carried out using both the B3LYP and M06 functionals. M06 calculations indicated favorable pi-pi interactions between either skimmianine or stauranthine and the guanine-cytosine base pair. Furthermore, the lowest-energy face-to-face orientation of stauranthine with guanine is consistent with favorable dipole-dipole orientations, favorable electrostatic interactions, and favorable frontier molecular orbital interactions. Likewise, the lowest-energy face-to-face orientation of stauranthine with the guanine-cytosine base pair reveals favorable electrostatic interactions as well as frontier molecular orbital interactions. Thus, not only can quinoline alkaloids dock intercalatively into DNA, but the docked orientations are also electronically favorable.

4-Amino-3-acetylquinoline-induced apoptosis of murine L1210 leukemia cells involves ROS-mitochondrial-mediated death signaling and activation of p38 MAPK

Quinolines are known to be multitarget agents with a broad spectrum of biological activity. In a previous study, we showed that newly prepared 4-amino-3-acetylquinoline (AAQ) possesses strong anticancer activities. In this study, we investigated whether AAQ has cytotoxicity in murine L1210 leukemia cells. Results from cell proliferation assays showed that AAQ caused significant decrease in cell number in a dose-dependent manner. The cell death induced by AAQ appeared to involve apoptosis, based on evidence from apoptotic DNA fragmentation, flow cytometry, fluorescence microscopy, and Western blot analyses. We found that AAQ-treated cells had activated p38 MAPK and that apoptosis was processed through a reactive oxygen species (ROS)-dependent mitochondrial pathway. In summary, our results suggest that AAQ can induce apoptosis, at least in part, through the activation of the p38 MAPK pathway in L1210 leukemia cells.