Structure-Activity Relationships of Synthetic Coumarins as HIV-1 Inhibitors

Furanocoumarins promote proteasomal degradation of viral HBx protein and down-regulate cccDNA transcription and replication of hepatitis B virus

Nucleot(s)ide analogues, the current antiviral treatments against chronic hepatitis B (CHB) infection, are non-curative due to their inability to eliminate covalently closed circular DNA (cccDNA) from the infected hepatocytes. Preclinical studies have shown that coumarin derivatives can effectively reduce the HBV DNA replication. We evaluated the antiviral efficacy of thirty new coumarin derivatives in cell culture models for studying HBV. Furanocoumarins Fc-20 and Fc-31 suppressed the levels of pre-genomic RNA as well as cccDNA, and reduced the secretion of virions, HBsAg and HBeAg. The antiviral efficacies of Fc-20 and Fc31 improved further when used in combination with the hepatitis B antiviral drug Entecavir. There was a marked reduction in the intracellular HBx level in the presence of these furanocoumarins due to proteasomal degradation resulting in the down-regulation of HBx-dependent viral genes. Importantly, both Fc-20 and Fc-31 were non-cytotoxic to cells even at high concentrations. Further, our molecular docking studies confirmed a moderate to high affinity interaction between furanocoumarins and viral HBx via residues Ala3, Arg26 and Lys140. These data suggest that furanocoumarins could be developed as a new therapeutic for CHB infection.

Biological evaluation of the novel 3,3'-((4-nitrophenyl)methylene)bis(4-hydroxy-2H-chromen-2-one) derivative as potential anticancer agents via the selective induction of reactive oxygen species-mediated apoptosis

Selective initiation of programmed cell death in cancer cells than normal cells is reflected as an attractive chemotherapeutic strategy. In the current study, a series of synthetic bis-coumarin derivatives were synthesized possessing reactive oxygen species (ROS) modulating functional groups and examined in four cancerous and two normal cell lines for their cytotoxic ability using MTT assay. Among these compounds, 3 l emerged as the most promising derivative in persuading apoptosis in human renal carcinoma cells (SKRC-45) among diverse cancer cell lines. 3 l causes significantly less cytotoxicity to normal kidney cells compared to cisplatin. This compound was able to induce apoptosis and cell-cycle arrest by modulating the p53 mediated apoptotic pathways via the generation of ROS, decreasing mitochondrial membrane potential, and causing DNA fragmentation. Unlike cisplatin, the 3 l derivative was found to inhibit the nuclear localisation of NF-κB in SKRC-45 cells. It was also found to reduce the proliferation, survival and migration ability of SKRC-45 cells by downregulating COX-2/ PTGES2 cascade and MMP-2. In an in vivo tumor model, 3 l showed an anticancer effect by reducing the mean tumor mass, volume and inducing caspase-3 activation, without affecting kidney function. Further studies are needed to establish 3 l as a promising anti-cancer drug candidate.

Polymeric surfactants as ideal substitutes for sustainable corrosion protection: A perspective on colloidal and interface properties

Surfactants are well known for their colloidal and corrosion inhibition potential (CIP) due to their strong propensity to interact with metallic surfaces. However, because of their small molecular size and the fact that they are only effective at relatively high concentrations, their application in aqueous phase corrosion inhibition is often restricted. Polymeric surfactants, a unique class of corrosion inhibitors, hold the potential to eradicate the challenges associated with using surfactants in corrosion inhibition. They strongly bond with the metallic surface and offer superior CIP because of their macromolecular polymeric structure and abundance of polar functional groups. In contrast to conventional polymeric corrosion inhibitors, the inclusion of polar functional groups also aids in their solubilization in the majority of popular industry-based electrolytes. Some of the major functional groups present in polymeric surfactants used in corrosion mitigation include O (ether), glycidyl (cyclic ether), -CONH2 (amide), -COOR (ester), -SO3H (sulfonic acid), -COOH (carboxyl), -NH2 (amino), - + NR3/- + NHR2/- + NH2R/- + NH3 (quaternary ammonium), -OH (hydroxyl), -CH2OH (hydroxymethyl), etc. The current viewpoint offers state-of-the-art information on polymer surfactants as newly developing ideal alternatives for conventional corrosion inhibitors. The industrial scale-up, colloidal, coordination, adsorption properties, and structural requirements of polymer surfactants have also been established based on the knowledge obtained from the literature. Finally, the challenges, drawbacks, and potential benefits of using polymer surfactants have also been discussed.

Novel Fluorescent Benzothiazolyl-Coumarin Hybrids as Anti-SARS-COVID-2 Agents Supported by Molecular Docking Studies: Design, Synthesis, X-ray Crystal Structures, DFT, and TD-DFT/PCM Calculations

This study revealed the design and preparation of new 3-(benzo[d]thiazol-2-yl)-2H-chromen-2-one derivatives 9a-h. The structures of the synthesized products were elucidated by their spectroscopic data and X-ray crystallography for compounds 9a and 9d. The prepared new compounds were measured for their fluorescence, and a good result indicated that the emission efficiency was decreased by increasing the electron-withdrawing groups from the unsubstituted compound 9a to the highly substituted derivative 9h (2 Br heavy atoms). On the other hand, the B3LYP/6-311G** theoretical level of theory was used to optimize the quantum mechanical calculations of the geometrical characteristics and energy of the novel compounds 9a-h under study. The electronic transition was investigated using the TD-DFT/PCM B3LYP approach, which uses time-dependent density functional calculations. Moreover, the compounds exhibited nonlinear optical properties (NLO) and a small HOMO-LUMO energy gap, which makes them easy to polarize. Furthermore, the acquired infrared spectra were compared with the expected harmonic vibrations of the substances 9a-h. On the other hand, binding energy analyses of compounds 9a-h with human corona virus nucleocapsid protein Nl63 (PDB ID: 5epw) were predicted using molecular docking and virtual screening tools. The results showed a promising binding and how these potent compounds were inhibiting the COVID-19 virus. Compound 9h was the most active anti-COVID-19 agent among all the synthesized benzothiazolyl-coumarin derivatives, as it forms five bonds. The presence of the two bromine atoms in its structure was responsible for the potent activity.

Recent advances in synthesis of sugar and nucleoside coumarin conjugates and their biological impact

Naturally occurring coumarin and sugar molecules have a diverse range of applications along with superior biocompatibility. Coumarin, a member of the benzopyrone family, exhibits a wide spectrum of medicinal properties, such as anti-coagulant, anti-bacterial, anti-tumor, anti-oxidant, anti-cancer, anti-inflammatory and anti-viral activities. The sugar moiety functions as the central scaffold for the synthesis of complex molecules, attributing to their excellent biocompatibility, well-defined stereochemistry, benign nature and outstanding aqueous solubility. When the coumarin moiety is conjugated with the sugar or nucleoside molecule, the resulting conjugates exhibit significant biological properties. Due to the remarkable growth of such bioconjugates in the field of science over the last decade, owing to their future prospect as a potential bioactive core, an update to this area is very much needed. The present review focusses on the synthesis, characterization and the various therapeutic applications of coumarin conjugates, i.e., sugar and nucleoside coumarin conjugates along with their perspective for future research.

Plant Coumarins with Anti-HIV Activity: Isolation and Mechanisms of Action

This review summarizes and systematizes the literature on the anti-HIV activity of plant coumarins with emphasis on isolation and the mechanism of their antiviral action. This review summarizes the information on the anti-HIV properties of simple coumarins as well as annulated furano- and pyranocoumarins and shows that coumarins of plant origin can act by several mechanisms: inhibition of HIV reverse transcriptase and integrase, inhibition of cellular factors that regulate HIV-1 replication, and transmission of viral particles from infected macrophages to healthy ones. It is important to note that some pyranocoumarins are able to act through several mechanisms or bind to several sites, which ensures the resistance of these compounds to HIV mutations. Here we review the last two decades of research on the anti-HIV activity of naturally occurring coumarins.

Immunostimulants for shrimp aquaculture: paving pathway towards shrimp sustainability

At present, food security is a matter of debate of global magnitude and fulfilling the feeding requirement of > 8 billion human populations by 2030 is one of the major concerns of the globe. Aquaculture plays a significant role to meet the global food requirement. Shrimp species such as Litopenaeus vannamei, Penaeus monodon, and Macrobrachium rosenbergii are among the most popular food commodities worldwide. As per Global Outlook for Aquaculture Leadership survey, disease outbreaks have been a matter of concern from the past many decades regarding the shrimp aquaculture production. Among the past disease outbreaks, white spot disease caused by the white spot syndrome virus is considered to be one of the most devastating ones that caused colossal losses to the shrimp industry. Since the virus is highly contagious, it spreads gregariously among the shrimp population; hence, practicing proper sanitization practices is crucial in order to have disease-free shrimps. Additionally, in order to control the disease, antibiotics were used that further leads to bioaccumulation and biomagnification of antibiotics in several food webs. The bioaccumulation of the toxic residues in the food webs further adversely affected human too. Recently, immunostimulants/antivirals were used as an alternative to antibiotics. They were found to enhance the immune system of shrimps in eco-friendly manner. In context to this, the present paper presents a critical review on the immunostimulants available from plants, animals, and chemicals against WSSV in shrimps. Looking into this scenario, maintaining proper sanitation procedures in conjunction with the employment of immunostimulants may be a viable approach for preserving shrimp aquaculture across the globe.

Corrosion mitigation for steel in acid environment using novel p-phenylenediamine and benzidine coumarin derivatives: synthesis, electrochemical, computational and SRB biological resistivity

Three novel p-phenylenediamine and benzidine coumarin derivatives were synthetized, namely: 4,4'-((((1,4-phenylenebis(azaneylylidene))bis(ethan-1-yl-1-ylidene))bis(2-oxo-2H-chromene-3,6-diyl))bis(diazene-2,1-diyl))dibenzenesulfonic acid (PhODB), 4,4'-(((-([1,1'-biphenyl]-4,4'-diylbis(azaneylylidene))bis(ethan-1-yl-1-ylidene))bis(2-oxo-2H-chromene-3,6-diyl))bis(diazene-2,1-diyl))dibenzenesulfonic acid (BODB) and 4,4'-(((-((3,3'-dimethoxy-[1,1'-biphenyl]-4,4'-diyl)bis(azaneylylidene))bis(ethan-1-yl-1-ylidene))bis(2-oxo-2H-chromene-3,6-iyl))bis(diazene-2,1-diyl))dibenzenesulfonic acid (DODB). Their chemical structures were proved by performing Fourier-transform infrared spectroscopy, proton nuclear magnetic resonance and mass spectrometry analysis. The synthesized p-phenylenediamine and benzidine coumarin derivatives were tested as corrosion inhibitors for mild steel (MS) in 1 M HCl solution using weight loss, electrochemical, morphological, and theoretical studies. The compound 3,3'-dimethoxy benzidine coumarin derivative (DODB) was proved to give the highest efficiency with 94.98% obtained from weight loss measurements. These compounds are mixed inhibitors, as seen by the polarization curves. Impedance diagrams showed that when the concentration of these derivatives rose, the double-layer capacitance fell and the charge transfer resistance increased. Calculated thermodynamic parameters were computed and the mechanism of adsorption was also studied for the synthesized p-phenylenediamine and benzidine coumarin derivatives. The ability of the synthesized derivatives to protect the surface against corrosion was investigated by scanning electron microscope (SEM), UV-visible spectroscopy and energy dispersive X-ray spectroscopy (EDX). Theoretical chemical calculations (DFT) and biological resistivity (SRB) were investigated.

An Update on Synthesis of Coumarin Sulfonamides as Enzyme Inhibitors and Anticancer Agents

Coumarin is an important six-membered aromatic heterocyclic pharmacophore, widely distributed in natural products and synthetic molecules. The versatile and unique features of coumarin nucleus, in combination with privileged sulfonamide moiety, have enhanced the broad spectrum of biological activities. The research and development of coumarin, sulfonamide-based pharmacology, and medicinal chemistry have become active topics, and attracted the attention of medicinal chemists, pharmacists, and synthetic chemists. Coumarin sulfonamide compounds and analogs as clinical drugs have been used to cure various diseases with high therapeutic potency, which have shown their enormous development value. The diversified and wide array of biological activities such as anticancer, antibacterial, anti-fungal, antioxidant and anti-viral, etc. were displayed by diversified coumarin sulfonamides. The present systematic and comprehensive review in the current developments of synthesis and the medicinal chemistry of coumarin sulfonamide-based scaffolds give a whole range of therapeutics, especially in the field of oncology and carbonic anhydrase inhibitors. In the present review, various synthetic approaches, strategies, and methodologies involving effect of catalysts, the change of substrates, and the employment of various synthetic reaction conditions to obtain high yields is cited.

Synthesis and Melanogenesis Effect of 7,8-Dimethoxy-4-Methylcoumarin via MAPK Signaling-Mediated Microphthalmia-Associated Transcription Factor Upregulation

Tyrosinase ultimately controls the melanogenesis rate of the skin, and tanning and haircare products generally induce the activation of tyrosinase. Moreover, various enzymes, including tyrosinase, tyrosinase-related protein 1 (TRP1), and tyrosinase-related protein 2 (TRP2), mediate melanogenesis in which microphthalmia-associated transcription factor (MITF) is a master regulator. One coumarin family member 7,8-dihydroxy-4-methylcoumarin (DHMC) shows extensive biological activities with beneficial health effects; however, it also induces cytotoxicity and its melanogenic effect has not been reported yet. Therefore, we first synthesized DHMC derivatives via methylation to obtain 7,8-dimethoxy-4-methylcoumairn (DMMC), and investigated the pro- or anti-melanogenic effects of DHMC and DMMC in B16-F10 melanoma cells as well as the underlying mechanism. DHMC showed cytotoxicity at all tested concentrations, whereas DMMC did not reduce cell viability, even at the high concentration. DMMC also drives the significant increase in intracellular melanin and tyrosinase activity. Moreover, DMMC induced MITF expression by significantly increasing tyrosinase activity, which activates the gene expression of TRP1 and TRP2. Western blotting confirmed that DMMC induced the activation of mitogen-activated protein kinase (MAPK) signaling by the phosphorylation of C-Jun N-terminal kinase (JNK), resulting in the increased melanin production and the decreased phosphorylation of protein kinase B. Collectively, this study showed the pro-melanogenic effect of DMMC and its potential as a safe tanning and dyeing agent.

Radical Scavenging Activity and Pharmacokinetic Properties of Coumarin-Hydroxybenzohydrazide Hybrids

Free radicals often interact with vital proteins, violating their structure and inhibiting their activity. In previous studies, synthesis, characterisation, and the antioxidative properties of the five different coumarin derivatives have been investigated. In the tests of potential toxicity, all compounds exhibited low toxicity with significant antioxidative potential at the same time. In this paper, the radical scavenging activity of the abovementioned coumarin derivatives towards ten different radical species was investigated. It was found that all investigated compounds show good radical scavenging ability, with results that are in correlation with the results published in the previous study. Three additional mechanisms of radical scavenging activity were investigated. It was found that all three mechanisms are thermodynamically plausible and in competition. Interestingly, it was found that products of the Double Hydrogen Atom Transfer (DHAT) mechanism, a biradical species in triplet spin state, are in some cases more stable than singlet spin state analogues. This unexpected trend can be explained by spin delocalisation over the hydrazide bridge and phenolic part of the molecule with a low probability of spin pairing. Besides radical-scavenging activity, the pharmacokinetic and drug-likeness of the coumarin hybrids were investigated. It was found that they exhibit good membrane and skin permeability and potential interactions with P-450 enzymes. Furthermore, it was found that investigated compounds satisfy all criteria of the drug-likeness tests, suggesting they possess a good preference for being used as potential drugs.

Retrieval of High Added Value Natural Bioactive Coumarins from Mandarin Juice-Making Industrial Byproduct

Cold pressed essential oil (CPEO) of mandarin (Citrus reticulata Blanco), a by-product of the juice-making industrial process known to contain large amounts of polymethoxyflavones, was exploited for its content in high added value natural coumarins. The study herein afforded a method referring to the evaporation of CPEO volatile fraction under mild conditions (reduced pressure and temperature below 35 °C) as azeotrope with isopropanol. This allowed the isolation of high added value coumarins from the non-volatile fragment using preparative High Performance Liquid Chromatography (HPLC). Pilot-scale application of this procedure afforded for each kg of CPEO processed the following natural bioactive coumarins in chemically pure forms: heraclenol (38-55 mg), 8-gerayloxypsoralen (35-51 mg), auraptene (22-33 mg), and bergamottin (14-19 mg). The structures of coumarins were verified by Nuclear Magnetic Resonance (NMR) spectroscopy and HPLC co-injection with authentic standards. Thus, the low market value mandarin CPEO with current value of 17 to 22 EUR/kg can be valorized through the production of four highly bioactive natural compounds worth 3479 to 5057 EUR/kg, indicating the great potentials of this methodology in the terms of the circular economy.

Anti-Inflammatory Effects of 6-Methylcoumarin in LPS-Stimulated RAW 264.7 Macrophages via Regulation of MAPK and NF-κB Signaling Pathways

Persistent inflammatory reactions promote mucosal damage and cause dysfunction, such as pain, swelling, seizures, and fever. Therefore, in this study, in order to explore the anti-inflammatory effect of 6-methylcoumarin (6-MC) and suggest its availability, macrophages were stimulated with lipopolysaccharide (LPS) to conduct an in vitro experiment. The effects of 6-MC on the production and levels of pro-inflammatory cytokines (interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α) and inflammatory mediators (nitric oxide (NO), prostaglandin E₂ (PGE₂)) in LPS-stimulated RAW 264.7 cells were examined. The results showed that 6-MC reduced the levels of NO and PGE₂ without being cytotoxic. In addition, it was demonstrated that the increase in the expression of pro-inflammatory cytokines caused by LPS stimulation, was decreased in a concentration-dependent manner with 6-MC treatment. Moreover, Western blot results showed that the protein levels of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), which increased with LPS treatment, were decreased by 6-MC treatment. Mechanistic studies revealed that 6-MC reduced the phosphorylation of the mitogen-activated protein kinase (MAPK) family and IκBα in the MAPK and nuclear factor-kappa B (NF-κB) pathways, respectively. These results suggest that 6-MC is a potential therapeutic agent for inflammatory diseases that inhibits inflammation via the MAPK and NF-κB pathways.

Nanoformulations of Coumarins and the Hybrid Molecules of Coumarins with Potential Anticancer Effects

Coumarins are the secondary metabolites of some plants, fungi, and bacteria. Coumarins and the hybrid molecules of coumarins are the compounds which have been widely studied for their potential anticancer effects. They belong to benzopyrone chemical class, more precisely benzo-α-pyrones, where benzene ring is fused to pyrone ring. In nature, coumarins are found in higher plants like Rutaceae and Umbelliferae and some essential oils like cinnamon bark oil, cassia leaf oil and lavender oil are also rich in coumarins. The six main classes of coumarins are furanocoumarins, dihydrofuranocoumarins, pyrano coumarins, pyrone substituted coumarins, phenylcoumarins and bicoumarins. As well as their wide range of biological activities, coumarins and the hybrid molecules of coumarins are proven to have an important role in anticancer drug development due to the fact that many of its derivatives have shown an anticancer activity on various cell lines. Osthol, imperatorin, esculetin, scopoletin, umbelliprenin, angelicine, bergamottin, limettin, metoxhalen, aurapten and isopimpinellin are some of these coumarins. This review summarizes the anticancer effects of coumarins and their hybrid molecules including the novel pharmaceutical formulations adding further information on the topic for the last ten years and basically focusing on the structureactivity relationship of these compounds in cancer.

Natural Products with Inhibitory Activity against Human Immunodeficiency Virus Type 1

Infections caused by human immunodeficiency virus (HIV) are considered one of the main public health problems worldwide. Antiretroviral therapy (ART) is the current modality of treatment for HIV-1 infection. It comprises the combined use of several drugs and can decrease the viral load and increase the CD4+ T cell count in patients with HIV-1 infection, thereby proving to be an effective modality. This therapy significantly decreases the rate of morbidity and mortality owing to acquired immunodeficiency syndrome (AIDS) and prolongs and improves the quality of life of infected patients. However, nonadherence to ART may increase viral resistance to antiretroviral drugs and transmission of drug-resistant strains of HIV. Therefore, it is necessary to continue research for compounds with anti-HIV-1 activity, exhibiting a potential for the development of an alternative or complementary therapy to ART with low cost and fewer side effects. Natural products and their derivatives represent an excellent option owing to their therapeutic potential against HIV. Currently, the derivatives of natural products available as anti-HIV-1 agents include zidovudine, an arabinonucleoside derivative of the Caribbean marine sponge (Tectitethya crypta), which inhibits the reverse transcriptase of the virus. This was the first antiviral agent approved for treatment of HIV infection. Additionally, bevirimat (isolated from Syzygium claviflorum) and calanolide A (isolated from Calophyllum sp.) are inhibitors of viral maturation and reverse transcription process, respectively. In the present review, we aimed to describe the wide repertoire of natural compounds exhibiting anti-HIV-1 activity that can be considered for designing new therapeutic strategies to curb the HIV pandemic.

Anti-Inflammatory Effects of 6,7-Dihydroxy-4-Methylcoumarin on LPS-Stimulated Macrophage Phosphorylation in MAPK Signaling Pathways

Coumarin derivatives, such as esculetin, have various physiological functions, including antioxidant, anti-inflammatory, antibacterial, antiviral, and anti-cancer. 6,7-Dihydroxy-4-methylcoumarin (6,7-DH-4MC) is a derivative of esculetin, and its anti-inflammatory effect and mechanism in macrophages have not been studied. In this study, the anti-inflammatory activity of 6,7-DH-4MC was evaluated by measuring the expression of inflammatory factors (NO and PGE2) and pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α) in LPS-stimulated RAW 264.7 macrophages. The results revealed that 6,7-DH-4MC significantly reduced NO levels and PGE2 expression without inducing cytotoxicity; it was confirmed that the inhibition of NO and PGE2 expression was related to iNOS and COX-2 downregulation in response to 6,7-DH-4MC treatment. Moreover, 6,7-DH-4MC decreased the levels of pro-inflammatory cytokines, such as IL-1β and IL-6, in a dose-dependent manner. Mechanistic studies revealed reduced phosphorylation of ERK and p38-MAPK upon 6,7-DH-4MC treatment. Furthermore, the degradation of IκB-α and phosphorylation of NF-κB in cells treated with LPS were interrupted by 6,7-DH-4MC treatment. These results suggest that 6,7-DH-4MC is a potential therapeutic agent for inflammatory diseases. To the best of our knowledge, this is the first report demonstrating the anti-inflammatory effects of 6,7-DH-4MC in RAW 264.7 cells via MAPK and NF-κB signaling pathways.

4-Hydroxy-7-Methoxycoumarin Inhibits Inflammation in LPS-activated RAW264.7 Macrophages by Suppressing NF-κB and MAPK Activation

Coumarins are natural products with promising pharmacological activities owing to their anti-inflammatory, antioxidant, antiviral, anti-diabetic, and antimicrobial effects. Coumarins are present in many plants and microorganisms and have been widely used as complementary and alternative medicines. To date, the pharmacological efficacy of 4-hydroxy-7-methoxycoumarin (4H-7MTC) has not been reported yet. Therefore, in this study, we investigated the anti-inflammatory effects of 4H-7MTC in LPS-stimulated RAW264.7 cells as well as its mechanisms of action. Cells were treated with various concentrations of 4H-7MTC (0.3, 0.6, 0.9, and 1.2 mM) and 40 μM L-N⁶-(1-iminoethyl)-L-lysine (L-NIL) were used as controls. LPS-stimulated RAW264.7 cells showed that 4H-7MTC significantly reduced nitric oxide (NO) and prostaglandin E₂ (PGE₂) production without cytotoxic effects. In addition, 4H-7MTC strongly decreased the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX-2). Furthermore, 4H-7MTC reduced the production of proinflammatory cytokines such as tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6. We also found that 4H-7MTC strongly exerted its anti-inflammatory actions by downregulating nuclear factor kappa B (NF-κB) activation by suppressing inhibitor of nuclear factor kappa B alpha (IκBα) degradation in macrophages. Moreover, 4H-7MTC decreased phosphorylation of extracellular signal-regulated kinase (ERK1/2) and c-Jun N-terminal kinase/stress-activated protein kinase (JNK), but not that of p38 MAPK. These results suggest that 4H-7MTC may be a good candidate for the treatment or prevention of inflammatory diseases such as dermatitis, psoriasis, and arthritis. Ultimately, this is the first report describing the effective anti-inflammatory activity of 4H-7MTC.

Coumarins and Coumarin-Related Compounds in Pharmacotherapy of Cancer

Cancer is one of the most common causes of disease-related deaths worldwide. Despite the discovery of many chemotherapeutic drugs that inhibit uncontrolled cell division processes for the treatment of various cancers, serious side effects of these drugs are a crucial disadvantage. In addition, multi-drug resistance is another important problem in anticancer treatment. Due to problems such as cytotoxicity and drug resistance, many investigations are being conducted to discover and develop effective anticancer drugs. In recent years, researchers have focused on the anticancer activity coumarins, due to their high biological activity and low toxicity. Coumarins are commonly used in the treatment of prostate cancer, renal cell carcinoma and leukemia, and they also have the ability to counteract the side effects caused by radiotherapy. Both natural and synthetic coumarin derivatives draw attention due to their photochemotherapy and therapeutic applications in cancer. In this review, a compilation of various research reports on coumarins with anticancer activity and investigation and a review of structure-activity relationship studies on coumarin core are presented. Determination of important structural features around the coumarin core may help researchers to design and develop new analogues with a strong anticancer effect and reduce the potential side effects of existing therapeutics.

Structure-Activity-Relationship and Mechanistic Insights for Anti-HIV Natural Products

Acquired Immunodeficiency Syndrome (AIDS), which chiefly originatesfroma retrovirus named Human Immunodeficiency Virus (HIV), has impacted about 70 million people worldwide. Even though several advances have been made in the field of antiretroviral combination therapy, HIV is still responsible for a considerable number of deaths in Africa. The current antiretroviral therapies have achieved success in providing instant HIV suppression but with countless undesirable adverse effects. Presently, the biodiversity of the plant kingdom is being explored by several researchers for the discovery of potent anti-HIV drugs with different mechanisms of action. The primary challenge is to afford a treatment that is free from any sort of risk of drug resistance and serious side effects. Hence, there is a strong demand to evaluate drugs derived from plants as well as their derivatives. Several plants, such as Andrographis paniculata, Dioscorea bulbifera, Aegle marmelos, Wistaria floribunda, Lindera chunii, Xanthoceras sorbifolia and others have displayed significant anti-HIV activity. Here, weattempt to summarize the main results, which focus on the structures of most potent plant-based natural products having anti-HIV activity along with their mechanisms of action and IC50 values, structure-activity-relationships and important key findings.

Antiestrogenic Activity and Possible Mode of Action of Certain New Nonsteroidal Coumarin-4-acetamides

The preparation of certain 2-(2-oxo-2H-chromen-4-yl)-N-substituted acetamides IIIa-h was planned as a step in the development of new modified nonsteroidal antiestrogens. The purity of target compounds IIIa-h was checked by thin-layer chromatography (TLC), and their structures were confirmed using various spectroscopic tools including IR, 1H-NMR, 13C-NMR, and MS spectroscopy. Viability tests were applied using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay to evaluate the cytotoxic effect of the synthesized compounds against two breast cancer cell lines, MCF-7 and MDA-MB-231. Compound IIIb proved the most active against MCF-7 cells, with an IC50 value of 0.32 μM. The results of an analysis of in vitro antiestrogenic activity indicated that only compound IIIb exhibited antiestrogenic activity; its IC50 value of 29.49 μM was about twice as potent as that of the reference compound, MIBP. The aromatase activity was evaluated for the synthesized target compounds IIIa-g and the intermediates Ib and IIa. A significant aromatase inhibition was observed for the intermediate Ib and compound IIIe, with IC50 values of 14.5 and 17.4 μM, respectively. Compound IIIb, namely 7-methoxy-4-(2-oxo-2-(piperidin-1-yl)ethyl)-2H-chromen-2-one, could be used as an antiestrogen and/or cytotoxic agent with selective activity against tumor cells.

Molecular dynamics and computational study of Mannich-based coumarin derivatives: potent tyrosine kinase inhibitor

The manifestation of bacterial UTI (Urinary Tract Infection) has been predominantly endemic, globally; eventually, the development of new UTI antibacterial agent(s) remains the call of the day. Herein, two series of Mannich-based 4-hydroxy coumarin derivatives, 7a-m and 8a-m were designed by suitable heterocyclic amines condensed with aldehydes. The synthesised molecules were interpreted by ¹H-NMR and ¹³C-NMR spectral analyses with in vitro antibacterial studies. The compound, 4-hydroxy-3-((4-hydroxy-3-methoxyphenyl)(morpholino)methyl)-2H-chromen-2-one 8l was the significant derivative against pathogenic bacteria Staphylococcus aureus and Escherichia coli with MIC values 12.50 and 25 µM, respectively. Computational assessments with the Lipinski's rule of five, ADMET properties and molecular docking studies revealed that analogues, 7f, 7l, 8d, 8j and 8k could be potent druggable molecules with significant binding affinity towards bacterial tyrosine kinase, as target. To understand the mode of binding and intrinsic stabilities of potent receptor-ligand complexes, each system was subjected molecular dynamics simulations for 100 ns. Inter-molecular contact analysis and intrinsic hydrogen-bond stability portrayed the analogues 8l form a number of non-bonded contacts with the receptor tyrosine kinase being mostly dominated by electrostatic and hydrophobic contacts. The results from the present structure-based designing approach might be a valuable tool towards identification of a new antibacterial drug candidate(s) against UTI in near future.Abbreviations4-HC4-hydroxy coumarinADMETabsorption, distribution, metabolism, excretion, toxicityDCE1,2-dichloroethaneDCMdichloromethaneDMSOdimethyl sulfoxideMDmolecular dynamicsMICminimum inhibitory concentrationNMRnuclear magnetic resonanceNPTisothermal isobaric ensemblesNVTcanonical ensemblesPCAprincipal component analysisPDBprotein data bankRgradius gyrationRMSFroot-mean-square fluctuationsRSMDroot-mean-square deviationUTIurinary Tract InfectionCommunicated by Ramaswamy H. Sarma.

Enhanced uptake, high selective and microtubule disrupting activity of carbohydrate fused pyrano-pyranones derived from natural coumarins attributes to its anti-malarial potential

Background

Malaria is one of the deadliest infectious diseases caused by protozoan parasite of Plasmodium spp. Increasing resistance to anti-malarials has become global threat in control of the disease and demands for novel anti-malarial interventions. Naturally-occurring coumarins, which belong to a class of benzo-α-pyrones, found in higher plants and some essential oils, exhibit therapeutic potential against various diseases. However, their limited uptake and non-specificity has restricted their wide spread use as potential drug candidates.

Methods

Two series of carbohydrate fused pyrano[3,2-c]pyranone carbohybrids which were synthesized by combination of 2-C-formyl galactal and 2-C-formyl glucal, with various freshly prepared 4-hydroxycoumarins were screened against Plasmodium falciparum. The anti-malarial activity of these carbohybrids was determined by growth inhibition assay on P. falciparum 3D7 strain using SYBR green based fluorescence assay. Haemolytic activity of carbohybrid 12, which showed maximal anti-malarial activity, was determined by haemocompatibility assay. The uptake of the carbohybrid 12 by parasitized erythrocytes was determined using confocal microscopy. Growth progression assays were performed to determine the stage specific effect of carbohybrid 12 treatment on Pf3D7. In silico studies were conducted to explore the mechanism of action of carbohybrid 12 on parasite microtubule dynamics. These findings were further validated by immunofluorescence assay and drug combination assay.

Results

2-C-formyl galactal fused pyrano[3,2-c]pyranone carbohybrid 12 exhibited maximum growth inhibitory potential against Plasmodium with IC₅₀ value of 5.861 µM and no toxicity on HepG2 cells as well as no haemolysis of erythrocytes. An enhanced uptake of this carbohybrid compound was observed by parasitized erythrocytes as compared to uninfected erythrocytes. Further study revealed that carbohybrid 12 arrests the growth of parasite at trophozoite and schizonts stage during course of progression through asexual blood stages. Mechanistically, it was shown that the carbohybrid 12 binds to α,β-heterodimer of tubulin and affects microtubule dynamics.

Conclusion

These findings show carbohydrate group fusion to 4-hydroxycoumarin precursor resulted in pyrano-pyranones derivatives with better solubility, enhanced uptake and improved selectivity. This data confirms that, carbohydrate fused pyrano[3,2-c]pyranones carbohybrids are effective candidates for anti-malarial interventions against P. falciparum.

Analysis of the role of DAMTC in lung adenocarcinoma cells based on the DNA microarrays

The present study aimed to investigate the effect of 7, 8-diacetoxy-4-methylcoumarin (DAMTC) on lung adenocarcinoma cells (A549) and analyze the molecular mechanism underlying DAMTC-treated lung adenocarcinoma. Gene expression profile GSE29698 was downloaded from the Gene Expression Omnibus database. The differentially expressed genes (DEGs) in 3 DAMTC-treated A549 samples were analyzed and compared with 3 DAMTC-untreated samples using the limma package. Gene Ontology (GO) and pathway enrichment analyses of DEGs were performed, followed by the functional annotation and protein-protein interaction (PPI) network construction. Finally, pathway crosstalk analysis was conducted. A total of 500 upregulated and 389 downregulated DEGs were identified. The upregulated and downregulated DEGs were enriched in different GO terms and pathways, including metabolic process, p53 signaling pathway and metabolic pathways. A total of 9 DEGs were determined to have node degrees >16 in the PPI network, including interleukin 6 (IL6), MDM2 oncogene, E3 ubiquitin protein ligase (MDM2), cell division cycle 42 (CDC42) and MYC associated factor X (MAX). Furthermore, numerous DEGs were identified to function as transcription factors and tumor suppressor genes, including histone deacetylase 3 and MAX. Additionally, apoptosis, tight junction, and endocytosis pathway were determined to cross-talk with small cell and non-small cell lung cancer. The DEGs (IL6, MDM2, CDC42 and MAX) involved in different pathways, including the p53 signaling pathway and endocytosis, may be the potential targets for DAMTC in lung adenocarcinoma. The elucidation of the underlying mechanism of the DAMTC effect may make it a potential drug.

Phototoxicity of 7-oxycoumarins with keratinocytes in culture

Seventy-one 7-oxycoumarins, 66 synthesized and 5 commercially sourced, were tested for their ability to inhibit growth in murine PAM212 keratinocytes. Forty-nine compounds from the library demonstrated light-induced lethality. None was toxic in the absence of UVA light. Structure-activity correlations indicate that the ability of the compounds to inhibit cell growth was dependent not only on their physiochemical characteristics, but also on their ability to absorb UVA light. Relative lipophilicity was an important factor as was electron density in the pyrone ring. Coumarins with electron withdrawing moieties - cyano and fluoro at C₃ - were considerably less active while those with bromines or iodine at that location displayed enhanced activity. Coumarins that were found to inhibit keratinocyte growth were also tested for photo-induced DNA plasmid nicking. A concentration-dependent alteration in migration on neutral gels caused by nicking was observed.

Photo-induced DNA interstrand cross-links formed by a coumarin-modified nucleoside

Coumarins are a class of naturally occurring compounds that have been shown to form photochemical DNA interstrand cross-links (ICLs). However, study of a coumarin base has not been explored. Using nucleophilic substitution and phosphoramidite chemistry, we synthesized a coumarin base-containing oligonucleotide. Upon exposure to long-wave ultraviolet light, the coumarin-modified oligonucleotide formed ICLs with complementary oligonucleotide containing dT and dC opposite the coumarin base, presumably through a [2 + 2] cycloaddition mechanism. Moderate yields with both bases were observed; though, dT has a higher reactivity than dC. Overall, this work provides new means for biochemical characterization of ICLs formed by coumarins.

Current Strategies for Inhibition of Chikungunya Infection

Increasing incidences of Chikungunya virus (CHIKV) infection and co-infections with Dengue/Zika virus have highlighted the urgency for CHIKV management. Failure in developing effective vaccines or specific antivirals has fuelled further research. This review discusses updated strategies of CHIKV inhibition and provides possible future directions. In addition, it analyzes advances in CHIKV lifecycle, drug-target development, and potential hits obtained by in silico and experimental methods. Molecules identified with anti-CHIKV properties using traditional/rational drug design and their potential to succeed in subsequent stages of drug development have also been discussed. Possibilities of repurposing existing drugs based on their in vitro findings have also been elucidated. Probable modes of interference of these compounds at various stages of infection, including entry and replication, have been highlighted. The use of host factors as targets to identify antivirals against CHIKV has been addressed. While most of the earlier antivirals were effective in the early phases of the CHIKV life cycle, this review is also focused on drug candidates that are effective at multiple stages of its life cycle. Since most of these antivirals require validation in preclinical and clinical models, the challenges regarding this have been discussed and will provide critical information for further research.

Synthesis of 2H-Chromenones from Salicylaldehydes and Arylacetonitriles

An efficient and convenient protocol for the synthesis of 2H-chromenones has been developed. In the presence of ^tBuOK in DMF, good to excellent yields of various chromenones were obtained from the corresponding salicylaldehydes and arylacetonitriles. No protection of inert gas atmosphere is required here.

Transcriptomic profiling of Melilotus albus near-isogenic lines contrasting for coumarin content

Coumarin and its derivatives are widely used as fragrances in industrial products and have medical value. The goal of the present study was to discover genes and pathways related to coumarin biosynthesis in Melilotus albus using transcriptome analysis. The genes of five M. albus near-isogenic lines (NILs) that had different coumarin content and β-glucosidase activity according to the investigation of pedigree were quantified and then analysed by RNA-Seq. Using transcriptome analysis, differentially expressed genes (DEGs) were identified in two pairwise comparisons that differed in coumarin content as well as in two pairwise comparisons that differed in β-glucosidase activity. Gene expression pattern analysis suggested similar transcriptional trends in the genotypes with the same coumarin levels. Furthermore, the Kyoto Encyclopedia of Genes and Genomes (KEGG) database of DEGs was used to identify functional pathways associated with coumarin biosynthesis. We identified 111 unigenes, with several DEGs among them possibly being related to coumarin synthesis pathways. Unigenes encoding a hexokinase, an abscisic acid receptor, a phenylalanine ammonia-lyase (PAL) and two peroxidases particularly showed correspondence with the coumarin content of different genotypes. These results will contribute to a better understanding of the coumarin biosynthesis in M. albus.

Therapeutic potential of coumarins as antiviral agents

Coumarins have received a considerable attention in the last three decades as a lead structures for the discovery of orally bioavailable non-peptidic antiviral agents. A lot of structurally diverse coumarins analogues were found to display remarkable array of affinity with the different molecular targets for antiviral agents and slight modifications around the central motif result in pronounced changes in its antiviral spectrum. This manuscript thoroughly reviews the design, discovery and structure-activity relationship studies of the coumarin analogues as antiviral agents focusing mainly on lead optimization and its development into clinical candidates.

Antileishmanial activity of prenylated coumarins isolated from Ferulago angulata and Prangos asperula

Leishmaniasis has a wide spectrum of signs and symptoms due to infection to numbers of Leishmania species and makes enormous mortality and morbidity. There are clues of antileishmanial effects of prenylated coumarins. Apiaceae family is one of the most important sources of coumarins. Air-dried aerial parts of Ferulago angulata and fruits of Prangos asperula were extracted with n-hexane, using a soxhlet apparatus. The solvents were evaporated under reduced pressure. Column chromatography and crystallization process resulted to isolation of three prenylated coumarins. ¹H-nuclear magnetic resonance, electron ionization Mass and Infrared spectra were used for elucidation of isolated compounds. Leishmanicidal activity of isolated coumarins was assessed on Leishmania major strain (MRHO/IR/75/ER) for the first time. Suberosin epoxide and suberosin were isolated from aerial parts of F. angulata and osthol was extracted from grounded fruits of P. asperula. Osthol showed a significant antileishmanial effect on promastigotes in early hours of exposure with IC₅₀ of 14.40 µg/mL but suberosin epoxide showed only a weak antileishmanial activity. IC₅₀ of osthol and suberosin epoxide after 48 h were 10.79 and 54.0 µg/mL, respectively. Suberosin showed no remarkable effect in these concentrations. This is the first report on the pharmacological activity of suberosin epoxide. Substantial difference between efficacies of two isomers, osthol and suberosin remarks the importance of prenyl substituent location on C-8.

Synthesis and evaluation of anticancer activity of 6-pyrazolinylcoumarin derivatives

A series of novel 6-pyrazolinylcoumarins has been synthesized via multi-step protocol. The synthetic procedure was based on the acetylation of hydroxycoumarins; Fries rearrangement and Claisen–Schmidt condensation; the target 6-[5-aryl-4,5-dihydropyrazol-3-yl]-5-hydroxy-7-methylcoumarins (33–49) were obtained under reactions of hydrazine and 2-aryl-5-methyl-2,3-dihydropyrano[2,3-f]chromen-4,8-diones as the last phase of the protocol. Anticancer activity screening in NCI60-cell lines assay allowed identification of compound 47 with the highest level of antimitotic activity with mean GI₅₀ value of 10.20 μM and certain sensitivity profile toward the Leukemia cell lines CCRF-CEM and MOLT-4 (GI₅₀/TGI values 1.88/5.06 μM and 1.92/4.04 μM respectively).

Pulchrin A, a New Natural Coumarin Derivative of Enicosanthellum pulchrum, Induces Apoptosis in Ovarian Cancer Cells via Intrinsic Pathway

Drug resistance presents a challenge in chemotherapy and has attracted research interest worldwide and particular attention has been given to natural compounds to overcome this difficulty. Pulchrin A, a new compound isolated from natural products has demonstrated novel potential for development as a drug. The identification of pulchrin A was conducted using several spectroscopic techniques such as nuclear magnetic resonance, liquid chromatography mass spectrometer, infrared and ultraviolet spectrometry. The cytotoxicity effects on CAOV-3 cells indicates that pulchrin A is more active than cisplatin, which has an IC50 of 22.3 μM. Significant changes in cell morphology were present, such as cell membrane blebbing and formation of apoptotic bodies. The involvement of phosphatidylserine (PS) in apoptosis was confirmed by Annexin V-FITC after a 24 h treatment. Apoptosis was activated through the intrinsic pathway by activation of procaspases 3 and 9 as well as cleaved caspases 3 and 9 and ended at the executioner pathway, with the occurrence of DNA laddering. Apoptosis was further confirmed via gene and protein expression levels, in which Bcl-2 protein was down-regulated and Bax protein was up-regulated. Furthermore, the CAOV-3 cell cycle was disrupted at the G0/G1 phase, leading to apoptosis. Molecular modeling of Bcl-2 proteins demonstrated a high- binding affinity, which inhibited the function of Bcl-2 proteins and led to cell death. Results of the current study can shed light on the development of new therapeutic agents, particularly, human ovarian cancer treatments.

Evaluation of the Antimalarial Effect of Ferulago angulata (Schlecht.) Boiss. Extract and Suberosin Epoxide Against Plasmodium berghei in Comparison with Chloroquine Using in-vivo Test

Resistance to most antimalarial drugs has encouraged the development of novel drugs. An alternative source for discovering such drugs is natural products. Some Ferulago species are used in folk medicine for their sedative, tonic and anti-parasitic effects. Besides, coumarins isolated from this genus found to have in vitro anti-leishmanicidal effect. The present study is aimed to evaluate the in-vivo antimalarial activity of Ferulago angulata (Schlecht.) Boiss. extract and suberosin epoxide, using suarian mice. A rodent malaria parasite, Plasmodium berghei was used to inoculate healthy male Swiss Albino mice of age 6-8 weeks and weight 23-27 g. Hydro-alcoholic extract of F. angulata (20, 100, 300, 600 mg/Kg) and suberosin epoxide suspension (10, 30, 50, 100 mg/Kg) were administered subcutaneously. Parameters including percentage of parasitemia, suppression of parasitemia and mean survival time were determined using standard test such as peter^٬s. Chemo-protective effects were exerted by the crude extract and suberosin epoxide. Maximum effect was observed with the larger doses of the crude extract and suberosin epoxide. Suberosin epoxide increased the survival time compared to chloroquine. However, the results of this study indicate that the plant has a promising anti-plasmodial activity against plasmodium berghei. Thus, it could be considered as a potential source of new antimalarial agents. Suberosin epoxide at the dose of 100 mg/Kg possesses relatively significant antimalarial effect. Chemical derivatization of the parent compound or preparation of the modified formulation is required to improve its systemic bioavailability.

Structural Insights into Substrate Specificity of Feruloyl-CoA 6'-Hydroxylase from Arabidopsis thaliana

Coumarins belong to an important class of plant secondary metabolites. Feruloyl-CoA 6’-hydroxylase (F6’H), a 2-oxoglutarate dependent dioxygenase (2OGD), catalyzes a pivotal step in the biosynthesis of a simple coumarin scopoletin. In this study, we determined the 3-dimensional structure of the F6’H1 apo enzyme by X-ray crystallography. It is the first reported structure of a 2OGD enzyme involved in coumarin biosynthesis and closely resembles the structure of Arabidopsis thaliana anthocyanidin synthase. To better understand the mechanism of enzyme catalysis and substrate specificity, we also generated a homology model of a related ortho-hydroxylase (C2’H) from sweet potato. By comparing these two structures, we targeted two amino acid residues and verified their roles in substrate binding and specificity by site-directed mutagenesis.

In vitro evaluation of 3-arylcoumarin derivatives in A549 cell line

Coumarins are naturally-occurring compounds with diverse and interesting biological activities. In the present study, we evaluated the in vitro cytotoxic effect of 8-(acetyloxy)-3-[4-(acetyloxy)phenyl]-2-oxo-2H-chromen-7-yl acetate (6); 8-(acetyloxy)-3-(4-methanesulfonyl phenyl)-2-oxo-2H-chromen-7-yl acetate (7); 4-(2-oxo-2H-chromen-3-yl)phenyl acetate (8); 3-(4-methanesulfonylphenyl)-2H-chromen-2-one (9); 4-(4-methyl-2-oxo-2H-chromen-3-yl)phenyl acetate (10); 3-(4-methanesulfonylphenyl)-4-methyl-2H-chromen-2-one (11); 8-(acetyloxy)-3-[4-(acetyloxy)phenyl]-4-methyl-2-oxo-2H-chromen-7-yl acetate (12); and 5-(acetyloxy)-3-[4-(acetyloxy) phenyl]-2-oxo-2H-chromen-7-yl acetate (13) in human lung (A549) cancer and normal lung (MRC-9) cell lines at different concentrations for 48 h using crystal violet dye binding assay. The cytotoxic effect of these coumarin derivatives were compared to the standard drug, docetaxel. Furthermore, the effect of the most active compound on the cell-cycle using propidium iodide, mitochondrial membrane potential (MMP) using tetramethyl rhodamine methyl ester (rhodamine-123) and reactive oxygen species (ROS) production using 2',7'-dichlorofluorescin diacetate (PCFDA) were also evaluated.

RESULTS

Compound 7: had the greatest cytotoxic effect (cytotoxic concentration, CC50=24 μM) and selectivity (MRC-9; CC50>100 μM; inactive) in the A549 cell line, and caused cells to arrest in the S phase of the cell cycle, loss of MMP and increased ROS production in a concentration-dependent manner.

CONCLUSION

These findings suggest that compound 7: could serve as a new lead for the development of novel synthetic compounds with enhanced anticancer activity.

Assessment of the genotoxic/clastogenic potential of coumarin derivative 6,7-dihydroxycoumarin (aesculetin) in multiple mouse organs

6,7-Dihydroxycoumarin (6,7-HC) (aesculetin) is a natural and synthetic coumarin derivative of great interest for use by humans due to their potent antioxidant properties. Considering that there are no reports that assess the in vivo genetic toxicity of 6,7-HC, the aim of the present study was to investigate its genotoxic potential in terms of DNA damage in peripheral blood, liver, bone marrow and testicular cells of Swiss albino mice by the comet assay, and its clastogenic/aneugenic potential in bone marrow cells using the micronucleus test. In addition, the ability of 6,7-HC to modulate the genotoxic effects induced by doxorubicin (DXR) was also preliminarily evaluated. Cytotoxicity was assessed by scoring polychromatic (PCE) and normochromatic (NCE) erythrocytes’ ratio. The test compound was administered orally at doses of 25, 50 and 500 mg kg⁻¹ isolated and also simultaneously to DXR (80 mg kg⁻¹). The results showed that 6,7-HC did not induce significant DNA damage in any of the analyzed cells, and also did not show any significant increase in micronucleated PCE at the three tested doses. The PCE/NCE ratio indicated no cytotoxicity. Moreover, the extent of DNA damage induced by DXR decreased significantly only in peripheral blood and testicular cells, and only at the lowest dose of 6,7-HC.

6-7-Dimethoxy-4-methylcoumarin suppresses pro-inflammatory mediator expression through inactivation of the NF-κB and MAPK pathways in LPS-induced RAW 264.7 cells

In this study, we investigated the ability of 6,7-dimethoxy-4-methylcoumarin (DMC) to inhibit lipopolysaccharide (LPS)-induced expression of pro-inflammatory mediators in mouse macrophage (RAW 264.7) cells, and the molecular mechanism through which this inhibition occurred. Our results indicated that DMC downregulated LPS-induced nitric oxide (NO) synthase (iNOS) and cyclooxygenase-2 (COX-2) expression, thereby reducing the production of NO and prostaglandin E2 (PGE2) in LPS-activated RAW 264.7 cells. Furthermore, DMC suppressed LPS-induced production of pro-inflammatory cytokines such as interleukin (IL)-1ß, IL-6, and tumor necrosis factor (TNF)-α. To elucidate the mechanism underlying the anti-inflammatory activity of DMC, we assessed its effects on the mitogen-activated protein kinase (MAPK) pathway and the activity and expression of nuclear transcription factor kappa-B (NF-κB). The experiments demonstrated that DMC inhibited LPS-induced phosphorylation of extracellular signal-regulated kinases (ERKs), c-Jun N-terminal kinase (JNK), and p38. In addition, it attenuated LPS-induced NF-κB activation via the inhibition of IκB-α phosphorylation. Taken together, these data suggest that DMC exerts its anti-inflammatory effects in RAW 264.7 cells through the inhibition of LPS-stimulated NF-κB and MAPK signaling, thereby downregulating the expression of pro-inflammatory mediators.