4-Phenylcoumarins as HIV transcription inhibitors

Binding of Mammea A/AA (MA) to calf thymus DNA revealed by the ratiometric absorbance of MA in the UV-visible range molecular dynamic simulations and TD-DFT calculations

The in vitro anti-proliferative activity of MA (5,7-dihydroxy-8-(3-methylbut-2-enyl)-6-(3-methyl-1-oxobutyl)-4-phenyl[1]2H-[1]benzopyran-2-one)on a variety of cancer cells was previously demonstrated. This work strives to understand the mechanisms by which MA exerts this biological activity. Thereafter, the binding of MA to calf thymus DNA was studied by monitoring the change in the UV-visible absorbance of MA. It was found that, the response of MA to binding with calf thymus DNA is characterised by an increase in the AS/AL ratio of the absorbance of the longest wavelength absorption band to the shortest one, and the appearance of a new band at about 377 nm assigned to S0→S1 transition, which is red shifted as compared to free MA. From the bands ratio, the binding constant is found to be 4.3x105 M-1, indicating strong binding. The deduced binding free energy, enthalpy and entropy are -7.7 kcal/mol, -10.89 ± 0.28 kcal/mol and -54.46 ± 4 J/K, respectively, indicating that MA binds to DNA by a non-bonding Van der Waals type interactions and hydrogen bonds. Further study with classical molecular dynamics shows that MA binds to DNA by intercalation, where it is positioned between two AT base pairs. Unlike isolated MA, TDDFT calculations on ten images extracted from the MD trajectory show that, the frontier molecular orbitals of the complex are distributed over the DNA and MA. This indicates a strong stacking interaction and then explains the hypochromism and the red shift of the S0→S1 transition. The present work demonstrates the potency of MA as antitumor compound and as absorbance-based molecular probe.Communicated by Ramaswamy H. Sarma.

Bioinspired Pyrano[2,3-f]chromen-8-ones: Ring C-Opened Analogues of Calanolide A: Synthesis and Anti-HIV-1 Evaluation

We have designed and synthesized a series of bioinspired pyrano[2,3-f]coumarin-based Calanolide A analogs with anti-HIV activity. The design of these new calanolide analogs involved incorporating nitrogen heterocycles or aromatic groups in lieu of ring C, effectively mimicking and preserving their bioactive properties. Three directions for the synthesis were explored: reaction of 5-hydroxy-2,2-dimethyl-10-propyl-2H,8H-pyrano[2,3-f]chromen-8-one with (i) 1,2,4-triazines, (ii) sulfonylation followed by Suzuki cross-coupling with (het)aryl boronic acids, and (iii) aminomethylation by Mannich reaction. Antiviral assay of the synthesized compounds showed that compound 4 has moderate activity against HIV-1 on enzymes and poor activity on the cell model. A molecular docking study demonstrates a good correlation between in silico and in vitro HIV-1 reverse transcriptase (RT) activity of the compounds when docked to the nonnucleoside RT inhibitor binding site, and alternative binding modes of the considered analogs of Calanolide A were established.

4-Phenylcoumarin derivatives as new HIV-1 NNRTIs: Design, synthesis, biological activities, and computational studies

A series of 4-phenylcoumarin derivatives was synthesized and evaluated for their cellular anti-HIV-1 and HIV-2 activities as well as their inhibitory effects against HIV-1 reverse transcriptase (RT). The hydrazone compound 8b and the ethylthiosemicarbazide derivative 4c showed the best inhibition activity against wild-type (WT) HIV-1. The promising compounds were further evaluated against HIV-1 RT and exhibited significant inhibitory activity with compound 8b showing comparable effect to the reference NNRTI Efavirenz (IC50 = 9.01 nM). Structure activity relationship study revealed the importance of 6-chloro and 4-phenyl substituents for optimum activity, as well as the 5-atoms linker (=N-NH-CO-CH2-O-) at position 7 of coumarin scaffold that can support the rotation and flexibility of compound 8b to fit well in the binding pocket. The molecular docking of compound 8b demonstrated a typical seahorse binding mode with better binding interactions that covered more residues when compared to Efavirenz.

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.

The structure characteristics, biosynthesis and health benefits of naturally occurring rare flavonoids

Rare flavonoids, a special subclass of naturally occurring flavonoids with diverse structures including pterocarpans, aurones, neoflavonoids, homoisoflavones, diphenylpropanes, rotenoids and 2-phenylethyl-chromones. They are mainly found in legumes with numerous health benefits. Rare flavonoids are regarded as minor flavonoids due to their very limited abundance in nature. This review gives an overview of the natural occurrences of rare flavonoids from previous literatures. Recent findings on the biosynthesis of rare flavonoids have been updated by describing their structural characteristics and classifications. Recent findings on the health benefits of rare flavonoids have also been compiled and discussed. Natural rare flavonoids with various characteristics from different subclasses from plant-based food sources are stated. They show a wide range of health benefits, including antibacterial, anticancer, anti-osteoporosis and antiviral activities. Studies reviewed suggest that rare flavonoids possessing different skeletons demonstrate different characteristic bioactivities by discussing their mechanism of actions and structure-activity relationships. Besides, recent advances on the biosynthesis of rare flavonoids, such as pterocarpans, rotenoids and aurones are well-known, while the biosynthesis of other subclasses remain unknown. The perspectives and further applications of rare flavonoids using metabolic engineering strategies also be expected.

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 coumarins as potential anti-SARS-CoV-2 agents supported by docking analysis

COVID-19 is a global pandemic first identified in China, causing severe acute respiratory syndrome. One of the therapeutic strategies for combating viral infections is the search for viral spike proteins as attachment inhibitors among natural compounds using molecular docking. This review aims at shedding light on the antiviral potential of natural products belonging to the natural-products class of coumarins up to 2020. Moreover, all these compounds were filtered based on ADME analysis to determine their physicochemical properties, and the best 74 compounds were selected. Using virtual-screening methods, the selected compounds were investigated for potential inhibition of viral main protease (Mpro), viral methyltransferase (nsp16/10 complex), viral recognition binding domain (RBD) of S-protein, and human angiotensin-converting enzyme 2 (ACE2), which is the human receptor for viral S-protein targets, using molecular-docking studies. Promising potential results against SARS-CoV-2 RNA-dependent RNA polymerase (RdRp) and methyltransferase (nsp16) are presented.

Coumarin-based derivatives with potential anti-HIV activity

Acquired immunodeficiency syndrome (AIDS), as a result of human immunodeficiency virus (HIV) infection which leads to severe suppression of immune functions, is an enormous world-wide health threat. The anti-HIV agents are critical for the HIV/AIDS therapy, but the generation of viral mutants and the severe side effects of the anti-HIV agents pose serious hurdles in the treatment of HIV infection, and creat an urgent need to develop novel anti-HIV agents. The plant-derived compounds possess structural and mechanistic diversity, and among them, coumarin-based derivatives have the potential to inhibit different stages in the HIV replication cycle, inclusive of virus-host cell attachment, cell membrane fusion, integration, assembly besides the conventional target like inhibition of the reverse transcriptase, protease, and integrase. Moreover, (+)-calanolide A, a coumarin-based natural product, is a potential anti-HIV agent. Thus, coumarin-based derivatives are useful scaffolds for the development of anti-HIV agents. This review article describes the recent progress in the discovery, structural modification, and structure-activity relationship studies of potent anti-HIV coumarin-based derivatives including natural coumarin compounds, synthetic hybrids, dimers, and other synthetic derivatives covering articles published between 2000 and 2020.

Bioactive Natural Antivirals: An Updated Review of the Available Plants and Isolated Molecules

Viral infections and associated diseases are responsible for a substantial number of mortality and public health problems around the world. Each year, infectious diseases kill 3.5 million people worldwide. The current pandemic caused by COVID-19 has become the greatest health hazard to people in their lifetime. There are many antiviral drugs and vaccines available against viruses, but they have many disadvantages, too. There are numerous side effects for conventional drugs, and active mutation also creates drug resistance against various viruses. This has led scientists to search herbs as a source for the discovery of more efficient new antivirals. According to the World Health Organization (WHO), 65% of the world population is in the practice of using plants and herbs as part of treatment modality. Additionally, plants have an advantage in drug discovery based on their long-term use by humans, and a reduced toxicity and abundance of bioactive compounds can be expected as a result. In this review, we have highlighted the important viruses, their drug targets, and their replication cycle. We provide in-depth and insightful information about the most favorable plant extracts and their derived phytochemicals against viral targets. Our major conclusion is that plant extracts and their isolated pure compounds are essential sources for the current viral infections and useful for future challenges.

Novel Schiff bases derived from N-aryl maleimide derivatives as an effective antimicrobial agent: Theoretical and experimental approach

A set of new Schiff bases of N-aryl 3- and 4-substituted maleimides has been prepared via condensation of N-aryl 3- and 4- substituted maleimides with p-toluene sulfonyl hydrazide in acidic medium at room temperature. The structures of synthesized compounds were characterized by IR, ¹H NMR, ¹³C NMR, MS spectral data, and further confirmed by single-crystal x-ray crystallography for 5c. The computational study was carried out using Gaussian 09 software by using the B3LYP/6-311+G(d,p) basis set. Single-crystal study results showed much closeness with computational study results. These novel compounds were screened for their antimicrobial activity against two pathogenic bacteria such as Escherichia coli (ATCC 8739) and Staphylococcus aureus (ATCC25923) and two pathogenic fungi such as Aspergillus niger (MCIM10231) and Candida albicans (MTCC6275). The investigation of antimicrobial screening data showed that the most of tested compounds are moderate to good microbial inhibitors.

New 4-phenylcoumarin derivatives as potent 3C protease inhibitors: Design, synthesis, anti-HAV effect and molecular modeling

A new series of 4-phenylcoumarin derivatives was synthesized starting from (2-oxo-4-phenyl-2H-chromen-7-yloxy) acetic acid hydrazide 3. Evaluation of the target compounds for their antiviral activity against hepatitis A virus revealed that the ethylthiosemicarbazide derivative 7b was the most potent virucidal agent (IC50 = 3.1 μg/ml, TI = 83). The Schiff's bases 14c and 14b demonstrated the highest virustatic effects against viral adsorption and replication, respectively (14c; IC50 = 8.5 μg/ml, TI = 88 and 14b; IC50 = 10.7 μg/ml, TI = 91). Furthermore, compounds 7b, 14b and 14c were tested against HAV 3C protease and showed significant inhibition effects (Ki = 1.903, 0.104 and 0.217 μM, respectively). The remarkable inhibitory effect expressed by the three target compounds against HAV 3C protease prompted us to expand our research on HRV 3C protease, a structurally related enzyme of the same family, and interestingly, the three target compounds displayed significant inhibitory effect against HRV 3C protease (IC50 = 16.10, 4.13 and 6.30 μM, respectively). Moreover, the active compounds 7b, 14b and 14c were docked within the pocket site of HAV 3C protease (PDB code: 2HAL) illustrating a strong H-profile with the key amino acids Gly170 and Cys172 similar to the co-crystallized ligand. Furthermore, 3D-pharmacophore and quantitative structure activity relationship (QSAR) models were generated to explore the structural requirements for the observed antiviral activity.

Pharmacological and Nutritional Effects of Natural Coumarins and Their Structure-Activity Relationships

Coumarins are fused benzene and pyrone ring systems with a wide spectrum of bioactivities, including antitumor, anti-inflammation, antiviral, and antibacterial effects. In this paper, the current development of coumarin-based drugs is introduced, and their structure-activity relationship is discussed by reviewing the relevant literature published in the past 20 years. Coumarin molecules can be customized by the target site to prevent systemic side effects by virtue of structural modification. The ortho-phenolic hydroxyl on the benzene ring has remarkable antioxidant and antitumor activities. Coumarins with aryl groups at the C-4 position have good activities in anti-HIV, antitumor, anti-inflammation, and analgesia. C-3 phenylcoumarins have strong anti-HIV and antioxidant effects. Tetracycline pyranocoumarins can significantly inhibit HIV; osthol structural analogues have antimicrobial activity. Praeruptorin C and its derivatives play an important role in lowering blood pressure and dilating coronary arteries, and khellactone derivatives have significant inhibitory effects on AIDS, cancer, and cardiovascular diseases. It is concluded that the specific site on the core structure of coumarin exhibits one or more activities due to the electronic or steric effects of the substituents. This review is intended to be conducive to rational design and development of more active and less toxic agents with a coumarin scaffold.

Medicinal Plants Used in the Treatment of Human Immunodeficiency Virus

Since the beginning of the epidemic, human immunodeficiency virus (HIV) has infected around 70 million people worldwide, most of whom reside is sub-Saharan Africa. There have been very promising developments in the treatment of HIV with anti-retroviral drug cocktails. However, drug resistance to anti-HIV drugs is emerging, and many people infected with HIV have adverse reactions or do not have ready access to currently available HIV chemotherapies. Thus, there is a need to discover new anti-HIV agents to supplement our current arsenal of anti-HIV drugs and to provide therapeutic options for populations with limited resources or access to currently efficacious chemotherapies. Plant-derived natural products continue to serve as a reservoir for the discovery of new medicines, including anti-HIV agents. This review presents a survey of plants that have shown anti-HIV activity, both in vitro and in vivo.

Antioxidant Activity of the Lignins Derived from Fluidized-Bed Fast Pyrolysis

A challenge in recent years has been the rational use of forest and agriculture residues for the production of bio-fuel, biochemical, and other bioproducts. In this study, potentially useful compounds from pyrolytic lignins were identified by HPLC-MS/MS and untargeted metabolomics. The metabolites identified were 2-(4-allyl-2-methoxyphenoxy)-1-(4-hydroxy-3-methoxyphenyl)-1-propanol, benzyl benzoate, fisetinidol, phenyllactic acid, 2-phenylpropionic acid, 6,3′-dimethoxyflavone, and vanillin. The 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity (DPPH), trolox equivalent antioxidant capacity (TEAC), and total phenolics content (TPC) per gram of pyrolytic lignin ranged from 14 to 503 mg ascorbic acid equivalents, 35 to 277 mg trolox equivalents, and 0.42 to 50 mg gallic acid equivalents, respectively. A very significant correlation was observed between the DPPH and TPC (r = 0.8663, p ≤ 0.0001), TEAC and TPC (r = 0.8044, p ≤ 0.0001), and DPPH and TEAC (r = 0.8851, p ≤ 0.0001). The polyphenolic compounds in the pyrolytic lignins which are responsible for radical scavenging activity and antioxidant properties can be readily profiled with HPLC-MS/MS combined with untargeted metabolomics. The results also suggest that DPPH, TEAC, and TPC assays are suitable methods for the measurement of antioxidant activity in a variety of pyrolytic lignins. These data show that the pyrolytic lignins can be considered as promising sources of natural antioxidants and value-added chemicals.

Neoflavonoids as Inhibitors of HIV-1 Replication by Targeting the Tat and NF-κB Pathways

Twenty-eight neoflavonoids have been prepared and evaluated in vitro against HIV-1. Antiviral activity was assessed on MT-2 cells infected with viral clones carrying the luciferase reporter gene. Inhibition of HIV transcription and Tat function were tested on cells stably transfected with the HIV-LTR and Tat protein. Seven 4-phenylchromen-2-one derivatives showed HIV transcriptional inhibitory activity but only the phenylchrome-2-one 10 inhibited NF-κB and displayed anti-Tat activity simultaneously. Compounds 10, 14, and 25, inhibited HIV replication in both targets at concentrations <25 μM. The assays of these synthetic 4-phenylchromen-2-ones may aid in the investigation of some aspects of the anti-HIV activity of such compounds and could serve as a scaffold for designing better anti-HIV compounds, which may lead to a potential anti-HIV therapeutic drug.

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.

3-Amidocoumarins as Potential Multifunctional Agents against Neurodegenerative Diseases

Monoamine oxidase (MAO) generates reactive oxygen species (ROS), which cause neuronal cell death, causing neurodegeneration. Agents that are able to concurrently inhibit MAO and scavenge free radicals represent promising multifunctional neuroprotective agents that could be used to delay or slow the progression of neurodegenerative diseases. In this work, variously substituted 3-amidocoumarins are described that exert neuroprotection in vitro against hydrogen peroxide in rat cortical neurons, as well as antioxidant activity in a 1,1-diphenyl-2-picrylhydrazyl (DPPH⋅) radical scavenging assay. Selective and reversible inhibitors of the MAO-B isoform were identified. Interestingly, in the case of the 3-benzamidocoumarins, substitution at position 4 with a hydroxy group abolishes MAO-B activity, but the compounds remain active in the neuroprotection model. Further evaluation of 3-heteroarylamide derivatives indicates that it is the nature of the heterocycle that determines the neuroprotective effects. Evaluation in a parallel artificial membrane permeability assay (PAMPA) highlighted the need to further improve the blood-brain barrier permeability of this compound class. However, the compounds described herein adhere to Lipinski's rule of five, suggesting that this novel scaffold has desirable properties for the development of potential drug candidates.

BF3·Et2O Catalysed 4-Aryl-3-phenyl-benzopyrones, Pro-SERMs, and Their Characterization

We have synthesized the novel 4-(4-hydroxy-benzyl)-3-phenyl-chromen-2-one which is a precursor of SERMs with a smaller number of steps and good yield. Two methodologies for the synthesis have been worked out. Anhydrous BF3·Et2O catalyzed reaction was found to be selective for product formation while anhydrous AlCl3, FeCl3, and SnCl4 catalyzed ones were nonselective.

Extraction, characterization and biological studies of phytochemicals from Mammea suriga

The present work involves extraction of phytochemicals from the root bark of a well-known Indian traditional medicinal plant, viz. Mammea suriga, with various solvents and evaluation of their in vitro antimicrobial and antioxidant activities using standard methods. The phytochemical analysis indicates the presence of some interesting secondary metabolites like flavonoids, cardiac glycosides, alkaloids, saponins and tannins in the extracts. Also, the solvent extracts displayed promising antimicrobial activity against Staphylococcus aureus, Bacillus subtilis and Cryptococcus neoformans with inhibition zone in a range of 20-33 mm. Further, results of their antioxidant screening revealed that aqueous extract (with IC₅₀ values of 111.51±1.03 and 31.05±0.92 μg/mL in total reducing power assay and DPHH radical scavenging assay, respectively) and ethanolic extract (with IC₅₀ values of 128.00±1.01 and 33.25±0.89 μg/mL in total reducing power assay and DPHH radical scavenging assay, respectively) were better antioxidants than standard ascorbic acid. Interestingly, FT-IR analysis of each extract established the presence of various biologically active functional groups in it.

Chemistry and Biological Activity of Coumarins at Molecular Level

Synthetic coumarins were prepared in high yields using ionic liquids as an environmental friendly alternative. 3,4-Dimethyl-7-hydroxycoumarin (3ab) and 3-isopropyl-4-methyl-5,7-dihydroxycoumarin (3bc) showed interesting activity against Taq DNA polymerase with IC50 values of 115.7 μM and 82.2 μM, respectively. Also, 4-methyl-7-hydroxycoumarin (3aa) and 4-methyl-5,7-dihydroxycoumarin (3ba) exhibited inhibitory activity against MMLV-RT with IC50 values of 23.5 μM and 18.3 μM, respectively. These inhibitors could have importance as antiretroviral chemotherapeutic agents and also for the development of antitumor drugs.

An efficient solvent-free synthesis of 2-hydroxy-2-(trifluoromethyl)-2H-chromenes using silica-immobilized L-proline

An efficient synthesis of 2-hydroxy-2-(trifluoromethyl)-2H-chromene-3-carboxylates was carried out under solvent-free conditions in an oven or microwave oven via the Knoevenagel condensation of salicylaldehydes with ethyl trifluoroacetoacetate followed by intramolecular cyclization in the presence of silica-immobilized L-proline. The structures of the title compounds were characterized by IR, ¹H-NMR, ¹³C-NMR, HRMS and X-ray single crystal diffraction. The improved method described herein is economical, easily-operated and environmentally friendly. Furthermore, the catalyst can be recovered conveniently and reused without obvious loss of activity.

Strategies to Block HIV Transcription: Focus on Small Molecule Tat Inhibitors

After entry into the target cell, the human immunodeficiency virus type I (HIV) integrates into the host genome and becomes a proviral eukaryotic transcriptional unit. Transcriptional regulation of provirus gene expression is critical for HIV replication. Basal transcription from the integrated HIV promoter is very low in the absence of the HIV transactivator of transcription (Tat) protein and is solely dependent on cellular transcription factors. The 5' terminal region (+1 to +59) of all HIV mRNAs forms an identical stem-bulge-loop structure called the Transactivation Responsive (TAR) element. Once Tat is made, it binds to TAR and drastically activates transcription from the HIV LTR promoter. Mutations in either the Tat protein or TAR sequence usually affect HIV replication, indicating a strong requirement for their conservation. The necessity of the Tat-mediated transactivation cascade for robust HIV replication renders Tat one of the most desirable targets for transcriptional therapy against HIV replication. Screening based on inhibition of the Tat-TAR interaction has identified a number of potential compounds, but none of them are currently used as therapeutics, partly because these agents are not easily delivered for an efficient therapy, emphasizing the need for small molecule compounds. Here we will give an overview of the different strategies used to inhibit HIV transcription and review the current repertoire of small molecular weight compounds that target HIV transcription.

Multiple heating rate kinetic parameters, thermal, X-ray diffraction studies of newly synthesized octahedral copper complexes based on bromo-coumarins along with their antioxidant, anti-tubercular and antimicrobial activity evaluation

Series of new Cu(II) complexes were synthesized by classical thermal technique. The biologically potent ligands (L) were prepared by refluxing 6-brom 3-acetyl coumarin with aldehydes in the presence of piperidine in ethanol. The Cu(II) complexes have been synthesized by mixing an aqueous solution of Cu(NO(3))(2) in 1:1 molar ratios with ethanolic bidentate ligands and Clioquinol. The structures of the ligands and their copper complexes were investigated and confirmed by the elemental analysis, FT-IR, (1)H NMR, (13)C NMR, mass spectral and powder X-ray diffraction studies respectively. Thermal behaviour of newly synthesized mixed ligand Cu(II) complexes were investigated by means of thermogravimetry, differential thermogravimetry, differential scanning calorimetry, electronic spectra and magnetic measurements. Dynamic scan of DSC experiments for Cu(II) complexes were taken at different heating rates (2.5-20 °C min(-1)). Kinetic parameters for second step degradation of all complexes obtained by Kissinger's and Ozawa's methods were in good agreement. On the basis of these studies it is clear that ligands coordinated to metal atom in a monobasic bidentate mode, by OO and ON donor system. Thus, suitable octahedral geometry for hexa-coordinated state has been suggested for the metal complexes. Both the ligands as well as its complexes have been screened for their in vitro antioxidant, anti-tubercular and antimicrobial activities. All were found to be significant potent compared to parent ligands employed for complexation.

3-Phenylcoumarins as inhibitors of HIV-1 replication

We have synthesized fourteen 3-phenylcoumarin derivatives and evaluated their anti-HIV activity. Antiviral activity was assessed on MT-2 cells infected with viral clones carrying the luciferase gene as reporter. Inhibition of HIV transcription and Tat function were tested on cells stably transfected with the HIV-LTR and Tat protein. Six compounds displayed NF-κB inhibition, four resulted Tat antagonists and three of them showed both activities. Three compounds inhibited HIV replication with IC₅₀ values < 25 µM. The antiviral effect of the 4-hydroxycoumarin derivative 19 correlates with its specific inhibition of Tat functions, while compound 8, 3-(2-chlorophenyl)coumarin, seems to act through a mechanism unrelated to the molecular targets considered in this research.

The Continuing Evolution of HIV-1 Therapy: Identification and Development of Novel Antiretroviral Agents Targeting Viral and Cellular Targets

During the past three decades, over thirty-five anti-HIV-1 therapies have been developed for use in humans and the progression from monotherapeutic treatment regimens to today's highly active combination antiretroviral therapies has had a dramatic impact on disease progression in HIV-1-infected individuals. In spite of the success of AIDS therapies and the existence of inhibitors of HIV-1 reverse transcriptase, protease, entry and fusion, and integrase, HIV-1 therapies still have a variety of problems which require continued development efforts to improve efficacy and reduce toxicity, while making drugs that can be used throughout both the developed and developing world, in pediatric populations, and in pregnant women. Highly active antiretroviral therapies (HAARTs) have significantly delayed the progression to AIDS, and in the developed world HIV-1-infected individuals might be expected to live normal life spans while on lifelong therapies. However, the difficult treatment regimens, the presence of class-specific drug toxicities, and the emergence of drug-resistant virus isolates highlight the fact that improvements in our therapeutic regimens and the identification of new and novel viral and cellular targets for therapy are still necessary. Antiretroviral therapeutic strategies and targets continue to be explored, and the development of increasingly potent molecules within existing classes of drugs and the development of novel strategies are ongoing.

Mammea E/BB, an isoprenylated dihydroxycoumarin protonophore that potently uncouples mitochondrial electron transport, disrupts hypoxic signaling in tumor cells

The mammea-type coumarin mammea E/BB (1) was found to inhibit both hypoxia-induced and iron chelator-induced hypoxia-inducible factor-1 (HIF-1) activation in human breast tumor T47D cells with IC(50) values of 0.96 and 0.89 μM, respectively. Compound 1 suppressed the hypoxic induction of secreted VEGF protein (T47D cells) and inhibited cell viability/proliferation in four human tumor cell lines. Compound 1 (at 5 and 20 μM) inhibited human breast tumor MDA-MB-231 cell migration. While the mechanisms that underlie their biological activities have remained unknown, prenylated mammea coumarins have been shown to be cytotoxic to human tumor cells, suppress tumor growth in animal models, and display a wide variety of antimicrobial effects. Mechanistic studies revealed that 1 appears to exert an assemblage of cellular effects by functioning as an anionic protonophore that potently uncouples mitochondrial electron transport and disrupts mitochondrial signaling in human tumor cell lines.

6-Butyryl-5-hy-droxy-4-phenyl-seselin

IN THE TITLE COUMARIN COMPOUND (SYSTEMATIC NAME: 6-butyryl-5-hy-droxy-8,8-dimethyl-4-phenyl-2H,8H-benzo[1,2-b;3,4-b']dipyran-2-one), C(24)H(22)O(5), also known as mammea A/AC cyclo D, the chromene and pyran rings are almost coplanar with a maximum deviation from the mean plane of 0.295 (2) Å. The attached phenyl group is inclined at 53.49 (8)° with respect to the chromene ring. The mol-ecular structure is stabilized by an intra-molecular O-H⋯O hydrogen bond. In the crystal, mol-ecules are linked into sheets parallel to (101) by inter-molecular C-H⋯O hydrogen bonds. Adjacent sheets are sustained by inter-molecular C-H⋯π and π-π [centroid-centroid distance = 4.471 (2) Å] inter-actions.

A new cytotoxic friedelane acid--pluricostatic acid--and other compounds from the leaves of Marila pluricostata

Bioassay-guided fractionation of the dichloromethane extract of the leaves of Marila pluricostata led to the isolation of 2α,3β-dihydroxy-D:A-friedoolean-28-oic acid (pluricostatic acid), a new friedelane triterpenoid, (1), ten known triterpenoids and three sterols. Their chemical structures were elucidated through spectroscopic analysis. The less polar fractions, on GC/MS analysis and comparison with a MS library, resulted in the identification of twenty four sesquiterpenoids. The new triterpenoid acid 1 showed cytotoxicity against the MCF-7, H-460, and SF-268 human cancer cell lines with GI₅₀ values from 1.2 to 3.3 μg/mL.