Design, synthesis and biological evaluation of novel non-nucleoside HIV-1 reverse transcriptase inhibitors with broad-spectrum chemotherapeutic properties

Quinoline hybrid derivatives as effective structural motifs in the treatment of tuberculosis: Emphasis on structure-activity relationships

Mycobacterium tuberculosis (MTB/Mtb) is the causative agent of tuberculosis (TB), a highly infectious serious airborne illness. TB usually affects the lungs, in 25 % of patients (children or immune impaired adults), mycobacteria can enter the blood stream and infect other bodily areas such the meninges, pleura, lymphatic system, genitourinary system, bones, and joints. Currently, the most challenging aspect of treating this illness is the ineffectiveness of the most potent first-line anti-TB medications, isoniazid, rifampin, pyrazinamide, and ethambutol, which can result in multidrug-resistant TB (MDR-TB), extensively drug-resistant TB (XDR-TB), and in rare instances, completely drug-resistant TB (TDR-TB). As a result, finding new pharmaceutical compounds to treat these diseases is a significant challenge for the scientific community. A number of bio-active molecules have been investigated in this quest, including quinoline, which is considered a promising candidate for the development of TB drugs. It is known that quinoline are low in toxicity and have a wide range of pharmacological properties. Researchers have investigated quinoline scaffolds as anti-TB drugs based on their biological spectrum. The objective of this review is to examine the recent development of quinoline and its structural characteristics crucial to its antitubercular (anti-TB) activity. A molecular analog of the TB treatment can be designed and identified with this information. As a result, future generation quinoline-based anti-TB agents with greater potency and safety can also be explored.

Isatin improves oligoasthenospermia caused by busulfan by regulating GSH/GPX4 axis to inhibit ferroptosis

Introduction

Ferroptosis, induced by iron overload and an imbalance in redox homeostasis, promotes the generation of reactive oxygen species (ROS), leading to iron-dependent lipid peroxides (LPO) and oxidative stress. Lipid peroxidation induced by reactive oxygen species is essential for the progression of spermatogenesis. However, its imbalance can lead to reproductive system damage and oligoasthenospermia, a critical cause of oligoasthenospermia. Isatin (ISA) is a naturally occurring compound that is widely distributed in lobsters, crustaceans, shellfish and various plants. It exhibits significant antioxidant and anti-aging properties, suggesting its potential as a therapeutic agent for the treatment of oligoasthenospermia. This study aimed to investigate the effects and mechanisms of ISA on oligoasthenospermia and to elucidate the underlying molecular pathways.

Methods

All mice were divided into normal group, model group and treatment group. Both model group and treatment group received a single intraperitoneal injection of 30 mg/kg BUS to create the model of oligoasthenospermia. After 2 weeks, the treatment group received different doses of 25, 50 and 100 mg/kg ISA by gavage for 28 days, and then mice were sacrificed and tested.

Results

The results demonstrated that ISA effectively reversed busulfan-induced reproductive system damage in mice. This included the restoration of testicular histomorphology, improvement in sperm concentration and motility, regulation of serum sex hormone levels, and normalization of various oxidative indices in testicular tissue. Furthermore, ISA successfully reversed testicular ferroptosis by restraining the translocation of nuclear factor erythroid 2-related factor 2 (NRF2) into the nucleus and improved oligoasthenospermia through the glutathione (GSH)/glutathione peroxidase 4 (GPX4) axis.

Discussion

ISA was found to effectively ameliorate oligoasthenospermia in mice, presenting a potential therapeutic option for patients with this condition.

Quinolines and isoquinolines as HIV-1 inhibitors: Chemical structures, action targets, and biological activities

Human immunodeficiency virus type 1 (HIV-1), a lentivirus that causes acquired immunodeficiency syndrome (AIDS), poses a serious threat to global public health. Since the advent of the first drug zidovudine, a number of anti-HIV agents acting on different targets have been approved to combat HIV/AIDS. Among the abundant heterocyclic families, quinoline and isoquinoline moieties are recognized as promising scaffolds for HIV inhibition. This review intends to highlight the advances in diverse chemical structures and abundant biological activity of quinolines and isoquinolines as anti-HIV agents acting on different targets, which aims to provide useful references and inspirations to design and develop novel HIV inhibitors for medicinal chemists.

A Review of the Development of Multitarget Molecules against HIV-TB Coinfection Pathogens

The human immunodeficiency virus (HIV) produces the pathologic basis of acquired immunodeficiency syndrome (AIDS). An increase in the viral load in the body leads to a decline in the number of T lymphocytes, compromising the patient's immune system. Some opportunistic diseases may result, such as tuberculosis (TB), which is the most common in seropositive patients. Long-term treatment is required for HIV-TB coinfection, and cocktails of drugs for both diseases are used concomitantly. The most challenging aspects of treatment are the occurrence of drug interactions, overlapping toxicity, no adherence to treatment and cases of resistance. Recent approaches have involved using molecules that can act synergistically on two or more distinct targets. The development of multitarget molecules could overcome the disadvantages of the therapies used to treat HIV-TB coinfection. This report is the first review on using molecules with activities against HIV and Mycobacterium tuberculosis (MTB) for molecular hybridization and multitarget strategies. Here, we discuss the importance and development of multiple targets as a means of improving adherence to therapy in cases of the coexistence of these pathologies. In this context, several studies on the development of structural entities to treat HIV-TB simultaneously are discussed.

Isatin derivatives as broad-spectrum antiviral agents: the current landscape

In recent decades, several viruses have resulted in large outbreaks with serious health, economic and social consequences. The current unprecedented outbreak of the new coronavirus, SARS-COV-2, necessitates intensive efforts for delivering effective therapies to eradicate such a deadly virus. Isatin is an opulent heterocycle that has been proven to provide tremendous opportunities in the area of drug discovery. Over the last fifty years, suitably functionalized isatin has shown remarkable and broad-spectrum antiviral properties. The review herein is an attempt to compile all of the reported information about the antiviral activity of isatin derivatives with an emphasis on their structure-activity relationships (SARs) along with mechanistic and molecular modeling studies. In this regard, we are confident that the review will afford the scientific community a valuable platform to generate more potent and cost-effective antiviral therapies based on isatin templates.

A Neuroprotective Dose of Isatin Causes Multilevel Changes Involving the Brain Proteome: Prospects for Further Research

Isatin (indole-2,3-dione) is an endogenous regulator, exhibiting a wide range of biological and pharmacological activities. At doses of 100 mg/kg and above, isatin is neuroprotective in different experimental models of neurodegeneration. Good evidence exists that its effects are realized via interaction with numerous isatin-binding proteins identified in the brain and peripheral tissues studied. In this study, we investigated the effect of a single dose administration of isatin to mice (100 mg/kg, 24 h) on differentially expressed proteins and a profile of the isatin-binding proteins in brain hemispheres. Isatin administration to mice caused downregulation of 31 proteins. However, these changes cannot be attributed to altered expression of corresponding genes. Although at this time point isatin influenced the expression of more than 850 genes in brain hemispheres (including 433 upregulated and 418 downregulated genes), none of them could account for the changes in the differentially expressed proteins. Comparative proteomic analysis of brain isatin-binding proteins of control and isatin-treated mice revealed representative groups of proteins sensitive to isatin administration. Control-specific proteins (n = 55) represent specific targets that interact directly with isatin. Appearance of brain isatin-binding proteins specific to isatin-treated mice (n = 94) may be attributed to the formation of new clusters of protein–protein interactions and/or novel binding sites induced by a high concentration of this regulator (ligand-induced binding sites). Thus, isatin administration produces multiple effects in the brain, which include changes in gene expression and also profiles of isatin-binding proteins and their interactomes. Further studies are needed for deeper insight into the mechanisms of the multilevel changes in the brain proteome induced by isatin. In the context of the neuroprotective action, these changes may be aimed at interruption of pathological links that begin to form after initiation of pathological processes.

Jatrorrhizine suppresses the antimicrobial resistance of methicillin-resistant Staphylococcus aureus

Bacterial resistance to antimicrobial agents, including multidrug resistance, is an increasing problem in the treatment of infectious diseases. The development of resistance-modifying agents represents a potential strategy to alleviate the spread of bacterial resistance to antibiotics. A checkerboard microdilution assay was used to determine the synergy of jatrorrhizine and the antibiotic, norfloxacin (NFX). A bacterial ethidium bromide efflux assay, reverse transcription semi-quantitative polymerase chain reaction analysis and molecular docking study were performed. The three-dimensional structure of NorA multidrug efflux pump (NorA) was generated using a multiple threading approach. A murine thigh infection model was used to evaluate the in vivo synergistic effect. As a natural product, jatrorrhizine exhibited little antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) SA1199B with a minimum inhibitory concentration (MIC) of 64 mg/l. According to the investigations of the mechanism, jatrorrhizine significantly inhibited bacterial drug efflux and the expression of NorA in the mRNA level as it can bind to NorA by hydrogen-bonds, hydrophobic and electrostatic interactions. The in vivo synergistical bactericidal activity of jatrorrhizine and NFX against MRSA was confirmed in a murine thigh infection model. As a novel resistance-modifying agent, jatrorrhizine exhibited in vitro and in vivo synergistic activities against MRSA, and inhibited bacterial drug efflux. The effects were mediated by the suppression of NorA mRNA expression and/or interactions with NorA efflux pump. These data support the hypothesis that jatrorrhizine is a potential agent for therapeutic use in infections caused by MRSA.

Quinolone derivatives: Potential anti-HIV agent-development and application

Acquired immune deficiency syndrome (AIDS)/human immunodeficiency virus (HIV) is one of the largest and most devastating public health pandemics throughout the world. The global pandemic of drug-sensitive HIV and the increasing threat from drug-resistant HIV result in an urgent need to develop more effective anti-HIV candidates. Quinolone represents a significant class of privileged heterocycles, and its derivatives possess promising in vitro and in vivo anti-HIV properties. The 4-quinolone elvitegravir has already been approved for the treatment of HIV; thus, quinolone derivatives might be promising candidates with anti-HIV activity. This review emphasizes quinolone derivatives with potential anti-HIV activity, covering articles published between 1992 and 2019. The structure-activity relationship is also discussed to provide insights for further development of more active quinolone derivatives.

Ciprofloxacin derivatives and their antibacterial activities

Bacterial infections represent a significant health threat globally, and are responsible for the majority of hospital-acquired infections, leading to extensive mortality and burden on global healthcare systems. The second generation fluoroquinolone ciprofloxacin which exhibits excellent antimicrobial activity and pharmacokinetic properties as well as few side effects is introduced into clinical practice for the treatment of various bacterial infections for around 3 decades. The emergency and widely spread of drug-resistant pathogens making ciprofloxacin more and more ineffective, so it's imperative to develop novel antibacterials. Numerous of ciprofloxacin derivatives have been synthesized for seeking for new antibacterials, and some of them exhibited promising potency. This review aims to summarize the recent advances made towards the discovery of ciprofloxacin derivatives as antibacterial agents and the structure-activity relationship of these derivatives was also discussed.

4-Quinolone derivatives and their activities against Gram positive pathogens

Gram-positive bacteria are responsible for a broad range of infectious diseases, and the emergency and wide spread of drug-resistant Gram-positive pathogens including MRSA and MRSE has caused great concern throughout the world. 4-Quinolones which are exemplified by fluoroquinolones are mainstays of chemotherapy against various bacterial infections including Gram-positive pathogen infections, and their value and role in the treatment of bacterial infections continues to expand. However, the resistance of Gram-positive organisms to 4-quinolones develops rapidly and spreads widely, making them more and more ineffective. To overcome the resistance and reduce the toxicity, numerous of 4-quinolone derivatives were synthesized and screened for their in vitro and in vivo activities against Gram-positive pathogens, and some of them exhibited excellent potency. This review aims to outlines the recent advances made towards the discovery of 4-quinolone-based derivatives as anti-Gram-positive pathogens agents and the critical aspects of design as well as the structure-activity relationship of these derivatives. The enriched SAR paves the way to the further rational development of 4-quinolones with a unique mechanism of action different from that of the currently used drugs to overcome the resistance, well-tolerated and low toxic profiles.

In-silico Studies Show Potent Inhibition of HIV-1 Reverse Transcriptase Activity by a Herbal Drug

Acquired immunodeficiency syndrome (AIDS) is a life threatening disease of the human immune system caused by human immunodeficiency virus (HIV). Effective inhibition of reverse transcriptase activity is a prominent, clinically viable approach for the treatment of AIDS. Few non-nucleoside reverse transcriptase inhibitors (NNRTIs) have been approved by the United States Food and Drug Administration (US FDA) as drugs for AIDS. In order to enhance therapeutic options against AIDS we examined novel herbal compounds of 4-thiazolidinone and its derivatives that are known to have remarkable antiviral potency. Our molecular docking and simulation experiments have identified one such herbal molecule known as (5E)-3-(2-aminoethyl)-5-benzylidene-1, 3-thiazolidine-2,4-dione that may bind HIV-1RT with high affinity to cause noncompetitive inhibition. Results are also compared with other US FDA approved drugs. Long de novo simulations and docking study suggest that the ligand (5E)-3-(2-aminoethyl)-5-benzylidene-1, 3-thiazolidine-2,4-dione (CID: 1656714) has strong binding interactions with Asp113, Asp110, Asp185 and Asp186 amino acids, all of which belong to one or the other catalytic pockets of HIV-1RT. It is expected that these interactions could be critical in the inhibitory activity of the HIV-1RT. Therefore, this study provides an evidence for consideration of (5E)-3-(2-aminoethyl)-5-benzylidene-1, 3-thiazolidine-2,4-dione as a valuable natural molecule in the treatment and prevention of HIV-associated disorders.

Synthesis, HIV-1 RT inhibitory, antibacterial, antifungal and binding mode studies of some novel N-substituted 5-benzylidine-2,4-thiazolidinediones

Background

Structural modifications of thiazolidinediones at 3^rd and 5^th position have exhibited significant biological activities. In view of the facts, and based on in silico studies carried out on thiazolidine-2,4-diones as HIV-1- RT inhibitors, a novel series of 2,4-thiazolidinedione analogs have been designed and synthesized.

Methods

Title compounds were prepared by the reported method. Conformations of the structures were assigned on the basis of results of different spectral data. The assay of HIV-1 RT was done as reported by Silprasit et al. Antimicrobial activity was determined by two fold serial dilution method. Docking study was performed for the highest active compounds by using Glide 5.0.

Results

The newly synthesized compounds were evaluated for their HIV-1 RT inhibitory activity. Among the synthesized compounds, compound 24 showed significant HIV-1 RT inhibitory activity with 73% of inhibition with an IC₅₀ value of 1.31 μM. Compound 10 showed highest activity against all the bacterial strains.

A molecular modeling study was carried out in order to investigate the possible interactions of the highest active compounds 24, 10 and 4 with the non nucleoside inhibitory binding pocket(NNIBP) of RT, active site of GlcN-6-P synthase and cytochrome P450 14-α-sterol demethylase from Candida albicans (Candida P450DM) as the target receptors respectively using the Extra Precision (XP) mode of Glide software.

Conclusion

A series of novel substituted 2-(5-benzylidene-2,4-dioxothiazolidin-3-yl)-N-(phenyl)propanamides (4–31) have been synthesized and evaluated for their HIV-1 RT inhibitory activity, antibacterial and antifungal activities. Some of the compounds have shown significant activity. Molecular docking studies showed very good interaction.

Monitoring metabolites from Schizophyllum commune interacting with Hypholoma fasciculare combining LESA-HR mass spectrometry and Raman microscopy

Microbial competition for territory and resources is inevitable in habitats with overlap between niches of different species or strains. In fungi, competition is brought about by antagonistic mycelial interactions which alter mycelial morphology, metabolic processes, secondary metabolite release, and extracellular enzyme patterns. Until now, we were not able study in vivo chemical interactions of different colonies growing on the same plate. In this report, we developed a fast and least invasive approach to identify, quantify, and visualize co culture-induced metabolites and their location of release within Schizophyllum commune. The pigments indigo, indirubin, and isatin were used as examples to show secondary metabolite production in the interaction zone with Hypholoma fasciculare. Using a combinatory approach of Raman spectroscopy imaging, liquid extraction surface analysis (LESA), and high-resolution mass spectrometry, we identified, quantified, and visualized the presence of indigo and indirubin in the interaction zone. This approach allows the investigation of metabolite patterns between wood degrading species in competition to gain insight in community interactions, but could also be applied to other microorganisms. This method advances analysis of living, still developing colonies and are in part not destructive as Raman spectroscopy imaging is implemented.

Synthesis, hematological, biochemical, and neurotoxicity screening of some mannich base hydrochlorides

BACKGROUND

Mannich bases are an important class of compounds in medicinal chemistry with a wide spectrum of biological activities, however, knowledge on their toxicity is limited.

MATERIALS AND METHODS

Two Mannich base hydrochlorides 1a (2-thienyl-β-dimethylaminoethyl ketone hydrochloride) and 1b (β-dimethylaminopropiophenone hydrochloride) were synthesized and characterized on the basis of their infrared and nuclear magnetic resonance spectral data. The potential effects of the synthesized compounds (5 mg/kg, i.p, during 30 days) on relative weight, hematological parameters, biochemical parameters, and neurotoxicity were tested using male Wistar rat.

RESULTS

The results showed that compound 1b alters body weight on the first 10 days (182%, P < 0.01) and on the last 10 days (107%, P < 0.01) of treatment. The same treatment decreases food intake (P < 0.01) and increases water intake (P < 0.05). Both compounds induced a deficit on rotarod test manifested by a decrease of grasping time (1a: 65.33%, P < 0.01; 1b: 60.55%, P < 0.01) and fall time (1a: 59.75%, P < 0.01; 1b: 56.81%, P < 0.01) only on the last day of training. Moreover, Mannich base 1b decreases the liver relative weight (22.24%, P < 0.01). It was also observed that both products decrease the total serum cholesterol (Ch) levels (1a: 52.87%, P < 0.01; 1b: 64.70%, P < 0.01). Interestingly, compounds 1a and 1b affect hematological parameters manifested by an increase of the number of white blood cells (1a: 32.29%, P < 0.05; 1b: 20.64%, P < 0.05) and red blood cells (RBCs) (1a: 12.57%, P < 0.05; 1b: 20.11%, P < 0.05), an increase of red cell hemoglobin concentration (1a: 10.48%, P < 0.05; 1b: 16.12%, P < 0.05) and of the volume occupied by RBCs or hematocrit (1a: 18.28%, P < 0.05; 1b: 15.56%, P < 0.05), and an increase of the number of platelets (1a: 16.80%, P < 0.05; 1b: 39.96%, P < 0.05) accompanied by a decrease in hemoglobin level only with the compound 1a (7.41%, P < 0.05).

CONCLUSION

These results show that both compounds 1a and 1b induced a hypoxia status associated to low level of Ch and liver toxicity. The deficit observed by rotarod could be explained by the myorelaxant effect of the used products.

Molecular docking of (5E)-3-(2-aminoethyl)-5-(2- thienylmethylene)-1, 3-thiazolidine-2, 4-dione on HIV-1 reverse transcriptase: novel drug acting on enzyme

The study of Human immunodeficiency virus (HIV) in humans and animal models in last 31 years suggested that it is a causative agent of AIDS. This causes serious pandemic public health concern globally. It was reported that the HIV-1 reverse transcriptase (RT) played a critical role in the life cycle of HIV. Therefore, inhibition of HIV-1RT enzyme is one of the major and potential targets in the treatment of AIDS. The enzyme (HIV-1RT) was successfully targeted by non nucleotide reverse transcriptase inhibitors (NNRTIs). But frequent application of NNRTIs led drug resistance mutation on HIV infections. Therefore, there is a need to search new NNRTIs with appropriate pharmacophores. For the purpose, a virtually screened 3D model of unliganded HIV-1RT (1DLO) was explored. The unliganded HIV-1RT (1DLO) was docked with 4-thiazolidinone and its derivatives (ChemBank Database) by using AutoDock4. The best seven docking solutions complex were selected and analyzed by Ligplot. The analysis showed that derivative (5E)-3-(2- aminoethyl)-5-(2- thienylmethylene)-1, 3-thiazolidine-2, 4-dione (CID 3087795) has maximum potential against unliganded HIV-1RT (1DLO). The analysis was done on the basis of scoring and binding ability. The derivative (5E)-3-(2- aminoethyl)-5-(2- thienylmethylene)-1, 3-thiazolidine-2, 4-dione (CID 3087795) indicated minimum energy score and highest number of interactions with active site residue and could be a promising inhibitor for HIV-1 RT as Drug target.

5-Methyl-3,3-bis-(4-methyl-piperazin-1-yl)-1-[2-(4-methyl-piperazin-1-yl)eth-yl]indolin-2-one

In the title compound, C₂₆H₄₃N₇O, each piperazine ring adopts a chair conformation. Two 1-methyl­piperazine rings bond to one Csp³ of the pyrrole ring via the piperazine N atoms, while the third one links to the N atom of the indolin-2-one unit through a flexible ethyl group with an almost syn conformation. In the crystal, mol­ecules are connected through methyl­ene–carbonyl C—H⋯O inter­actions into an infinite chain along the c axis. The almost parallel arrays are stacked, forming a three-dimensional framework.

5-Methyl-3,3-bis-(morpholin-4-yl)-1-[2-(morpholin-4-yl)eth-yl]-2,3-dihydro-1H-indol-2-one

In the title compound, C(23)H(34)N(4)O(4), the morpholine rings adopt chair conformations. The N atom of the indol-2-one group is linked to the N atom of one morpholine ring through a flexible ethyl group with an almost cif conformation. In the crystal, molecules are linked by C-H⋯O interactions into infinite chains along the c direction. The almost parallel infinite chains are further inter-connected via other sets of C-H⋯O inter-actions, forming a three-dimensional framework.

Synthesis and Antiviral Studies of Novel N-Sulphonamidomethyl piperazinyl Fluoroquinolones

A series of novel N-Sulphonamidomethyl piperzinyl fluoroquinolones were synthesized and screened antiviral activity. Eight compounds were synthesized through modifying the N⁴-hydrogen of piperazine in fluoroquinolones with formaldehyde and sulphanomides by Mannich reactions. The structures of the synthesized compounds were characterized by means of their IR and ¹H-NMR spectral data. Synthesized compounds were screened for antiviral activity against influenza A (H1N1, H3N2, H5N1) and influenza B viruses in MDCK cell culture. The antiHIV activities of the new compounds were screened for antiviral activity against replication of HIV-1(III_B) in MT-4 cells. Cytotoxicity of the synthesized compounds was also tested in mock-infected MDCK and MT-4 cells. Compound CF-SD and CF-SDM inhibits the influenza A (H1N1) and compound GF-SDM inhibit the replication of influenza A (H5N1) and B in MDCK cells. All compounds displayed cytostatic propertity in MT-4 cells. Among the compounds tested, GF-SDM (CC₅₀=39.44 μM) most toxic compound in this series.

Synthesis, antibacterial and potential anti-HIV activity of some novel imidazole analogs

A series of 1-(2-methyl-4-nitro-imidazol-1-yl)-3-arylaminopropan-2-ones (2a-e), 2-methyl-5-nitro-1-{2-[arylmethoxy]ethyl}-1H-imidazoles (5a-d), and N-(3-hydroxyphenyl)-2-(substituted imidazol-1-yl)alkanamides (8a-e) were synthesized with the aim to develop novel imidazole analogs with broad-spectrum chemotherapeutic properties. Title compounds were evaluated for their anti-HIV and antibacterial activities.

HIV-1 NNRTIs: structural diversity, pharmacophore similarity, and implications for drug design

Nonnucleoside reverse transcriptase inhibitors (NNRTIs) nowadays represent very potent and most promising anti-AIDS agents that specifically target the HIV-1 reverse transcriptase (RT). However, the effectiveness of NNRTI drugs can be hampered by rapid emergence of drug-resistant viruses and severe side effects upon long-term use. Therefore, there is an urgent need to develop novel, highly potent NNRTIs with broad spectrum antiviral activity and improved pharmacokinetic properties, and more efficient strategies that facilitate and shorten the drug discovery process would be extremely beneficial. Fortunately, the structural diversity of NNRTIs provided a wide space for novel lead discovery, and the pharmacophore similarity of NNRTIs gave valuable hints for lead discovery and optimization. More importantly, with the continued efforts in the development of computational tools and increased crystallographic information on RT/NNRTI complexes, structure-based approaches using a combination of traditional medicinal chemistry, structural biology, and computational chemistry are being used increasingly in the design of NNRTIs. First, this review covers two decades of research and development for various NNRTI families based on their chemical scaffolds, and then describes the structural similarity of NNRTIs. We have attempted to assemble a comprehensive overview of the general approaches in NNRTI lead discovery and optimization reported in the literature during the last decade. The successful applications of medicinal chemistry strategies, crystallography, and computational tools for designing novel NNRTIs are highlighted. Future directions for research are also outlined.

Design of potential reverse transcriptase inhibitor containing Isatin nucleus using molecular modeling studies

Two Dimensional (2D) and Three Dimensional (3D) Quantitative Structure-Activity Relationship (QSAR) studies were performed for correlating the chemical composition of Isatin analogues and their anti-HIV activity using Multiple Linear Regression (MLR) Analysis and k Nearest Neighbor Molecular Field Analysis (kNN MFA), respectively. New Chemical Entities (NCEs) were designed using results of QSAR studies. Binding affinities of designed NCEs were studied on Reverse Transcriptase enzyme using docking studies and their ADME properties were also predicted. Finally most promising compounds were selected from molecular modeling studies. Five compounds containing Isatin nucleus were synthesized and tested for their anti-HIV activity by performing Reverse Transcriptase Assay. Three compounds showed significant Reverse Transcriptase inhibiting activity compared to standard Navirapine. Structure-Activity Relationships were also discussed bases on obtained molecular modeling and experimental data.

Synthesis of zidovudine derivatives with anti-HIV-1 and antibacterial activities

Twelve novel zidovudine derivatives were prepared by modifying 5 '-hydroxyl group of sugar moiety (1-8) and 5-methyl group of thymidine nucleus (9-12) and characterized spectrally. The compounds were evaluated for anti-HIV-1, antitubercular and antibacterial activities. Compound (3-azido-tetrahydro-5- (3,4-dihydro-5-methyl-2,4-dioxopyrimidin-1(2H)-yl)furan-2-yl)methyl 7-(4-(2-phenylacetoyloxy)-3,5- dimethylpiperazin-1-yl)-5-(2-phenylacetoyloxyamino)-1-cyclopropyl-6,8-difluoro-1,4-dihydro-4-oxoquinoline-3-carboxylate (5) was found to be the most potent anti-HIV-1 agent with EC(50) of 0.0012 microM against HIV-1(IIIB) and CC(50) of 34.05 microM against MT-4 with selectivity index of 28,375. Compound 5 inhibited Mycobacterium tuberculosis with MIC of 1.72 microM and inhibited four pathogenic bacteria with MIC of less than 1 microM.

[18F]- and [11C]-labeled N-benzyl-isatin sulfonamide analogues as PET tracers for apoptosis: synthesis, radiolabeling mechanism, and in vivo imaging study of apoptosis in Fas-treated mice using [11C]WC-98

The radiolabeled isatin sulfonamide caspase-3 inhibitor, [18F] 2 (WC-II-89), is a potential PET radiotracer for noninvasive imaging of apoptosis. The radiolabeling mechanism was studied by 13C NMR, ESI/MS, and computational calculations. It was found that the high electrophilicity of the C3 carbonyl group in the isatin ring, which served as a trap for [18F]fluoride, was responsible for the failure of the radiolabeling via nucleophilic substitution of the mesylate group in 7a by [18F]fluoride. Once treated with a strong base, 7a opened the isatin ring completely to form an isatinate intermediate 16, which lost the ability to trap [18F]fluoride, thereby allowing the displacement of the mesylate group to afford the 18F-labeled isatinate 17. [18F] 17 can be converted to isatin [18F] 2 efficiently under acidic conditions. The ring-opening and re-closure of the isatin ring under basic and acidic conditions were confirmed by reversed phase HPLC analysis, ESI/MS and 13C NMR studies. Computational studies of model compounds also support the above proposed mechanism. Similarly, the ring-opening and re-closure method was used successfully in the synthesis of the 11C labeled isatin sulfonamide analogue [11C] 4 (WC-98). A microPET imaging study using [11C] 4 in the Fas liver apoptosis model demonstrated retained activity in the target organ (liver) of the treated mice. Increased caspase-3 activation in the liver was verified by the fluorometric caspase-3 enzyme assay. Therefore, this study provides a useful method for radio-synthesis of isatin derivative radiotracers for PET and SPECT studies, and [11C] 4 is a potential PET radiotracer for noninvasive imaging of apoptosis.

Prodrugs for the treatment of neglected diseases

Recently, World Health Organization (WHO) and Medicins San Frontieres (MSF) proposed a classification of diseases as global, neglected and extremely neglected. Global diseases, such as cancer, cardiovascular and mental (CNS) diseases represent the targets of the majority of the R&D efforts of pharmaceutical companies. Neglected diseases affect millions of people in the world yet existing drug therapy is limited and often inappropriate. Furthermore, extremely neglected diseases affect people living under miserable conditions who barely have access to the bare necessities for survival. Most of these diseases are excluded from the goals of the R&D programs in the pharmaceutical industry and therefore fall outside the pharmaceutical market. About 14 million people,mainly in developing countries, die each year from infectious diseases. From 1975 to 1999,1393 new drugs were approved yet only 1% were for the treatment of neglected diseases[3]. These numbers have not changed until now, so in those countries there is an urgent need for the design and synthesis of new drugs and in this area the prodrug approach is a very interesting field. It provides, among other effects, activity improvements and toxicity decreases for current and new drugs, improving market availability. It is worth noting that it is essential in drug design to save time and money, and prodrug approaches can be considered of high interest in this respect. The present review covers 20 years of research on the design of prodrugs for the treatment of neglected and extremely neglected diseases such as Chagas' disease (American trypanosomiasis), sleeping sickness (African trypanosomiasis), malaria, sickle cell disease, tuberculosis, leishmaniasis and schistosomiasis.

Evaluation of antimycobacterial and DNA gyrase inhibition of fluoroquinolone derivatives

The antimycobacterial activity (both in vitro and in vivo) and DNA gyrase inhibition of newly synthesized fluoroquinolone derivatives were tested against Mycobacterium tuberculosis H(37)Rv and Mycobacterium smegmatis, respectively. Among the synthesized compounds, compound F11 was found to exhibit the most potent in vitro antimycobacterial activity with a MIC value of 0.78 microg/ml, and a selectivity index of more than 80 while not being cytotoxic to the Vero cell line up to 62.5 microg/ml. When evaluated for in vivo antimycobacterial activity, compound F11 demonstrated a paramount decrease of bacterial load in lung and spleen tissues compared to the control and better than the standard drug ciprofloxacin.

Synthesis, anti-HIV and antitubercular activities of lamivudine prodrugs

The synthesis of a novel series of lamivudine prodrugs involving N4-substitution with isatin derivatives is described. The in-vitro antiretroviral activities indicated that compound 3b was found to be equipotent to lamivudine with EC50 of 0.0742+/-0.04 microM. Lamivudine prodrugs bearing fluoroquinoles antibacterial showed 92-100% inhibition against Mycobacterium tuberculosis strain H37Rv at 6.25 microg ml(-1). At pH 7.4, 37 degrees C, the hydrolytic t(1/2) ranged between 120 and 240 min.

Synthesis and evaluation of anti-HIV activity of isatin β-thiosemicarbazone derivatives

On the basis of pharmacophoric modelling studies of existing NNRTIs, a series of isatin beta-thiosemicarbazone derivatives was synthesized and evaluated for their anti-HIV activity in HTLV-III(B) strain in the CEM cell line. Three compounds showed significant anti-HIV activity, whereupon compound 6 was found to be the most active compound with an EC(50) value of 2.62 microM and a selectivity index of 17.41, while not being cytotoxic to the cell line at a CC(50) value of 44.90 microM. Other tested compounds exhibited marked activity below their toxicity threshold.

Isatin: role in stress and anxiety

(Indoledione 2,3) isatin is an endogenous indole found both in mammalian brain and peripheral tissues. Isatin concentration in blood can exceed 1 microM and tissue concentrations vary from < 0.1 to 10 microM. Its level in the brain and periphery is increased by stress. Isatin has a wide spectrum of behavioural and metabolic effects. It is anxiogenic at lower doses and sedative at higher doses. Its most potent known in vitro actions are as an antagonist of atrial natriuretic peptide (ANP) function and NO signaling. In this review, we discuss isatin and stress in animal models, the few human studies, and also what it is known to date about the molecular mechanisms of its action. We suggest the possibility that isatin and its analogues may be interesting new pharmacological agents; Isatin antagonists may be anxiolytic, and isatin agonists may activate the HPA axis.