Mycobactin Analogues with Excellent Pharmacokinetic Profile Demonstrate Potent Antitubercular Specific Activity and Exceptional Efflux Pump Inhibition.

In this study, we have designed and synthesized pyrazoline analogues that partially mimic the structure of mycobactin, to address the requirement of novel therapeutics to tackle the emerging global challenge of antimicrobial resistance (AMR). Our investigation resulted in the identification of novel lead compounds 44 and 49 as potential mycobactin biosynthesis inhibitors against mycobacteria. Moreover, candidates efficiently eradicated intracellularly surviving mycobacteria. Thermofluorimetric analysis and molecular dynamics simulations suggested that compounds 44 and 49 bind to salicyl-AMP ligase (MbtA), a key enzyme in the mycobactin biosynthetic pathway. To the best of our knowledge, these are the first rationally designed mycobactin inhibitors to demonstrate an excellent in vivo pharmacokinetic profile. In addition, these compounds also exhibited more potent whole-cell efflux pump inhibition than known efflux pump inhibitors verapamil and chlorpromazine. Results from this study pave the way for the development of 3-(2-hydroxyphenyl)-5-(aryl)-pyrazolines as a new weapon against superbug-associated AMR challenges.

A Critical Observation on the Design and Development of Reported Peptide Inhibitors of DENV NS2B-NS3 Protease in the Last Two Decades.

Dengue is one of the neglected tropical diseases, which remains a reason for concern as cases seem to rise every year. The failure of the only dengue vaccine, Dengvaxia® , has made the problem more severe and humanity has no immediate respite from this global burden. Dengue virus (DENV) NS2B-NS3 protease is an attractive target partly due to its role in polyprotein processing. Also, since it is among the most conserved domains in the viral genome, it could produce a broad scope of opportunities toward antiviral drug discovery in general. This review has made a detailed analysis of each case of the design and development of peptide inhibitors against DENV NS2B-NS3 protease in the last two decades. Also, we have discussed the reasons attributed to their inhibitory activity, and wherever possible, we have highlighted the concerns raised, challenges met, and suggestions to improve the inhibitory activity. Thus, we attempt to take the readers through the designing and development of reported peptide inhibitors and gain insight from these developments, which could further contribute toward strategizing the designing and development of peptide inhibitors of DENV protease with improved properties in the coming future.

A short survey of dengue protease inhibitor development in the past 6 years (2015-2020) with an emphasis on similarities between DENV and SARS-CoV-2 proteases.

Dengue remains a disease of significant concern, responsible for nearly half of all arthropod-borne disease cases across the globe. Due to the lack of potent and targeted therapeutics, palliative treatment and the adoption of preventive measures remain the only available options. Compounding the problem further, the failure of the only dengue vaccine, Dengvaxia®, also delivered a significant blow to any hopes for the treatment of dengue fever. However, the success of Human Immuno-deficiency Virus (HIV) and Hepatitis C Virus (HCV) protease inhibitors in the past have continued to encourage researchers to investigate other viral protease targets. Dengue virus (DENV) NS2B-NS3 protease is an attractive target partly due to its role in polyprotein processing and also for being the most conserved domain in the viral genome. During the early days of the COVID-19 pandemic, a few cases of Dengue-COVID 19 co-infection were reported. In this review, we compared the substrate-peptide residue preferences and the residues lining the sub-pockets of the proteases of these two viruses and analyzed the significance of this similarity. Also, we attempted to abridge the developments in anti-dengue drug discovery in the last six years (2015-2020), focusing on critical discoveries that influenced the research.

The Mycobactin Biosynthesis Pathway: A Prospective Therapeutic Target in the Battle against Tuberculosis.

The alarming rise in drug-resistant clinical cases of tuberculosis (TB) has necessitated the rapid development of newer chemotherapeutic agents with novel mechanisms of action. The mycobactin biosynthesis pathway, conserved only among the mycolata family of actinobacteria, a group of intracellularly surviving bacterial pathogens that includes Mycobacterium tuberculosis, generates a salicyl-capped peptide mycobactin under iron-stress conditions in host macrophages to support the iron demands of the pathogen. This in vivo essentiality makes this less explored mycobactin biosynthesis pathway a promising endogenous target for novel lead-compounds discovery. In this Perspective, we have provided an up-to-date account of drug discovery efforts targeting selected enzymes (MbtI, MbtA, MbtM, and PPTase) from the mbt gene cluster (mbtA-mbtN). Furthermore, a succinct discussion on non-specific mycobactin biosynthesis inhibitors and the Trojan horse approach adopted to impair iron metabolism in mycobacteria has also been included in this Perspective.

Two new anticancer phenolic derivatives from leaves of Piper betle Linn.

In this study, phytochemical analyses of the chloroform extract of Piper betle L. var. haldia and maghai, Piperaceae, leaves led to the isolation of two new phenolic derivatives: 1-n-decanoyl hydroxy-benzoic acid/1-n-decanoyl phenol (H2) and 3-butylphenol (M1) on the basis of spectroscopic data 1D NMR (1H, 13C) and 2D NMR (1H - 1H COSY, HMBC) as well as ESI-MS, FT-IR and HR-ESI-MS analyses. Compounds H2 and M1 showed excellent antioxidant DPPH free radical scavenging activity with IC50 values of 10.66 µ/mL and 13.65 µg/mL compared to ascorbic acid as a standard antioxidant with an IC50 value of 2.52 µg/mL. Evaluation of cytotoxic activity against two human oral cancer cell lines (SCC-40 and SCC-29B) showed significant effect with GI50 values of 24.08 and 33.08 µg/mL for compound H2 and 35.03 and 47.06 µg/mL for compound M1, compared to Doxorubicin® as a standard cytotoxic drug with GI50 value of < 10 µg/mL.

The new ether derivative of phenylpropanoid and bioactivity was investigated from the leaves of Piper betle L.

A new ether derivative of phenylpropanoid compound, γ-(γ'-isohydroxychavicol)-chavicol octanyl ether (K1) along with one known phenylpropanoid named allyl-pyrocatechol or hydroxychavicol (2) were isolated from Piper betle var. kali collected from Tumluk district, West Bengal India. We first report the presence of compound K1 in the genus Piper. Their structures were established on the basis of various spectroscopic analyses. Compounds K1 and 2 showed excellent antioxidant DPPH free radical scavenging activity with IC50 values of 4.61 and 4.12 µg/mL compared to ascorbic acid as a standard antioxidant drug with IC50 value of 3.42 µg/mL, respectively. Evaluation of in vitro cytotoxic activities of compounds K1 and 2 showed significant effects against human oral cancer cell lines (AW13516 and AW8507), human hepatoma cell lines (HEPG2 and PLC-PRF-5) and a human pancreatic cell line (MIA-PA-CA-2), compared to Doxorubicin® as a standard cytotoxic drug with GI50 values of <10 and 18.18 µg/mL.

Quinazolinone derivative BNUA-3 ameliorated [NDEA+2-AAF]-induced liver carcinogenesis in SD rats by modulating AhR-CYP1B1-Nrf2-Keap1 pathway.

Cytochrome P450 1B1, considered as one of the novel chemotherapeutic targets involved in cancer prevention and therapy is also associated with the conversion of procarcinogens into their active metabolites. The aryl hydrocarbon receptor (AhR) is responsible for mediating different biological responses to a wide variety of environmental pollutants and also causes transcriptional activation of cytochrome P450 enzymes including CYP1B1 and thus plays a pivotal role for initiating cancer and its progression. On the other hand, active carcinogenic metabolites and reactive oxygen species-mediated stress alter different molecular signalling pathways and gene expressions. Quinazoline derivatives are recognized for their diversified biological activities including anticancer properties. The current study was designed for evaluation of chemotherapeutic efficacy of a synthetic quinazolinone derivative BNUA-3 against hepatocellular cancer in Sprague-Dawley (SD) rats. A detailed in vivo analysis was performed by administrating BNUA-3 (15, 30 mg/kg b.w. for 28 days, i.p.) in N-Nitrosodiethylamine + 2-Acetylaminofluorene induced partially hepatectomized liver cancer in SD rats. This was followed by morphological evaluations, biochemical estimations and analysis of different mRNA and protein expressions. The results demonstrated the potency of BNUA-3 in efficient restoration of the altered morphology of liver, its protective effect against lipid peroxidation, enzymic and non-enzymic antioxidants levels in liver tissue which was disrupted after cancer induction. The study also demonstrated downregulation of AhR, CYP1B1 and Keap1 expressions with subsequent augmentation of protective Nrf2, HO-1, NQO1 and GSTA1 expressions thus, revealing the chemotherapeutic potency of BNUA-3 in inhibiting liver carcinogenesis through AhR/CYP1B1/Nrf2/Keap1 pathway.

A novel druggable interprotomer pocket in the capsid of rhino- and enteroviruses.

Rhino- and enteroviruses are important human pathogens, against which no antivirals are available. The best-studied inhibitors are "capsid binders" that fit in a hydrophobic pocket of the viral capsid. Employing a new class of entero-/rhinovirus inhibitors and by means of cryo-electron microscopy (EM), followed by resistance selection and reverse genetics, we discovered a hitherto unknown druggable pocket that is formed by viral proteins VP1 and VP3 and that is conserved across entero-/rhinovirus species. We propose that these inhibitors stabilize a key region of the virion, thereby preventing the conformational expansion needed for viral RNA release. A medicinal chemistry effort resulted in the identification of analogues targeting this pocket with broad-spectrum activity against Coxsackieviruses B (CVBs) and compounds with activity against enteroviruses (EV) of groups C and D, and even rhinoviruses (RV). Our findings provide novel insights in the biology of the entry of entero-/rhinoviruses and open new avenues for the design of broad-spectrum antivirals against these pathogens.

Scaffold Based Search on the Desferithiocin Archetype.

Iron overload disorder and diseases where iron mismanagement plays a crucial role require orally available iron chelators with favourable pharmacokinetic and toxicity profile. Desferrithiocin (DFT), a tridentate and orally available iron chelator has a favourable pharmacokinetic profile but its use has been clinically restricted due to its nephrotoxic potential. The chemical architecture of the DFT has been naturally well optimized for better iron chelation and iron clearance from human biological system. Equally they are also responsible for its toxicity. Hence, subsequent research has been devoted to develop a non-nephrotoxic analogue of DFT without losing its iron clearance ability. The review has been designed to classify the compounds reported till date and to discuss the structure activity relationship with reference to modifications attempted at different positions over pyridine and thiazoline ring of DFT. Compounds are clustered under two major classes: (i) Pyridine analogues and (ii) phenyl analogue and further each class has been further subdivided based on the presence or absence and the number of hydroxy functional groups present over pyridine or phenyl ring of the DFT analogues. Finally a summary and few insights into the development of newer analogues are provided.

Cink4T, a quinazolinone-based dual inhibitor of Cdk4 and tubulin polymerization, identified via ligand-based virtual screening, for efficient anticancer therapy.

Inhibition of cyclin dependent kinase 4 (Cdk4) prevents cancer cells from entering the early G0/G1 phase of the cell division cycle whereas inhibiting tubulin polymerization blocks cancer cells' ability to undergo mitosis (M) late in the cell cycle. We had reported earlier that two non-planar and relatively non-toxic fascaplysin derivatives, an indole and a tryptoline, inhibit Cdk4 with IC50 values of 6.2 and 10 µM, respectively. Serendipitously, we had also found that they inhibited tubulin polymerization. The molecules were efficacious in mouse tumor models. We have now identified Cink4T in a 59-compound quinazolinone library, designed on the basis of ligand-based virtual screening, as a compound that inhibits Cdk4 and tubulin. Its IC50 value for Cdk4 inhibition is 0.47 µM and >50 µM for inhibition of Cdk1, Cdk2, Cdk6, Cdk9. Cink4T inhibits tubulin polymerization with an IC50 of 0.6 µM. Molecular modelling studies on Cink4T with Cdk4 and tubulin crystal structures lend support to these observations. Cancer cell cycle analyses confirm that Cink4T blocks cells at both G0/G1 and M phases as it should if it were to inhibit both Cdk4 and tubulin polymerization. Our results show, for the very first time, that virtual screening can be used to design novel inhibitors that can potently block two crucial phases of the cell division cycle.

Phytoestrogens and their synthetic analogues as substrate mimic inhibitors of CYP1B1.

Phytoestrogens are class of natural compounds that shares structural similarity with estrogen and has the capacity to alter the fertilization in mammals. Till early 1990s, the natural phytoestrogens as well as their synthetic analogues were explored for their fertility modulating activity. During late 1990s, two findings renewed the interest on phytoestrogens as means to control hormone induced cancer: (i) revelation of overexpression of CYP1B1 in breast & ovarian cancer and (ii) protection offered by alphanapthoflavone (ANF) against hormone induced cancer. The objective of the review is to summarize the CYP1B1 inhibitory activity of phytoestrogens and their synthetic analogues reported till date. This review is an attempt to classify phytoestrogens and their synthetic analogues on their chemical architecture rather than simply by their chemical class (flavones, stilbenes etc.). This provides a broader sense to cluster many chemical classes under a particular chemical architecture/framework. Accordingly, we divided the phytoestrogen into three different classes based on two aryl groups (Ar) separated by linker (X), which may be either cyclic (c) or linear (l). The number in subscript to X denotes number of atoms: (i) Ar-cX4-Ar, (ii) Ar-lX3-Ar and (iii) Ar-lX2-Ar. This provides an opportunity to cluster flavones, quinolines and quinazolinones under Ar-cX4-Ar class, while biphenyl ureas and chalcones under Ar-lX3-Ar class. We believe in coming years many chemical scaffolds may be clustered under this framework.

Crystal structures and Hirshfeld surface analyses of 2-[(4,6-di-amino-pyrimidin-2-yl)sulfan-yl]-N-(pyridin-2-yl)acetamide and 2-[(4,6-di-amino-pyrimidin-2-yl)sulfan-yl]-N-(pyrazin-2-yl)acetamide.

In the title compounds, C11H12N6OS (I) and C10H11N7OS (II), the di-amino-pyrimidine ring makes dihedral angles of 71.10 (9)° with the pyridine ring in (I) and 62.93 (15)° with the pyrazine ring in (II). The ethanamine group, -CH2-C(=O)-NH- lies in the plane of the pyridine and pyrazine rings in compounds (I) and (II), respectively. In both compounds, there is an intra-molecular N-H⋯N hydrogen bond forming an S(7) ring motif and a short C-H⋯O inter-action forming an S(6) loop. In the crystals of both compounds, mol-ecules are linked by pairs of N-H⋯N hydrogen bonds, forming inversion dimers with R22(8) ring motifs. In (I), the dimers are linked by N-H⋯O and N-H⋯N hydrogen bonds, forming layers parallel to (1[Formula: see text] [Formula: see text]). The layers are linked by offset π-π inter-actions [inter-centroid distance = 3.777 (1) Å], forming a three-dimensional supra-molecular structure. In (II), the dimers are linked by N-H⋯O, N-H⋯N and C-H⋯O hydrogen bonds, also forming a three-dimensional supra-molecular structure.

New chemical constituents from the Piper betle Linn. (Piperaceae).

The phytochemical investigation of chloroform extract from Piper betle var. haldia, Piperaceae, leaves has resulted in the isolation of two new chemical constituents which were identified as 1-n-dodecanyloxy resorcinol (H1) and desmethylenesqualenyl deoxy-cepharadione-A (H4), on the basis of spectroscopic data 1D NMR (1H and 13C) and 2D NMR (1H-1H COSY and HMBC) as well as ESI-MS, FT-IR and HR-ESI-MS analyses. Compounds H1 and H4 showed excellent antioxidant DPPH free radical scavenging activity with IC50 values of 7.14 µg/mL and 8.08 µg/mL compared to ascorbic acid as a standard antioxidant drug with IC50 value of 2.52 µg/mL, respectively. Evaluation of cytotoxic activity against human hepatoma cell line (PLC-PRF-5) showed moderate effect with the GI50 values of 35.12 µg/mL for H1, 31.01 µg/mL for H4, compared to Doxorubicin® as a standard cytotoxic drug with GI50 value of 18.80 µg/mL.

Crystal structures of 2-[(4,6-di-amino-pyrimidin-2-yl)sulfan-yl]-N-(2,4-di-methyl-phen-yl)acetamide and 2-[(4,6-di-amino-pyrimidin-2-yl)sulfan-yl]-N-(3-meth-oxy-phen-yl)acetamide.

In the title compounds, C14H17N5OS (I) and C13H15N5O2S (II), the dihedral angle between the pyrimidine and benzene rings is 58.64 (8)° in (I) and 78.33 (9)° in (II). In both compounds, there is an intra-molecular C-H⋯O hydrogen bond, and in (II) there is also an intra-molecular N-H⋯N hydrogen bond present. In the crystals of both compounds, a pair of N-H⋯N hydrogen bonds links the individual mol-ecules to form inversion dimers with R22(8) ring motifs. In (I), the dimers are linked by N-H⋯O and C-H⋯O hydrogen bonds, enclosing R21(14), R21(11) and R21(7) ring motifs, forming layers parallel to the (100) plane. There is also an N-H⋯π inter-action present within the layer. In (II), the inversion dimers are linked by N-H⋯O hydrogen bonds enclosing an R44(18) ring motif. The presence of N-H⋯O and C-H⋯O hydrogen bonds generate an R21(6) ring motif. The combination of these various hydrogen bonds results in the formation of layers parallel to the (1-11) plane.

Crystal structures of N-(4-chloro-phen-yl)-2-[(4,6-di-amino-pyrimidin-2-yl)sulfan-yl]acetamide and N-(3-chloro-phen-yl)-2-[(4,6-di-amino-pyrimidin-2-yl)sulfan-yl]acetamide.

The title compounds, C12H12ClN5OS, (I), and C12H12ClN5OS, (II), are 2-[(di-amino-pyrimidin-2-yl)sulfan-yl]acetamides. Compound (II), crystallizes with two independent mol-ecules (A and B) in the asymmetric unit. In each of the mol-ecules, in both (I) and (II), an intra-molecular N-H⋯N hydrogen bond forms an S(7) ring motif. The pyrimidine ring is inclined to the benzene ring by 42.25 (14)° in (I), and by 59.70 (16) and 62.18 (15)° in mol-ecules A and B, respectively, of compound (II). In the crystal of (I), mol-ecules are linked by pairs of N-H⋯N hydrogen bonds, forming inversion dimers with an R22(8) ring motif. The dimers are linked via bifurcated N-H⋯O and C-H⋯O hydrogen bonds, forming corrugated layers parallel to the ac plane. In the crystal of (II), the A mol-ecules are linked through N-H⋯O and N-H⋯Cl hydrogen bonds, forming layers parallel to (100). The B mol-ecules are also linked by N-H⋯O and N-H⋯Cl hydrogen bonds, also forming layers parallel to (100). The parallel layers of A and B mol-ecules are linked via N-H⋯N hydrogen bonds, forming a three-dimensional structure.

Computer-Aided Structure Based Drug Design Approaches for the Discovery of New Anti-CHIKV Agents.

BACKGROUND: Chikungunya is a viral infection caused by Chikungunya virus (CHIKV), an arbovirus transmitted through mosquito (Aedes aegypti and Aedes albopictus) bite. The virus from sylvatic cycle in Africa mutated to new vector adaptation and became one of the major emerging and re-emerging viral infections in the past decade, affecting more than 40 countries. Efforts are being made by many researches to develop means to prevent and control the infection through vaccines and vector control strategy. On the other hand, search for novel chemotherapeutic agents for the treatment of infected patients is on. Approach of repurposed drug is one way of identifying an existing drug for the treatment of CHIKV infection. OBJECTIVE: Review the history of CHIKV nsp2 protease inhibitors derived through structure-based computer-aided drug design along with phytochemicals identified as anti-CHIKV agents. METHODS: A survey on CHIKV inhibitors reported till date has been carriedout. The data obtained were organized and discussed under natural substances and synthetic derivatives obtained as result of rational design. RESULTS: The review provides a well organized content in chronological order that has highly significant information for medicinal chemist who wish to explore the area of Anti-CHIKV drug design and development. Natural compounds with different scaffolds provides an opportunity to explore Ligand based drug design (LBDD), while rational drug design approaches provides opportunity to explore the Structure based drug design. CONCLUSION: From the presented mini-review, readers can understand that this area is less explored and has lots of potential in anti-CHIKVviral drug design & development. of reported literature inferred that, unlike other viral proteases, the nsP2 protease can be targeted for CHIKV viral inhibition. The HTVS process for the identification of anti-CHIK agents provided a few successive validated lead compounds against CHIKV infections.

Bioactive phenylpropanoid analogues from Piper betle L. var. birkoli leaves.

Phytochemical analyses of the chloroform extract of Piper betle L. var. birkoli, Piperaceae, leaves led to the isolation of two new phenylpropanoid analogues: bis-chavicol dodecanoyl ester (2) and bis-hydroxychavicol dodecanoyl ester (3), along with one known compound: allyl-3-methoxy-4-hydroxybenzene (1) on the basis of spectroscopic data 1D (1H and 13C) and 2D (1H-1H COSY and HMBC) NMR, as well as ESI-MS, FT-IR, HR-ESI-MS and LC-ESI-MS. Compound 2 and 3 exhibited excellent antioxidant DPPH radical scavenging activity with IC50 values of 12.67 µg/mL and 1.08 µg/mL compared to ascorbic acid as a standard antioxidant drug with IC50 value of 6.60 µg/mL. Evaluation of cytotoxic activity against two human oral cancer cell lines (AW13516 and AW8507) showed significant effect with GI50 values of 19.61 and 23.01 µg/mL for compound 2 and 10.25 and 13.12 µg/mL for compound 3, compared to Doxorubicin® as a standard cytotoxic drug with GI50 value of < 10 µg/mL.

Crystal structures of 2-[(4,6-di-amino-pyrimidin-2-yl)sulfan-yl]-N-(naphthalen-1-yl)acetamide and 2-[(4,6-di-amino-pyrimidin-2-yl)sulfan-yl]-N-(4-fluoro-phen-yl)acetamide.

The title compounds, C16H15N5OS, (I), and C12H12FN5OS, (II), are [(di-amino-pyrimidine)-sulfan-yl]acetamide derivatives. In (I), the pyrimidine ring is inclined to the naphthalene ring system by 55.5 (1)°, while in (II), the pyrimidine ring is inclined to the benzene ring by 58.93 (8)°. In (II), there is an intra-molecular N-H⋯N hydrogen bond and a short C-H⋯O contact. In the crystals of (I) and (II), mol-ecules are linked by pairs of N-H⋯N hydrogen bonds, forming inversion dimers with R22(8) ring motifs. In the crystal of (I), the dimers are linked by bifurcated N-H⋯(O,O) and C-H⋯O hydrogen bonds, forming layers parallel to (100). In the crystal of (II), the dimers are linked by N-H⋯O hydrogen bonds, also forming layers parallel to (100). The layers are linked by C-H⋯F hydrogen bonds, forming a three-dimensional architecture.

Progress and prospects on DENV protease inhibitors.

New treatments are desperately required to combat increasing rate of dengue fever cases reported in tropical and sub-tropical parts of the world. Among the ten proteins (structural and non-structural) encoded by dengue viral genome, NS2B-NS3 protease is an ideal target for drug discovery. It is responsible for the processing of poly protein that is required for genome replication of the virus. Moreover, inhibitors designed against proteases were found successful in Human Immuno-deficiency Virus (HIV) and Hepatitis C Virus (HCV). Complete molecular mechanism and a survey of inhibitors reported against dengue protease will be helpful in designing effective and potent inhibitors. This review provides an insight on molecular mechanism of dengue virus protease and covers up-to-date information on different inhibitors reported against dengue proteases with medicinal chemistry perspective.

Monoamine Oxidase Inhibitory Activity of Novel Pyrazoline Analogues: Curcumin Based Design and Synthesis.

A series of new 2-methoxy-4-(5-phenyl-4,5-dihydro-1H-pyrazol-3-yl)phenolderivatives, 4-13, were synthesized and tested for their human MAO inhibitory activity. All the compounds were found to be selective and reversible toward hMAO-A except 4, a selective inhibitor of hMAO-B and 12, a nonselective inhibitor. Compound 7 was found to be a potent inhibitor of hMAO-A with Ki = 0.06 ± 0.003 µM and was having selectivity index of (SI = 1.02 × 10(-5)). It was found to be better than standard drug, Moclobemide (hMAO-A with Ki = 0.11 ± 0.01 µM) with selectivity index of SI = 0.049. Molecular docking simulation was carried out to understand the crucial interactions responsible for selectivity and potency.