Synthesis and antimicrobial activity of knipholone analogs

In the present study, we use knipholone as a prototype molecule to identify new anti-infective agents. Since knipholone is insoluble in water, which would have a detrimental effect on its bioavailability and efficacy, we synthesized knipholone Mannich base derivatives (2-4) that have better predicted solubility and investigated their in vitro antimicrobial activity against eight pathogenic bacterial and fungal strains. The chemical structures of compounds 1-4 were elucidated from their 1H and 13C NMR data, and their antimicrobial activity evaluation was carried out by a broth microdilution MTT assay. Compound 3 exhibited the strongest efficacy against Staphylococcus epidermidis, with MIC value of 9.7 µg/mL. While 4 exhibited the best activity against Staphylococcus aureus, with an MIC value of 19.5 µg/mL, and was the only one to significantly inhibit the fungus Trichophyton mentagrophytes (MIC = 78.2 µg/mL). The study provides evidence for the antibacterial activity of aminoalkyl derivatives of knipholone.

Mushroom tyrosinase enzyme catalysis: synthesis of larvicidal active geranylacetone derivatives against Culex quinquesfasciatus and molecular docking studies

The grindstone process, which uses tyrosinase as a catalyst, was used to create analogues of geranylacetone. Tyrosinase was used to prepare the Mannich base under favourable reaction conditions, resulting in a high yield. All synthesized compounds were characterized using FTIR, Nuclear magnetic resonance, and mass spectral analyses. The active geranylacetone derivatives (1a-l) were investigated for larvicidal activity against Culex quinquefasciatus; compound 1b (LD50:20.7 μg/mL) was noticeably more effective than geranylacetone (LD50: >100 μg/mL) and permethrin (LD50: 24.4 μg/mL) lead compounds because of their ability to kill larvae and use them as pesticides. All compounds (1a-1l) were found to be low toxic, whereas compounds 1b, 1d, and 1k were screened for antifeedant screening of non -aquatic target for the toxicity measurement against marine fish Oreochromis mossambicus at 100 μg/mL caused 0% mortality in within 24 h. Molecular docking studies of synthesised compound 1b and permethrin docked with 3OGN, compound 1b demonstrated a greater binding affinity (-9.6 kcal/mol) compared to permethrin (-10.5 kcal/mol). According to these results, the newly synthesised geranylacetone derivatives can serve as lead molecules of larvicides agents.

Synthesis and antitumor activity evaluation of coumarin Mannich base derivatives

Twenty-one new coumarin Mannich base derivatives (11a-u) were synthesized, which exhibited antiproliferation activities in HepG2 (liver cancer), A549 (lung cancer), MCF-7 (breast cancer), and HT-29 (colon cancer). Most of the target compounds showed the most potent activity against HepG2 cells compared with other cancer cells, compound 11g showed the strongest antiproliferative activity (2.10 μM) against HepG2, even superior to the positive control drug 5-FU(5.49 μM). The nitric oxide (NO) release of all compounds in HepG2 cells was determined, of which compound 11g showed high levels of NO release (10.8 μM). Notably, the solubility of compound 11g increased 13-fold compared with the lead 8. The preliminary cytotoxicity studies suggest that 11g had little effect on LO2 cells(normal liver cells, >50 μM). The effect of compound 11g on the apoptosis of HepG2 cells was also studied, and the results showed that the induction effect of compound 11g on apoptosis is a concentration-dependent manner. Our results indicate that compound 11g might be a promising lead for further studies.

Cu (II)-catalyzed: synthesis of imidazole derivatives and evaluating their larvicidal, antimicrobial activities with DFT and molecular docking studies

This paper deals with the evaluation of novel imidazole molecules for their antimicrobial and larvicidal activities. A series of imidazole derivatives 1(a-f) and 2(a-e) were prepared by the Mannich base technique using a Cu(II) catalyst. The Cu(phen)Cl2 catalyst was found to be more effective than other methods. FTIR, elemental analyses, mass spectrometry, 1H NMR, and 13C NMR spectroscopy were performed to elucidate the structures of the synthesised compounds. Antimicrobial and larvicidal activities were investigated for all compounds. The antibacterial activity of compounds (2d) and (2a) were highly active in S.aureus (MIC: 0.25 μg/mL) and K.pneumoniae (MIC: 0.25 μg/mL) compared to ciprofloxacin. Compound (1c) was significantly more effective than clotrimazole in C.albicans (MIC: 0.25 μg/mL). Molecular docking studies of compound 2d showed a higher binding affinity for the 1BDD protein (- 3.4 kcal/mol) than ciprofloxacin (- 4.4 kcal/mol). Compound 1c had a higher binding affinity (- 6.0 kcal/mol) than clotrimazole (- 3.1 kcal/mol) with greater frontier molecular orbital energy and reactivity properties of compound 1c (∆E gap = 0.13 eV). The activity of compound 1a (LD50: 34.9 μg/mL) was more effective in the Culex quinquefasciatus than permethrin (LD50: 35.4 μg/mL) and its molecular docking binding affinity for 3OGN protein (- 6.1 kcal/mol). These newly synthesised compounds can act as lead molecules for the development of larvicides and antibiotic agents.

Design and synthesis of neoteric benzylidene amino-benzimidazole scaffolds for antioxidant and anti-inflammatory activity

Aim: To design a series of neoteric benzylidene amino-benzimidazole derivatives and to synthesize and evaluate them for anti-inflammatory and antioxidant potential. Methods: The designed target scaffolds were synthesized and appraised for in vitro antioxidant action and in vivo anti-inflammatory potential. AutoDock Vina software was employed for design; the Mannich reaction was used for synthesis; and antioxidant and anti-inflammatory potential were demonstrated by the 2,2-diphenyl-1-picryl hydrazyl free-radical scavenging assay and carrageenan-induced paw edema method, respectively. Results: Methyl-incorporating molecules 3-(2-((2-methylbenzylidene)amino)-1H-benzo[d]imidazol-1-yl)-1-phenylpropan-1-one (6c) and 3-(2-((4-methylbenzylidene)amino-1H-benzo[d]imidazol-1-yl)-1-phenylpropan-1-one (6j) showed remarkable antioxidant and anti-inflammatory action, followed by compounds 6f, 6e and 6i containing 3-CH₃, 2-OH, 4-F substituents, respectively. Conclusion: The designed analogs were dynamically confined within the active site of cyclooxygenase-2, and in vitro and in vivo results agreed with molecular docking studies.

Semisynthesis, biological activities, and mechanism studies of Mannich base analogues of magnolol/honokiol as potential α-glucosidase inhibitors

Magnolol and honokiol, derived from a Magnolia officinalis Rehd. et Wils, are a class of natural biphenolic lignans. Currently, the discovery of new α-glucosidase inhibitors from natural analogues is of interest. Here, four series of thirty new Mannich base analogues of magnolol/honokiol were prepared and evaluated for their α-glucosidase inhibitory activities. Among these Mannich base analogues of magnolol/honokiol, 3k and 3l exhibited more potent inhibitory effects on α-glucosidase than the reference drug acarbose, and their IC50 values were 14.94 ± 0.17 µM and 13.78 ± 1.42 µM, respectively. Some interesting structure-activity relationships (SARs) were also analyzed. The enzyme inhibition kinetics indicated that 3k and 3l were noncompetitive inhibitors. This result was in agreement with molecular docking studies, where the binding sites of 3k and 3l to α-glucosidase were different from that of the competitive inhibitor acarbose to α-glucosidase. Moverover, compounds 3k and 3l exhibited low toxicity to normal cells (LO2). Thus, analogues 3k and 3l could be deeply developed for the discovery of natural products based antidiabetic candidates.

Anticancer activity of Mannich bases: a review of recent literature

This report summarizes the latest published data on the antiproliferative action and cytotoxic activity of Mannich bases, a structurally heterogeneous category of chemical entities that includes compounds which are synthesized via the grafting of an aminomethyl function onto diverse substrates by means of the Mannich reaction. The present overview of the topic is an update to the information assembled in a previously published review that covered the literature up to 2014.

Hf(OTf)4-Catalyzed Three-Component Synthesis of N-Carbamate-Protected β-Amino Ketones

Hafnium(IV) triflate (Hf(OTf)₄) has been identified as a potent catalyst for the direct three-component synthesis of β-carbamate ketones. This new method, featuring a low catalyst loading, fast reaction rate, and solvent-free conditions, provided facile access to a diversity of carbamate-protected Mannich bases. A mechanistic investigation indicated that the three-component reaction proceeds via sequential aldol condensation and aza-Michael addition, but not the Mannich-type pathway.

Synthesis and Cytotoxic Activity of Novel Indole Derivatives and Their in silico Screening on Spike Glycoprotein of SARS-CoV-2

This work investigated the interaction of indole with SARS-CoV-2. Indole is widely used as a medical material owing to its astounding biological activities. Indole and its derivatives belong to a significant category of heterocyclic compounds that have been used as a crucial component for several syntheses of medicine. A straightforward one-pot three-component synthesis of indole, coupled with Mannich base derivatives 1a-1j, was synthesized without a catalyst. The products were confirmed by IR, 1H-NMR, 13C-NMR, mass spectra, and elemental analysis. The indole derivatives were tested for cytotoxic activity, using three cancer cell lines and normal cell lines of Human embryonic kidney cell (HEK293), liver cell (LO2), and lung cell (MRC5) by MTT assay using doxorubicin as the standard drug. The result of cytotoxicity indole compound 1c (HepG2, LC50-0.9 μm, MCF-7, LC50-0.55 μm, HeLa, LC50-0.50 μm) was found to have high activity compared with other compounds used for the same purpose. The synthesized derivatives have revealed their safety by exhibiting significantly less cytotoxicity against the normal cell line (HEK-293), (LO2), and (MRC5) with IC50 > 100 μg/ml. Besides, we report an in silico study with spike glycoprotein (SARS-CoV-2-S). The selective molecules of compound 1c exhibited the highest docking score -2.808 (kcal/mol) compared to other compounds. This research work was successful in synthesizing a few compounds with potential as anticancer agents. Furthermore, we have tried to emphasize the anticipated role of indole scaffolds in designing and discovering the much-awaited anti-SARS CoV-2 therapy by exploring the research articles depicting indole moieties as targeting SARS CoV-2 coronavirus.

Naphthalimide-phenanthroimidazole incorporated new fluorescent sensor for "turn-on" Cu2+ detection in living cancer cells

In recent years, fluorescent sensors have emerged as attractive imaging probes due to their distinct responses toward bio-relevant metal ions. However, the bioimaging application main barrier is the 'turn-off' response toward paramagnetic metal ions such as Cu²⁺ under physiological conditions. Herein, we report a new sensor (2-methyl(4-bromo-N-ethylpiperazinyl-1,8-naphthalimido)-4-(1H-phenanthro[9,10-d]imidazole-2-yl) phenol)NPP with multifunctional (Naphthalimide, Piperazine, Phenanthroimidazole) units for fluorescent and colourimetric detection of Cu²⁺ in an aqueous medium. Both absorption and fluorescence spectral titration strategies were used to monitor the Cu²⁺-sensing property of NPP. The NPP displays a weak emission at ca. 455 nm, which remarkably enhances (⁓3.2-fold) upon selective binding of Cu²⁺ over a range of metal ions, including other paramagnetic metal ions (Mn²⁺, Fe³⁺, Co²⁺). The stoichiometry, binding constant (K_a) and the LOD (limit of detection) of NPP toward Cu²⁺ ions were found to be 1:1, 5.0 (± 0.2) × 10⁴ M^-1 and 6.5 (± 0.4) × 10^-7 M, respectively. We have also used NPP as a fluorescent probe to detect Cu²⁺ in live (human cervical HeLa) cancer cells. The emission intensity of NPP was almost recovered in HeLa cells by incubating 'in situ' the derived Cu²⁺ complex (NPP-Cu²⁺) in the presence of a benchmark chelating agent such as EDTA (ethylenediaminetetraacetate). The fluorescent emission of NPP was reverted significantly in each cycle upon sequencial addition of Cu²⁺ and EDTA to the NPP solution. Overall, NPP is a novel, simple, economic and portable sensor that can detect Cu²⁺ in biological and environmental scenarios.

Dopamine-Mediated Vanillin Multicomponent Derivative Synthesis via Grindstone Method: Application of Antioxidant, Anti-Tyrosinase, and Cytotoxic Activities

Purpose

This study aimed to determine the extent of contribution of dopamine to antioxidant and anti-tyrosinase activities, by dopamine addition to vanillin. This study achieved the synthesis of dopamine-associated vanillin Mannich base derivatives prepared via a one-step reaction involving a green chemistry approach, and investigation of antioxidant and anti-tyrosinase activities.

Methods

Novel one-pot synthesis of Mannich base dopamine-connected vanillin (1a-l) derivatives can be achieved via green chemistry without using a catalyst. Newly-prepared compounds were characterised with FTIR and NMR (¹H and ¹³C) spectra, mass spectra, and elemental analyses. In total, 12 compounds (1a-l) were synthesised and their antioxidant and anti-tyrosinase activities evaluated. Antioxidant activities of 2,2-diphenyl-1-picrylhydrazyl (DPPH), nitric oxide (NO), hydrogen peroxide (H₂O₂), and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and diammonium assays, ABTS^•+ radical scavenging, and linoleic acid peroxidation were used to screen all synthesised compounds (1a-l) for anti-tyrosinase activities and cytotoxicity against MCF-7 and Vero cell lines;.

Results

The compound 1k inhibited (IC₅₀:11.02µg/mL) the DPPH-scavenging activity to a greater extent than the standard BHT (IC₅₀:25.17µg/mL), and showed high activity in H₂O₂ and NO scavenging assays. Compound 1e was more potent (96.21%) against ABTS and compound 1k was more potent (95.28%) against 2,2ʹ-azobis(2-amidinopropane)dihydrochloride antioxidant than the standard trolox. All synthesised compounds were screened for anti-tyrosinase inhibitory activity. Compound 1e had higher activity against tyrosinase (IC₅₀=10.63 µg/mL), than kojic acid (IC₅₀=21.52µg/mL), and was more cytotoxic (GI₅₀ 0.01µM) against MCF-7 cell line than the doxorubicin standard and other tested compounds.

Conclusion

In this study, all compounds were found to possess significant antioxidant and anti-tyrosinase activities. Compounds 1e and 1k performed well, compared with other compounds, in all assays. In addition, this study successfully identified several promising molecules that exhibited antioxidant and anti-tyrosinase activities.

Antimicrobial and cytotoxic activities of isoniazid connected menthone derivatives and their investigation of clinical pathogens causing infectious disease

BACKGROUND

This work is development of new molecules of isoniazid derivatives as dealing with potential of antimicrobial activity against clinical pathogens causing infectious disease. Antimicrobial of novel Mannich base derivatives can be achieved via one-pot synthesis in green chemistry approach. This method offers efficient, mild reaction conditions and high yields. In this study, totally 12 compounds (1a-l) was prepared and screened for cytotoxic and antimicrobial activities.

MATERIALS AND METHODS

Newly synthesised compounds were conformed via FT- IR, ¹H, and ¹³C NMR (Nuclear Magnetic Resonance), and mass spectra analysis. All compounds were checked antibacterial activity against gram-positive bacteria of Enterococcus faecalis, Staphylococcus aureus and gram-negative bacteria of Pseudomonas aeruginosa, Klebsiella pneumoniae and Escherichia coli. All compounds were checked against antifungal activity against Aspergillus fumigatus, Candida albicans, Cryptococcus neoformans, Aspergillus niger, and Microsporum audouinii. All compounds were screened for cytotoxic activity against the MCF-7 (Michigan Cancer Foundation-7) cancer cell line.

RESULT

The compound 1g was highly (MIC: 0.25 μg/mL) active against gram-negative bacterial of P. aeruginosa, whereas other compounds 1e and 1h were more active (MIC: 2 μg/mL) in K. pneumoniae and also 1g (MIC: 2 μg/mL) was more active in E. faecalis than standard ciprofloxacin. Antifungal screening, the compound 1b was highly active (MIC: 0.25 μg/mL) against C. albicance,1g (MIC: 2 μg/mL) and 1h (MIC: 4 μg/mL) was significant of active against A. fumigatus, and the compound 1c (MIC: 4 μg/mL) was extremely active in M. audouinii than clotrimazole. Compound 1g (GI₅₀ = 0.01 μM) exhibited high activity against the MCF-7 cell line, while 1b (GI₅₀ = 0.02 μM) was equipotent active compared with standard doxorubicin.

CONCLUSION

A novel set of isoniazid derivatives (1a-l) and 1h were synthesized and screened for antimicrobial and cytotoxic activities. We found some highly active molecules, which are evidencing to be a potential treatment of bacterial and fungal infection candidates.

Novel Mannich bases of ciprofloxacin with improved physicochemical properties, antibacterial, anticancer activities and caspase-3 mediated apoptosis

The design, synthesis and identification of a novel series of Mannich bases of ciprofloxacin was reported. Naphthol derivatives 2a and 2b showed highly potent cytotoxic activity among the tested compounds. Compound 2a showed broad spectrum antiproliferative activity with GI₅₀ of 2.5-6.79 µM with remarkable selectivity towards renal and prostate cancers with selectivity ratios ranging from 0.17 to 6.79. Independently, 2a showed outstanding activity against colon cancer HOP-92 cell lines with IC₅₀ of 6.66 µM while 2b showed highly potent activity against ovarian cancer cell lines with IC₅₀ of 0.97 µM. Results showed that 2b induced cell cycle arrest at G2/M phase and apoptosis; compound 2b showed over-expression of caspase-3 protein level (449.2 ± 7.95) compared to doxorubicin (578.7 ± 14.4 pg/mL). Meanwhile, compounds 2a and 2b experienced outstanding activity against both Gram-positive and Gram-negative microorganisms. Interestingly, compound 2j experienced high activity against Escherichia coli and Pseudomonas aeruginosa with MIC of 0.036 and 0.043, respectively. Compound 2d revealed 27 folds and 22 folds, respectively increasing of activity over ciprofloxacin against Staphylococcus aureus and MRSA(reference strain). Compound 2d showed high activity against Staphylococcus aureus, MRSA (reference strain) and MRSA (clinical strain) with MIC of 0.57, 0.52, 0.082 µg/mL, respectively. Interestingly, the most active tested compounds were found to have promising physicochemical and drug likeness properties. The Mannich bases 2j, 2d and 2g showed promising antibacterial activities, while naphthols 2a and 2b showed promising antiproliferative and antibacterial activities that require further optimization.

Discovery, Synthesis, and Biological Evaluation of Dunnianol-Based Mannich Bases against Methicillin-Resistant Staphylococcus aureus (MRSA)

Dunnianol, a natural sesqui-neoligan derived from the leaves and stems of Illicium simonsii Maxim, has been found to possess moderate antibacterial activity. To improve the antibacterial activity and solubility of dunnianol, a series of dunnianol-based Mannich bases were prepared and evaluated for their antibacterial activities. The most promising compound, 5a', exhibited excellent antibacterial activity against Staphylococcus aureus and clinically isolated methicillin-resistant Staphylococcus aureus (MRSA) with MIC values of 1 to 2 μg/mL. Structure-activity relationships indicated that the introduction of (dimethylamino)methyl at the ortho position of the phenolic hydroxyl group of dunnianol could obtain a more active compound. A mechanism study revealed that 5a' killed MRSA more rapidly than did vancomycin by disrupting the cell membrane. Moreover, 5a' was not susceptible to drug resistance development and also showed low toxicity and good antibacterial efficacy in vivo. These results indicate that the dunnianol-based Mannich base 5a' could be a promising antibiotic candidate for further research.

Semisynthesis of novel magnolol-based Mannich base derivatives that suppress cancer cells via inducing autophagy

Magnolol, a natural bioactive neolignan, was found in the bark of a traditional Chinese medicine Magnoliae officinalis ("Hou Po" in Chinese). In this study, thrity-two magnolol-based Mannich base derivatives 3a-p and 4a-p were synthesized, and evaluated for their anti-proliferative activities against a panel of human tumor cell lines (T47D, MCF-7, Hela and A549). Among all derivatives, compound 3p displayed the most potent antiproliferative activity against T47D, MCF-7 and Hela cell lines with IC₅₀ values of 0.91, 3.32 and 1.71 μM, respectively. Compared with the parental magnolol and the positive drug cisplatin, 3p exhibited up to 76.1-fold and 10.3-fold enhancement of cytotoxic effect on T47D cancer cells, respectively. Mechanism study revealed that the most potent derivative 3p suppressed cancer cells via inducing autophagy. Moreover, 3p also possessed suppressive effects on migration of T47D and Hela cancer cells. In addition, some interesting structure-activity relationships (SARs) were also summarized.

Synthesis, density functional theory study and in vitro antimicrobial evaluation of new benzimidazole Mannich bases

The tri-component synthesis of novel chiral benzimidazole Mannich bases, by reaction between benzimidazole, aqueous 30% formaldehyde and an amine, the biological evaluation and DFT studies of the new compounds are reported here. The ¹H-NMR, ¹³C-NMR, FTIR spectra and elemental analysis confirm the structures of the new compounds. All synthesized compounds were screened by qualitative and quantitative methods for their in vitro antibacterial activity against 4 bacterial strains. DFT studies were accomplished using GAMESS 2012 software and HOMO-LUMO analysis allowed the calculation of electronic and structural parameters of the chiral Mannich bases. The geometry of 1-methylpiperazine, the cumulated Mullikan atomic charges of the two heteroatoms and of the methyl, and the value of the global electrophilicity index (ω = 0.0527) of the M-1 molecule is correlated with its good antimicrobial activity. It was found that the presence of saturated heterocycles from the amine molecule, 1-methyl piperazine and morpholine, respectively, contributes to an increased biological activity, compared to aromatic amino analogs, diphenylamino-, 4-nitroamino- and 4-aminobenzoic acid. The planarity of the molecules, specific bond lengths and localization of HOMO-LUMO orbitals is responsible for the best biological activities of the compounds.

Novel Mannich base 3FB3FA8H induces apoptosis by upregulating P53 pathway in neuroblastoma cells

P53 plays an important role in maintaining genetic stability and development of resistance against tumors. Dysregulation of P53 gene is one of the key factors contributing to the etiology of neuroblastoma which causes cells to evade apoptosis. Activating P53 pathway can be a therapeutic alternative to the currently available medicinal strategies. Mannich bases have been known to possess various biological activities including the anticancer activity. In this study, we have targeted the P53 pathway by novel Mannich base (3FB3FA8H) which can be a future prospect to cure neuroblastoma. 3FB3FA8H has shown modulation of P53 pathway leading to apoptosis of neuroblastoma cells. Mitochondrial membrane permeability is also increased by 3FB3FA8H which may be a consequence of P53 pathway modulation. 3FB3FA8H increases the mRNA levels of P53 leading to activation of BAX. Inclining BAX/BCL2 ratio towards apoptotic BAX leads to cleavage of caspase 3, ultimately, causing apoptosis. Series of experiments provide the evidence that Mannich base 3FB3FA8H leads to P53-mediated apoptosis. Inducing apoptosis by this mechanism could be of central importance in reducing tumor burden which can be a good prospect for neuroblastoma patients.

Semisynthesis and biological evaluation of some novel Mannich base derivatives derived from a natural lignan obovatol as potential antifungal agents

Obovatol, a novel lignan isolated from the leaf and stem bark of Magnolia obovata Thunb exhibits many important biological activities. To discover natural-product-based potential fungicides with novel structural skeletons, a series of Mannich base derivatives were prepared by the C-4-aminomethylated modification of obovatol and all synthesized compounds were evaluated for antifungal activities in vitro against several phytopathogenic fungi using the spore germination method and the mycelium growth rate method. Furthermore, their structures were also characterized by ¹H NMR, ¹³C NMR, and HR-MS, and compound 2k was further analyzed by single-crystal X-ray diffraction. Among all of the derivatives, compounds 2b (IC₅₀ = 28.68 µg/mL) and 2g (IC₅₀ = 16.90 µg/mL) demonstrated greater inhibition of Botrytis cinerea spore germination than two positive controls, hymexazol and difenoconazole. Compounds 2c, 2f, and 2g displayed potent mycelial growth inhibition of B. cinerea with an average inhibition rate (AIR) of >90% at a concentration of 100 µg/mL. Additionally, the structure-activity relationships (SARs) suggested that the introduction of a diethylamino, pyrrolyl, 1-methyl-piperazinyl or 1-ethyl-piperazinyl groups on the C-4 position of obovatol may be more likely to yield potential antifungal compounds than the introduction of 4-phenyl-piperazinyl or 4-phenyl-piperidinyl groups.

Synthesis and Antibacterial Evaluation of Mannich Bases Derived from 1,2,4-Triazole

The series of novel Mannich bases were synthesized and evaluated for their in vitro antibacterial activity against Gram-positive and Gram-negative bacterial strains. The results showed that all compounds were less active than the drugs used as reference, but some of them had moderate potency against Staphylococcus epidermidis ATCC 12228 and Bacillus subtilis ATCC 6633. The presence of a phenyl ring in the position 4 of piperazine seems to be necessary for antibacterial activity in this class of compounds.

Antimalarial Pyrido[1,2- a]benzimidazole Derivatives with Mannich Base Side Chains: Synthesis, Pharmacological Evaluation, and Reactive Metabolite Trapping Studies

A novel series of pyrido[1,2- a]benzimidazoles bearing Mannich base side chains and their metabolites were synthesized and evaluated for in vitro antiplasmodium activity, microsomal metabolic stability, reactive metabolite (RM) formation, and in vivo antimalarial efficacy in a mouse model. Oral administration of one of the derivatives at 4 × 50 mg/kg reduced parasitemia by 95% in Plasmodium berghei-infected mice, with a mean survival period of 16 days post-treatment. The in vivo efficacy of these derivatives is likely a consequence of their active metabolites, two of which showed potent in vitro antiplasmodium activity against chloroquine-sensitive and multidrug-resistant Plasmodium falciparum ( P. falciparum) strains. Rapid metabolism was observed for all the analogues with <40% of parent compound remaining after 30 min of incubation in liver microsomes. RM trapping studies detected glutathione adducts only in derivatives bearing 4-aminophenol moiety, with fragmentation signatures showing that this conjugation occurred on the phenyl ring of the Mannich base side chain. As with amodiaquine (AQ), interchanging the positions of the 4-hydroxyl and Mannich base side group or substituting the 4-hydroxyl with fluorine appeared to block bioactivation of the AQ-like derivatives though at the expense of antiplasmodium activity, which was significantly lowered.

Synthesis, biological evaluation and molecular dynamics studies of 1,2,4-triazole clubbed Mannich bases

The present work highlightsthe synthesis of a newer biologically active Mannich bases contributing 4-((4-fluorobenzylidene)amino)-5-(pyridin-4-yl)-4H-1,2,4-triazole-3-thiol and various heterocyclic amines via N-Mannich reaction by the conventional method as well as microwave heating approach as a part of an environmentally benign synthetic protocol. All the synthesized compounds were characterized by spectral analysis and were screened for in vitro antimicrobial, antitubercular and antiprotozoal activity. The compound 4k was found to be most active respectively against S. aureus (MIC 12.5 μM) and C. albicans (MIC 100 μM). The derivative 4 g displayed potency against L.mexicana and T. cruzi with IC₅₀ value 1.01 and 3.33 μM better than reference drug Miltefosina and Nifurtimox. The compound 4b displayed excellent potency against M. tuberculosis (MIC 6.25 μM) in the primary screening. The computational studies revealed for that Mannich derivative (4b) showed a high affinity toward the active site of enzyme which provides a strong platform for new structure-based design efforts. The Lipinski's parameters showed good drug-likeness properties and can be developed as an oral drug candidate.

Some Brief Notes on Theoretical and Experimental Investigations of Intramolecular Hydrogen Bonding

A review of selected literature data related to intramolecular hydrogen bonding in ortho-hydroxyaryl Schiff bases, ortho-hydroxyaryl ketones, ortho-hydroxyaryl amides, proton sponges and ortho-hydroxyaryl Mannich bases is presented. The paper reports on the application of experimental spectroscopic measurements (IR and NMR) and quantum-mechanical calculations for investigations of the proton transfer processes, the potential energy curves, tautomeric equilibrium, aromaticity etc. Finally, the equilibrium between the intra- and inter-molecular hydrogen bonds in amides is discussed.

Antifungal and anthelmintic activity of novel benzofuran derivatives containing thiazolo benzimidazole nucleus: an in vitro evaluation

A novel series of thiazolo[3,2-a]benzimidazole derivatives containing benzofuran nucleus (5a-l) have been synthesized. The key intermediate, substituted benzimidazol-sulfanyl benzofuran ethanone (3a-d) was prepared by refluxing the mixture of substituted 2-acetyl benzofuran and substituted 2-mercaptobenzimidazole in acetic acid. The cyclisation of compounds (3a-d) using polyphosphoric acid furnished the corresponding 6-substituted benzofuran thiazolo[3,2-a]benzimidazoles (4a-d). Further, the cyclized compounds (4a-d) were subjected for Mannich reaction to give corresponding Mannich bases (5a-l). All newly synthesized compounds were screened for antifungal and anthelmintic activity. Amongst the tested compounds, 4b and 4d exhibited potential antifungal activity. From the anthelmintic activity data, it was found that the compounds 3a, 3b and 5i were found to be more effective against the tested earthworm Pheretima posthuma. In correlation to anthelmintic activity, the selected compounds were subjected for molecular docking studies and the compounds 3a and 5i have emerged as active anthelmintic agents with maximum binding affinity (-3.7 and -5.4 kcal/mol).

Hesperetin derivatives: Synthesis and anti-inflammatory activity

Sixteen novel hesperetin derivatives containing Mannich base moiety were designed and synthesized and their anti-inflammatory activities were evaluated by inhibiting tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in mouse RAW264.7 macrophages. Compounds 3a-3k showed better hydrophilic, while compounds 3l-3p with aromatic groups was hydrophobic. The anti-inflammatory activity of title compounds was correlated with logP values, among them, compounds 3c, 3e and 3i with minus logP values exhibited best anti-inflammatory activity through decreasing both IL-6 and TNF-α. Furthermore, the expression of LPS-induced notch1 and inos was reduced by compounds 3c, 3e, and 3i, and compound 3e attenuated LPS-induced inos protein levels in a dose-dependent manner.

First principles and DFT supported investigations on vibrational spectra and electronic structure of 2-((phenylamino)methyl)isoindoline-1,3-dione--an antioxidant active Mannich base

The 2-((phenylamino)methyl)isoindoline-1,3-dione (PID) is a synthesized Mannich base which has significant antioxidant activity and biological importance. Quantum mechanical calculations on energy, geometry and vibrational wavenumber of PID were computed using ab initio HF and density functional theory (DFT/B3LYP) methods with 6-31+G/6-311++G(d,p) basis sets. Optimized geometrical parameters obtained by HF and DFT calculations were indicatively agreement with experimental crystal geometry. The experimental FT-Raman and FT-IR spectra of PID has been recorded and analyzed by comparing with simulated spectra. The (1)H and (13)C NMR spectra of title molecule records the chemical shift resulted from shielding and deshielding effects. Natural bond orbital (NBO) analysis has been carried out to calculate various intramolecular interactions that are accountable for the stabilization of this Mannich base. The predicted HOMO-LUMO gap offers interesting information on intramolecular charge transfer and reactivity of the molecular system. Molecular electrostatic potential (MEP) imprint visualize the reactive sites in PID, which is also supported by Mulliken, ESP, Hirshfeld and NBO charges. Thermodynamic properties of PID at various temperatures have been calculated at B3LYP/6-311++G(d,p) in gas phase and the correlations between standard entropies (S), internal energy (E or U) and standard heat capacity (C) with different temperatures.

Crystal structure of 2,4-bis-(2-chloro-phen-yl)-7-tert-pent-yl-3-aza-bicyclo[3.3.1]nonan-9-one

The title compound, C₂₅H₂₉Cl₂NO, which is a chloro analog of 2,4-bis­(2-bromo­phen­yl)-7-(tert-pent­yl)-3-aza­bicyclo­[3.3.1]nonan-9-one [Park, Ramkumar & Parthiban (2012). Acta Cryst. E68, o2946], exists in a twin-chair conformation with an equatorial orientation of the 2-chloro­phenyl groups. The tert-pentyl group on the cyclo­hexa­none adopts an exocyclic equatorial position and is disordered between two orientations in a ratio 0.520 (8):0.480 (8). The crystal packing shows no directional contacts beyond van der Waals contacts.

Crystal structure of 2,6-bis-(2,5-di-meth-oxy-phen-yl)-3,5-di-methyl-piperidin-4-one

In the title mol-ecule, C23H29NO5, the central piperidine ring has a chair conformation. The planes of the two benzene rings are inclined each to other at 61.7 (1)°. The crystal packing exhibits no directional inter-actions only van der Waals contacts.

In Silico vibrational spectroscopic investigation on antioxidant active Mannich base 1-[anilino (phenyl) methyl] pyrrolidine-2,5-dione

The antioxidant active Mannich base 1-[anilino (phenyl) methyl] pyrrolidine-2,5-dione (APMPD) have been synthesized and its FT-IR and FT-Raman vibrational spectra were recorded within the region of 4000cm(-1), 50cm(-1) respectively. The molecular geometric parameters of APMPD have been computed using HF and DFT model theories. The energies of APMPD are calculated for all the eight possible conformers using B3LYP method at 6-311++G(d,p) basis set. From the computational results, the M1 conformer was identified as the most stable conformer of APMPD. The stable conformer was compared with experimental crystal geometry, which again fortifies the results of conformer analysis. The fundamental vibrations of the molecule are assigned according to the characteristic region and the literature report. The predicted highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy gap provide vivid idea on charge transfer behavior of APMPD. The molecular electrostatic potential (MEP) and Mulliken charge analysis indicate the feasible electrophilic and nucleophilic reactive sites on APMPD. The thermodynamic properties (heat capacity, entropy, and enthalpy) of the title compound at various temperatures are calculated in gas phase.

Synthesis, pharmacological screening and in silico studies of new class of Diclofenac analogues as a promising anti-inflammatory agents

A novel series of 5-[2-(2,6-dichlorophenylamino)benzyl]-3-(substituted)-1,3,4-oxadiazol-2(3H)-thione (4a-k) derivatives have been synthesized by the Mannich reaction of 5-[2-(2,6-dichlorophenylamino)benzyl]-1,3,4-oxadiazol-2(3H)-thione (3) with an appropriately substituted primary/secondary amines, in the presence of formaldehyde and absolute ethanol. Structures of these novel compounds were characterized on the basis of physicochemical, spectral and elemental analysis. The title compounds (4a-k) were screened for in vivo acute anti-inflammatory and analgesic activities at a dose of 10mg/kg b.w. Compound 4k exhibited the most promising and significant anti-inflammatory profile while compounds 4a, 4d, 4e, 4i, and 4j showed moderate to good inhibitory activity at 2nd and 4thh, respectively. These compounds were also found to have considerable analgesic activity (acetic acid induced writhing model) and antipyretic activity (yeast induced pyrexia model). In addition, the tested compounds were also found to possess less degree of ulcerogenic potential as compared to the standard NSAIDs. Compounds that displayed promising anti-inflammatory profile were further evaluated for their inhibitory activity against cyclooxygenase enzyme (COX-1/COX-2), by colorimetric COX (ovine) inhibitor screening assay method. The results revealed that the compounds 4a, 4e, 4g and 4k exhibited effective inhibition against COX-2. In an attempt to understand the ligand-protein interactions in terms of the binding affinity, docking studies were performed using Molegro Virtual Docker (MVD-2013, 6.0) for those compounds, which showed good anti-inflammatory activity. It was observed that the binding affinities calculated were in agreement with the IC50 values.

Synthesis, characterisation and evaluation of N-mannich bases of 2-substituted Benzimidazole derivatives

RATIONALE

Benzimidazoles and its derivatives represent one of the mainly biological active classes of literature.

AIM

In this present study aimed to synthesize N-mannich bases derivatives compounds bearing of 2-substituted benzimidazole moiety, in order to investigate their possible biological activity.

METHOD

Benzimidazole compounds were prepared from the condensation reaction between ortho phenylene diamine and various acids. Mannich base of newly synthesized Benzimidazole derivatives were synthesized from 2-substituted Benzimidazoles by reacting with secondary amines. The purity of the compounds was ascertained by melting point (m.p) and thin layer chromatography (TLC). Structures of the synthesized compounds were elucidated by spectral data. Antimicrobial assay was performed by microbroth dilution method. Bacterial genomic DNA cleavage was assessed by Agarose gel electrophoresis. Toxicity of the most effective compounds was studied by Brine-shrimp lethality assay.

RESULT

Among the synthesized compounds, compound 5E (a) and (b) was establish to be the most potent against all tested microorganisms. This two compounds exhibited complete bacterial DNA cleavage and non-toxic.

CONCLUSION

These results suggest that it an interesting compound compared to the current therapeutic agents and are considered to investigate further for the same.

Synthesis and antioxidant activity of novel Mannich base of 1,3,4-oxadiazole derivatives possessing 1,4-benzodioxan

A new series of Mannich base of 1,3,4-oxadiazole derivatives possessing 1,4-benzodioxan (6a-6ae) were synthesized and characterized by (1)H NMR, ESI-MS and elemental analysis. The structure of 6b was further confirmed by single crystal X-ray diffraction. All these novel compounds were screened for their in vitro antioxidant activity employing 2,2'-diphenyl-1-picrylhydrazyl radical (DPPH), 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonate) cationic radical (ABTS(+)) and ferric reducing antioxidant power (FRAP) scavenging assays. Due to the combination of 1,4-benzodioxan, 1,3,4-oxadiazoles and substituted phenyl ring, most of them exhibited nice antioxidant activities. In all of these three assays mentioned above, compounds 6f and 6e showed significant radical scavenging ability comparable to the commonly used antioxidants, BHT and Trolox. Seven compounds with representative substituents or activities were selected for further assays in chemical simulation biological systems-inhibition of microsomal lipid peroxidation (LPO) and protection against 2,2'-azobis (2-amidinopropane hydrochloride) (AAPH) induced DNA strand breakage, in which, 6f and 6e were demonstrated to be of the most potent antioxidant activities.

Antimicrobial and antiurease activities of newly synthesized morpholine derivatives containing an azole nucleus

2-[6-(Morpholin-4-yl)pyridin-3-ylamino]acetohydrazide (4) was obtained starting from 6-morpholin-4-ylpyridin-3-amine (2) via the formation of ester (3) and then converted to the corresponding Schiff bases (5, 6) with the reaction with aromatic aldehydes. The carbothioamide (9), obtained from the reaction of hydrazide with phenylisothiocyanate, was converted to the corresponding 1,2,4-triazole (11) and 1,3,4-thiadiazole (12) derivatives by the treatment with NaOH or H2SO4, respectively. The cyclocondenzation of 9 with 4-chlorophenacyl bromide or ethyl bromoacetate produced the corresponding 1,3-thiazole (10) or 1,3-thiazolidine derivatives (13), respectively. Antimicrobial and antiurease activities of newly synthesized compounds were investigated. Some of them were found to be active on M. smegmatis, and they displayed activity toward C. albicans and S. cerevisiae in high concentration. Compound 10 proved to be the most potent showing an enzyme inhibition activity with an IC50 = 2.37 ± 0.19 μM.

Synthesis, Antiviral and Cytotoxicity Studies of Novel N-substituted Indophenazine Derivatives

A series of novel N-substituted indophenazine derivatives were synthesised and screened for antiviral activity against a panel of human pathogenic viruses. New compounds were synthesised through modifying the N-hydrogen of indophenazine moiety with different substitution and formaldehyde by Mannich reaction. The structure of the synthetic compounds was characterised by means of infra red and nuclear magnetic resonance spectral data. The compound 10H-indolo-2-Amino pyridine [3,2-b] quinoxalines inhibits Herpes simplex virus-1 and vaccinia virus at a concentration of 12 μg/ml, and the cytotoxicy was found to be 100 μg/ml. 4-Aminobenzene sulfonamide-10H-indolo [3,2-b] quinoxalines inhibit vaccinia virus at a concentration of 12 μg/ml and cytotoxicy was found to be 100 μg/ml. The anti-HIV activities of the new compounds were also screened for in vitro antiviral activity against replication of HIV-1 (IIIB) and HIV-2 (ROD) in MT-4 cells using zidovudine (AZT) as standard. Pthalimide derivative inhibited the replication of HIV-2 (EC₅₀=11.60 μg/ml and CC₅₀=61.63 μg/ml) in MT-4 cells.