Zeba N. Siddiqui

Thermal solvent-free synthesis of novel pyrazolyl chalcones and pyrazolines as potential antimicrobial agents.

A novel approach was adopted for the synthesis of series of new pyrazolyl chalcones (3a-c) by the reaction of 5-chloro-3-methyl-1-phenylpyrazole-4-carboxaldehyde (1) with different 5-acetylbarbituric acid derivatives (2a-c) under thermal solvent-free condition. The chalcones were then converted to the corresponding pyrazolines (4a-c) under the same condition in excellent yields. All the synthesized compounds were characterized using elemental analysis and spectral data (IR, (1)H NMR, and mass spectrometry). The synthesized compounds were tested for their antimicrobial activity by disk diffusion assay with slight modifications against Gram-positive, Gram-negative strains of bacteria as well as fungal strains. The investigation of antimicrobial screening revealed that compounds (3a-4c) showed good antibacterial and antifungal activities, respectively. Among the screened compounds, 3b showed more potent inhibitory activity (MIC=12.5 μg/ml) nearly to that of standard antibiotics ciprofloxacin, griseofulvin and fluconazole.

Zn(Proline)2: a novel catalyst for the synthesis of dicoumarols

A novel, greener approach was adopted for the synthesis of dicoumarols (3a–j) using Zn(Proline)2 as a mild, non-toxic, Lewis acid catalyst in water employing 4-hydroxycoumarin (1) and aromatic/heteroaromatic aldehydes (2a–j). The catalytic activity results suggest that the methodology adopted offers several advantages such as mild reaction conditions, low loading of catalyst, quantitative yields, short reaction time and operational simplicity.

Friedlander synthesis of novel benzopyranopyridines in the presence of chitosan as heterogeneous, efficient and biodegradable catalyst under solvent-free conditions

Efficient synthesis of benzopyrano[4,3-b]pyridine derivatives was achieved from 4-amino-3-formylcoumarin and different active methylene compounds under solvent-free thermal heating at 80 °C via Friedlander condensation in the presence of chitosan as heterogeneous, basic green catalyst. The present methodology is a novel green approach to benzopyranopyridine. It offers several advantages such as shorter reaction time, mild reaction conditions, simple operational procedure, use of recyclable and biodegradable catalyst.

Effects of Ocimum sanctum and Camellia sinensis on stress-induced anxiety and depression in male albino Rattus norvegicus

Objective: The aim of this study was to study the ameliorative effects of Ocimum sanctum and Camellia sinensis on stress-induced anxiety and depression. Materials and Methods: The study was carried out using male albino rats (200 ± 50 g). The effect of O. sanctum and C. sinensis was evaluated for anxiety and depression using elevated plus maze (EPM) test, open field test (OFT), forced swim test (FST), and tail suspension test (TST). Result: Restraint stress (3 h/day for six consecutive days) induced a significant reduction in both the percentage number of entries and time spent in open arms in EPM, and these changes were reversed with post-treatment of aqueous extract of O. sanctum and C. sinensis (100 mg/kg for 6 days). Restraint stress-induced (a) increased latency and (b) decreased ambulation and rearing were also reversed by O. sanctum and C. sinensis in OFT. A significant increase in immobility period was observed in FST and TST after restraint stress. O. sanctum and C. sinensis significantly reduced the immobility times of rats in FST and TST. Conclusion: O. sanctum and C. sinensis possess anxiolytic and antidepressant activities.

Synthesis and biological activity of heterocycles from chalcone

The chalcone 3 was synthesized from 3-acetyl-4-hydroxy coumarin and 3-formylchromone by refluxing in ethanol in the presence of a catalytic amount of pyridine. 3 was converted to bipyrazoles 4a-b by treatment with hydrazine and phenylhydrazine. The compounds were screened for their antibacterial activity.

Microwave-assisted solvent-free synthesis of biologically active novel heterocycles from 3-formylchromones

A series of novel chromone derivatives have been synthesized employing 3-formylchromones and 5-acetyl-1,3-dimethylbarbituric acid as starting materials both under conventional heating method and microwave irradiation technique in good yields. The synthesized compounds were screened in vitro antibacterial activity against the representative panel of two Gram-positive bacteria and two Gram-negative bacteria. The synthesized compounds were also tested for their inhibitory action against three strains of fungus. The various compounds show potent inhibitory action against test organisms.

Zn(Proline)2-catalyzed Knoevenagel condensation under solvent-free/aqueous conditions and biological evaluation of products

A novel approach was adopted for the synthesis of series of Knoevenagel condensation products from 5-chloro-3-methyl-1-phenylpyrazole-4-carboxaldehyde with different cyclic active methylene compounds, using water soluble and recyclable Zn(Proline)2 as a Lewis acid catalyst both under solvent-free condition and using water as a reaction medium in good yields. In each conversion, the catalyst was successfully recovered and recycled without significant loss in yield and selectivity. The compounds were screened for their antimicrobial activity.

Unprecedented single-pot protocol for the synthesis of novel bis-3,4-dihydropyrimidin-2(1H)-ones using PEG-HClO4 as a biodegradable, highly robust and reusable solid acid green catalyst under solvent-free conditions

A solvent-free, environmentally benign, and simple one-pot multi-component protocol has been developed for the efficient synthesis of novel bis-3,4-dihydropyrimidin-2(1H)-one derivatives (4a–o) in excellent yields using perchloric acid-modified PEG-6000 (PEG-HClO4) as a biodegradable and reusable catalyst at ambient temperature. This novel and green protocol has the advantages of shorter reaction times, high conversions, use of an inexpensive catalyst and simple experimental procedure, as compared to the conventional methods. The PEG-HClO4 catalyst is characterized by using FTIR, powder XRD and SEM-EDX analyses. The catalyst can be reused several times without significant loss of its catalytic activity.

Synthesis of 4-Hydroxycoumarin Heteroarylhybrids as Potential Antimicrobial Agents

A new series of 4‐hydroxycoumarin derivatives 3a–d was synthesized by the reaction of 3‐bromo‐4‐hydroxy coumarin 1 with various heteroaldehydes 2a–d in good yields. The synthesized compounds were characterized on the basis of their elemental and spectral (IR, 1H‐NMR and mass spectrometry) analysis. All target compounds were evaluated for their in‐vitro antimicrobial activity against Streptococcus pyogenes, methicillin‐resistant Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumonia, and Escherichia coli bacterial strains and fungal cultures of Candida albicans, Aspergillus fumigatus, Trichophyton mentagrophytes, and Penicillium marneffei by disk diffusion assay with slight modifications. The minimum inhibitory concentration (MIC) was determined for the test compounds as well as for reference standards. Among the tested compounds, 3a has shown the most potent antibacterial as well as antifungal activities.

Perchloric acid modified-cellulose: a versatile, novel and biodegradable heterogeneous solid acid catalyst for single-pot synthesis of novel bis-pyran annulated heterocyclic scaffolds under solvent-free conditions

A one-pot multi-component, green, and highly efficient protocol has been developed for the synthesis of novel bis-pyran annulated heterocyclic scaffolds (4a–r) using cellulose–perchloric acid (CPA) as an eco-friendly, biodegradable and recyclable catalyst in excellent yields under solvent-free conditions. Other remarkable features of this environmentally benign protocol are short reaction time, a wide range of functional group tolerance, use of inexpensive heterogeneous catalyst, and high yield of products via a simple experimental and work-up procedure as compared to the conventional methods. The cellulose–HClO4 (CPA) catalyst is characterized by using FTIR, powder XRD and SEM–EDX analyses. The stability of the catalyst was evaluated by TG/DTA characterization techniques. The catalyst can be recycled several times with a slight loss of its catalytic activity.