Rangappa S. Keri

Derivatives of benzimidazole pharmacophore: Synthesis, anticonvulsant, antidiabetic and DNA cleavage studies

In seeking broad spectrum pharmacological activities of benzimidazole derivatives, a group of 4-thiazolidinones 5(a-j) and 1,3,4-oxadiazoles 6(a-j) containing 2-mercapto benzimidazole moiety were synthesized and screened for in vivo anticonvulsant activity by Maximal Electroshock (MES) model and antidiabetic activity using Oral Glucose Tolerance Test (OGTT). Compounds (5c), (5d), (5g) and (5i) exhibited potent anticonvulsant results and (6c), (6d), (6h) and (6i) showed excellent antidiabetic activities and also pharmacophore derived from active molecules suggested that presence of -OH group was a common feature in all active compounds. In DNA cleavage studies, compound (5d) cleaved DNA completely as no trace of DNA was found. On the other hand, a sharp streak was found for compounds (5c), (6a) and (6d).

Synthesis and evaluation of in vitro anti-microbial and anti-tubercular activity of 2-styryl benzimidazoles.

A new series of novel 5-(nitro/bromo)-styryl-2-benzimidazoles (1-12) has been synthesized by simple, mild and efficient synthetic protocol by attempted condensation of 5-(nitro/bromo)-o-phenylenediamine with trans-cinnamic acids in ethylene glycol. Screening for in vitro anti-tubercular activity against Mycobacterium tuberculosis H(37) Rv, anti-bacterial activity against Staphylococcus aureus, Escherichia coli, Enterococcus faecalis, Klebsiella pneumoniae bacterial strains and anti-fungal activity against Candida albicans and Asperigillus fumigatus fungal strains were carried out. Compounds 5, 7, 8, 9, 11 showed higher anti-tubercular activity and compounds 7, 8, 10, 11, 12 have proved to be effective with MIC (microg/ml) and emerged as lead molecules showing excellent activities against a panel of microorganisms. All synthesized compounds were characterized using IR, (1)H, (13)C NMR, GC-MS and elemental analysis.

Analgesic, anti-pyretic and DNA cleavage studies of novel pyrimidine derivatives of coumarin moiety.

A novel series of 4-[4-(6-phenyl-pyrimidin-4-yl)-phenoxymethyl]-chromen-2-ones [5-7(a-e)] were synthesized from various 4-bromomethyl coumarins 1(a-e). The synthesized compounds were screened for in-vivo analgesic and anti-pyretic activities at a dose of 25 and 100 mg/kg body weight (b.w), respectively. Among them, compounds 5(d), 6(c) and 7(d) exhibited significant analgesic activity comparable with standard drug analgin using Tail-flick model. Compounds 5(a) and 7(a-d) showed significant anti-pyretic activities comparable with standard drug aspirin using yeast-induced pyrexia model. DNA cleavage study by agarose gel electrophoresis method was also studied. Qualitative SAR studies indicate that, compounds with amino group at 2-position of pyrimidine ring enhances analgesic and anti-pyretic activities and compounds with hydroxyl and thio group at 2-position of pyrimidine ring increase DNA cleavage activities.

2-Azetidinone derivatives: design, synthesis, in vitro anti-microbial, cytotoxic activities and DNA cleavage study.

A novel series of 3-chloro-4-[4-(2-oxo-2H-chromen-4-ylmethoxy)-phenyl]-1-phenyl-azetidin-2-one derivatives (5a-j) have been synthesized from 4-aryloxymethylcoumarins (1a-e) and 4-aryliminomethyl-phenols (3a-b). The title compounds were screened for their in vitro anti-bacterial and anti-fungal activities. Results revealed that, compounds (5c), (5f), (5h) and (5j) showed excellent anti-microbial activity against a panel of microorganisms. Brine shrimp bioassay was also carried out to study their in vitro cytotoxic properties among which (5h) and (5j) displayed potent cytotoxic activity against Artemia salina. The DNA cleavage activity of some compounds was studied by agarose gel electrophoresis method. All synthesized compounds were characterized using IR, (1)H NMR, (13)C NMR, MS and elemental analysis.

Microwave assisted, one-pot synthesis of 5-nitro- 2-aryl substituted-1H-benzimidazole libraries: Screening in vitro for antimicrobial activity

The efficient and rapid synthesis of 5-nitro-2-aryl substituted-1H-benzimidazole libraries (1a-1j) has been established. Thus, both microwave and conventional cyclo-condensation of 4-nitro ortho-phenylenediamine with various phenoxyacetic acids were carried out in the presence of HCl catalyst. The microwave synthesis route afforded advantages, such as good to excellent yields, shorter reaction time (2.5–3.5 min), readily available starting material, and simple purification procedure, which distinguish the present protocol from other existing methods used for the synthesis of benzimidazole libraries. Bioassay indicated that all the compounds showed in vitro antimicrobial activity against Vancomycin resistant enteroccoccus, Staphylococcus aureus, Micrococcus, Bacillus subtilis (gram-positive bacteria) and Shigella dysentery, Escherichia coli (gram-negative bacteria) and Candida albicans, Aspergillus niger, Penicillium (fungi). The minimum inhibitory concentration (MIC) was determined for test compounds as well as for reference standards.

Application of the electrodialytic pilot plant for fluoride removal

Removal of fluorine from water was investigated by electrodialysis (ED) method. In order to check the efficacy of ED unit, parameters like applied potential, the pH; initial fluoride concentrations and flow rates were varied. Significant results were obtained with concentrations of less than 10 ppm. Results were satisfactory in meeting the maximum contaminate level (MCL) of 0.01 ppm for fluoride. Effect of working parameters on energy consumption was investigated using ion-exchange membranes. Results of this study are useful for designing and operating different capacities of ED plants for recovering different ions. The ED plant was found to be satisfactory to produce a good quality drinking water from the simulated mixture by removing the unwanted ions.

Synthesis, in-vitro Microbial and Cytotoxic Studies of New Benzimidazole Derivatives

Several new classes of benzimidazole derivatives were synthesized and evaluated for in‐vitro antimicrobial and cytotoxic activities. The results showed that all synthesized compounds exhibited moderate antimicrobial activity, and compounds 2, 4, and 13 displayed cytotoxic activity (as LD50) at the concentration 1×10–3 M against Artemia salina.

Synthesis, in-vitro antimicrobial and cytotoxic studies of novel azetidinone derivatives.

Developing novel antimicrobial drugs is increasingly important in the modern pharmaceutical industry. A series of novel 3‐chloro‐4‐[4‐(2‐oxo‐2H‐chromen‐4‐ylmethoxy)phenyl]‐1‐phenylazetidin‐2‐ones 5a–o have been synthesized from 4‐bromomethylcoumarins 1a–e and 4‐aryliminomethyl‐phenols 3a–c. These compounds were screened for their in‐vitro antibacterial activity against two Gram‐positive (Staphylococcus aureus and Vancomycin resistant enteroccoccus) and two Gram‐negative (Escherichia coli and Shigella dysentery) bacterial strains and antifungal activity against Aspergillus fumigatus, Candida albicans, and Penicillium. Results revealed that compounds 5c, 5f, 5h, 5j, and 5m showed excellent activity against a panel of microorganisms. The brine‐shrimp bioassay was also carried out to study their in‐vitro cytotoxic properties and two compounds, 5h and 5m, possessing LD50 = 7.154×10–4 M and 5.782×10–4 M, respectively, displayed potent cytotoxic activity against Artemia salina. The presence of a chlorine group in the coumarin moiety, its effect on their antibacterial, antifungal, and cytotoxic activities is discussed. All newly synthesized compounds were characterized by elemental analysis, IR, 1H‐NMR, 13C‐NMR, and MS.

New Schiff's Base and 2-Azetidinone Derivatives of 3-Benzo[4,5]imidazo[2,1-b]thiazol-3-yl-chromen-2-one by Vilsmeier–Haack Formylation

A new Schiffs base and 2-azetidinone derivatives obtained via the corresponding 3-benzo [4,5] imidazo [2,1-b] thiazol-3-yl-chromen-2-one by Vilsmeier–Haack formylation scaffold is described. Our design is aimed at obtaining new triheterocyclic and tetraheterocyclic derivatives.

RETRACTED ARTICLE: Synthesis, anti-bacterial, anti-fungal and cytotoxic properties of novel pyrimidine derivatives from chromen-2-one moiety

This article has been retracted due to self-plagiarism; a significant proportion of the content was previously published in another journal.