Synthesis and evaluation of antioxidant activity of new quinoline-2-carbaldehyde hydrazone derivatives: bioisosteric melatonin analogues.

Overproduction of reactive oxygen species results in oxidative stress that can cause fatal damage to vital cell structures. It is known that the use of antioxidants could be beneficial in the prevention or delay of numerous diseases associated with oxidative stress. Melatonin (MLT) is known as a powerful free-radical scavenger and antioxidant. It was found that indole ring of MLT can be employed by bioisosteric replacement by other aromatic rings. Quinoline derivatives constitute an important class of compounds for new drug development. Owing to quinoline and hydrazones appealing physiological properties and are mostly found in numerous biologically active compounds a series of quinoline-2-carbaldehyde hydrazone derivatives were synthesized as bioisosteric analogues of MLT, characterized and in vitro antioxidant activity was investigated by evaluating their reducing effect against oxidation of a redox-sensitive fluorescent probe. Cytotoxicity potential of all compounds was investigated both by lactate dehydrogenase leakage assay and by MTT assay.

Synthesis and potent antistaphylococcal activity of some new 2-[4-(3,4-dimethoxyphenoxy)phenyl]-1,N-disubstituted-1H-benzimidazole-5-carboxamidines.

A series of new 2-[4-(3,4-dimethoxyphenoxy)phenyl]-1,N-disubstituted-1H-benzimidazole-5-carboxamidines (23-33) have been synthesized and evaluated for their potential antistaphylococcal activity. Cytotoxic effects of the compounds were investigated by the neutral red uptake (NRU) cytotoxicity test. Most of the compounds exhibited good MICs values against Staphylococcus aureus and methicillin-resistant S. aureus (MRSA). Compound 28 with N-cyclohexylcarboxamidine group at the 5-position was found to be the most potent agent, with the MIC value of 3.12 µg/mL.

Synthesis and antistaphylococcal activity of N-substituted-1H-benzimidazole-sulphonamides.

A series of N-substituted-1H-benzimidazole-5(6)-sulfonamides and 3-(5,6-dichloro-1H-benzimidazol-2-yl)-N-substituted benzensulfonamides were synthesized and evaluated for antibacterial activity against Staphylococcus aureus and methicillin-resistant S. aureus (MRSA). Certain compounds inhibit bacterial growth with low MIC (microg/mL) values. The most active compounds 30, 31, and 32 have the lowest MIC values with 0.39 to 0.19 microg/mL. Among the compounds having sulfonamido moities, 16, 23, and 24 exhibited the strongest antibacterial activity with 1.56 microg/mL MIC values.

Synthesis and evaluation of in vitro antioxidant capacities of some benzimidazole derivatives.

New, except 1d, melatonin analogue benzimidazole derivatives were synthesized and characterized in the present study. The potential role of melatonin as an antioxidant by scavenging and detoxifying ROS raised the possibility that compounds that are analogous to melatonin can also be used for their antioxidant properties. Therefore the antioxidant effects of the newly synthesized compounds were investigated in vitro by means of their inhibitory effect on hydrogen peroxide-induced erythrocyte membrane lipid peroxidation (EMLP) and on various erythrocyte antioxidant enzymes viz. superoxide dismutase (SOD), catalase (CAT) and glucose-6-phosphate dehydrogenase (G6PD). The synthesized benzimidazole derivatives showed remarkable antioxidant activity in vitro in the H2O2-induced EMLP system. Furthermore their effects on various antioxidant enzymes are discussed and evaluated from the perspective of structure- activity relationships.