To face physicochemical and biological stresses, living organisms evolved endogenous chemical responses based on gas exchange with the atmosphere and on formation of nitric oxide (NO(*)) and oxygen derivatives. The combination of these species generates a complex network of variable extension in space and time, characterized by the nature and level of the reactive oxygen (ROS) and nitrogen species (RNS) and of their organic and inorganic scavengers. Among the latter, this review focusses on natural 3-substituted indolic structures. Tryptophan-derived indoles are unsensitive to NO(*), oxygen and superoxide anion (O(2)(*-)), but react directly with other ROS/RNS giving various derivatives, most of which have been characterized. Though the detection of some products like kynurenine and nitroderivatives can be performed in vitro and in vivo, it is more difficult for others, e.g., 1-nitroso-indolic compounds. In vitro chemical studies only reveal the strong likelihood of their in vivo generation and biological effects can be a sign of their transient formation. Knowing that 1-nitrosoindoles are NO donors and nitrosating agents indicating they can thus act both as mutagens and protectors, the necessity for a thorough evaluation of indole-containing drugs in accordance with the level of the oxidative stress in a given pathology is highlighted.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1600-079X.2008.00580.x

Potential role of tryptophan derivatives in stress responses characterized by the generation of reactive oxygen and nitrogen species

Synthesis, physicochemical properties and antimicrobial activity of some new benzimidazole derivatives

Oxidative damage to DNA has important implications for human health and has been identified as a key factor in the onset and development of numerous diseases. Thus, it is evident that preventing DNA from oxidative damage is crucial for humans and for any living organism. Melatonin is an astonishingly versatile molecule in this context. It can offer both direct and indirect protection against a wide variety of damaging agents and through multiple pathways, which may (or may not) take place simultaneously. They include direct antioxidative protection, which is mediated by melatonin’s free radical scavenging activity, and also indirect ways of action. The latter include, at least: (i) inhibition of metal-induced DNA damage; (ii) protection against non-radical triggers of oxidative DNA damage; (iii) continuous protection after being metabolized; (iv) activation of antioxidative enzymes; (v) inhibition of pro-oxidative enzymes; and (vi) boosting of the DNA repair machinery. The rather unique capability of melatonin to exhibit multiple neutralizing actions against diverse threatening factors, together with its low toxicity and its ability to cross biological barriers, are all significant to its efficiency for preventing oxidative damage to DNA.

https://www.mdpi.com/1420-3049/23/3/530/pdf

Melatonin: A Versatile Protector against Oxidative DNA Damage

Carbon and its derivatives, as the high performance material, occupy a special place in electrochemistry due to its ‐in many ways‐ extreme properties. Recent trends and advances in the electrochemistry of carbon‐based electrodes are reviewed. The varieties of carbon‐based electrodes, their basic physicochemical properties and some characteristics are surveyed. Special attention is paid to the possibilities of carbon‐based electrodes in electroanalytical investigation in pharmaceutical dosage forms and biological samples using modern electrochemical techniques. This review includes a summary of the rules that must be considered for drug analysis from its dosage forms and biological samples using carbon‐based electrodes. The present review is the first comprehensive report on the heterogeneous and homogeneous carbon electrodes, and an addition to many excellent reviews on carbon electrodes in the literature. This review summarizes some of the recent developments and applications of carbon‐based ele...

Electroanalytical Application of Carbon Based Electrodes to the Pharmaceuticals

Many different techniques, such as UV/vis absorption, IR spectroscopy, fluorescence and Raman spectroscopy are routinely applied in chemical (micro-)analysis and chemical imaging, and a large variety of instruments is commercially available. Up to now, opto- or photoacoustic (PA) and other optothermal (OT) methods are less common and only a limited number of instruments reached a level of application beyond prototypes in research laboratories. The underlying principle of all these techniques is the detection of local heating due to the conversion of light into heat by optical absorption. Considering the versatility, robustness and instrumental simplicity of many PA techniques, it is surprising that the number of commercial instruments based on such approaches is so sparse. The impetus of this review is to summarize basic principles and possible applications described in the literature, in order to foster routine application of these techniques in industry, process analysis and environmental screening. While the terms OT and PA methods cover a very wide range of methods and physical phenomena, this review will concentrate on techniques with applications for analytical measurements.

https://iopscience.iop.org/article/10.1088/0957-0233/23/1/012001/pdf

Photoacoustic spectroscopy for analytical measurements

Some 6-fluoro-5-substituted-benzimidazole derivatives in which indole and 1,1,4,4-tetramethyl-1,2,3,4-tetrahydro-naphthalene groups were attached to the 2-position of the benzimidazole ring were synthesized and tested for antioxidant properties in vitro. Almost all the synthesized compounds at the 10(-3) M concentrations showed superoxide anion scavenging activity. Compounds 5, 3, 9, 4, 17 and 13 have strong inhibitory effects on superoxide anion formation (98%, 93%, 91%, 88%, 85% and 81%, respectively) at 10(-3) M concentration and these results are better than 30 IU of superoxide dismutase (SOD) (76%). Compound 11 is the most effective scavenger of 2,2-diphenyl-1-picrylhydrazyl (DPPH) stable free radical at 10(-3)M (61%) concentration.

https://www.tandfonline.com/doi/pdf/10.1080/14756360500131706

Synthesis and antioxidant properties of novel benzimidazoles containing substituted indole or 1,1,4,4-tetramethyl-1,2,3,4-tetrahydro-naphthalene fragments

Novel retinoid derivatives containing a benzimidazole moiety were synthesized and tested for their antimicrobial activity. Their antimicrobial activities against methicillin-resistant Staphylococcus aureus (MRSA), Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, Candida krusei and Candida albicans were evaluated. While some of the compounds exhibited moderate activity against MRSA, S. aureus, E. faecalis, C. krusei and C. albicans, none of the compounds showed activity against E. coli and P. aeruginosa.

Antimicrobial activities of some tetrahydronaphthalene-benzimidazole derivatives.

To understand antioxidant activity and the role played by melatonin, we have designed and tested several new compounds. We present the results in terms of structure-activity relationships, focusing on the lack of the methoxy group and the influence of the amide side chain. Antioxidant activity of melatonin and some new melatonin analogue indole derivatives were investigated, using lipid peroxidation and superoxide anion radical scavenger activity assays, in rat liver tissue homogenate. Most of the compounds were found to be very potent inhibitors of malondialdehyde (MDA) formation at 10−3M. Inhibition rates ranged from 75-44 %. However, no significant inhibitory effect was obtained on superoxide anion formation. Consequently, it can be concluded that these compounds exhibit important LP activity compared to melatonin.

A comparative study: Evaluation of antioxidant activity of melatonin and some indole derivatives

Synthesis and potent antifungal activity against Candida species of some novel 1H‐benzimidazoles

Benzimidazole is a heterocyclic aromatic organic compound which has been an important pharmacophore and privileged structure in medicinal chemistry. Substituted benzimidazoles have considerable interest as compounds with a wide spectrum of biological activity and low toxicity. Benzimidazole derivatives are structurally related to purine nucleoside bases, which allow them to interact easily with the biopolymers of the living systems. Different substituted benzimidazoles have an extensive range of biological activities including: antiviral, antifungal, antimicrobial, antiprotozoal, antiinflammatory, anticancer, antioxidant, anticoagulant, antidiabetic and antihypertensive activities. Infectious diseases are those whose incidence in humans has increased during the past few decades. They cause suffering and death and an enormous financial burden. Antimicrobial drugs have saved the lives of millions of people. However, the dramatic increase in drug-resistant microbes is threatening to reverse medical progress of the past 50 years. Benzimidazoles are very effective compounds with respect to their bacteria inhibitory activity. Biochemical and pharmacological studies have showed that these molecules are effective against various strains of microorganisms. Some benzimidazole compounds inhibit the biosynthesis of ergosterol, required in the cell membrane of fungi and protozoa and a useful target for antifungal drugs. The result of many efforts to develop new molecules for effective antimicrobials reveals that the benzimidazoles are still one of the most versatile class of compounds against microbes.

Zeynep Ates-Alagoz

Papers

Synthesis and antioxidant properties of novel benzimidazoles containing substituted indole or 1,1,4,4-tetramethyl-1,2,3,4-tetrahydro-naphthalene fragments

Antimicrobial activities of some tetrahydronaphthalene-benzimidazole derivatives.

A comparative study: Evaluation of antioxidant activity of melatonin and some indole derivatives

Synthesis and potent antifungal activity against Candida species of some novel 1H‐benzimidazoles

Antimicrobial Activities of 1-H-Benzimidazole-based Molecules.