In vitro and in vivo anti-pigmentation effects of 2-mercaptobenzimidazoles as nanomolar tyrosinase inhibitors on mammalian cells and zebrafish embryos: Preparation of pigment-free zebrafish embryos

Recently, 10 2-mercaptobenzo[d]imidazole (2-MBI) compounds (1-10) were synthesized. Although all 2-MBI compounds are tyrosinase inhibitors that inhibit mushroom tyrosinase at extremely low concentrations (IC50 values: 20-740 nM) and effectively inhibit the browning of apples, to our knowledge, no studies have determined whether 2-MBI compounds inhibit mammalian tyrosinase. Mammalian tyrosinase is different from mushroom tyrosinase in its distribution within the cell and has structural characteristics that are different from mushroom tyrosinase in amino acid sequence and in the presence of a quaternary structure. Thus, the effect of the 10 2-MBI compounds on mammalian tyrosinase activity was investigated in B16F10 cells. Six compounds (1-6) exhibited stronger intracellular tyrosinase inhibition than that of kojic acid and phenylthiourea (PTU), which are known to be the most potent tyrosinase inhibitors; their strong tyrosinase inhibitory activity robustly inhibited intracellular melanin production in B16F10 cells. None of the tested 2-MBI compounds exhibited appreciable cytotoxicity in HaCaT and B16F10 cells. To confirm the anti-melanogenic efficacy of the 2-MBI compounds in vivo, a zebrafish embryo model was used. At concentrations 100 times lower than kojic acid, most 2-MBI compounds demonstrated much stronger depigmentation efficacy than that of kojic acid, and three 2-MBI compounds (2-4) showed depigmentation activity similar to or more potent than that of PTU, resulting in nearly pigment-free zebrafish embryos. These results suggest that 2-MBI compounds may be potential therapeutic agents for hyperpigmentation-related disorders.

Design, synthesis and biological profile of heterocyclic benzimidazole analogues as prospective antimicrobial and antiproliferative agents

Background

Nitrogen containing heterocycles are widely used and investigated by pharmaceutical industry, as they are important in discovery and designing of new drug molecules. Drugs with a benzimidazole nucleus possess exclusive structural features and electron-rich atmosphere, which enable them to bind to a number of biologically important targets and result in a wide range of activities. This has served as the basis of the present study whereby new scaffolds with benzimidazole moiety were designed and synthesized.

Methods

The structures of synthesized compounds were confirmed by physicochemical and spectral means. The synthesized compounds were screened for their antimicrobial and antiproliferative activities by tube dilution and Sulforhodamine B (SRB) assays, respectively.

Results and conclusion

The in vitro biological screening results revealed that compound Z24 exhibited promising antimicrobial and anticancer activities which are comparable to standards.

Design, synthesis and therapeutic potential of 3-(2-(1H-benzo[d]imidazol-2-ylthio)acetamido)-N-(substituted phenyl)benzamide analogues

Background

The emergence of bacterial resistance is a major public health problem. It is essential to develop and synthesize new therapeutic agents with better activity. The mode of actions of certain newly developed antimicrobial agents, however, exhibited very limited effect in treating life threatening systemic infections. Therefore, the advancement of multi-potent and efficient antimicrobial agents is crucial to overcome the increased multi-drug resistance of bacteria and fungi. Cancer, which remains as one of the primary causes of deaths and is commonly treated by chemotherapeutic agents, is also in need of novel and efficacious agents to treat resistant cases. As such, a sequence of novel substituted benzamides was designed, synthesized and evaluated for their antimicrobial and anticancer activities.

Methodology

All synthesized compounds were characterized by IR, NMR, Mass and elemental analysis followed by in vitro antimicrobial studies against Gram-positive (Staphylococcus aureus), Gram-negative (Salmonella typhi and Klebsiella pneumoniae) bacterial and fungal (Candida albicans and Aspergillus niger) strains by the tube dilution method. The in vitro anticancer evaluation was carried out against the human colorectal carcinoma cell line (HCT116), using the Sulforhodamine B assay.

Results, discussion and conclusion

Compound W6 (MIC_{sa, st, kp} = 5.19 µM) emerged as a significant antibacterial agent against all tested bacterial strains i.e. Gram-positive (S. aureus), Gram-negative (S. typhi, K. pneumoniae) while compound W1 (MIC_{ca, an} = 5.08 µM) was most potent against fungal strains (A. niger and C. albicans) and comparable to fluconazole (MIC = 8.16 µM). The anticancer screening demonstrated that compound W17 (IC₅₀ = 4.12 µM) was most potent amongst the synthesized  compounds and also more potent than the standard drug 5-FU (IC₅₀ = 7.69 µM).

One pot Click chemistry: A three component reaction for the synthesis of 2-mercaptobenzimidazole linked coumarinyl triazoles as anti-tubercular agents

2-Propargylthiobenzimidazole 1, 4-bromomethyl coumarins/1-aza-coumarins 2/3 and sodium azide have been reacted in one pot under Click chemistry conditions to give exclusively 1,4-disubstituted triazoles 5a-n. Anti-tubercular assays against M. tuberculosis (H37Rv) coupled with in silico molecular docking studies indicated that dimethyl substituents 5c and 5d showed promising activity with higher C-score values.