Direct Comparison of the Lowest Effect Concentrations of Mutagenic Reference Substances in Two Ames Test Formats

The Ames assay is the standard assay for identifying DNA-reactive genotoxic substances. Multiple formats are available and the correct choice of an assay protocol is essential for achieving optimal performance, including fit for purpose detection limits and required screening capacity. In the present study, a comparison of those parameters between two commonly used formats, the standard pre-incubation Ames test and the liquid-based Ames MPF™, was performed. For that purpose, twenty-one substances with various modes of action were chosen and tested for their lowest effect concentrations (LEC) with both tests. In addition, two sources of rat liver homogenate S9 fraction, Aroclor 1254-induced and phenobarbital/β-naphthoflavone induced, were compared in the Ames MPF™. Overall, the standard pre-incubation Ames and the Ames MPF™ assay showed high concordance (>90%) for mutagenic vs. non-mutagenic compound classification. The LEC values of the Ames MPF™ format were lower for 17 of the 21 of the selected test substances. The S9 source had no impact on the test results. This leads to the conclusion that the liquid-based Ames MPF™ assay format provides screening advantages when low concentrations are relevant, such as in the testing of complex mixtures.

Design, Synthesis, Characterization, Computational Study and In-vitro Antioxidant and Anti-inflammatory Activities of Few Novel Pyrazol-3-one Derivatives

Aim: To design, synthesize and perform computational study on a few Novel pyrazol-3-one derivatives. Study design: Experimental study. Methodology: A series of 6-aryl substituted pyrimidine azodyes were synthesized by coupling phenyl pyrimidine 2-amine with different aromatic amines. The synthetic compounds were screened for their in-vitro antioxidant and anti-inflammatory activities. The Computational study of designed compounds was done by OCHEM, Molinspiration cheminformatics, Datawarrior, and Swiss ADME. DPPH assay was used to determine the antioxidant activity and heat hemolysis method for anti-inflammatory activity. Results: Molinspiration, Data Warrior, Ochem which are helpful to predict molecule general properties, bioactive scores, toxicity, and drug-likeness. Data Warrior results inferred that the compounds possess moderately active towards mutagenic (compound 2, 11), reproductive (compound 6, 7, 8), and highly active towards Tumorogenic (compound 2) toxicities. OCHEM results showed that most of the synthesized compounds were found to be non-inhibitors of all the subtypes of cytochrome P450 except compound 8. All compounds under this study were effective scavengers of free radicals except the compounds 1, 2, 6, 10. Invitro Anti-inflammatory studies have shown that the compounds (6, 7, 8, 9, 13) active toward heat hemolysis. Conclusion: The synthesized compounds were comprehensively studied and targets were identified rendering them as lead molecules for further development of newer agents with greater efficacy and safety.

Comment on “A commensal strain of Staphylococcus epidermidis protects against skin neoplasia” by Nakatsuji et al.

A recent article in Science Advances described the striking discovery that the commensal Staphylococcus epidermidis strain MO34 displays antimicrobial and antitumor activities by producing a small molecule, identified as the nucleobase analog 6-N-hydroxylaminopurine (6-HAP). However, in contradiction to the literature, the authors claimed that 6-HAP is nonmutagenic and proposed that the toxic effect of 6-HAP results from its ability to inhibit, in its base form, DNA synthesis. To resolve the discrepancy, we proved by genetic experiments with bacteria and yeast that extracts of MO34 do contain a mutagenic compound whose effects are identical to chemically synthesized 6-HAP. The MO34 extract induced the same mutation spectrum as authentic 6-HAP. Notably, the toxic and mutagenic effects of both synthetic and MO34-derived 6-HAP depended on conversion to the corresponding nucleotide. The nucleobase 6-HAP does not inhibit DNA synthesis in vitro, and we conclude that 6-HAP exerts its biological activity when incorporated into DNA.

Formation, Detection and Removal of NDMA in Water Treatment Process

N-Nitrosodimethylamine(NDMA) is known as a carcinogenic and mutagenic compound ,and in recent years, it has been found to be a novel disinfection by-product of the chloramination process.The NDMA precursors are considered as dimethylamine(DMA) and tertiary amines with dimethylamine functional groups. There are four pathways to NDMA formation: nitrosation, unsymmetrical dimethylhydrazine(UDMH) oxidation, chlorinated UDMH oxidation and hydroxylamine pathway. Formation of NDMA is affected by the presence of free chlorine and bromide, and pH is also a sensitive fator.The detection and analytical methods of NDMA are usually spectrophotometry，thin-layer chromatography, GC, LC and GC/MS.To improve the detection precision, GC/MS/MS and GC/HRMS are applied in detecting the trace NDMA. The methods of NDMA removal are UV degradation, the resin and several types of zeolite adsorption, UV/ozone and UV/hydrogen peroxide advanced oxidation technologies. Ozone also can oxidate percursors,so it can control the NDMA yield indirectly.