Iodonitrotetrazolium丨CAS 146-68-9

Iodonitrotetrazolium丨CAS 146-68-9 (commonly abbreviated as INT) is a redox indicator and a tetrazolium salt used primarily in biochemical and microbiological assays. Chemically known as 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyl tetrazolium chloride, INT is a yellow to pale-colored crystalline powder that turns into a deep red formazan dye upon reduction.

1. Cell Viability and Cytotoxicity Assays
● INT is widely used in colorimetric assays to assess cell viability, cell proliferation, and cytotoxic effects of drugs or environmental agents.
● Mechanism: Viable cells with active metabolism reduce INT into an insoluble red formazan product, which accumulates in or around cells.
● Commonly used as an alternative to MTT and XTT assays.
2. Microbial Metabolism Testing
● Used in bacterial and yeast culture testing to detect metabolic activity. INT reduction indicates living, metabolically active microorganisms.
● Employed in water quality testing, antibiotic susceptibility assays, and food microbiology.
3. Enzyme Activity Detection
● Iodonitrotetrazolium丨CAS 146-68-9 is used as a chromogenic substrate for enzyme activity, particularly in dehydrogenase assays. Enzymes catalyze reactions that produce reducing agents (e.g., NADH), which reduce INT to its colored form.
● It is often coupled with glucose dehydrogenase, lactate dehydrogenase, or succinate dehydrogenase assays.
4. Tissue Staining and Histochemistry
● In histology, INT is used to detect viable tissues. It stains viable, enzyme-active tissues red due to the localized reduction of the salt.
● Used in cardiac tissue viability assessments after infarction (in animal studies) and neuroanatomical studies.
5. Plant Physiology
● Applied in plant stress studies to evaluate root viability, respiration, and photosynthetic activity under various stress conditions (e.g., drought, salt, cold).
● INT staining of plant tissues helps identify active regions and damage due to stress or aging.

1. High Sensitivity and Specificity
● INT provides a clear, visual color change upon reduction, allowing rapid and accurate detection of metabolic activity.
2. Versatile Application
● Usable in biological, microbial, plant, and environmental assays-suitable for broad laboratory use from diagnostics to research.
3. Quantifiable Colorimetric Output
● The red formazan product formed can be easily quantified using a spectrophotometer (usually at 490–500 nm), providing objective measurement of results.
4. Low Toxicity
● Compared to some other tetrazolium salts, INT is relatively non-toxic to cells, especially in short-term exposures, allowing live cell imaging or assays without immediate cell damage.
5. Stable and Easy to Use
● INT is stable under normal laboratory conditions and is soluble in various solvents, making it convenient for a wide range of protocols.

Conclusion
Iodonitrotetrazolium丨CAS 146-68-9 is a valuable biochemical reagent for detecting metabolic activity, enzyme function, and cell viability across a wide range of scientific disciplines. Its simple, robust redox chemistry, high sensitivity, and visible colorimetric output make it a popular choice in labs working in microbiology, cell biology, toxicology, plant science, and histopathology. Whether used in quantitative assays or visual staining, INT remains a reliable and versatile tool for biological research and diagnostics.