Phenol Red sodium salt  (Synonyms: Phenolsulfonephthalein sodium salt)

Phenol red (Phenolsulfonephthalein) sodium salt is a pH indicator dye. Phenol Red sodium salt is also an antagonist of rat P2X1R. Phenol Red sodium salt enhances the halogenating activity of myeloperoxidase. Phenol Red sodium salt shows a distinct color change from pink to yellow in a positive pH reaction^[1][2][3][4].

Guide (The following is our recommended protocol. This protocol is only a guide and should be modified according to your specific needs).
Phenol Red sodium salt acts as an indicator of AChE activity^[4]
1.Solutions Preparation
Concentration of Phenol Red sodium salt in water is set to 500 µM.
2. Reaction
1) Thirty-five microliters of PBS, 25 µL of PBS 7.4 or tacrine solution, 20 µL of Phenol Red sodium salt, and 20 µL of 5 mM AChCl are consequently added to the surface of paper with immobilized AChE.
2) After 5 min of incubation, the surface of the paper is photographed using a smart phone camera placed on a 3D-printed, tube-shaped holder.
Note: in neutral pH of PBS 7.4, Phenol red gives a red color. After addition of AChCl, immediately forming acetic acid acidifying medium and the Phenol Red sodium salt turns yellow.

MedChemExpress (MCE) has not independently confirmed the accuracy of these methods. They are for reference only.

376.36

C₁₉H₁₃NaO₅S

34487-61-1

Solid

Red to black

O=S1(OC(C2=CC=C(O[Na])C=C2)(C3=CC=C(O)C=C3)C4=CC=CC=C41)=O

Room temperature in continental US; may vary elsewhere.

Store at room temperature, keep dry and cool

* Please refer to the solubility information to select the appropriate solvent. Once prepared, please aliquot and store the solution to prevent product inactivation from repeated freeze-thaw cycles.
Storage method and period of stock solution: -80°C, 1 year; -20°C, 6 months. When stored at -80°C, please use it within 1 year. When stored at -20°C, please use it within 6 months.

• [1]. Morgan A, et al. Caution for the routine use of phenol red - It is more than just a pH indicator. Chem Biol Interact. 2019;310:108739.  [Content Brief]

  [2]. Peltzer D, et al. Rapid and simple colorimetric loop-mediated isothermal amplification (LAMP) assay for the detection of Bovine alphaherpesvirus 1. J Virol Methods. 2021;289:114041.  [Content Brief]

  [3]. King BF, et al. Antagonism of ATP responses at P2X receptor subtypes by the pH indicator dye, Phenol red. Br J Pharmacol. 2005 Jun;145(3):313-22.  [Content Brief]

  [4]. Kostelnik A, et al. Color Change of Phenol Red by Integrated Smart Phone Camera as a Tool for the Determination of Neurotoxic Compounds. Sensors (Basel). 2016 Sep 7;16(9):1212.  [Content Brief]