Table 4.

Comparison of experimental methods for the verification of redox cycling.

Assay	Principle	Feature	Readout
Phenol red-HRP assay	Based on the H2O2-dependent horseradish peroxidase mediated oxidation of phenol red that produces a change in its absorbance at 610 nm in alkaline pH, and readily detects H2O2 generation	Can produce promiscuous effects in enzymes and cell-based analysis	Enzyme and cell inhibition
Surrogate assay	Using the conversion of resazurin to resorufin redox reaction in the presence of DTT and compounds to detect small molecule redox activity	Easy to operate and can be applied to pharmaceutical targets that perform redox chemistry or targets with functional groups susceptible to redox modification	Enzyme inhibition