**3.3 Superoxide radical scavenging capability**

This experiment had been completed based on the method mentioned in [43]. Superoxide radical scavenging assay actually estimated the scavenging efficiency of sample by reducing the nitro blue tetrazolium (NBT) by providing electron. The reaction mixture or solution was a combination of nonenzymatic phenazine methosulfate (PMS), nicotinamide adenine dinucleotide (NADH), phosphate buffer, and samples with various concentrations, and it was then incubated for 5 min at room temperature. The PMS-NADH system created free radical in the solution mixture. In the presence of sample solutions, the NBT was reduced into purple formazan. The overall activity has been evaluated by taking absorbance via spectrophotometer at 562 nm. All the tests had been operated for three times for better accuracy and blank has been determined to calculate the amount of formazan that has been produced, and quercetin has been taken as a standard for this experiment.


**Table 4.**

*Hydroxyl radical scavenging data analysis for standard catechin and crystal compound.*

#### *3.3.1 Data interpretation of superoxide radical scavenging assay*

According to **Table 5**, the IC50 value for catechin was 26.79 (*μg*/ml), and crystal compound was 29.04 (*μg*/ml), which was satisfactory result for this in vitro test.
