# Concentration-Response Relationships of the Non-enzymatic Scavenging Activity of Ethyl Pyruvate Against Multiple Free Radicals

## TL;DR

This study shows how ethyl pyruvate can scavenge various free radicals in a concentration-dependent way, suggesting it may help protect against oxidative stress.

## Contribution

The paper provides new concentration-response data for ethyl pyruvate's non-enzymatic scavenging activity against multiple free radicals.

## Key findings

- Ethyl pyruvate scavenged six free radicals with varying reaction rate constants.
- It did not scavenge tert-butyl peroxyl radical, tert-butyl hydroperoxide, DPPH, or tyrosyl radical.
- The activity suggests ethyl pyruvate may protect against oxidative stress through free radical scavenging.

## Abstract

Background

Pyruvate is a metabolic intermediate of energy metabolism that connects glycolysis and the tricarboxylic acid cycle. It also acts as an antioxidant, although it is unstable in solution. Ethyl pyruvate is a derivative of pyruvate with stability and lipid solubility and has been reported to have antioxidative activity. This study aimed to illustrate the concentration-response relationships of the non-enzymatic scavenging activity of ethyl pyruvate against multiple free radicals in vitro.

Methodology

Eight kinds of free radicals and singlet oxygen were generated in sample tubes. The direct scavenging activities of ethyl pyruvate against free radicals were evaluated by electron spin resonance spectroscopy using the spin-trapping method. Reaction rate constants were estimated from half-maximal inhibitory concentrations of concentration-response relationships.

Results

Ethyl pyruvate significantly scavenged the following six species of free radicals in concentration-dependent manners: hydroxyl radical (kethyl pyruvate = 1.4 × 108 M-1s-1), superoxide anion (4.6 × 103 M-1s-1), tert-butoxyl radical (0.91 × kCYPMPO), ascorbyl free radical (0.77 × kedaravone), singlet oxygen (0.19 × k4-OH_TEMP), and nitric oxide (8.6 M-1s-1). However, ethyl pyruvate did not scavenge tert-butyl peroxyl radical, tert-butyl hydroperoxide, 2,2-diphenyl-1-picrylhydrazyl, and tyrosyl radical.

Conclusions

It is speculated that the protective activity of ethyl pyruvate against oxidative stress might be attributable to non-enzymatic free radical scavenging activity.