Purpose
Ketamine, an anesthetic used for general anesthesia, has been reported to have anti-oxidative activity; ketamine is preventive against oxidative stress including ischemia/reperfusion injury and inflammation. We hypothesized that ketamine directly scavenges free radicals thereby acting as an antioxidant.
Methods
Free radical scavenging activity of ketamine was evaluated against six species of free radicals by electron spin resonance spectroscopy with the spin-trapping method. Fluorescence-based assays of cellular viability after oxidative stress was assessed using alamarBlue. Anti-oxidative activity was assessed by TBARS assay.
Results
Ketamine significantly scavenged the following free radicals in dose-dependent manners; hydroxyl radical, tert-butoxyl radical, ascorbyl free radical with reaction rate constants around one order of magnitude smaller than those of edaravone, and nitric oxide with three orders of magnitude smaller. Ketamine also scavenged superoxide anion and tert-butyl peroxyl radical at higher concentrations. Cellular viability of MRC5 cells exposed to 300 μM hydrogen peroxide was significantly improved in the presence of 1 μM ketamine. Ketamine significantly inhibited lipid oxidation in a dose dependent manner.
Conclusions
Ketamine dose-dependently scavenged multiple free radicals including hydroxyl radical. It is speculated that ketamine is protective of perioperative oxidative stress, at least partially, via non-enzymatic free radical scavenging activity.