Specificity and properties of propofol as an antioxidant free radical scavenger.

The active component of the anesthetic propofol (2,6-diisopropylphenol), which structurally resembles butylated hydroxy-toluene (BHT), a known free radical scavenger, was examined and compared to BHT with regard to its dose-dependent radical scavenging activity. Studies on the ameliorating effect of propofol in inhibiting radical production revealed that it preferentially scavenges organoradical species. In aqueous suspension it is more efficient than BHT as a free radical scavenger of riboflavin radicals and in blocking formation of malondialdehyde degradation products generated from lipid hydroperoxides of arachidonic acid. Neither propofol nor BHT showed any radical scavenging activities at concentration ranges less than 10 micrograms/ml. Propofol quenched radicals generated by photoillumination of riboflavin by 50% at 30 micrograms/ml. Under the same conditions BHT still showed no radical scavenging activity. At 50 micrograms/ml propofol the formation of malondialdehyde degradation products of arachidonic acid formed by illuminating arachidonic acid in test mixtures containing riboflavin was decreased by 38% compared to a decrease of only 24% with BHT substituted in place of propofol. The concentration of propofol required to ameliorate free radicals is approximately an order of magnitude higher than therapeutic doses of propofol used in anesthesia, suggesting that its scavenging activity during anesthesia is likely very limited.