A comparison of the relative antioxidant potency of L-ergothioneine and idebenone

Summary Background L‐ergothioneine (EGT) is a stable antioxidant found in food plants as well as in animal tissue undergoing relatively high levels of oxidative stress. Idebenone is a stable analog of the antioxidant coenzyme Q10. All are potent antioxidants found in skincare products, but their relative potencies are not well described. Aims To establish the physiological relevance of EGT by examining transcription of the EGT transporter gene OCTN‐1 and production of the receptor protein in skin fibroblasts. In addition, to compare the inhibition of lipid peroxide formation by coenzyme Q10 and EGT. Furthermore, to compare the peroxide‐scavenging abilities of EGT and idebenone in both simple solution and in cell cultures exposed to ultraviolet A (UVA). Methods OCTN‐1 expression and production in cultured fibroblasts were measured through real‐time reverse transcription‐PCR and Western blotting, respectively. Alloxan‐induced lipid peroxidation in liposomes was used to evaluate the inhibition of lipid peroxide formation. The abilities of EGT and idebenone to directly scavenge hydroxyl radicals produced by H2O2 were determined. Finally, we irradiated fibroblasts with UVA340 radiation and compared antioxidant capabilities to scavenge free radicals. Results We found that OCTN‐1 is expressed and readily detectable in cultured human fibroblasts. EGT was more efficient in inhibiting lipid peroxide formation than coenzyme Q10 or idebenone. Samples treated with EGT had significantly less peroxide than those treated with idebenone 120 min after adding the antioxidants to H2O2. EGT acted significantly quicker and more efficiently in capturing reactive oxygen species (ROS) after UVA340 irradiation. Conclusions EGT is a natural skin antioxidant, as evidenced by the presence of the EGT transporter in fibroblasts. EGT is a more powerful antioxidant than either coenzyme Q10 or idebenone due to its relatively greater efficiency in directly scavenging free radicals and in protecting cells from UV‐induced ROS.