Ethylbisiminomethylguaiacol Manganese Chloride

Also-called-like-this: EUK-134
What-it-does: antioxidant

An interesting synthetic molecule that mimics two antioxidant skin enzymes superoxide dismutase (SOD) and catalase

If you are wondering what the heck SOD and catalase are, here is a little background: they are two smart enzymes found in our bodies that speed up the conversion of the evil, cell damaging free radicals (such as superoxide radicals) into friendly and harmless things such as water and oxygen. We wrote some more about SOD here.

So this unpronounceable guy is actually a nice molecule that mimics the behavior of the natural enzymes in our skin. Estee Lauder likes this ingredient, uses it and has done some studies to prove that Ethylbisiminomethylguaiacol Manganese Chloride, aka EUK-134, can nicely protect the cells from UVB damage. They hypothesize that "EUK-134, via direct protection of the membrane from UVB-induced oxidative damage, reduces oxidative stress induced MAPK signaling and consequently lowers the level of p53 induction. The protection conferred by EUK-134 results in a significant increase in cell survival following UVB irradiation."

Another study (also by Estee Lauder) found that EUK-134 lowers hydroperoxide levels at the surface of UVA-exposed skin in vivo and concluded that this salen–manganese compound is a "unique cosmetic tool to protect the skin surface from accumulating oxidative damage". 

Other than that, we found a study that examined a serum to manage skin redness in sensitive, pale skin types and contained EUK-134 along with a bunch of other ingredients. The formula examined did reduce facial redness so EUK-134 seems to be tolerated well even by redness-prone, sensitive skin types