Fundamental kinetic and selectivity properties of the anti-aging, antioxidant-active ingredient EUK-134.

EUK-134 is a manganese-salen complex, derived from the parent molecule EUK-8, and is widely used in anti-aging skincare formulations because of its potent antioxidant activity, resulting from the catalytic decomposition of reactive oxygen species (ROS). Despite this popularity, the fundamental kinetic properties (k) that govern its efficacy and overall recyclability are not well understood, limiting the understanding of its behavior and further optimization in skincare products and therapeutic applications. Importantly, this knowledge gap makes comparisons to newly developed molecules a challenge. As a result, the present study investigates the efficiency, sustained activity, and selectivity of EUK-134 over EUK-8 by evaluating the turnover number (TON), the turnover frequency (TOF), and the overall kinetic constant (k) under pseudo-first-order conditions. The results indicate that while EUK-134 exhibits high catalase-like activity and moderate selectivity, the robustness of this activity decreases significantly with continued cycles of exposure to H2O2. The results reported here provide the necessary kinetic benchmarks to compare future small molecules against the current gold standard, EUK-134. By establishing the parameters through this study, more affordable and optimized biomimetic catalysts can be explored moving forward.