Tri-Manganese(III) Salen-based Cryptands: A Metal Cooperative Antioxidant Strategy that Overcomes Ischemic Stroke Damage In vivo.

Oxidative stress is one of the hallmarks of ischemic stroke. Catalase-based (CAT) biomimetic complexes are emerging as promising therapeutic candidates that are expected to act as neuroprotectants for ischemic stroke by decreasing the damaging effects from H2O2. Unfortunately, these molecules result in the unwanted produc-tion of the harmful hydroxyl radical, HO•. Here, we report a series of salen-based tri-manganese (Mn(III)) me-tallocryptands 1-3 that function as catalase biomimetics. These cage-like molecules contain a unique "active site" with three Mn centers in close proximity, an arrangement designed to facilitate metal cooperativity for the effective dismutation of H2O2 with minimal HO• production. In fact, significantly greater oxygen produc-tion is seen for 1-3 as compared to the monomeric Mn(Salen) complex, 1c. The most promising system, 1, was studied in further detail and found to confer a greater therapeutic benefit both in vitro and in vivo than the monomeric control system, 1c, as evident from inter alia studies involving a rat model of ischemic stroke dam-age and supporting histological analyses. We thus believe that metallocryptand 1 and its analogues represent a new and seemingly promising strategy for treating oxidative stress related disorders.