Mn(III)TMPyP is a manganese-porphyrin which acts as a superoxide dismutase (SOD) mimetic and peroxynitrite decomposition catalyst. SOD mimetics described to date are unstable and are capable of catalyzing undesired side-reactions in addition to the dismutation of the superoxide radical (O2-). Mn(III)TMPyP is an SOD mimetic with increased stability to pH and hydrogen peroxide. The rate constant for superoxide dismutation and peroxynitrite decomposition are 3.9 x 107 M-1s-1 and ~2 x 106 M-1s-1, respectively. Mn(III)TMPyP protected and enhanced the growth of SOD E. coli with a doubling time of 60 minutes (as compared to 240 minutes of the control) at 25 µM.
Pheophytin a, a chlorophyll isolated from S. vermiculata extracts, demonstrates antioxidant activity with IC50 values of 200.5 and 137.7 μg mL for SOD and NO, respectively. It also exhibits reducing power (IC50 = 4.2 μg mL) and a cytotoxic effect on the MCF-7 cell line (IC50 = 35.9 μg mL) [1].