Hint from an Enzymatic Reaction: Superoxide Dismutase Models Efficiently Suppress Colorectal Cancer Cell Proliferation.

Superoxide dismutases (SODs) are essential antioxidant enzymes that prevent massive superoxide radical production and thus protect cells from damage induced by free radicals. However, this concept has rarely been applied to directly impede the function of driver oncogenes, thus far. Here, leveraging efforts from SOD model complexes, we report the novel finding of biomimetic copper complexes that efficiently scavenge intracellularly generated free radicals and, thereby, directly access the core consequence of colorectal cancer suppression. We conceived four structurally different SOD-mimicking copper complexes that showed distinct disproportionation reaction rates of intracellular superoxide radical anions. By replenishing SOD models, we observed a dramatic reduction of intracellular reactive oxygen species (ROS) and adenine 5'-triphosphate (ATP) concentrations that led to cell cycle arrest at the G2/M stage and induced apoptosis in vitro and in vivo. Our results showcase how nature-mimicking models can be designed and fine-tuned to serve as a viable chemotherapeutic strategy for cancer treatment.

Catalytic approach to in vivo metabolism of atractylenolide III using biomimetic iron-porphyrin complexes.

Atractylenolide III (AT-III) is a pharmacologically effective phytochemical and is known to be oxygenated during systemic metabolism mainly by cytochrome P450 enzymes (CYP450s), iron-containing porphyrin-based oxygenases. In rat plasma samples, the oxygenated metabolite of orally ingested AT-III was determined using liquid chromatography/mass spectrometry and the oxygenated form of AT-III was maintained at higher levels than the original form of AT-III. In situ catalytic reactions using the iron(iv)-oxo porphyrin π-cation radical complex, [(tmp+˙)FeIV(O)]+, demonstrated that both H-atom abstraction and an oxygen rebound mechanism participated in the oxygenation process of AT-III. Density functional theory (DFT) confirmed the oxidative transformation occurred at the 4th and 10th carbon positions of AT-III. Co-treatment with acetaminophen had different effects between in vivo and in situ models of AT-III metabolism. AT-III was metabolized via an oxygenation process in the rat body, where CYP450 and other O2-activating metalloenzymes might participate in the metabolism. The present work provided the oxidative metabolism of AT-III using an in vivo model parallel with in situ biomimetic reaction models.