Cholesterol Reactivity Redux

A reactivity study involving cholesterol may provide an alternative explanation for earlier reports suggesting that ozone (O₃) is produced in the body and that this event is linked to certain illnesses (J. Am. Chem. Soc., DOI: 10.1021/ja804162d). Prior studies indicate that the immune system generates ozone as part of the inflammatory response. By examining human arterial plaques and brain tissues, the researchers who carried out those studies uncovered unusual cholesterol oxidation products thought to be relevant in disease development. The compounds featured an oxidatively cleaved double bond—the hallmark of an ozonolysis reaction. Now, a team led by Derek A. Pratt of Queen's University, Kingston, Ontario, has found evidence that such reactivity is not unique to ozone. Pratt and coworkers show that the product of the reaction between cholesterol and singlet oxygen—an excited state of O₂—undergoes acid-catalyzed decomposition (shown). The product distribution from their laboratory reaction more closely reproduces the observations in the tissues than the distribution from a typical ozonolysis, they say.