Why Have Clinical Trials of Antioxidants to Prevent Neurodegeneration Failed? - A Cellular Investigation of Novel Phenothiazine-Type Antioxidants Reveals Competing Objectives for Pharmaceutical Neuroprotection.

Purpose: Only a fraction of the currently established low-molecular weight antioxidants exhibit cytoprotective activity in living cells, which is considered a prerequisite for their potential clinical usefulness in Parkinson's disease or stroke. Post hoc structure-activity relationship analyses have predicted that increased lipophilicity and enhanced radical stabilization could contribute to such cytoprotective activity.

Methods: We have synthesized a series of novel phenothiazine-type antioxidants exhibiting systematic variation in their lipophilicity and radical stabilization.

Is the chromanol head group of vitamin E nature's final truth on chain-breaking antioxidants?

Tocopherol is believed to be the most potent naturally occurring chain-breaking antioxidant. Hence, its refined phenolic head group chromanol may represent an optimum evolutionary solution to the problem of free-radical chain reactions in the lipid bilayer. To test the universal validity of this assumption beyond phenolic head groups, we have synthesized aromatic amine analogues of vitamin E and trolox with otherwise closely matching physicochemical properties: NH-toc and NH-trox.

Phenothiazine: the seven lives of pharmacology's first lead structure.

Rooted in the early days of organic dye chemistry, the phenothiazine structure and its derivatives have since held a prominent place in pharmacology and biomedicine. Initially used for histochemical stains of plasmodia by Paul Ehrlich, anthelmintic and antibiotic properties of phenothiazines were globally exploited in the 1930s and 1940s. Clinical use of N-substituted phenothiazines as antihistaminics (1940s), sedatives and antipsychotics (1950s) followed and continues to this day.