Radical modulation activity of benzo[a]phenothiazine.

12H-Benzo[a]phenothiazine generated radical(s) under alkaline conditions, and enhanced the radical intensity of sodium ascorbate and sodium 5,6-benzylidene-L-ascorbate. Phenothiazine and chlorpromazine hydrochloride did not produce radicals, nor affect the radical intensity of ascorbates. 12H-Benzo[a]phenothiazine scavenged the superoxide anion and hydroxyl radical, more efficiently than phenothiazine and chlorpromazine hydrochloride. The radical modulation activity of 12H-benzo[a]phenothiazine might explain at least in part the ability of this compound to induce monocytic differentiation and apoptosis in human myelogenous leukemic cell lines.