SEMIQUINONE PRODUCTION BY LIPOPHILIC O-NAPHTHOQUINONES

Several beta-lapachone analogues, the o-naphthoquinones CG 10-248, CG 9-442 and CG 8-935, were reduced to their semiquinones by sodium boroh ydride, the liver NADPH-P450 reductase system and Crithidia fasciculat a cells, in anaerobic solutions. ESR spectra of the radical anions sho wed hyperfine spin couplings located at protons of the naphthalene rin g. Borohydride reduction of another o-naphthoquinone, mansonone E, yie lded spin couplings located at the naphthalene and methyl groups proto ns. The symmetrical polarized carbonyl groups were essential for elect ron capture and semiquinone production. These observations support the idea that quinones are capable of redox-cycling and oxygen radical ge neration.