CHOLESTEROL INTERACTION WITH FREE-RADICALS PRODUCED FROM CARBON-TETRACHLORIDE OR BROMOTRICHLOROMETHANE BY EITHER CATALYTIC DECOMPOSITION ORVIA LIVER MICROSOMAL ACTIVATION

The reaction between cholesterol (Ch) and trichloromethyl or trichloro methyl peroxyl radicals was studied. The latter were generated from CC l4 either by benzoyl peroxide (BP) catalysis or via thermal activation or by liver microsomal NADPH-dependent biotransformation of CBrCl3. T he structure of the products formed was elucidated by gas chromatograp hy-mass spectrometry (GC/MS). Under aerobic conditions and using therm al activation of CCl4, the formation of 6 products was observed. Two ( I and II) were dehydrated Ch derivatives (one also having a third doub le bond) (I). Another product was a Delta(5)-3 ketone derivative of Ch (III). Two additional reaction products were determined as ketocholes terols (IV and V). One chloro Oh was also formed (VI). At low concentr ations of BP, reaction was more extensive than under thermal activatio n, and the formation of peaks I to IV was also observed. When the reac tion was conducted anaerobically and using thermal activation of CCl4 to generate radicals, only products I and II were formed in low yield. Under anaerobic conditions, but using catalyst, compounds I and III w ere produced plus two new isomeric ketocholesterol derivatives (VIII a nd IX) and also a compound having an extra hydroxyl group on the Oh st ructure (X). In order to check whether similar reactions are observabl e under biological experimental conditions, we used activation of CBrC l3 by liver microsomes. The incubation using only microsomes (without CBrCl3 or NADPH) showed two ketocholesterol peaks (A and B). In the pr esence of CBrCl3 we could detect peak B and hydroxycholesterol (C) and two others, ketocholesterols (D and E). D was the only peak showing c lose similarity (spectrum and retention time) to one of those observed in the chemical reaction system (V). The reaction of CBrCl3 in the pr esence of NADPH showed peaks B, C, D and E, in low abundance and a 7-k etocholesterol (F). If some of the reaction products reported here wer e formed during the intoxication with these haloalkanes, significant b iological consequences might be expected.