BIOLOGICAL-ACTIVITIES OF NATURAL AND SYNTHETIC CAROTENOIDS - INDUCTION OF GAP JUNCTIONAL COMMUNICATION AND SINGLET OXYGEN QUENCHING

Induction of gap junctional communication (GJC) and antioxidant activi ties of carotenoids have been considered as biochemical mechanisms und erlying the cancer-preventive properties of these compounds, beta-Caro tene and other carotenoids, including those lacking provitamin A activ ity, proved to be active in both these parameters, The beta-carotene a nalogs retrodehydro-beta-carotene, echinenone, cryptoxanthin (3-hydrox y-beta-carotene), 4-hydroxy-beta-carotene and canthaxanthin stimulate GJC and efficiently deactivate singlet molecular oxygen, beta-Carotene is less active than its retro-dehydro analog with respect to O-1(2)-q uenching but GJC is similar, The five-membered ring analog of canthaxa nthin, dinor-canthaxanthin, has less effect on GJC as compared with th e parent compound but exhibits increased singlet oxygen quenching, Str aight-chain polyene dialdehydes are quenchers of singlet oxygen, the e fficiency increasing with the number of conjugated double bonds, Howev er, none of these compounds significantly induce GJC, These data indic ate that the two properties of carotenoids addressed in this study may operate independent of each other.