Antioxidant activities of natural 9-cis and synthetic all-trans beta-carotene assessed by human neutrophil chemiluminescence

Much attention has been focused on the biological activity of geometrical i somers of beta -carotene. In the present study, the in vitro antioxidant ac tivities of a natural 9-cis beta -carotene purified from Dunaliella bardawi l and synthetic all-trans beta -carotene were studied using enhanced human neutrophil chemiluminescence upon stimulation with opsonized zymosan. Lucig enin-dependent chemiluminescence was used for largely measuring superoxide anion (O-2(-)) production, luminol-dependent chemiluminescence with sodium azide (NaN3) and horseradish peroxidase (HRP) was used for measuring hydrog en peroxide (H2O2) production, and luminol-dependent chemiluminescence with out oxidant metabolism modulator was used for determination of myeloperoxid ase (MPO)-mediated production. With beta -carotene concentration of 1.4 mu M, neutrophils showed a decrease:in lucigenin-dependent chemiluminescence t o 75% and 78% of controls (p<0.05) by natural 9-cis carotene and synthetic all-trans beta -carotene, respectively. With beta -carotene concentration o f 1.86 mu M, neutrophils also showed a decrease in luminol-dependent chemil uminescence in the presence of NaN3 and HRP to 86% and 81% of controls (p<0 .05) by natural 9-cis beta -carotene and synthetic all-trans beta -carotene , respectively. On the other hand, neutrophils did not show a statistically significant difference in any chemiluminescence assay by the same concentr ation of natural 9-cis beta -carotene and synthetic all-trans beta -caroten e. These results suggest that, up to the concentration of 1.86 mu M, natura l 9-cis beta -carotene and-synthetic all-trans beta -carotene exert equal a ntioxidant activities assessed by enhanced human neutrophil chemiluminescen ce. (C) 1999 Elsevier Science Inc.