Carotenoids with anti-Helicobacter pylori activity from Golden delicious apple

Previously it was reported that hypophasic carotenoids of Golden delicious apple peel showed potent anti-H. pylori activity (MIC(50) = 36 microg/mL), comparable to metronidazole (MIC(50) = 45 microg/mL). To further investigate the involved active carotenoids of the apple peel extracts, seven carotenoids were isolated for the current study: (all-E)-luteoxanthin, (all-E)-neoxanthin, (9'Z)-neoxanthin, (all-E)-antheraxanthin, (all-E)-violaxanthin, (9Z)-violaxanthin and (all-E)-lutein. The MIC(50) values of (all-E)-luteoxanthin, (all-E)-neoxanthin and (9'Z)-neoxanthin were 7.9, 11 and 27 microg/mL, respectively. Other carotenoids and beta,beta-carotene did not exhibit potent anti-H. pylori activity (MIC(50) > 100 microg/mL). An examination of structure and function suggested that active carotenoids contained a monofuranoid ring or an allenic bond in addition to an epoxy group and an additional two or three hydroxyl substituents on the side group.