Isolation and spectral characterization of thermally generated multi-Z-isomers of lycopene and the theoretically preferred pathway to di-Z-isomers.

Lycopene has a large number of geometric isomers caused by E/Z isomerization at arbitrary sites within the 11 conjugated double bonds, offering varying characteristics related to features such as antioxidant capacity and bioavailability. However, the geometric structures of only a few lycopene Z-isomers have been thoroughly identified from natural sources. In this study, seven multi-Z-isomers of lycopene, (9Z,13'Z)-, (5Z,13Z,9'Z)-, (9Z,9'Z)-, (5Z,13'Z)-, (5Z,9'Z)-, (5Z,9Z,5'Z)-, and (5Z,9Z)-lycopene, were obtained from tomato samples by thermal isomerization, and then isolated by elaborate chromatography, and fully assigned using proton nuclear magnetic resonance. Moreover, the theoretically preferred pathway from (all-E)-lycopene to di-Z-isomers was examined with a computational approach using a Gaussian program. Fine-tuning of the HPLC separation conditions led to the discovery of novel multi-Z-isomers, and whose formation was supported by advanced theoretical calculations.

Safety assessment of a natural tomato oleoresin containing high amounts of Z-isomers of lycopene prepared with supercritical carbon dioxide.

BACKGROUND: Z-isomers of lycopene, which are abundantly present in processed tomato products, are more bioavailable than (all-E)-lycopene found predominantly in raw tomatoes. Despite extensive studies on the bioavailability and biological activities of Z-isomers of lycopene, detailed studies on their safety and toxicology are limited. RESULTS: The geno-, acute and subacute toxicities of tomato oleoresin that contained high amounts of lycopene Z-isomers (10.9% lycopene with 66.3% Z-isomer content) and had been prepared with supercritical carbon dioxide were investigated. The oleoresin was non-mutagenic in the Ames test with and without metabolic activation (S9 mix). The medial lethal dose (LD50 ) of the oleoresin in rats, as determined by a single-dose oral test, was more than 5000 mg kg body weight-1 (bw) [361 mg (Z)-lycopene kg bw-1 ]. In the 4-week repeated-dose oral toxicity test, rats were administered oleoresin at 4500 mg kg-1 day-1 [325 mg (Z)-lycopene kg bw-1 day-1 ]. There were no clinically significant changes with respect to vital signs, physical examination outcomes and laboratory test values during the test period. CONCLUSION: Based on our findings and as supported by its long history of consumption, tomato oleoresin that contains high amounts of Z-isomers of lycopene prepared with supercritical carbon dioxide can be considered as safe for human consumption. © 2016 Society of Chemical Industry.