Kinetic studies of lycopene isomerization in a tributyrin model system at gastric pH.
A semi-preparative HPLC method was developed in order to isolate and purify the 13-cis-lycopene isomer in tomato-based materials. The result was compared with the naturally predominant all-trans-lycopene isomer, in terms of stability to gastric pH at physiological temperature in a tributyrin model system. Kinetic experiments confirmed that lycopene isomerization is a reversible reaction, and under these conditions the all-trans isomer is more stable than the 13-cis isomer. In addition, it was found that at gastric pH 13-cis-lycopene would predominantly isomerize to the all-trans form rather than undergo oxidation/breakdown. A simulation based on the rate constants calculated in the kinetic study indicated that at gastric pH the lycopene isomeric distribution aimed toward an equilibrium characterized by approx 16% 13-cis-, 16% 9-cis-, and 68% all-trans-lycopene. This study suggests that pH-driven isomerization in the stomach is at least partially responsible for the relatively high cis-lycopene proportion found in vivo.
Moraru
Catalin
C
Department of Food Science, Center for Advanced Food Technology, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08901, USA.
Lee
Tung-Ching
TC
D002338:Carotenoids / Q000737:chemistry*; D004355:Drug Stability; D006863:Hydrogen-Ion Concentration; D007536:Isomerism; D007700:Kinetics; D000077276:Lycopene; D018551:Solanum lycopersicum / Q000737:chemistry; D008956:Models, Chemical; D013270:Stomach / Q000737:chemistry*; D014280:Triglycerides / Q000737:chemistry*
D014280:Triglycerides; D002338:Carotenoids; C005830:tributyrin; D000077276:Lycopene