Partition of indicaxanthin in membrane biomimetic systems. A kinetic and modeling approach.
The solubilization site of indicaxanthin (Ind) in lipid bilayers was investigated by the kinetics of Ind oxidation by peroxyl radicals in water and in aqueous/L-alpha-dipalmitoyl-phosphatidylcholine (DPPC) vesicles, pH 7.4, and 37.0 and 48.0 degrees C, that is, in a gel-like and a crystal liquidlike bilayer state, respectively. The time-dependent Ind absorbance decay, matched with a successful simulation of the reaction kinetic mechanism by Gepasi software, supported a multistep pathway. Computer-assisted analysis allowed calculation of the rate constants associated with the reactions involved, the values of which decreased with increasing DPPC concentration. The binding constant calculated according to a pseudo two-phase distribution model did not vary with the physicochemical state of the vesicle, indicating location of Ind in a region whose state is not affected by temperature changes, at the interface between hydrophobic core and hydrophilic head groups. Other measurements carried out in the presence of dimyristoyl-phosphatidylcholine vesicles, indicated that the phytochemical was confined to the aqueous phase.
Turco Liveri
Maria Liria
ML
Dipartimento di Chimica Fisica F. Accascina, Viale delle Scienze, Pad. 17, Università degli Studi di Palermo, Palermo, Italy.
Sciascia
Luciana
L
Allegra
Mario
M
Tesoriere
Luisa
L
Livrea
Maria A
MA
D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry; D050860:Betaxanthins / Q000737:chemistry*; D007700:Kinetics; D008051:Lipid Bilayers / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry; D010084:Oxidation-Reduction; D010545:Peroxides / Q000737:chemistry; D011725:Pyridines / Q000737:chemistry*; D012984:Software; D014867:Water / Q000737:chemistry
D050860:Betaxanthins; D008051:Lipid Bilayers; D008081:Liposomes; D010545:Peroxides; D011725:Pyridines; C469628:indicaxanthin; D014867:Water; D015060:1,2-Dipalmitoylphosphatidylcholine; C049375:perhydroxyl radical