Carotenoid incorporation into natural membranes from artificial carriers: liposomes and beta-cyclodextrins

Liposomes and beta -cyclodextrin (beta -CD) have been used as carriers for the incorporation of three dietary carotenoids (beta -carotene (BC), lutein (LUT) and canthaxanthin (CTX)) into plasma, mitochondrial, microsomal and nuclear membrane fractions from pig liver cells or the retinal epithelial c ell line D407. The uptake dynamics of the carotenoids from the carriers to the organelle membranes and their incorporation yield (IY) was followed by incubations at pH 7.4 for up to 3 h. The mean IYs saturated between 0.1 and 0.9 after 10-30 min of incubation, depending on membrane characteristics ( cholesterol to phospholipid ratio) and carotenoid specificity. Mitochondria l membranes (more fluid) favour the incorporation of BC (non-polar), while plasma membranes (more rigid) facilitate the incorporation of lutein, the m ost polar carotenoid. A high susceptibility of BC to degradation in the mic rosomal suspension was observed by parallel incubations with/without 2,6-di -t-butyl-p-cresol (BHT) as antioxidant additive. The beta -CD carrier showe d to be more effective for the incorporation of lutein while BC was incorpo rated equally into natural membranes either from liposomes or from cyclodex trins. The presence of cytosol in the incubation mixture had no significant effects on the carotenoid incorporations. (C) 2001 Elsevier Science Irelan d Ltd. All rights reserved.