Bioavailability of biomimetic zeaxanthin aggregates in humans
Nutritional Sciences
Final Report Abstract
Carotenoids are fat‐soluble natural pigments, imparting yellow, orange, and red color hues to many fruits and vegetables. The frequent dietary intake of carotenoids has earlier been associated with a lower incidence of several chronic diseases such as age‐related macular degeneration (AMD) and cancer. However, prior to exerting any potential health benefit, carotenoids need to be released from the food, micellized in the small intestine, and then resorbed by the human body; i.e. they need to be bioavailable. The bioavailability of carotenoids from complex foods has been observed to be extremely variable and, thus far, has only been insufficiently understood. Among a number of potential factors, the influence of the natural deposition form of the lipophilic carotenoids within the commonly aqueous food matrix has been suggested to represent a key factor for explaining the observed variations. Generally, carotenoids are considered poorly bioavailable when prevailing in solid‐crystalline state, and highly bioavailable when dissolved in lipids. In contrast to such well‐known forms present, e.g., in carrots and tomatoes, further naturally‐occurring physical deposition forms like liquid‐crystalline, J‐aggregated forms have recently been discovered in a number of most popular plant foods such as bell pepper, mango, and papaya. In such liquid‐crystalline, J‐aggregated forms, the carotenoid molecules are believed to be packed less tightly, i.e. at larger intermolecular distances than those in solid‐crystalline and so‐called H‐aggregated forms, ultimately being potentially more bioavailable due to their facilitated and faster liberation from the food during human digestion. However, previous studies comparing carotenoid bioavailability from different foods have failed to establish a clear cause‐and‐effect relationship of the physical deposition form and the bioavailability, because the used different foods had also differed in other matrix‐related traits such as the rigidity of the plant cell walls. In order to allow an unbiased comparison of the bioavailability of differently aggregated forms, their biomimetic production and formulation into identical food matrices represents a clear prerequisite. Therefore, in the presented project, we developed a novel aggregation and formulation comprising a biomimetic, presumably liquid‐crystalline, J‐aggregated form of esterified zeaxanthin ‐ a carotenoid important for eye and brain health. Furthermore, a solid‐crystalline H‐aggregated form of zeaxanthin was produced under identical formulation conditions. The solvent displacement procedure allowed the targeted aggregation of dissolved carotenoids in an aqueous phase. Specific hydrocolloids as macromolecular emulsifiers, low molecular carbohydrates as fillers, and antioxidants like α‐ tocopherol and ascorbic acid allowed the encapsulation of the produced aggregates, yielding a stable powder form. Carotenoid content as well as aggregate form (H‐ and J‐type) remained stable over a period of at least 78 days at 25 °C. The produced aggregate powders were subjected to a series of preliminary in vitro digestion simulations in order to allow the selection of the most promising candidates for the subsequent two‐way crossover human study. The latter study revealed zeaxanthin to be 23% more bioavailable from the above mentioned J‐aggregated than from the H‐aggregated formulation. Furthermore, we also observed the J‐aggregated form to be of a greater stability as well as of a more intense orange color than the respective H‐aggregated zeaxanthin. These observations might open further applications of such novel biomimetic J‐aggregates as colorants for food and beverages. In brief, the presented project contributed to a better understanding of the influence of naturally occurring aggregate forms on carotenoid bioavailability. The reported findings support the hypothesis that the high bioavailability of carotenoids from plant foods with liquid‐crystalline carotenoid aggregates is directly related to the physical deposition form of the carotenoids. These findings might be of interest for improving current nutritional classifications, e.g., in terms of provitamin A activity equivalents listed in many nutrition fact tables. The derivation of these equivalents from the carotenoid content of a food does not yet include any inherent differences in bioavailability, although striking variations are known. The physical carotenoid deposition form might serve as a rational classification factor. Furthermore, we also achieved to biomimetically produce a most promising J‐aggregated form of zeaxanthin, being potentially useful for novel carotenoid supplements or colorants for food and beverages in the future.
Publications
- Effect of aggregation form on bioavailability of zeaxanthin in humans: a randomised cross-over study. British Journal of Nutrition, Vol. 118.2017, Issue 9, pp. 698-706.
Hempel, J., Fischer, A., Fischer, M., Högel, J., Bosy‐Westphal, A., Carle, R., Schweiggert, R.M.
(See online at https://doi.org/10.1017/S0007114517002653) - Structural diversity, deposition forms, and bioavailability of carotenoids from plant foods. Habilitation, Faculty of Natural Sciences (University of Hohenheim, Stuttgart, Germany, 2017.
Schweiggert, R.M.
- Ultrastructural deposition forms and bioaccessibility of carotenoids and carotenoid esters from goji berries (Lycium barbarum L.). Food Chemistry, Vol. 218. 2017, pp. 525‐533.
Hempel, J., Schädle, C.N., Sprenger, J., Heller, A., Carle, R., Schweiggert, R.M.
(See online at https://doi.org/10.1016/j.foodchem.2016.09.065) - Studies into carotenoid deposition forms in plants and nutraceutical formulations with special reference to their influence on carotenoid bioavailability. Institute of Food Science and Biotechnology, Faculty of Natural Sciences, University of Hohenheim (S
Hempel, J.
(See online at https://doi.org/10.2370/9783844059434)
