Effects of dietary fat type and emulsification on carotenoid absorption: a randomized crossover trial.

BACKGROUND: Although emerging evidence has suggested that the type and emulsification of dietary fat may be important to carotenoid absorption, these effects have not yet been validated in a human trial. OBJECTIVES: This study aimed to examine the effects of dietary fat type and emulsification on the bioaccessibility and bioavailability of carotenoids from a carotenoid-rich salad. METHODS: An identical salad was used for the in vitro and the human trial. This was paired with 28 g of one of the following 4 different fats: 1) nonemulsified olive oil, 2) emulsified olive oil, 3) nonemulsified coconut oil, and 4) emulsified coconut oil. The bioaccessibility of total carotenoids (TCs) was assessed by a simulated in vitro digestion model. Sixteen subjects consumed salad with 4 test fats in random order, and plasma triglyceride and carotenoid (lutein, zeaxanthin, α-carotene, ß-carotene, and lycopene) concentrations were determined hourly for 10 h following the consumption. The absorption of TC and individual carotenoids was evaluated by the positive incremental AUC (iAUC) of plasma carotenoid concentrations. RESULTS: The bioaccessibility of TC was greater with olive oil (24.0%) than with coconut oil (14.9%), and with the oil being emulsified (23.5%) rather than that being nonemulsified (15.4%). Similarly, the positive iAUC1-10h of TC, α-carotene, and lycopene were 55.2%, 110.8%, and 45.8%, respectively, higher with olive oil than with coconut oil. Emulsified fat induced 40.0% greater positive iAUC1-10h of TC than nonemulsified fat. CONCLUSIONS: The type and emulsification of dietary fat are both essential to carotenoid absorption. Findings from this study may provide scientific support for designing excipient emulsions as potential dietary strategies to optimize the absorption of fat-soluble compounds. This study was registered at clinicaltrials.gov as NCT04323826.

Development of organogel-based emulsions to enhance the loading and bioaccessibility of 5-demethylnobiletin.

5-Demethylnobiletin (5-DMN), identified in the aged citrus peels, has received increasing attentions due to its outstanding bioactivity among citrus polymethoxyflavones (PMFs). However, the poor water solubility and high crystallinity limit its oral bioavailability. Besides, the solubility of 5-DMN in the oil is very limited, which restricts its loading capacity in emulsions for bioavailability enhancement. In this study, an organogel formulation was developed to improve the solubility of 5-DMN in medium-chain triacylglycerols by 3.5 times higher without crystal formation during 5-day storage at room temperature. Increasing the gelator (i.e., sugar ester) concentration led to the increase of viscosity and a gel-like structure of the organogel. The ternary phase diagram of organogel-based emulsions was explored, and 40% organogel was selected as the oil phase for emulsion preparation. Increasing the concentration of Tween 80 from 0% to 6% decreased the droplet size and viscoelasticity of the emulsions. Two in vitro models, the pH-stat lipolysis model and TNO gastro-intestinal model (TIM-1), were applied to investigate the bioaccessibility of 5-DMN in different delivery systems. Compared with the conventional emulsion and oil suspension, the pH-stat lipolysis demonstrated that the organogel-based emulsion was the most efficient tool to enhance 5-DMN bioacccessibility. Moreover, TIM-1 digestive study indicated that 5-DMN bioaccessibility delivered by organogel-based emulsions was about 3.26-fold higher than that of oil suspension. Our results suggested that the organogel-based emulsion was an effective delivery route to enhance the loading and bioaccessibility of lipophilic compounds of high crystallinity.

Comparative Analyses of Bioavailability, Biotransformation, and Excretion of Nobiletin in Lean and Obese Rats.

Nobiletin, one of the prevalent polymethoxyflavones in citrus peels, was reported to possess various health benefits. We conducted the excretion study and pharmacokinetics study of nobiletin via oral administration and intravenous injection and 15 day consecutive dosing study using the high fat diet-induced obese rats and their lean counterparts. By comparing the demethylated metabolite profiles in the urine and feces, gut microbiota demonstrated greater biotransformation activity on nobiletin than the host. The absolute oral bioavailability of nobiletin in lean (22.37% ± 4.52%) and obese (18.67% ± 4.80%) rats has a negligible statistically significant difference (P > 0.05). However, a higher extent of demethylated metabolites was found in the feces and plasma of obese rats than lean rats (P < 0.05). Moreover, the consecutive dosing of nobiletin might lead to a higher extent of demethylated metabolites in the plasma and in feces. These results suggested that gut microbiota played important roles in nobiletin metabolism.