Organic Synthesis of New Secosteroids from Fucosterol, Its Intestinal Absorption by Caco-2 Cells, and Simulation of the Biological Activities of Vitamin D.

We previously examined the cellular uptake of six types of vitamin D in human intestinal Caco-2 cells. Since vitamins D5-D7 were commercially unavailable, we synthesized these compounds organically before studying them. This process led us to understand that new secosteroids could be generated as vitamin D candidates, depending on the sterol used as the starting material. We obtained two new secosteroids-compounds 3 and 4-from fucosterol in the current study. We investigated the intestinal absorption of these compounds using Caco-2 cells cultured in Transwells and compared the results with vitamin D3, a representative secosteroid. The intestinal absorption of compound 4 was comparable to that of vitamin D3. Compound 3 showed similar uptake levels but transported about half as much as vitamin D3. These compounds demonstrated intestinal absorption at the cellular level. Vitamin D is known for its diverse biological activities manifest after intestinal absorption. Using PASS online simulation, we estimated the biological activity of compound 3's activated form. In several items indicated by PASS, compound 3 exhibited stronger biological activity than vitamins D2-D7 and was also predicted to have unique biological activities.

Effect of an Emulsified Formulation on Vegetable Carotenoid Bioaccessibility.

We investigated the effect of neutral lipids, polar lipids, and an emulsified formulation (EMF) on carotenoid bioaccessibility in an in vitro digestion assay of vegetables. These reagents enhanced carotenoid bioaccessibility. Contrary to our previous report, they also exhibited effects on lutein. Bile extracts/pancreatin concentrations also participated in the bioaccessibility. The EMF, which consisted of lower amounts of oil, had the same effect on lutein as rapeseed oil. These reagents also showed effects in the aging model, with more reduced bile extract/pancreatin concentrations, suggesting that lipids and EMF contributed to carotenoid bioaccessibility in bile/pancreatic juice secretions due to aging and disease.

Uptake of Vitamins D2, D3, D4, D5, D6, and D7 Solubilized in Mixed Micelles by Human Intestinal Cells, Caco-2, an Enhancing Effect of Lysophosphatidylcholine on the Cellular Uptake, and Estimation of Vitamins D' Biological Activities.

Vitamins D have various biological activities, as well as intestinal calcium absorption. There has been recent concern about insufficient vitamin D intake. In addition to vitamins D2 and D3, there are lesser-known vitamins D4-D7. We synthesized vitamins D5-D7, which are not commercially available, and then evaluated and compared the mixed micelles-solubilized vitamins D uptake by Caco-2 cells. Except for vitamin D5, the uptake amounts of vitamins D4-D7 by differentiated Caco-2 cells were similar to those of vitamins D2 and D3. The facilitative diffusion rate in the ezetimibe inhibited pathway was approximately 20% for each vitamin D type, suggesting that they would pass through the pathway at a similar rate. Lysophosphatidylcholine enhanced each vitamin D uptake by approximately 2.5-fold. Lysophosphatidylcholine showed an enhancing effect on vitamin D uptake by reducing the intercellular barrier formation of Caco-2 cells by reducing cellular cholesterol, suggesting that increasing the uptakes of vitamins D and/or co-ingesting them with lysophosphatidylcholine, would improve vitamin D insufficiency. The various biological activities in the activated form of vitamins D4-D7 were estimated by Prediction of Activity Spectra for Substances (PASS) online simulation. These may have some biological activities, supporting the potential as nutritional components.

Effect of dispersed form on the bioavailability of ß-carotene from daily intake in humans.

In a randomized double-blind crossover study, a canned beverage was prepared using an emulsion dispersion formulation (EM) of ß-carotene and a crystal dispersion formulation (CR) of ß-carotene; the beverages were ingested by human subjects daily for 2 weeks to compare the ß-carotene bioavailability. EM-ß-carotene enhanced the ß-carotene concentrations in human plasma approximately 4-fold, but CR-ß-carotene showed no statistically significant enhancement. Bioaccessibility is the ratio of the solubilized fraction to the whole amount ingested. Bioaccessibility of ß-carotene from EM-ß-carotene was higher than that from CR-ß-carotene in an in vitro digestion test. Contrarily, ß-carotene from CR-ß-carotene, consists of all-trans-ß-carotene, was higher than that from EM-ß-carotene, consists of a mixture of cis and all-trans-ß-carotene, on the uptake by intestinal Caco-2 cells, suggesting that bioaccessibility was a critical factor in ß-carotene bioavailability in this study. EM-ß-carotene thus has potential as a food coloring agent with value added because it enhances ß-carotene bioavailability.

3'-hydroxy-ε,ε-caroten-3-one inhibits the differentiation of 3T3-L1 cells to adipocytes.

An oxidative metabolite of lutein, 3'-hydroxy-ε,ε-caroten-3-one, inhibited the differentiation of 3T3-L1 cells to adipocytes and the subsequent triacylglycerol production, but lutein did not. The α,ß-unsaturated carbonyl structure of 3'-hydroxy-ε,ε-caroten-3-one was considered to participate in the inhibitory effect, suggesting that this lutein metabolite has the potential to prevent metabolic syndrome.

Effects of fats and oils on the bioaccessibility of carotenoids and vitamin E in vegetables.

The low bioavailability of lipophilic micronutrients is mainly caused by their limited solubilization to an aqueous micelle, which hinders their ability to be taken up by the intestines. Bioaccessibility is the ratio of the solubilized portion to the whole amount ingested. We evaluated in this study the effects of individual fats and oils and their constituents on the bioaccessibility of carotenoids and vitamin E in vegetables by simulated digestion. Various fats and oils and long-chain triacylglycerols enhanced the bioaccessibility of ß-carotene present in spinach, but not of lutein and α-tocopherol, which are less hydrophobic than ß-carotene. Free fatty acid, monoacylglycerol, and diacylglycerol also enhanced the bioaccessibility of ß-carotene present in spinach. In addition to the long-chain triacylglycerols, their hydrolyzates formed during digestion would facilitate the dispersion and solubilization of ß-carotene into mixed micelles. Dietary fats and oils would therefore enhance the bioaccessibility of hydrophobic carotenes present in vegetables.