Insights on the Bioaccessibility of Natural Pigments from Diatom Chaetoceros calcitrans.

This study aimed to investigate the bioaccessibility of carotenoids and chlorophylls from the biomass of microalgae Chaetoceros calcitrans. The samples were submitted to an in vitro digestion protocol, and the compounds were determined by HPLC-PDA-MS/MS. A total of 13 compounds were identified in all tests. After in vitro digestion, the relative bioaccessibility of carotenoids and chlorophylls ranged from 4 to 58%. The qualitative profile of carotenoids reflected the initial sample, with all-E-zeaxanthin (57.2%) being the most bioaccessible compound, followed by all-E-neochrome (31.26%), the latter being reported for the first time in the micellar fraction. On the other hand, among the chlorophylls only pheophytin a (15.01%) was bioaccessible. Furthermore, a chlorophyll derivative (Hydroxypheophytin a') was formed after in vitro digestion. Considering all compounds, xanthophylls (12.03%) and chlorophylls (12.22%) were significantly (p < 0.05) more bioaccessible than carotenes (11.22%). Finally, the considerable individual bioaccessibilities found, especially for zeaxanthin, demonstrate the bioactive potential of this bioresource. However, the large reduction in the totality of compounds after in vitro digestion suggests that additional technological strategies should be explored in the future to increase the efficiency of micellarization and enhance its bioactive effects.

Bioaccessibility of microalgae-based carotenoids and their association with the lipid matrix.

The composition of microalgae can contribute to nutritious and functional diets. Among the functional compounds, carotenoids are in focus since positive effects on human health have been established, which are in turn related to their bioaccessibility. In addition to essential nutrients, our hypothesis was that microalgae biomasses could be used as sources of bioaccessible carotenoids. Thus, this study determined for the first time the bioaccessibility of carotenoids from biomass of Scenedesmus bijuga and Chlorella sorokiniana and their possible relationship with the lipid composition of the matrix. The samples were submitted to in vitro digestion protocol, and carotenoids were determined by HPLC-PDA-MS/MS. Individual bioaccessibility of carotenoids was ≥ 3.25%. In general, compounds in their cis conformation were more bioaccessible than trans; and total carotenes more than total xanthophylls. Twelve compounds were bioaccessible from the biomass of S. bijuga, and eight in C. sorokiniana. In S. bijuga, the bioaccessibility of total carotenoids was 7.30%, and the major bioaccessible carotenoids were 9-cis-ß-carotene (43.78%), 9-cis-zeaxanthin (42.30%) followed by 9-cis-lutein (26.73%); while in C. sorokiniana, the total bioaccessibility was 8.03%, and 9-cis-ß-carotene (26.18%), all-trans-ß-carotene (13.56%), followed by 13-cis-lutein (10.71%) were the major compounds. Overall, the total content of lipids does not influence the bioaccessibility of total carotenoids. Still, the lipid composition, including structural characteristics such as degree of saturation and chain length of the fatty acid, impacts the promotion of individual bioaccessibility of carotenes and xanthophylls of microalgae. Finally, the results of this study can assist the development of microalgae-based functional food ingredients and products.

Insights on the intestinal absorption of chlorophyll series from microalgae.

The bioaccessibility and subsequent uptake by Caco-2 human intestinal cells of chlorophyll pigments from Scenedesmus obliquus were determined for the first time. In order to evaluate the impact of different types of the matrix on bioaccessibility of chlorophyll from microalgae, three different products were evaluated: isolated chlorophyll extract (ICE); wet ultrasonicated biomass (WUB); and whole dried biomass (WDB). The samples were submitted to in vitro digestion model according to the INFOGEST protocol, and Caco-2 cells determined the intestinal uptake. Chlorophyll pigments were determined by HPLC-PDA-MS/MS. A total of ten chlorophyll pigments (8,318.48 µg g-1) were separated in S. obliquus biomass, with chlorophyll a (3,507.76 µg g-1) and pheophytin a' (1,598.09 µg g-1) the major ones. After in vitro digestion, all tested products showed bioaccessible chlorophylls. However, the total bioaccessibility results were as follows: ICE (33.45%), WUB (2.65%), WDB (0.33%). Five compounds were bioaccessible in ICE, three in WUB, and one in WDB. The hydroxypheophytin a showed the highest bioaccessibility (212%) in ICE, while pheophytin a' in WUB (11%) and WDB (2%). As a result, bioavailability estimates of ICE using the Caco-2 cell showed hydroxypheophytin a (102.53%), followed by pheophytin a' (64.69%) as the chlorophyll pigments most abundant in intestinal cells. In summary, from a nutritional perspective, these three types of the matrix (WDB, WUB, and ICE) influence the promotion of chlorophyll bioaccessibility. In this way, the data suggest that chlorophylls bioaccessibility from ICE is greater than that in WDB and WUB. Therefore, ICE should be considered a product that provides bioavailable chlorophyll and could be the best choice, such as ingredients in the development of functional foods chlorophyll-based.