In Vitro Bioaccessibility of Carotenoids and Chlorophylls in a Diverse Collection of Spinach Accessions and Commercial Cultivars

Inhibitory effects of chlorophyll pigments on the bioaccessibility of β-carotene: Influence of chlorophyll structure and oil matrix

Chlorophylls and β-carotene are fat-soluble phytochemicals in daily diets, while their bioaccessibility interaction remains unknown. Eight dietary chlorophylls and their derivatives (chlorophyll a, chlorophyll b, pheophytin a, pheophytin b, chlorophyllide a, chlorophyllide b, pheophorbide a, pheophorbide b) were combined with β-carotene in six different oil matrices (corn oil, coconut oil, medium-chain triglycerides, peanut oil, olive oil and fish oil) and were subjected to in vitro digestion. Generally, chlorophylls significantly decreased β-carotene bioaccessibility by competitive incorporation into micelles. Dephytylated chlorophylls had a greater inhibitory effect on the micellarization and bioaccessibility of β-carotene compared to phytylated chlorophylls. In their co-digestion system, olive oil group exhibited the smallest particle size and biggest zeta potential in both digesta and micelles. For chlorophylls, the phytol group and their levels are key factors, which was also buttressed by the mice model where additional supplementation of pheophorbide a significantly hindered the accumulation of β-carotene and retinoids compounds.

The Effects of Nitrogen Application and Varietal Variation on the Product Quality and In Vitro Bioaccessibility of Bioactive Compounds of Baby Spinach Varieties Grown in a Soilless Growth Medium

Baby spinach is becoming increasingly popular as a salad ingredient and needs high fertiliser rates to grow well and attain higher-quality leaves (dark green leaves). Chemical fertilisers, especially nitrogen (N), boost yields. There are many risks associated with nitrogen fertilisation. Additionally, spinach contains phenolic compounds and carotenoids. Nitrogen fertilisation affects growth, development, yield and metabolites. This study examined the impact of lower concentrations of N (0, 30, 60, 90, 120, 150 mg/L) on yield and colour properties [light intensity (L*) colour coordinates, unique for green colour (a*) and yellow colour (b*)], as well as the impact of varying N concentrations on the total phenolic content and p-coumaric acid, quercetin, ferulic acid, kaempferol, lutein, zeaxanthin, β-carotene and antioxidant activities in the baby spinach varieties 'Acadia', 'Crosstrek' and 'Traverse', and it was established that N fertilisation improves phytochemical bioaccessibility and antioxidant activity. In a split strip plot design, three baby spinach varieties were treated with different N concentrations, including 0, 30, 60, 90, 120 and 150 mg/L. For 40 days, three baby spinach varieties were grown on soilless Mikskaar Professional substrate 300. During both seasons, 'Crosstrek' had the highest fresh mass (921.4 g/m2, 856.3 g/m2) at 120 mg/L N, while 'Traverse' had the highest fresh mass at 554.8 g/m2 and at 564.3 g/m2 at 90 mg/L N and did not differ significantly from 90 to 150 mg/L N during either season. During both seasons, 'Acadia' at 90 mg/L N increased fresh mass to 599 g/m2 and 557.9 g/m2. The variety × N supply interaction significantly affected the leaf colour; chlorophyll content across seasons; the levels of bioactive compounds, p-coumaric acid, quercetin, ferulic acid, kaempferol, lutein, zeaxanthin and β-carotene in spinach varieties; the in vitro bioaccessibility; and the antioxidant activity. Varietal differences influenced the bioaccessibility of phenolic compounds and carotenoid components. The appropriate N levels can be used during plant cultivation to optimise the bioaccessibility of this spinach variety. Thus, fertilising 'Traverse' with 90 mg/N mL increased the in vitro bioaccessibility of β-carotene (35.2%), p-coumaric acid (7.13%), quercetin (8.29%) and ferulic acid (1.92%) without compromising the yield.

Genotype and ripening method affect carotenoid content and bio-accessibility in banana

Bananas (Musa spp.) are a target crop for provitamin A carotenoids (pVACs) biofortification programs aiming at reducing the negative impact on health caused by vitamin A deficiency in vulnerable populations. However, studies to understand the effect of ripening methods and stages and the genotype on carotenoid content and bioaccessibility in the banana germplasm are scarce. This study evaluated carotenoid content and bioaccessibility in 27 different banana accessions at three maturation stages and two ripening methods (natural ripening and ethylene ripening). Across most accessions, total carotenoid content (TCC) increased from unripe to ripe fruit; only two accessions showed a marginal decrease. The ripening method affected carotenoid accumulation; 18 accessions had lower TCC when naturally ripened compared with the ethylene ripening group, while nine accessions showed higher TCC when ripened with exogenous ethylene, suggesting that treating bananas with exogenous ethylene might directly affect TCC accumulation, but the response is accession dependent. Additionally, carotenoid bioaccessibility varied across genotypes and was correlated with the amount of soluble starch and resistant starch. These findings highlight the importance of ripening methods and genotypes in maximizing banana carotenoid content and bioaccessibility, which could contribute to improving pVACs delivery in biofortification programs.

Trait stacking simultaneously enhances provitamin A carotenoid and mineral bioaccessibility in biofortified Sorghum bicolor

Vitamin A, iron, and zinc deficiencies are major nutritional inadequacies in sub-Saharan Africa and disproportionately affect women and children. Biotechnology strategies have been tested to individually improve provitamin A carotenoid or mineral content and/or bioaccessibility in staple crops including sorghum (Sorghum bicolor). However, concurrent carotenoid and mineral enhancement has not been thoroughly assessed and antagonism between these chemical classes has been reported. This work evaluated two genetically engineered constructs containing a suite of heterologous genes to increase carotenoid stability and pathway flux, as well as phytase to catabolize phytate and increase mineral bioaccessibility. Model porridges made from transgenic events were evaluated for carotenoid and mineral content as well as bioaccessibility. Transgenic events produced markedly higher amounts of carotenoids (26.4 μg g^-1 DW) compared to null segregants (4.2 μg g^-1 DW) and wild-type control (Tx430; 3.7 μg g^-1 DW). Phytase activation by pre-steeping flour resulted in significant phytate reduction (9.4 to 4.2 mg g^-1 DW), altered the profile of inositol phosphate catabolites, and reduced molar ratios of phytate to iron (16.0 to 4.1), and zinc (19.0 to 4.9) in engineered material, suggesting improved mineral bioaccessibility. Improved phytate : mineral ratios did not significantly affect micellarization and bioaccessible provitamin A carotenoids were over 23 times greater in transgenic events compared to corresponding null segregants and wild-type controls. A 200 g serving of porridge made with these transgenic events provide an estimated 53.7% of a 4-8-year-old child's vitamin A estimated average requirement. These data suggest that combinatorial approaches to enhance micronutrient content and bioaccessibility are feasible and warrant further assessment in human studies.

In vitro bioaccessibility and uptake of β-carotene from encapsulated carotenoids from mango by-products in a coupled gastrointestinal digestion/Caco-2 cell model

β-carotene is a carotenoid with provitamin A activity and other health benefits, which needs to become bioavailable upon oral intake to exert its biological activity. A better understanding of its behaviour and stability in the gastrointestinal tract and means to increase its bioavailability are highly needed. Using an in vitro gastrointestinal digestion method coupled to an intestinal cell model, we explored the stability, gastrointestinal bioaccessibility and cellular uptake of β-carotene from microparticles containing carotenoid extracts derived from mango by-products. Three types of microparticles were tested: one with the carotenoid extract as such, one with added inulin and one with added fructooligosaccharides. Overall, β-carotene was relatively stable during the in vitro digestion, as total recoveries were above 68 %. Prebiotics in the encapsulating material, especially inulin, enhanced the bioaccessibility of β-carotene almost 2-fold compared to microparticles without prebiotics. Likewise, β-carotene bioaccessibility increased proportionally with bile salt concentrations during digestion. Yet, a bile salts level above 10 mM did not contribute markedly to β-carotene bioaccessibility of prebiotic containing microparticles. Cellular uptake experiments with non-filtered gastrointestinal digests yielded higher absolute levels of β-carotene taken up in the epithelial cells as compared to uptake assays with filtered digests. However, the proportional uptake of β-carotene was higher for filtered digests (24 - 31 %) than for non-filtered digests (2 - 8 %). Matrix-dependent carotenoid uptake was only visible in the unfiltered medium, thereby pointing to possible other cellular transport mechanisms of non-micellarized carotenoids, besides the concentration effect. Regardless of a filtration step, inulin-amended microparticles consistently resulted in a higher β-carotene uptake than regular microparticles or FOS-amended microparticles. In conclusion, encapsulation of carotenoid extracts from mango by-products displayed chemical stability and release of a bioaccessible β-carotene fraction upon gastrointestinal digestion. This indicates the potential of the microparticles to be incorporated into functional foods with provitamin A activity.

Boosting the Bioaccessibility of Dietary Bioactives by Delivery as Protein-Polyphenol Aggregate Particles

Protein-polyphenol aggregate particles concurrently fortify a functional food product with healthy dietary proteins and concentrated polyphenols. However, what impact does ingestion of aggregate particles have on ultimate health relevance of either the polyphenolic molecules in the matrix or the protein molecules? Because human health benefits are contingent on bioavailability after ingestion, the fate of these molecules during transit in the gastrointestinal tract (GIT) will dictate their utility as functional food ingredients. This brief review explores diverse applications of protein-polyphenol particles in the food industry and the bioaccessibility of both bioactive polyphenolic compounds and edible proteins. Evidence to date suggests that complexation of phytoactive polyphenolics effectively enhances their health-relevant impacts, specifically because the phytoactives are protected in the protein matrix during transit in the GIT, allowing intact, non-degraded molecules to reach the colon for catabolism at the gut microbiome level, a prerequisite to realize the health benefits of these active compounds.

Spray-dried and freeze-dried protein-spinach particles; effect of drying technique and protein type on the bioaccessibility of carotenoids, chlorophylls, and phenolics

The effects of protein carrier and drying technique on the concentration and bioaccessibility of lipophilic compounds (lutein, β-carotene, chlorophylls a and b) and hydrophilic flavonoids in freeze-dried (FD) or spray-dried (SD) spinach juice and protein-spinach particles were investigated. Carotenoid and chlorophyll contents were highest in FD spinach juice without protein (147 and 1355 mg/100 g, respectively). For both SD and FD protein-spinach particles, SPI best protected carotenoids and chlorophylls (123 and 1160 mg/g, respectively), although the bioaccessibility of lipophilic compounds in WPI particles was higher than SPI particles (p < 0.05). For flavonoids, the drying technique was more important than the type of carrier, since FD particles had higher total flavonoids than SD. However, SD particles had higher bioaccessibility for most flavonoids (40-90 %) compared to FD (<20 %). The drying method and protein carrier can be designed to produce protein-spinach ingredients with desired concentration of compounds and bioaccessibility.

Influence of food composition on chlorophyll bioaccessibility

Chlorophylls are ingested and effectively absorbed by our organism daily, but the effect of food composition on its bioaccessibility is unknown. Therefore, the present research analyses the chlorophyll bioaccessibility of ten commercial foods (guacamole, virgin olive oil, tortellini, basil hummus, creamed spinach, vegetable pasta, green tea chocolate, avocado and kiwi juices, and pesto sauce), selected based on their different nutritional (fat, fiber, protein, and carbohydrates) and chlorophyll composition and content. The most unexpected result was to correlate chlorophyll degradation during in vitro digestion with the salt content of the digested food. Surprisingly, independently of the foods' nutritional composition or the chlorophyll content, the chlorophyll profile after in vitro digestion was formed by 90% pheophytins and 10% chlorophylls and pheophorbides. Such a pattern can only be modified when the ingested food contains a high proportion of pheophorbides (˃20%) that prevailed up to the mixed micelles.

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 and intestinal cell uptake of carotenoids and chlorophylls differ in powdered spinach by the ingredient form as measured using in vitro gastrointestinal digestion and anaerobic fecal fermentation models

Insights into food matrix factors impacting bioavailability of bioactive carotenoids and chlorophylls from fruits and vegetable ingredients are essential to understanding their ability to promote health. The stability and bioaccessibility of carotenoids and chlorophylls were assessed from dehydrated, spray-dried, freeze-dried and fresh spinach ingredient forms using in vitro models simulating upper gastrointestinal (GI) digestion and lower GI anaerobic fecal fermentation. Intestinal transport of bioaccessible bioactives from both upper and lower GI compartments was assessed using the Caco-2 human intestinal cell model. Differences in carotenoid and chlorophyll contents were observed between ingredient forms and these influenced bioaccessibility. Lower carotenoid and chlorophyll contents in spray dried spinach resulted in the lowest total bioaccessible content among all spinach treatments (5.8 ± 0.2 μmoles per g DW carotenoid and chlorophyll). The total bioaccessible content was statistically similar between freeze-dried (12.5 ± 0.6 μmoles per g DW), dehydrated (12.5 ± 3.2 μmoles per g DW), and fresh spinach (14.2 ± 1.2 μmoles per g DW). Post anaerobic fermentation, cellular accumulation of carotenoids was higher (17.57-19.52 vs. 5.11-8.56%), while that of chlorophylls was lower (3.05-5.27 vs. 5.25-6.44%), compared to those observed following upper GI digestion. Collectively, these data suggest that spinach forms created by various drying technologies deliver similar levels of bioaccessible spinach bioactives and that the lower GI tract may serve as a site for significant absorption fostered by interactions with gut microbial communities that liberate additional bioactives from the spinach matrix.

In Vitro Bioaccessibility Protocol for Chlorophylls

The daily ingestion of chlorophylls has been estimated at 50 g, but the knowledge about their bioaccessibility is limited. Different in vitro models have been utilized to estimate their potential bioavailability, but among other factors, the diversity of structures, chemical properties, and lability of chlorophylls hamper the investigations. By the first time, three extreme food matrices, one rich in fiber (vegetable puree), one rich in fat (virgin olive oil), and one liquid (fruit juice), have been assayed for chlorophyll bioaccessibility, controlling crucial variables. Chlorophyll polarity and food matrix were the determining factors, but surprisingly, chlorophyll bioaccessibility was affected during the application of the in vitro standardized protocol. Therefore, the present research has identified the reactions that can be biased during the estimation of chlorophyll bioaccessibility, defining a specific protocol in the function of chlorophyll structures.

An anchored chromosome-scale genome assembly of spinach improves annotation and reveals extensive gene rearrangements in euasterids

Spinach (Spinacia oleracea L.) is a member of the Caryophyllales family, a basal eudicot asterid that consists of sugar beet (Beta vulgaris L. subsp. vulgaris), quinoa (Chenopodium quinoa Willd.), and amaranth (Amaranthus hypochondriacus L.). With the introduction of baby leaf types, spinach has become a staple food in many homes. Production issues focus on yield, nitrogen-use efficiency and resistance to downy mildew (Peronospora effusa). Although genomes are available for the above species, a chromosome-level assembly exists only for quinoa, allowing for proper annotation and structural analyses to enhance crop improvement. We independently assembled and annotated genomes of the cultivar Viroflay using short-read strategy (Illumina) and long-read strategies (Pacific Biosciences) to develop a chromosome-level, genetically anchored assembly for spinach. Scaffold N50 for the Illumina assembly was 389 kb, whereas that for Pacific BioSciences was 4.43 Mb, representing 911 Mb (93% of the genome) in 221 scaffolds, 80% of which are anchored and oriented on a sequence-based genetic map, also described within this work. The two assemblies were 99.5% collinear. Independent annotation of the two assemblies with the same comprehensive transcriptome dataset show that the quality of the assembly directly affects the annotation with significantly more genes predicted (26,862 vs. 34,877) in the long-read assembly. Analysis of resistance genes confirms a bias in resistant gene motifs more typical of monocots. Evolutionary analysis indicates that Spinacia is a paleohexaploid with a whole-genome triplication followed by extensive gene rearrangements identified in this work. Diversity analysis of 75 lines indicate that variation in genes is ample for hypothesis-driven, genomic-assisted breeding enabled by this work.

Design and Nutrient Analysis of a Carotenoid-Rich Food Product to Address Vitamin A and Protein Deficiency

Worldwide undernutrition affects over 820 million individuals and is the underlying cause of over 50% of all childhood deaths. Sweet potatoes have been promoted to address vitamin A (vitA) deficiency, with a single, orange-fleshed sweet potato (OFSP) providing enough vitA, as β-carotene, to meet daily needs. However, the bioavailability of β-carotene is dependent on the presence of dietary fat, which is not provided by OFSP, and it lacks some essential amino acids. Therefore, in an attempt to create a food product that meets daily vitA requirements with adequate bioavailability and complete protein, we designed and assessed a sweet potato, peanut paste, and legume product. The final food product formulation, developed through computer modeling, resulted in a 65/5/35 (w/w/w) formulation in a 250 g serving and ~330 kcal. We then confirmed the nutrient content of macronutrients, and essential amino acids, zinc, and iron contents. Total β-carotene was assessed by HPLC and was lower than predicted through computer modeling, likely due to losses through thermal processing and/or degradation from storage. The results of this project indicate that the three ingredients can be combined into a single 250 g food product to provide >300 kcal energy, complete protein, and micronutrients in a more bioavailable form.

Cancer interception by interceptor molecules: mechanistic, preclinical and human translational studies with chlorophylls

Before 'cancer interception' was first advocated, 'interceptor molecules' had been conceived as a sub-category of preventive agents that interfered with the earliest initiation steps in carcinogenesis. Three decades ago, a seminal review cataloged over fifty synthetic agents and natural products that were known or putative interceptor molecules. Chlorophylls and their derivatives garnered much interest based on the potent antimutagenic activity in the Salmonella assay, and the subsequent mechanistic work that provided proof-of-concept for direct molecular complexes with planar aromatic carcinogens. As the 'interceptor molecule' hypothesis evolved, mechanistic experiments and preclinical studies supported the view that chlorophylls can interact with environmental heterocyclic amines, aflatoxins, and polycyclic aromatic hydrocarbons to limit their uptake and bioavailability in vivo. Support also came from human translational studies involving ultralow dose detection in healthy volunteers, as well as intervention in at-risk subjects. Antimutagenic and antigenotoxic effects of natural and synthetic chlorophylls against small alkylating agents also highlighted the fact that non-interceptor mechanisms existed. This gave impetus to investigations broadly related to free radical scavenging, anti-inflammatory effects, immune modulation and photodynamic therapy. Therapeutic aspects of chlorophylls also were investigated, with evidence for cell cycle arrest and apoptosis in human cancer cells. As the science has evolved, new mechanistic leads continue to support the use and development of chlorophylls and their porphyrin derivatives for cancer interception, beyond the initial interest as interceptor molecules.

Influence of simulated food and oral processing on carotenoid and chlorophyll in vitro bioaccessibility among six spinach genotypes

Increasing the density of micronutrients and phytochemicals in vegetable foods through plant breeding and processing is of value for consumers. However, the extent to which interactions between genetics and processing (G × P) can be leveraged for green leafy vegetables to improve the delivery of such compounds is unknown. Using spinach as a model, a three-phase in vitro digestion method with and without simulated oral processing (mastication) and coupling to a Caco-2 human intestinal cell culture model was used to determine whether bioaccessibility and intestinal uptake of carotenoids and chlorophylls can be modified from six spinach genotypes, fresh or processed as blanched, sterilized, and juiced products. Carotenoid and chlorophyll bioaccessibility varied significantly with the genotype (p < 0.001) and processing treatment (p < 0.001), with processing having a more profound influence on the bioaccessibility, decreasing micellarization of phytochemicals from juiced (25.8-29.3%), to fresh (19.5-27.9%), to blanched (14.9-20.5%), and sterilized spinach (10.4-13.0%). Oral mastication had a significant influence on the carotenoid bioaccessible content of sterilized spinach (0.3-0.5 μmoles per g DW) as compared to fresh spinach (0.1-0.3 μmoles per g DW), most likely due to the additive effect of thermal processing and mastication on facilitating digestive breakdown of the spinach matrix. Caco-2 accumulation of carotenoid and chlorophyll was modestly but significantly (<0.001) lower in fresh spinach (2.4%) compared to other treatment samples (3.7-4.8%). These results suggest that the genotype, processing treatment, and genotype × processing (G × P) interaction may affect carotenoid and chlorophyll bioaccessibility in spinach and that food processing remains a dominant factor in modulating the bioavailability of these phytochemicals.

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.

Development of a genetic framework to improve the efficiency of bioactive delivery from blueberry

In the present study, we applied a novel high-throughput in vitro gastrointestinal digestion model to phenotype bioaccessibility of phenolics in a diverse germplasm collection representing cultivated highbush blueberries. Results revealed significant (P < 0.05) differences between accessions, years, and accession by year interaction for relative and absolute bioaccessibility of flavonoids and phenolic acids. Broad sense heritability estimates revealed low to moderate inheritances of relative and absolute bioaccessibility, suggesting that besides environmental variables, genetics factors could control bioaccessibility of phenolics. Acylated anthocyanins had significantly higher relative bioaccessibility than non-acylated anthocyanins. Correlation analysis indicated that relative bioaccessibility did not show significant association with fruit quality or raw concentration of metabolites. The study also identified accessions that have high relative and absolute bioaccessibility values. Overall, combining the bioaccessibility of phenolics with genetic and genomic approaches will enable the identification of genotypes and genetic factors influencing these traits in blueberry.