Bioaccessibility and antioxidant activity of phenolic acids, flavonoids, and anthocyanins of encapsulated Thai rice bran extracts during in vitro gastrointestinal digestion

Foliar application of iron impacts flavonoid glycosylation and promotes flavonoid metabolism in coloured rice

Coloured rice is known as a healthcare food owing its rich flavonoid content. To better understand the effects of iron on the flavonoid metabolism of coloured rice grains, different concentrations of FeSO4 were foliar sprayed on to red rice Yuhongdao 5815 (RR) and black rice Nanheinuo (BR). The results revealed the association of iron with the increased accumulation of anthocyanins in BR and proanthocyanins in RR along with enhancements in their antioxidant capacities and total flavonoid contents. Metabolomic analysis revealed that the differential metabolites between the iron treated coloured rice and the control primarily occurred because of the O-linked glycosylation of aglycones, which are involved in the flavonoid pathway. RR exhibited a significantly higher number of differential metabolites compared with BR. Thus, foliar FeSO4 application affects the O-linked glycosylation and positively regulates flavonoid metabolism.

Differential Effects of In Vitro Simulated Digestion on Antioxidant Activity and Bioaccessibility of Phenolic Compounds in Purple Rice Bran Extracts

Pigmented rice varieties are abundant in phenolic compounds. Antioxidant activity and bioaccessibility of phenolic compounds are modified in the gastrointestinal tract. After in vitro simulated digestion, changes in antioxidant activity and bioaccessibility of phenolic compounds (phenolic acids, flavonoids, and anthocyanins) in purple rice brans (Hom Nil and Riceberry) were compared with undigested crude extracts. The digestion method was conducted following the INFOGEST protocol. Antioxidant activity was determined using the ferric-reducing antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity assays. The bioaccessibility index (BI) was calculated from the ratio of digested to undigested soluble phenolic content. Overall results showed that the in vitro simulated digested rice brans had lower antioxidant activity and lower total phenolic, flavonoid, and anthocyanin contents. However, the concentration of sinapic acid was stable, while other phenolic acids (gallic, protocatechuic, vanillic, ρ-coumaric, and ferulic acids) degraded after the oral, gastric, and intestinal phases. The BI of sinapic, gallic, vanillic, and ferulic acids remained stable, and the BI of quercetin was resistant to digestion. Conversely, anthocyanins degraded during the intestinal phase. In conclusion, selective phenolic compounds are lost along the gastrointestinal tract, suggesting that controlled food delivery is of further interest.

Recent development of carrier materials in anthocyanins encapsulation applications: A comprehensive literature review

Anthocyanins are natural polyphenols belonging to the flavonoid family that possess a variety of putative health benefits when consumed in a balanced diet. However, applications of anthocyanins in, for example, functional foods are limited due to poor stability, degradation, and low transmembrane efficiency. To maintain bioactivities of anthocyanins and optimize their use, various carrier materials have been developed. Here, we reviewed the uses of the different carrier materials (organic/inorganic, micro/nano) for anthocyanin encapsulation and delivery over the past five years. The performance of different materials and interactions between anthocyanins and these materials are described. Lastly, we give our perspective on the future development trend of anthocyanin encapsulation strategies.

Effect of gastrointestinal digestion on the stability, antioxidant activity, and Caco-2 cellular transport of pigmented grain polyphenols

Grain polyphenols are known to possess several health properties. However, their digestive stability and intestinal absorption have not been fully elucidated. This study investigated the fate of pigmented grain polyphenols in the digestive system. Purple rice, purple barley, purple wheat, and blue wheat extracts were subjected to simulated gastric and intestinal phase digestion, followed by Caco-2 cellular transport. Phenolic profiling and antioxidant activity were determined using benchtop assays and an ultra-high-performance liquid chromatography-2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid free radical) (UHPLC-ABTS•+) system. The results demonstrated a decrease in the total phenolic content of extracts after digestion, with purple rice extract retaining the highest phenolic content (79%) and ABTS•+antioxidant activity (31%). Antioxidant activity was retained the most during the gastric phase; however, dominant antioxidant compounds were not detected after intestinal digestion. Significant variations in phenolic composition and radical scavenging activity were detected after digestion. Protocatechuic acid, vanillic acid, apigenin, and chrysoeriol were all transported across the intestinal barrier. The findings of this study provide novel insights into the in vitro stability and antioxidant activity of cereal grain polyphenols after simulated digestion.

A View on the Chemical and Biological Attributes of Five Edible Fruits after Finishing Their Shelf Life: Studies on Caco-2 Cells

We studied five common perishable fruits in terms of their polyphenols dynamic, minerals distribution, scavenger activity and the effects of 50% ethanolic extracts on the viability of Caco-2 cells in vitro, over a period of time between T = 0 and T = 5/7 days, typically the end of their shelf life. Altogether, there were few changes found, consisting of either an increase or a decrease in their chemical and biological attributes. A slow decrease was found in the antioxidant activity in apricot (-11%), plum (-6%) and strawberry (-4%) extracts, while cherry and green seedless table grape extracts gained 7% and 2% antioxidant potency, respectively; IC50 values ranged from 1.67 to 5.93 μg GAE/μL test extract. The cytotoxicity MTS assay at 24 h revealed the ability of all 50% ethanol fruit extracts to inhibit the Caco-2 cell viability; the inhibitory effects ranged from 49% to 83% and were measured at 28 µg GAE for strawberry extracts/EES, from 22 µg to 45 µg GAE for cherry extracts/EEC, from 7.58 to 15.16 µg GAE for apricot extracts/EEA, from 12.50 to 25.70 µg GAE for plum extracts/EEP and from 21.51 to 28.68 µg GAE for green table grape extracts/EEG. The MTS anti-proliferative assay (72 h) also revealed a stimulatory potency upon the Caco-2 viability, from 34% (EEA, EEG) and 48% (EEC) to 350% (EES) and 690% (EEP); therefore fruit juices can influence intestinal tumorigenesis in humans.

Advances in protein-based microcapsules and their applications: A review

Due to their excellent emulsification, biocompatibility, and biological activity, proteins are widely used as microcapsule wall materials for encapsulating drugs, natural bioactive substances, essential oils, probiotics, etc. In this review, we summarize the protein-based microcapsules, discussing the types of proteins utilized in microcapsule wall materials, the preparation process, and the main factors that influence their properties. Additionally, we conclude with examples of the vital role of protein-based microcapsules in advancing the food industry from primary processing to deep processing and their potential applications in the biomedical, chemical, and textile industries. However, the low stability and controllability of protein wall materials lead to degraded performance and quality of microcapsules. Protein complexes with polysaccharides or modifications to proteins are often used to improve the thermal instability, pH sensitivity, encapsulation efficiency and antioxidant capacity of microcapsules. In addition, factors such as wall material composition, wall material ratio, the ratio of core to wall material, pH, and preparation method all play critical roles in the preparation and performance of microcapsules. The application area and scope of protein-based microcapsules can be further expanded by optimizing the preparation process and studying the microcapsule release mechanism and control strategy.

Microencapsulation by spray-drying and freeze-drying of extract of phenolic compounds obtained from ciriguela peel

Microcapsules of ciriguela peel extracts obtained by ultrasound-assisted extraction were prepared by spray drying, whose results were compared with those of freeze-drying as a control. The effects of spray-drying air temperature, feed flow rate and ratio of encapsulating agents (maltodextrin and arabic gum) were studied. Encapsulation efficiency, moisture content, total phenolic compounds (TPC), water activity, hygroscopicity, solubility, colorimetric parameters, phenolic profile by HPLC/DAD, simulated gastrointestinal digestion and morphology of spray-dried and freeze-dried microcapsules were evaluated, as well as their stability of TPC during 90 days storage at 7 and 25 °C. Spray-dried extract showed higher encapsulation efficiency (98.83%) and TPC (476.82 mg GAE g-1) than freeze-dried extract. The most abundant compounds in the liquid extract of ciriguela peel flour were rutin, epicatechin gallate, chlorogenic acid and quercetin. Rutin and myricetin were the major flavonoids in the spray-dried extract, while quercetin and kaempferol were in the freeze-dried one. The simulated gastrointestinal digestion test of microencapsulated extracts revealed the highest TPC contents after the gastric phase and the lowest one after the intestinal one. Rutin was the most abundant compound after the digestion of both spray-dried (68.74 µg g-1) and freeze-dried (93.98 µg g-1) extracts. Spray-dried microcapsules were of spherical shape, freeze-dried products of irregular structures. Spray-dried microcapsules had higher phenolic compounds contents after 90 days of storage at 7 °C compared to those stored at 25 °C, while the lyophilized ones showed no significant difference between the two storage temperatures. The ciriguela agro-industrial residue can be considered an interesting alternative source of phenolic compounds that could be used, in the form of bioactive compounds-rich powders, as an ingredient in pharmaceutical, cosmetic and food industries.

In vitro bioaccessibility evaluation of chlorophyll pigments in single and binary carriers

Chlorophyll was extracted and microencapsulated using different carrier agents. Subsequently, in vitro digestion was performed, and the bioaccessibility of chlorophyll in the different encapsulation systems was carried out. The zeta potential, particle size, and PDI were significantly modified after the micellarization of digested microcapsules. I-W-Chl presented with the highest total chlorophyll recovery and micellarization rate of 54% and 43%, respectively. In the aqueous micellar fraction, the different encapsulation systems had total chlorophylls, pheophytins, and pheophorbides ranging from 13 to 49%, 42 - 77%, and 3 - 22% respectively. The bioaccessibility of total chlorophyll pigment ranging from 7% to 20% is given in the following order: I-W-Chl > WPI-Chl > Z-Chl > Ca-Chl > SCChl^V > SCChl^C. The result established in this study shows that the carrier agent type could inhibit or mediate the bioaccessibility of chlorophyll with the potential to be an efficient delivery system for health promoting compounds.

Bioaccessibility and bioactive potential of different phytochemical classes from nutraceuticals and functional foods

Nutraceuticals and functional foods are composed of especially complex matrices, with polyphenols, carotenoids, minerals, and vitamins, among others, being the main classes of phytochemicals involved in their bioactivities. Despite their wide use, further investigations are needed to certify the proper release of these phytochemicals into the gastrointestinal medium, where the bioaccessibility assay is one of the most frequently used method. The aim of this review was to gather and describe different methods that can be used to assess the bioaccessibility of nutraceuticals and functional foods, along with the most important factors that can impact this process. The link between simulated digestion testing of phytochemicals and their in vitro bioactivity is also discussed, with a special focus on the potential of developing nutraceuticals and functional foods from simple plant materials. The bioactive potential of certain classes of phytochemicals from nutraceuticals and functional foods is susceptible to different variations during the bioaccessibility assessment, with different factors contributing to this variability, namely the chemical composition and the nature of the matrix. Regardless of the high number of studies, the current methodology fails to assume correlations between bioaccessibility and bioactivity, and the findings of this review indicate a necessity for updated and standardized protocols.

Simulated Gastrointestinal Digestion of Chestnut (Castanea sativa Mill.) Shell Extract Prepared by Subcritical Water Extraction: Bioaccessibility, Bioactivity, and Intestinal Permeability by In Vitro Assays

Chestnut shells (CSs) are an appealing source of bioactive molecules, and constitute a popular research topic. This study explores the effects of in vitro gastrointestinal digestion and intestinal permeability on the bioaccessibility and bioactivity of polyphenols from CS extract prepared by subcritical water extraction (SWE). The results unveiled higher phenolic concentrations retained after gastric and intestinal digestion. The bioaccessibility and antioxidant/antiradical properties were enhanced in the following order: oral < gastric ≤ intestinal digests, attaining 40% of the maximum bioaccessibility. Ellagic acid was the main polyphenol in the digested and undigested extract, while pyrogallol-protocatechuic acid derivative was only quantified in the digests. The CS extract revealed potential mild hypoglycemic (<25%) and neuroprotective (<75%) properties before and after in vitro digestion, along with upmodulating the antioxidant enzymes' activities and downregulating the lipid peroxidation. The intestinal permeation of ellagic acid achieved 22.89% after 240 min. This study highlighted the efficacy of the CS extract on the delivery of polyphenols, sustaining its promising use as nutraceutical ingredient.

Structures, Sources, Identification/Quantification Methods, Health Benefits, Bioaccessibility, and Products of Isorhamnetin Glycosides as Phytonutrients

In recent years, people have tended to consume phytonutrients and nutrients in their daily diets. Isorhamnetin glycosides (IGs) are an essential class of flavonoids derived from dietary and medicinal plants such as Opuntia ficus-indica, Hippophae rhamnoides, and Ginkgo biloba. This review summarizes the structures, sources, quantitative and qualitative analysis technologies, health benefits, bioaccessibility, and marketed products of IGs. Routine and innovative assay methods, such as IR, TLC, NMR, UV, MS, HPLC, UPLC, and HSCCC, have been widely used for the characterization and quantification of IGs. All of the therapeutic effects of IGs discovered to date are collected and discussed in this study, with an emphasis on the relevant mechanisms of their health-promoting effects. IGs exhibit diverse biological activities against cancer, diabetes, hepatic diseases, obesity, and thrombosis. They exert therapeutic effects through multiple networks of underlying molecular signaling pathways. Owing to these benefits, IGs could be utilized to make foods and functional foods. IGs exhibit higher bioaccessibility and plasma concentrations and longer average residence time in blood than aglycones. Overall, IGs as phytonutrients are very promising and have excellent application potential.

Flavonoids as a therapeutical option for the treatment of thrombotic complications associated with COVID-19

The SARS-CoV-2 outbreak has been one of the largest public health crises globally, while thrombotic complications have emerged as an important factor contributing to mortality. Therefore, compounds that regulate the processes involved in thrombosis could represent a dietary strategy to prevent thrombotic complications involved in COVID-19. In August 2022, various databases were consulted using the keywords "flavonoids", "antiplatelet", "anticoagulant", "fibrinolytic", and "nitric oxide". Studies conducted between 2019 and 2022 were chosen. Flavonoids, at concentrations mainly between 2 and 300 μM, are capable of regulating platelet aggregation, blood coagulation, fibrinolysis, and nitric oxide production due to their action on multiple receptors and enzymes. Most of the studies have been carried out through in vitro and in silico models, and limited studies have reported the in vivo and clinical effect of flavonoids. Currently, quercetin has been the only flavonoid evaluated clinically in patients with COVID-19 for its effect on D-dimer levels. Therefore, clinical studies in COVID-19 patients analyzing the effect on platelet, coagulant, fibrinolytic, and nitric oxide parameters are required. In addition, further high-quality studies that consider cytotoxic safety and bioavailability are required to firmly propose flavonoids as a treatment for the thrombotic complications implicated in COVID-19.

Efficient extraction, excellent activity, and microencapsulation of flavonoids from Moringa oleifera leaves extracted by deep eutectic solvent

A deep eutectic solvent (choline chloride (ChCl)-urea) was chosen to extract flavonoids from Moringa oleifera leaves (FMOL), the condition of extraction was tailor-made, under the optimal extraction conditions (material-to-liquid ratio of 1:60 g/mL, extraction time of 80 min, extraction temperature of 80 °C), the highest extraction efficiency reached 63.2 ± 0.3 mg R/g DW, and nine flavonoids were identified. Then, the biological activities including antioxidant activities, antibacterial activities, and anti-tumor activities were systematically studied. FMOL was superior to positive drugs in terms of antioxidant activity. As to DPPH investigation, the IC50 of FMOL and Vc were 64.1 ± 0.7 and 176.1 ± 2.0 µg/mL; for the ABTS, the IC50 of FMOL and Vc were 9.5 ± 0.3 and 38.2 ± 1.2 µg/mL, the FRAP value of FMOL and Vc were 15.5 ± 0.6 and 10.2 ± 0.4 mg TE/g, and ORAC value of FMOL and Vc were 4687.2 ± 102.8 and 3881.6 ± 98.6 µmol TE/g. The bacteriostatic (MICs were ≤ 1.25 mg/mL) activities of FMOL were much better than propyl p-hydroxybenzoate. Meanwhile, FMOL had comparable inhibitory activity with genistein on tumor cells, IC50 was 307.8 µg/mL, and could effectively induce apoptosis in HCT116. Microcapsules were prepared with xylose-modified soybean protein isolate and gelatin as wall materials; after that, the intestinal release of modified FMOL microcapsules was 86 times of free FMOL. Therefore, this study confirmed that FMOL extracted with ChCl/urea has rich bioactive components, and microencapsulated FMOL has potential application in food industry.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s13399-023-03877-8.

Effects of encapsulation methods on bioaccessibility of anthocyanins: a systematic review and meta-analysis

Anthocyanins have multiple health benefits. However, they are prone to degradation during gastrointestinal digestion, impeding their utilization. Various encapsulation systems have been proposed to improve their bioaccessibility and bioavailability. This review aims to provide a systematic evaluation and meta-analysis of published studies examining the effect of microencapsulation on the bioaccessibility of anthocyanins. A comprehensive and systematic literature search of three databases (Scopus, PubMed, and Web of Science) was conducted. Studies were selected according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses criteria and were reviewed independently by two investigators. Overall, 34 articles were included in the systematic review and 24 were included in the meta-analysis. The fold changes in bioaccessibility between encapsulated and non-encapsulated anthocyanins from eligible studies were calculated. The median and 95% confidence intervals (CI) of the fold changes for spray-drying (median 1.23, 95% CI 0.91-1.92), freeze-drying (median 1.19, 95% CI 0.61-1.28), simple coacervation (median 1.80, 95% CI 1.41-3.20), and complex coacervation (median 1.61, 95% CI 0.21-25.00) were calculated. Simple coacervation showed a promising protection against degradation during in vitro digestion. However, when a large number of anthocyanins cannot be released from the microparticles during digestion, encapsulation impedes the bioaccessibility of anthocyanins.

Bioaccessibility and Antioxidant Activity of Polyphenols from Pigmented Barley and Wheat

Polyphenols in pigmented cereals are believed to enhance health outcomes through their antioxidant properties. This study aimed to characterise polyphenols from Hordeum vulgare (purple barley), Triticum turgidum (purple wheat) and Triticum aestivum (blue wheat) in order to evaluate their bioaccessibility and antioxidant activity. An ultra-high performance liquid chromatography mass spectrometry coupled with an online 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) system was used to identify the polyphenols and quantify their relative antioxidant levels. Simulated gastrointestinal digestion of the cereals allowed for the assessment of polyphenol bioaccessibility using benchtop assays. Between cereals, the bioaccessible phenolic content was similar following digestion, but the antioxidant activity was significantly different (purple barley > purple wheat > blue wheat; p < 0.01). Among the polyphenols identified, flavan-3-ols and anthocyanins were the least bioaccessible whereas flavones were the most bioaccessible after digestion. This study demonstrated that these pigmented cereal varieties are sources of bioaccessible polyphenols with antioxidant activity. These findings may aid in utilising these pigmented grains for the future design and development of novel functional food products with enhanced health properties.

Employ of Anthocyanins in Nanocarriers for Nano Delivery: In Vitro and In Vivo Experimental Approaches for Chronic Diseases

Anthocyanins are among the best-known phenolic compounds and possess remarkable biological activities, including antioxidant, anti-inflammatory, anticancer, and antidiabetic effects. Despite their therapeutic benefits, they are not widely used as health-promoting agents due to their instability, low absorption, and, thus, low bioavailability and rapid metabolism in the human body. Recent research suggests that the application of nanotechnology could increase their solubility and/or bioavailability, and thus their biological potential. Therefore, in this review, we have provided, for the first time, a comprehensive overview of in vitro and in vivo studies on nanocarriers used as delivery systems of anthocyanins, and their aglycones, i.e., anthocyanidins alone or combined with conventional drugs in the treatment or management of chronic diseases.