Water-soluble Pigments Research Articles

Understanding the molecular structure of natural anthocyanins during recovery with ionic liquids: A combined COSMO-RS and experimental study

Anthocyanins, water-soluble vacuolar pigments found in various fruits and vegetables, exhibit vibrant red, purple, or blue hues contingent upon their pH levels. The stability of these pigments depends on pH. Due to that, conventional extraction methods use volatile organic acidic solvents in solid-liquid extractions (SLE). Despite the widespread use of such solvents, the molecular mechanisms governing the stability of anthocyanins during SLE with different solvents remain inadequately explored. This study aimed to enhance the understanding of anthocyanin stability by identifying alternative neoteric solvents, specifically hydrophilic ionic liquids (ILs). A COSMO-RS prescreening was conducted to evaluate the impact of solvent cations and anions on the anthocyanin skeleton during extraction from grape pomace. The results revealed that acetate-based ILs exhibited the highest affinity for anthocyanins. However, experimental validation demonstrated that hydrogen sulfate anion-based ILs, particularly [bmim][HSO4], yielded the most favorable outcomes, with approximately 4 mg/g of total anthocyanin equivalent at 298.15K while maintaining low pH values ensuring stability for anthocyanin molecules. Interestingly, the choice of cations within the ILs did not significantly influence the results. The main extraction mechanism is attributed to hydrogen bonding interaction. Thus, this research not only identifies an effective solvent for anthocyanin extraction but also sheds light on the crucial role of the neoteric solvent's acid characteristics in maintaining the structural integrity of these valuable pigments.

Progressive Analytical Techniques Utilized for the Detection of Contaminants Attributed to Food Safety and Security

Food analysis and authentication are very crucial to assure safety, quality, and integrity of food and food-related products. Analysis of food products not only ensures the quality of food but also gives information about composition, physical characteristics, flavor, shelf-life, safety, microstructure, and processibility. Consequently, food is now regarded as an inexpensive means of preventing disease while also serving as a source of energy. Typically, a wide range of distinct chemical components make up the chemical composition of food. Furthermore, during processing or storage, food is always susceptible to structural alterations. Therefore, to assess the nutritional value and the quality of food products, food components must be analyzed and quantified. Food analysis mainly includes the preparation, examination, and identification of major food components, such as dietary fiber, phenolic compounds, carbohydrates, proteins, amino acids, peptides, enzymes, phospholipids, pesticides, alcohols, fat-soluble and water-soluble vitamins, organic acids, organic bases, bittering agents, pigments, and aroma compounds, as well as minor components including preservatives, antioxidants, colorants. Therefore, there are several advanced analytical techniques, including spectroscopy, mass spectrometry, chromatography, NMR, HSI, MALDI-TOF, RT-PCR, biosensors, etc. have been vital in the food science domain due to their high selectivity and sensitivity. This review emphasizes implementing various analytical techniques to analyze food safety and security.

Anthocyanins in Vascular Health and Disease: Mechanisms of Action and Therapeutic Potential.

Unhealthy lifestyles have placed a significant burden on individuals' cardiovascular health. Anthocyanins are water-soluble flavonoid pigments found in a wide array of common foods and fruits. Anthocyanins have the potential to contribute to the prevention and treatment of cardiovascular disease by improving lipid profiles and vascular function, reducing blood glucose levels and blood pressure, and inhibiting inflammation. These actions have been demonstrated in numerous clinical and preclinical studies. At the cellular and molecular level, anthocyanins and their metabolites could protect endothelial cells from senescence, apoptosis, and inflammation by activating the phosphoinositide 3-kinase/protein kinase B/endothelial nitric oxide synthases, silent information regulator 1 (SIRT1), or nuclear factor erythroid2-related factor 2 pathways and inhibiting the nuclear factor kappa B, Bax, or P38 mitogen-activated protein kinase pathways. Furthermore, anthocyanins prevent vascular smooth muscle cell from platelet-derived growth factor -induced or tumor necrosis factor-α-induced proliferation and migration by inhibiting the focal adhesion kinase and extracellular regulated protein kinases signaling pathways. Anthocyanins could also attenuate vascular inflammation by reducing the formation of oxidized lipids, preventing leukocyte adhesion and infiltration of the vessel wall, and macrophage phagocytosis of deposited lipids through reducing the expression of cluster of differentiation 36 and increasing the expression of ATP-binding cassette subfamily A member 1 and ATP-binding cassette subfamily G member 1. At the same time, anthocyanins could lower the risk of thrombosis by inhibiting platelet activation and aggregation through down-regulating P-selectin, transforming growth factor-1, and CD40L. Thus, the development of anthocyanin-based supplements or derivative drugs could provide new therapeutic approaches to the prevention and treatment of vascular diseases.

Storage Stability and Sensory Properties of Raha Sweet Colored with Crude and Purified Red Grape Anthocyanins and Synthetic Food Colorant.

Anthocyanins (ANCs) are water-soluble pigments that are useful as nutraceuticals due to their health benefits. This study was performed to evaluate the storage stability of purified and crude red grape ANCs in Raha Sweet (RS) during storage and to evaluate its sensory properties. ANCs were extracted from red grape pomace and purified with a macroporous resin. RS was prepared and colored with a synthetic food dye, Carmoisine (control), and ANCs (crude and purified). Pigments were extracted from RS weekly for a period of seven weeks and the absorbance was read spectrophotometrically. RS colored with ANCs was evaluated for its color and other sensory properties against another RS colored with the control. Results showed that the degradation of ANCs in RS followed the first-order reaction model, unlike the control, which showed no degradation during storage. The half-life of crude ANCs was three times higher than that of the purified ones, and RS colored with ANCs received a significantly (p < 0.05) lower score for color than that of RS colored with the control. ANCs could provide the food industry with a natural alternative to synthetic dyes to color foods with high sugar content that are stored for a short period of time.

Enzymatic acylation of cyanidin-3-O-glucoside with aromatic and aliphatic acid methyl ester: Structure–stability relationships of acylated derivatives

Anthocyanins are water-soluble pigments, but they tend to be unstable in aqueous solutions. Modification of their molecular structure offers a viable approach to alter their intrinsic properties and enhance stability. Aromatic and aliphatic acid methyl esters were used as acyl donors in the enzymatic acylation of cyanidin-3-O-glucoside (C3G), and their analysis was conducted using ultraperformance liquid chromatography–mass spectrometry (UPLC-MS). The highest conversion rate achieved was 96.41 % for cyanidin-3-O-(6″-feruloyl) glucoside. Comparative evaluations of stability revealed that aromatic acyl group–conjugated C3G exhibited superior stability enhancement compared with aliphatic acyl group derivatives. The stability of aliphatic C3G decreased with increasing carbon chain length. The molecular geometries of different anthocyanins were optimized, and energy level calculations using density functional theory (DFT) identified their sites with antioxidant activities. Computational calculations aligned with the in vitro antioxidant assay results. This study provided theoretical support for stabilizing anthocyanins and broadened the application of acylated anthocyanins as food colorants and nutrient supplements.

Phytochemical Analysis of Anthocyanins Extracted from the Flowers of Two Dahlia Cultivars and their Cytotoxic Properties

Dahlia Cav. is a genus of ornamental plants that belongs to the Asteraceae family. These plants are visually pleasing and contain biologically active substances such as flavonoids, hydroxycinnamic acids, organic acids, and inulin. Among these substances, anthocyanins are especially noteworthy. These water-soluble vacuolar pigments of a glycoside nature have significant health benefits, including antioxidant, antidiabetic, hypocholesterolemic, anticancer, cardioprotective, and hypotensive properties. The purpose of this study was to evaluate the content of anthocyanins by spectrophotometry and the composition by HPLC in the extracts from flowers of two varieties of dahlias ('La Baron' and 'Colorado Classic') grown in Ukraine, as well as to evaluate the cytotoxic effect of these extracts. According to HPLC analysis, among 18 revealed anthocyanins the fower of ‘La Baron’ cultivar had the highest concentration of cyanidin-3-O-arabinoside (31.85%) and cyanidin-3-O-galactoside (23.01%) while ‘Colorado Classic’ accumulated more delphinidin-3-O-arabinoside (39.80%) and Delphinidin-3-O-galactoside (23.15%). Our study also found that malvidin, peonidin, and petunidin played a minor role in the coloration of the flowers. The total amount of anthocyanins was slightly higher in the flowers of the ‘La Baron’ cultivar (1.250%) compared to the ‘Colorado Classic’ one (1.138%). To determine the toxicity of anthocyanins, it was used an in vitro model of bone marrow cells (BMC) and found that the cytoprotective and cytotoxic activities of the anthocyanins were dose-dependent. Based on these findings, the study concluded that there is potential for developing new herbal medicinal products using dahlia flowers with a significant content of anthocyanins.

Genetic and Biotechnological Approaches to Improve Fruit Bioactive Content: A Focus on Eggplant and Tomato Anthocyanins.

Anthocyanins are a large group of water-soluble flavonoid pigments. These specialized metabolites are ubiquitous in the plant kingdom and play an essential role not only in plant reproduction and dispersal but also in responses to biotic and abiotic stresses. Anthocyanins are recognized as important health-promoting and chronic-disease-preventing components in the human diet. Therefore, interest in developing food crops with improved levels and compositions of these important nutraceuticals is growing. This review focuses on work conducted to elucidate the genetic control of the anthocyanin pathway and modulate anthocyanin content in eggplant (Solanum melongena L.) and tomato (Solanum lycopersicum L.), two solanaceous fruit vegetables of worldwide relevance. While anthocyanin levels in eggplant fruit have always been an important quality trait, anthocyanin-based, purple-fruited tomato cultivars are currently a novelty. As detailed in this review, this difference in the anthocyanin content of the cultivated germplasm has largely influenced genetic studies as well as breeding and transgenic approaches to improve the anthocyanin content/profile of these two important solanaceous crops. The information provided should be of help to researchers and breeders in devising strategies to address the increasing consumer demand for nutraceutical foods.

Emendation of Rhodomonas marina (Cryptophyceae): insights from morphology, molecular phylogeny and water-soluble pigment in an Arctic isolate

Rhodomonas (Cryptophyceae) and species assigned to this genus have undergone numerous taxonomic revisions. This also applies to R. marina studied here as it was originally assigned as a species of Cryptomonas and later considered a variation of R. baltica, the type species. Despite being described more than 130 years ago, R. marina still lacks a comprehensive characterization. Light and electron microscopy were employed to delineate a strain from western Greenland. The living cells were 18 μm long and 9 μm wide, elliptical in shape with a pointed to rounded posterior and truncated anterior in lateral view. Two sub-equal flagella emerged from a vestibulum, where also a furrow extended. In transmission electron microscopy, the furrow was associated with a tubular gullet and the pyrenoid embedded in a deeply lobed chloroplast. The chloroplast contained DNA in perforations and was surrounded by starch grains. A tubular nucleomorph was enclosed within the pyrenoid matrix. In scanning electron microscopy, the inner periplast consisted of rectangular plates with rounded edges and posteriorly these were replaced by a sheet-like structure. The water-soluble pigment was Crypto-Phycoerythrin type I (Cr-PE 545). A phylogenetic inference based on SSU rDNA confirmed the identity of strain S18 as a species of Rhodomonas as it clustered with congeners but also Rhinomonas, Storeatula, and Pyrenomonas. These genera formed a monophyletic clade separated from a diverse assemblage of other cryptophyte genera. To further explore the phylogeny of R. marina a concatenated phylogenetic analysis based on the SSU rDNA-ITS1-5.8S rDNA-ITS2- LSU rDNA region was performed but included only closely related species. The secondary structure of nuclear internal transcribed spacer 2 was predicted and compared to similar structures in related species. Using morphological and molecular signatures as diagnostic features the description of R. marina was emended.

Amorosia littoralis Mantle & D. Hawksw. survives as root endophyte of mangroves and produces water soluble melanin pigment

Melanins are heterogenous biopolymers produced by many macro and microorganisms. They enhance the ecological fitness of the producer organisms by improving their virulence and protecting them from radiation, osmotic and heat stresses. Fungi synthesise either DOPA or DHN melanin and deposit them on their cell walls. Some fungal isolates produce water soluble melanin (pyomelanin) which is excerted out of the hyphae into the surrounding environment. Pyomelanin, a polymer of homogentisate, exhibits antimicrobial, UV screening, antioxidative, and anti-inflammatory activities and recent studies also show that pyomelanin could find use in space travel as radiation shield. However, scant literature is available on fungi with ability to produce pyomelanin. We report for the first time that Amorosia littoralis occurs as a root endophyte in mangrove species including Avicennia marina, Bruguiera cylindrica and Bruguiera gymnorhiza and produces pyomelanin. Considering the various technological uses of pyomelanin, this study underscores the need to explore fungi of different habitats to identify hyperproducers and to obtain chemically diverse pyomelanin.

Research Progress on the Extraction and Purification of Anthocyanins and Their Interactions with Proteins.

Anthocyanins, as the most critical water-soluble pigments in nature, are widely present in roots, stems, leaves, flowers, fruits, and fruit peels. Many studies have indicated that anthocyanins exhibit various biological activities including antioxidant, anti-inflammatory, anti-tumor, hypoglycemic, vision protection, and anti-aging. Hence, anthocyanins are widely used in food, medicine, and cosmetics. The green and efficient extraction and purification of anthocyanins are an important prerequisite for their further development and utilization. However, the poor stability and low bioavailability of anthocyanins limit their application. Protein, one of the three essential nutrients for the human body, has good biocompatibility and biodegradability. Proteins are commonly used in food processing, but their functional properties need to be improved. Notably, anthocyanins can interact with proteins through covalent and non-covalent means during food processing, which can effectively improve the stability of anthocyanins and enhance their bioavailability. Moreover, the interactions between proteins and anthocyanins can also improve the functional characteristics and enhance the nutritional quality of proteins. Hence, this article systematically reviews the extraction and purification methods for anthocyanins. Moreover, this review also systematically summarizes the effect of the interactions between anthocyanins and proteins on the bioavailability of anthocyanins and their impact on protein properties. Furthermore, we also introduce the application of the interaction between anthocyanins and proteins. The findings can provide a theoretical reference for the application of anthocyanins and proteins in food deep processing.

Recent microencapsulation trends for enhancing the stability and functionality of anthocyanins: a review.

Anthocyanins (ACNs) are water-soluble pigments in various fruits and vegetables known for their high antioxidant activity. They are used as natural food colorants and preservatives and have several medicinal benefits. However, their application in functional foods and nutraceuticals is often compromised by their low stability to heat, oxygen, enzymes, light, pH changes, and solubility issues. Spray drying has emerged as an effective microencapsulation technique to enhance the shelf life, quality, and stability of ACNs. This manuscript reviews the latest scientific developments in spray drying microencapsulation of ACNs-rich fruit extracts. Process optimization and the stability and physicochemical properties of the spray-dried, microencapsulated ACNs-rich powders are discussed. This review also covers functional food and nutraceutical applications and introduces novel encapsulation methods, such as freeze-drying, supercritical carbon dioxide (SC-CO2), coacervation, drum drying, and electrospraying, highlighting their potential in improving the utility of ACNs-rich fruit extracts.

A novel pathogenic species of genus Stenotrophomonas: Stenotrophomonas pigmentata sp. nov.

Stenotrophomonas is a prominent genus owing to its dual nature. Species of this genus have many applications in industry and agriculture as plant growth-promoting rhizobacteria and microbial biological control agents, whereas species such as Stenotrophomonas maltophilia are considered one of the leading gram-negative multi-drug-resistant bacterial pathogens because of their high contribution to the increase in crude mortality and significant clinical challenge. Pathogenic Stenotrophomonas species and most clinical isolates belong to the Stenotrophomonas maltophilia complex (SMc). However, a strain highly homologous to S. terrae was isolated from a patient with pulmonary tuberculosis (TB), which aroused our interest, as S. terrae belongs to a relatively distant clade from SMc and there have been no human association reports. The pathogenicity, immunological and biochemical characteristics of 610A2T were systematically evaluated. 610A2T is a new species of genus Stenotrophomonas, which is named as Stenotrophomonas pigmentata sp. nov. for its obvious brown water-soluble pigment. 610A2T is pathogenic and caused significant weight loss, pulmonary congestion, and blood transmission in mice because it has multiple virulence factors, haemolysis, and strong biofilm formation abilities. In addition, the cytokine response induced by this strain was similar to that observed in patients with TB, and the strain was resistant to half of the anti-TB drugs. The pathogenicity of 610A2T may not be weaker than that of S. maltophilia. Its isolation extended the opportunistic pathogenic species to all 3 major clades of the genus Stenotrophomonas, indicating that the clinical importance of species of Stenotrophomonas other than S. maltophilia and potential risks to biological safety associated with the use of Stenotrophomonas require more attention.

Betacyanins from red pitahaya (Hylocereus polyrhizus) exhibit antiviral response against influenza A virus

Seasonal influenza affects millions of lives worldwide, with the influenza A virus (IAV) responsible for pandemics and annual epidemics, causing the most severe illnesses resulting in patient hospitalizations or death. With IAV threatening the next global influenza pandemic, it is a race against time to search for antiviral drugs. Betacyanins are unique nitrogen-containing and water-soluble reddish-violet pigments that have been reported to possess antiviral properties against the dengue virus. This study aimed to examine the antiviral effect of betacyanins from red pitahaya (Hylocereus polyrhizus) on IAV-infected lung epithelial A549 cells. HPLC and LC-MS analysis of extracted betacyanin showed four betacyanins in the betacyanin fraction: phyllocactin, hylocerenin, betanin, and isobetanin. Cytotoxicity assay showed that betacyanin fractions were not cytotoxic to A549 cells at concentrations below 100 μg/mL. Betacyanin fraction concentrations of 12.5, 25.0, and 50.0 μg/mL prevented the formation of viral cytopathic effect and reduced virus titer in IAV-infected cells up to 72 h. A downregulation of protein and mRNA nucleoprotein expression levels was observed after treatment with 25.0 and 50.0 μg/mL of betacyanin fraction after 24 h, thereby providing evidence for the antiviral activity of betacyanin from red pitahaya against IAV in vitro.

A Fruit-Expressed MYB Transcription Factor Regulates Anthocyanin Biosynthesis in Atropa belladonna.

Anthocyanins are water-soluble flavonoid pigments that play a crucial role in plant growth and metabolism. They serve as attractants for animals by providing plants with red, blue, and purple pigments, facilitating pollination and seed dispersal. The fruits of solanaceous plants, tomato (Solanum lycopersicum) and eggplant (Solanum melongena), primarily accumulate anthocyanins in the fruit peels, while the ripe fruits of Atropa belladonna (Ab) have a dark purple flesh due to anthocyanin accumulation. In this study, an R2R3-MYB transcription factor (TF), AbMYB1, was identified through association analysis of gene expression and anthocyanin accumulation in different tissues of A. belladonna. Its role in regulating anthocyanin biosynthesis was investigated through gene overexpression and RNA interference (RNAi). Overexpression of AbMYB1 significantly enhanced the expression of anthocyanin biosynthesis genes, such as AbF3H, AbF3'5'H, AbDFR, AbANS, and Ab3GT, leading to increased anthocyanin production. Conversely, RNAi-mediated suppression of AbMYB1 resulted in decreased expression of most anthocyanin biosynthesis genes, as well as reduced anthocyanin contents in A. belladonna. Overall, AbMYB1 was identified as a fruit-expressed R2R3-MYB TF that positively regulated anthocyanin biosynthesis in A. belladonna. This study provides valuable insights into the regulation of anthocyanin biosynthesis in Solanaceae plants, laying the foundation for understanding anthocyanin accumulation especially in the whole fruits of solanaceous plants.

Theoretical Study of Cyanidin-Resveratrol Copigmentation by the Functional Density Theory.

Anthocyanins are colored water-soluble plant pigments. Upon consumption, anthocyanins are quickly absorbed and can penetrate the blood-brain barrier (BBB). Research based on population studies suggests that including anthocyanin-rich sources in the diet lowers the risk of neurodegenerative diseases. The copigmentation caused by copigments is considered an effective way to stabilize anthocyanins against adverse environmental conditions. This is attributed to the covalent and noncovalent interactions between colored forms of anthocyanins (flavylium ions and quinoidal bases) and colorless or pale-yellow organic molecules (copigments). The present work carried out a theoretical study of the copigmentation process between cyanidin and resveratrol (CINRES). We used three levels of density functional theory: M06-2x/6-31g+(d,p) (d3bj); ωB97X-D/6-31+(d,p); APFD/6-31+(d,p), implemented in the Gaussian16W package. In a vacuum, the CINRES was found at a copigmentation distance of 3.54 Å between cyanidin and resveratrol. In water, a binding free energy ∆G was calculated, rendering -3.31, -1.68, and -6.91 kcal/mol, at M06-2x/6-31g+(d,p) (d3bj), ωB97X-D/6-31+(d,p), and APFD/6-31+(d,p) levels of theory, respectively. A time-dependent density functional theory (TD-DFT) was used to calculate the UV spectra of the complexes and then compared to its parent molecules, resulting in a lower energy gap at forming complexes. Excited states' properties were analyzed with the ωB97X-D functional. Finally, Shannon aromaticity indices were calculated and isosurfaces of non-covalent interactions were evaluated.

Optimization of ultrasound pre-treatment and the effect of different drying techniques on antioxidant capacity, bioaccessibility, structural and thermal properties of purple cabbage

Some of the challenges of purple cabbage post-harvest processing and shelf-life is the preservation of its bioactive compounds, especially anthocyanins– a water-soluble pigment of interest due to their health-promoting benefits. The current study proposes the application of ultrasound (US) as a pretreatment prior to convective drying (CD), freeze-drying (FD), spray drying (SD), or spouted bed drying (SB). For this, a Box-Behnken Design (BBD) evaluated the effect of the different drying techniques and selected US amplitudes (20–70 %) and times (4–12 min) on the antioxidant capacity, bioaccessibility, and structural and thermal properties of purple cabbage. The results demonstrated that the amplitude of 80.35 % and 8 min of US, yielded the highest total phenolic compounds (TPC) (80.46 mg GAE/100 g), total anthocyanins (TA) (9.85 mg/100 g), and antioxidant activity (29.74 µM Fe2SO4/g) levels. SD and SB stood out for preserving bioactive compounds, increasing solubility, and reducing powder hygroscopicity. In the Scanning Electron Microscopy (SEM) analysis, CD, FD, and SB exhibited irregular and rough surfaces, while SD displayed spherical particles. Changes in the intensities of Fourier-Transform Infrared Spectroscopy (FT-IR) spectra, especially in the bonds (C = C, 1020 cm−1) in SD and SB, suggest alterations in molecular interactions due to processing and the adjuvant. Differential scanning calorimetry (DSC) indicated that SD displayed greater thermal stability. In conclusion, US pre-treatment and appropriate selection of drying techniques significantly influenced the properties of purple cabbage powder, bringing insights for the food industry regarding the use of drying as a post-harvested treatment of purple cabbage.

The effects of environmental factors on the synthesis of water-soluble Monascus red pigments via submerged fermentation: a review.

Monascus pigments (MPs) have been used as natural food pigments for many years. There is a high demand for Monascus red pigments (MRPs) to enhance color and for antibacterial and cancer prevention therapies in food and medicine. Most MRPs are not water soluble, and the yield of water-soluble MRPs is naturally low. On the other hand, water-soluble MRP is more cost effective for application in industrial mass production. Therefore, it is important to improve the yield of water-soluble MRPs. Environmental factors have a significant influence on the synthesis of water-soluble MRPs, which is crucial for the development of industrial production of water-soluble MRPs. This review introduces the biosynthetic pathways of water-soluble MRPs and summarizes the effects of environmental factors on the yield of water-soluble MRPs. Acetyl coenzyme A (acetyl-CoA) is a precursor for MPs synthesis. Carbon and nitrogen sources and the carbon/nitrogen ratio can impact MP production by regulating the metabolic pathway of acetyl-CoA. Optimization of fermentation conditions to change the morphology of Monascus can stimulate the synthesis of MPs. The appropriate choice of nitrogen sources and pH values can promote the synthesis of MRPs from MPs. Additives such as metal ions and non-ionic surfactants can affect the fluidity of Monascus cell membrane and promote the transformation of MRPs into water-soluble MRPs. This review will lay the foundation for the industrial production of water-soluble MRPs. © 2024 Society of Chemical Industry.

Physicochemical properties and antibacterial activity evaluation of new indigo extract from Baphicacanthus cusia (Nees) Bremek prepared by chemical conversion method

The effect of acidolysis time, hydrochloric acid concentration, ozonization time and pH on the yield of indigo were investigated by single factor experiment using dried leaves of Baphicacanthus cusia (Nees) Bremek (DLB) as raw material. On this basis, the technological condition for preparing new indigo extract (NIE) by directional chemical conversion method was optimized by orthogonal experiment. Then, the physiochemical properties of NIE were analyzed by combustion assay, nitric acid assay, thin layer chromatography identification assay, moisture detection and water-soluble pigment observation assay. Moreover, UPLC-Q-TOF-MS/MS technology was utilized to compare chemical composition difference between the NIE and traditional indigo naturalis (TIN). Finally, NIE emulsion was prepared by ultrasound assisted high pressure homogenization method and its stability, antibacterial activity as well as antibacterial mechanism were evaluated. The experimental results showed that optimum process for preparing NIE were hydrochloric acid concentration of 2 %, ozonization time of 3 min, pH of 7 and acidolysis time of 1 h; Under this condition, the content and yield of indigo in the NIE were significantly improved, which could reach up to 42.6 ± 0.28 % and 2.26 ± 0.04 %, separately. NIE possessed similar physiochemical properties with TIN described in Chinese pharmacopoeia 2020, and had more diverse active ingredients than TIN. The prepared NIE emulsion demonstrated excellent stability, whether at dark or bright place, and no matter at low temperature (4 ℃) or room temperature (25 ℃), the particle size, PDI, pH and indigo content of which displayed little variation. In addition, the NIE emulsion owned good inhibitory activity against S. aureus, and its MIC and MBC values were 40 and 80 μg/mL, respectively. Moreover, NIE emulsion exhibited antibacterial effect by influencing cell membrane integrity, Ca2+-Mg2+-ATPase activity on the cell membrane and intracellular Ca2+ levels of S. aureus. All of above results will lay the foundation for the green and sustainable utilization of Baphicacanthus cusia (Nees) Bremek.

PH-dependent stability of major betalains in the encapsulated beetroot extracts (Beta vulgaris L.).

Betalain is a water-soluble pigment contained in Caryophyllales plants. It not only holds potential as a natural food colorant but also offers various health benefits, acting as an antioxidant. This study focused on analyzing the pH-dependent stability of encapsulated betalain pigments extracted from red beetroot (Beta vulgaris L.) using methods such as absorption spectroscopy, HPLC, and LC-MS. The major pigments identified were vulgaxanthin I, betanin, isobetanin, and neobetanin, alongside minor components, including three betaxanthin species and a degradation product known as betalamic acid. Spectrophotometric analyses revealed that above pH 8, the betalain peak at 435nm decreased and red-shifted to a peak at 549nm, a shift that could be reversed through neutral pH treatment. At pH 11, a new broad peak appeared at 410nm and was identified as betalamic acid. To assess the pH-dependency of each betalain, the targeted betalains were separated and quantified through HPLC after incubation across a wide pH range of 2-11 and during storage. After 3 days of storage in highly alkaline conditions (pH 10-11), major betalains, with the exception of neobetanin, underwent significant degradation. Conversely, these pigments displayed relative stability in acidic conditions. In contrast, neobetanin showed vulnerability to acidic conditions but exhibited tolerance to alkaline pH levels of 10-11. The degradation product, betalamic acid, demonstrated a similar susceptibility to alkaline pH as betanins. In conclusion, the significant stability decrease under highly alkaline conditions results not only from the hydrolytic reaction of betalains but also from the degradation of betalamic acid itself. PRACTICAL APPLICATION: Encapsulation methods are used to enhance the stability of betalains against temperature variations; however, the effects of pH, especially when considering individual betalain species, are not well understood. Despite betalains exhibiting similar features and being suitable for a wide pH range from acid to alkaline conditions, they are significantly affected by alkaline pH levels exceeding 10, as well as by storage duration. This study demonstrated the application of encapsulation to pH-dependent stability, and the findings offer valuable insights and a fresh perspective on betalains as red biocolorants, extending their potential application to a wide range of pH-controlled food products.

Fabrication and characterization of anthocyanin-loaded double Pickering emulsions stabilized by β-cyclodextrin

Anthocyanins, one of the important water-soluble pigments, are sensitive to environmental factors, which limits the application of anthocyanins in food field. In order to overcome this limitation, double Pickering emulsions stabilized by β-cyclodextrin were developed. The optimum preparation conditions of the emulsions were determined firstly and the performance and structure of emulsions were investigated. Results showed that the optimum preparation conditions of emulsions were the ratio of (W1/O): W2 = 6:4 and 4 % β-cyclodextrin concentration. Optical microscope and confocal laser scanning microscope results confirmed that β-cyclodextrin adsorbed onto the surface of droplets forming stable double Pickering emulsions structure. In vitro gastrointestinal digestion experiments proved that double Pickering emulsions played a controlled-release effect in the small intestine. Rheological analysis proved that the emulsions exhibited elastic properties and demonstrated shear thinning behavior. The emulsions showed excellent stability under centrifugation and thermal conditions. These findings will promote anthocyanins’ application in daily diet.