Versatile solvent systems for the separation of betalains from processed Beta vulgaris L. juice using counter-current chromatography

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 435 nm decreased and red-shifted to a peak at 549 nm, a shift that could be reversed through neutral pH treatment. At pH 11, a new broad peak appeared at 410 nm 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.

Comprehensive Betalain Profiling of Djulis (Chenopodium formosanum) Cultivars Using HPLC-Q-Orbitrap High-Resolution Mass Spectrometry

Betalains are water-soluble pigments that may be used as alternatives to artificial colorants in the food industry. In addition, the betalain profile may be of taxonomic significance to some higher plants. Djulis (Chenopodium formosanum) is an emerging crop grown by Taiwan aboriginal communities, and its various cultivars contain different betalain compositions. To develop an authenticity method for evaluating djulis cultivars, we performed comprehensive betalain profiling with HPLC-Q-Orbitrap high-resolution mass spectrometry (HRMS). An HRMS method for betalain annotation was developed and used to identify 68 betalains, including 10 betacyanins, 24 betacyanin derivatives, and 34 betaxanthins. The profile of betacyanins and their derivatives could be utilized to classify different cultivars of djulis, while betaxanthins were less informative. Furthermore, the betalain profiles were indicative of the geographic origin of djulis. This HRMS method and analytical platform for betalains may be helpful to guide further investigations of natural pigments in other plants.

High-speed countercurrent chromatography for isolation and enrichment of betacyanins from fresh and dried leaves of Atriplex hortensis L. var. "Rubra"

Betacyanins and their decarboxylated derivatives from fresh and dried edible leaves of Atriplex hortensis L. var. "Rubra" were fractionated for the first time by high-speed countercurrent chromatography. Pigments present in fresh leaf extract were separated in systems: ethanol - acetonitrile - n-propanol - ammonium sulphate - water (0.5:0.5:0.5:1.2:1.0, v/v/v/v/v) (tail-to-head mode) and tert-butyl methyl ether - n-butanol - acetonitrile - water with 0.7% heptafluorobutyric acid (2:2:1:5, v/v/v/v) (head-to-tail mode). The mobile phase flow rate was 2 mL/min and the retention of the stationary phase was 79.8 and 75.2%, respectively. Pigments from dried leaves were separated in a similar ion-pair system with heptafluorobutyric acid in different volume proportions 1:3:1:5 (head-to-tail mode) and the flow rate of the mobile phase 3 mL/min. The stationary phase retention was 64.0%. The application of the countercurrent chromatography for the fractionation of betacyanins from leaves of Atriplex hortensis enabled to isolate and pre-concentrate the pigments for further low- and high-resolution liquid chromatographic-tandem mass spectrometric detection. This study revealed the presence of 10 betacyanins in fresh and 16 in dried leaves of Atriplex hortensis. Two compounds were not previously identified in the whole Amaranthaceae family. Additionally, instead of (iso)amaranthin, celosianin and its epimer were dominant betacyanins in the Atriplex hortensis.

Multi-colored shades of betalains: recent advances in betacyanin chemistry

Covering: 2001 to 2021Betacyanins cover a class of remarkable natural red-violet plant pigments with prospective chemical and biological properties for wide-ranging applications in food, pharmaceuticals, and the cosmetic industry. Betacyanins, forming the betalain pigment group together with yellow betaxanthins, have gained much attention due to the increasing social awareness of the positive impact of natural products on human health. Betalains are commercially recognized as natural food colorants with preliminarily ascertained, but to be further investigated, health-promoting properties. In addition, they exhibit a remarkable structural diversity based on glycosylated and acylated varieties. The main research directions for natural plant pigments are focused on their structure elucidation, methods of their separation and analysis, biological activities, bioavailability, factors affecting their stability, industrial applications as a plant-based food, natural colorants, drugs, and cosmetics as well as methods for high-yield production and stabilization. This review covers period of the last two decades of betacyanin research. In the first part of the review, we present an updated classification of all known betacyanins and their derivatives identified by chemical means as well as by mass spectrometric and NMR techniques. In the second part, we review the current research reports focused on the chemical properties of the pigments (decarboxylation, oxidation, conjugation, and chlorination reactions as well as the acyl group migration phenomenon) and describe the semi-synthesis of natural and artificial fluorescent betalamic acid conjugates, showing various prospective research directions.

Validation of aqueous two-phase extraction method

Nowadays, consumer interest in food with natural ingredients has increased. This need has led to the research of new sources and green extraction methods. Betalains are compounds responsible for giving color to cacti fruits. The aim is to obtain low-sugar betacyanins extracts from jiotilla Escontria chiotilla using aqueous two-phase systems (ATPS) to color food with the extract. The effect of principal parameters of ATPS (Ethyl alcohol- KH₂PO₄/K₂HPO₄) as tie-line length (TL;40,50 and 70), phase volume ratios (Vr; 1 and 3) on the partitioning of betacyanins, betaxanthins, total sugars, reducing sugars, and antioxidant activity in the extract was evaluated. The yields were determined from the top and bottom phases of the aforementioned parameters. Multivariate analysis of variance (MANOVA, α = 0.05) showed that TLL and Vr were statistically significant (P < 0.05). The lowest bottom sugar yield (25.78 ± 3.14%) corresponds to TLL = 40, Vr = 3. Under these conditions, the corresponding value for betacyanins yield is 62.98±4.52%. For the first time, the ATPS was used to extract betacyanins from cactus fruit.•Escontria chiotilla, as a biological source, contained a high percent of betalains•Aqueous two-phase systems (ATPS) was statistically optimized•The developed method enriches the valorization of environmentally related plants waste materials.

Identification of Novel Low-Weight Sulfhydryl Conjugates of Oxidized 5-O- and 6-O-Substituted Betanidin Pigments

The formation of conjugates of oxidized betacyanin pigments with selected low-weight sulfhydryl scavengers was studied. Short-lived quinonoids, quinone methides, and aminochromes derived from oxidized betacyanins are able to form adducts with different efficiencies. In this report, mass spectrometric and NMR identifications of CS-linked conjugates of cysteine, cysteamine, N-acetylcysteine, and dl-dithiolthreitol with quinonoid forms generated through oxidation of betanidin, betanin, and gomphrenin is presented. An adduct that formed between cysteine and quinonoid generated from betanin by its oxidation and decarboxylation (2-decarboxy-xanbetanin) was detected and reported for the first time. The most stable gomphrenin CS-conjugate, N-acetylcysteinylated gomphrenin, was isolated by semipreparative chromatography and its structure was established by NMR analysis. This enabled to confirm the conjugation position at carbon C-4 and to indicate the presence of a dopachromic intermediate during oxidation of gomphrenin. Conjugation of betacyanins with thiol-bearing moieties may generate new molecules with modified chemical and biological properties. Obtained results confirm that gomphrenin is capable of forming CS-conjugates with higher efficiency than betanin.

The applicability of high-speed counter current chromatography to the separation of natural antioxidants

Antioxidants play an essential role in human health, as they have been found to be capable of lowering the incidence of many diseases, such as cancer and angiocardiopathy. Currently, more attention is paid to natural antioxidants because of the possible insecurity of synthetic antioxidants. Thus, the development of efficient techniques or methods to separate antioxidants from natural sources is requested urgently. High-speed counter current chromatography (HSCCC) is a unique support-free liquid-liquid chromatographic technique and has been widely applied in the field of separation of natural products. In this review, we summarize and analyze the related researches on the application of HSCCC in the separation of various natural antioxidants so far. The purpose of the article is to provide a certain theoretical support for the separation of natural antioxidants by HSCCC, and to make full use of advantages of HSCCC in the separation of bioactive components. In particular, some key problems associated with the separation strategies, the structural categories of natural antioxidants, solvent system choices, and the application of different elution modes in HSCCC separation, are summarized and commented. We expect that the content reviewed can offer more evidence for the development of the field of natural antioxidants separation, so as to achieve large-scale preparation of natural antioxidants.

Ultrasound and Microwave Assisted Extraction of Opuntia Fruit Peels Biocompounds: Optimization and Comparison Using RSM-CCD

Ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE) of bioactive compounds, peels from Opuntia engelmannii cultivar (cv.) Valencia were optimized by response surface methodology. Randomized extraction runs were performed for each of the technologies employed in order to build effective models with maximum (bioactive molecules content and yield) and minimum (antioxidant activity) responses. A 5-level, 4-factor central composite design was used to obtain target responses as a function of extraction time (t), solid to liquid ratio (S/L), methanol concentration (metOH), and temperature (T). Specific response optimization for each technology was analyzed, discussed, and general optimization from all the responses together was also gather. The optimum values for each factor were: t = 2.5 and 1.4 min, S/L = 5 and 5 g/L, metOH = 34.6 and 0% of methanol and T = 30 and 36.6 °C, achieving maximum responses of 201.6 and 132.9 mg of betalains/g, 13.9 and 8.0 mg of phenolic acids/g, 2.4 and 1.5 mg of flavonoids/g, 71.8% and 79.1% of extractable solid and IC₅₀ values for the antioxidant activity of 2.9 and 3.6, for UAE and MAE, respectively. The present study suggested UAE as the best extraction system, in order to maximize recovery of bioactive compounds with a high antioxidant activity.

Conjugation of Oxidized Betanidin and Gomphrenin Pigments from Basella alba L. Fruits with Glutathione

Formation of glutathionic conjugates with quinonoid forms generated through oxidation of betanidin and gomphrenin obtained from fruits of Basella alba L. was studied by high-performance liquid chromatography coupled with triple quadrupole tandem mass spectrometry (HPLC-DAD-ESI-MS/MS) and ion-trap time-of-flight high-resolution mass spectrometry (LCMS-IT-TOF). The conjugates were studied for the aim of trapping the formed quinonoids by glutathione which would indicate a presence of specific quinonoid structures in reaction products of the pigments with 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) cation radicals. The structure of betanidin conjugate, which was formed with high efficiency, was established by NMR analysis. In the case of gomphrenin conjugate, its structure was tentatively indicated as analogous to betanidin conjugate by MS ⁿ fragmentation paths. In contrast, no detectable glutathionic conjugate of betanin quinonoid (quinone methide) was present in similar betanin reaction mixtures. As a result of additional experiments performed during oxidation of gomphrenin by ABTS cation radicals in the absence of glutathione, except for decarboxylated and dehydrogenated gomphrenin derivatives, generation of betanidin and its derivatives was observed which indicated that the subsequent dopachromic intermediate rearrangement affected hydrolysis of the glucosidic bond. This is in contrast to betanin which is not deglucosylated in the same conditions during the oxidation. The obtained results shed some light on the oxidation pathways of various glycosylated betacyanins with gomphrenin being presumably the most potent antioxidant ascertained in this group of pigments.

Isolation of high-purity peptide Val-Val-Tyr-Pro from Globin Peptide using MCI gel column combined with high-speed counter-current chromatography

Peptides have gained increased interest over the past several decades because of their therapeutics. In this research, a strategy combining MCI gel column chromatography and high-speed countercurrent chromatography was developed for the separation of high-purity peptide Val-Val-Tyr-Pro from Globin Peptide. First, the fraction of Val-Val-Tyr-Pro mixtures with a purity of 15.8% was obtained by using MCI gel column with a mixture of ethanol/water (20:80, v/v/v). Then, the high-purity Val-Val-Tyr-Pro was separated by high-speed countercurrent chromatography with a aqueous two phase systems of ethanol/acetonitrile/iso-propyl alcohol/(NH₄ )₂ SO_{4 Saturated solution} /H₂ O (0.5:0.5:0.25:1.5:0.7,v/v). The ammonium sulfate from high-speed countercurrent chromatography fractions was removed from target compound by MCI gel column chromatography using ethanol/water in stepwise elution mode. A 78 mg of Val-Val-Tyr-Pro was successfully purified with the purities of 98.80% from 30 g crude Globin Peptide. The amino acid sequence of the Val-Val-Tyr-Pro was determined by electrospray ionization high resolution tandem mass spectrometry. The method presents a practical strategy for the large-scale separation of pure peptide Val-Val-Tyr-Pro from Globin Peptide, and provides a reference method for obtaining high-purity peptide from other polypeptide mixtures.

Application of HPCCC Combined with Polymeric Resins and HPLC for the Separation of Cyclic Lipopeptides Muscotoxins A⁻C and Their Antimicrobial Activity

Muscotoxins are cyanobacterial cyclic lipopeptides with potential applications in biomedicine and biotechnology. In this study, Desmonostoc muscorum CCALA125 strain extracts were enriched by polymeric resin treatment, and subjected to HPCCC affording three cyclic lipopeptides (1–3), which were further repurified by semi-preparative HPLC, affording 1, 2, and 3, with a purity of 86%, 92%, and 90%, respectively. The chemical identities of 2–3 were determined as muscotoxins A and B, respectively, by comparison with previously reported ESI-HRMS/MS data, whereas 1 was determined as a novel muscotoxin variant (muscotoxin C) using NMR and ESI-HRMS/MS data. Owing to the high yield (50 mg), compound 2 was broadly screened for its antimicrobial potential exhibiting a strong antifungal activity against Alternaria alternata, Monographella cucumerina, and Aspergillus fumigatus, with minimum inhibitory concentration (MIC) values of 0.58, 2.34, and 2.34 µg/mL; respectively, and weak antibacterial activity against Bacillus subtilis with a MIC value of 37.5 µg/mL. Compounds 1 and 3 were tested only against the plant pathogenic fungus Sclerotinia sclerotiorum due to their low yield, displaying a moderate antifungal activity. The developed chromatographic method proved to be an efficient tool for obtaining muscotoxins with potent antifungal properties.

An overview of recent progress in solvent systems, additives and modifiers of counter current chromatography

Solvent systems are critical to counter current chromatography (CCC). Appropriate additives and modifiers can be used to improve the separation efficiency of CCC.

Thermal Degradation of Major Gomphrenin Pigments in the Fruit Juice of Basella alba L. (Malabar Spinach)

Generation of decarboxylated and dehydrogenated gomphrenins during heating of Basella alba L. fruit juice containing high levels of betacyanin pigments was monitored by LC-DAD-ESI-MS/MS. The presence of principal decarboxylation products, 2-, 17-, and 2,17-decarboxy-gomphrenins, their diastereomers, as well as minor levels of their dehydrogenated derivatives are reported. In addition, determination of molecular masses of decarboxylated gomphrenins by high-resolution mass spectrometry (LCMS-IT-TOF) was performed. Enzymatic deglucosylation of decarboxylated and dehydrogenated gomphrenins resulted in the generation of betanidin diagnostic derivatives for further identification processes. In addition, experiments were conducted to prove that the position of glucosylation of the chromophoric part of betacyanins (betanidin part) has decisive influence on different chromatographic properties of their decarboxylated derivatives.

Centrifugal partition chromatography in a biorefinery context: Separation of monosaccharides from hydrolysed sugar beet pulp

A critical step in the bioprocessing of sustainable biomass feedstocks, such as sugar beet pulp (SBP), is the isolation of the component sugars from the hydrolysed polysaccharides. This facilitates their subsequent conversion into higher value chemicals and pharmaceutical intermediates. Separation methodologies such as centrifugal partition chromatography (CPC) offer an alternative to traditional resin-based chromatographic techniques for multicomponent sugar separations. Highly polar two-phase systems containing ethanol and aqueous ammonium sulphate are examined here for the separation of monosaccharides present in hydrolysed SBP pectin: l-rhamnose, l-arabinose, d-galactose and d-galacturonic acid. Dimethyl sulfoxide (DMSO) was selected as an effective phase system modifier improving monosaccharide separation. The best phase system identified was ethanol:DMSO:aqueous ammonium sulphate (300gL(-1)) (0.8:0.1:1.8, v:v:v) which enabled separation of the SBP monosaccharides by CPC (200mL column) in ascending mode (upper phase as mobile phase) with a mobile phase flow rate of 8mLmin(-1). A mixture containing all four monosaccharides (1.08g total sugars) in the proportions found in hydrolysed SBP was separated into three main fractions; a pure l-rhamnose fraction (>90%), a mixed l-arabinose/d-galactose fraction and a pure d-galacturonic acid fraction (>90%). The separation took less than 2h demonstrating that CPC is a promising technique for the separation of these sugars with potential for application within an integrated, whole crop biorefinery.

Separation of phenolic acids and flavonoids from Trollius chinensis Bunge by high speed counter-current chromatography

In this work, eleven compounds were successfully separated from Trollius chinensis Bunge by using a two-step high-speed counter-current chromatography (HSCCC) method. NRTL-SAC (nonrandom two-liquid segment activity coefficient) method, a newly developed solvent system selection strategy, was applied to screening the suitable biphasic liquid systems. Hexane/ethyl acetate/ethanol/water (3:7:3:7, v/v) solvent system was used in the first step, while the hexane/ethyl acetate/methanol/water (1:2:1:2, 1:4:1:4, 1:9:1:9, v/v) systems were employed in the second step. The chemical structures of the separated compounds were identified by UV, high resolution ESI-MS and MS/MS data. The separated compounds are 3,4-dihydroxyphenylethanol (1), vanillic acid (2), orientin (3), vitexin (4), veratric acid (5), 2″-O-(3‴, 4‴-dimethoxybenzoyl) orientin (6), 2″-O-feruloylorientin (7), 2″-O-feruloylvitexin (8), 2″-O-(2‴-methylbutyryl) vitexin (9), 2″-O-(2‴-methylbutyryl) isoswertiajaponin (10), 2″-O-(2‴-methylbutyryl) isoswertisin (11). The results demonstrate that HSCCC is a powerful tool for the separation of compounds from extremely complex samples.

Two-step separation of nostotrebin 6 from cultivated soil cyanobacterium (Nostoc sp.) by high performance countercurrent chromatography

High performance countercurrent chromatography (HPCCC) was successfully applied for the separation of nostotrebin 6 from cultivated soil cyanobacteria in a two-step operation. A two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water (4:5:4:5, v/v/v/v) was employed for the HPCCC separation. In the first-step operation, its neutral upper phase was used as stationary phase and its basic lower phase (1% NH3 in lower phase) was employed as mobile phase at a flow rate of 1 mL/min. In the second operation step, its neutral upper phase was used as stationary phase, whereas both its neutral lower phase and basic lower phase were employed as mobile phase with a linear gradient elution at a flow rate of 0.8 mL/min. The revolution speed and temperature of the separation column were 1,000 rpm and 30 °C, respectively. Using HPCCC followed by clean-up on Sephadex LH-20 gel, 4 mg of nostotrebin 6 with a purity of 99% as determined by HPLC/DAD-ESI-HRMS was obtained from 100 mg of crude extract. The chemical identity of the isolated compound was confirmed by comparing its spectroscopic data (UV, ESI-HRMS, ESI-HRMS2) with those of an authentic standard and data available in the literature.