Influence of trans-cis isomerisation of coumaric acid substituents on colour variance and stabilisation in anthocyanins

Characterization and Quantification of the Major Bioactive Compounds in Mexican Purple Tomatoes

The present work carries out a quantitative analysis of the major bioactive compounds found in the native Mexican purple tomatoes. Total phenolic content ranged from 7.54 to 57.79 mg TPC/g DM, total flavonoid content ranged from 1.89 to 16.93 mg TFC/g DM, total anthocyanin content ranged from 0.29 to 2.56 mg TAC/g DM, and total carotenoid content ranged from 0.11 to 0.75 mg TCC/ g DM. In addition, 14 phenolic acids were identified, among which caffeoylquinic acid derivatives were the most abundant compounds with chlorogenic acid concentration up to 9.680 mg/g DM, together with flavonoids, such as rutin and quercetin-hexoxide. The qualitative analysis also showed the presence of 9 acylated anthocyanins and 2 carotenoids with significant functional features. As for anthocyanins, their chemical structures disclosed special structural features: glycosylated anthocyanins exhibited cis-trans hydroxycinnamic moieties and petunidin-3-(trans-p-coumaroyl)-rutinoside-5-glucoside was reported to be the main anthocyanin, whitin the range of concentrations between 0.160 and 1.143 mg/g DM.

Inhibitory effects of the anthocyanins from Lycium ruthenicum Murray on angiotensin-I-converting enzyme: in vitro and molecular docking studies

BACKGROUND

Lycium ruthenicum Murray (LRM), a perennial shrub plant belonging to the Solanaceae family, is rich in anthocyanins, which have anti-inflammatory, antioxidant, lipid-lowering, intestinal flora regulating, and other pharmacological qualities. This study was primarily aimed to investigate the inhibitory effect of different anthocyanin purities from LRM on angiotensin-I-converting enzyme (ACE) activity in vitro. Moreover, the inhibitory mechanism was further analyzed by molecular docking technology.

RESULTS

Two main anthocyanin isomers were identified by ultra-performance liquid chromatography-tandem mass spectrometry and proton/carbon-13 nuclear magnetic resonance, namely petunidin-3-O-[rhamnopyranosyl-(trans-p-coumaroyl)]-5-O-(β-d-glucopyranoside) (trans-Pt3R5G) and petunidin-3-O-[rhamnopyranosyl-(cis-p-coumaroyl)]-5-O-(β-d-glucopyranoside) (cis-Pt3R5G), with a molar ratio of 9:1. Three purification grades of Pt3R5G all showed excellent inhibitory effects on ACE, with the half maximal inhibitory concentration (IC50 ) values being 0.562, 0.421, and 0.106 mg·mL-1 . Increasing the purity may reduce the IC50 within a certain concentration range. An enzymatic kinetic experiment showed that the inhibitory effect of Pt3R5G on ACE was reversible and non-competitive: Pt3R5G and substrate were not in competition for the active sites of ACE. Molecular docking technology further revealed the possible mechanism was that Pt3R5G and ACE amino acid residues were interacting by hydrogen bonds to exert the inhibitory effect.

CONCLUSION

The results indicated that Pt3R5G from LRM was highly effective at inhibiting ACE activity in vitro, with the hydrogen bonds of Pt3R5G and ACE amino acid residues exerting the inhibition. As a potential plant-based ACE inhibitor, Pt3R5G can be used as a functional ingredient for antihypertensive effects. © 2023 Society of Chemical Industry.

Characterization, antioxidant, and neuroprotective effects of anthocyanins from Nitraria tangutorum Bobr. fruit

An anthocyanin-rich extract was obtained from Nitraria tangutorum Bobr. fruit, namely ANF, and its composition, antioxidant and neuroprotective effects were studied. Nine anthocyanins were identified from the ANF using UPLC-Triple-TOF/MS analysis, and cyanidin-3-[2''-(6'''-coumaroyl)-glucosyl]-glucoside (C3G) is the most abundant anthocyanin (87.06%). ANF exhibited high ferric reducing antioxidant power (FRAP) and ABTS radical scavenging activity. The online HPLC-DPPH screening revealed that C3G contributed the highest antioxidant capacity. ANF showed potential neuroprotective effects by relieving d-Galactose-induced memory deficits, reducing overexpression of receptor for advanced glycation end products (RAGE) and amyloid-beta42 (Aβ42) in the hippocampus of rats. Besides, ANF could inhibit oxidative stress by reducing the levels of reactive oxygen species (ROS) and malondialdehyde (MDA) in the hippocampus, while elevating amounts of total superoxide dismutase (T-SOD) and glutathione (GSH) in the serum of rats. Thus, ANF has great potential in the development of food and health products related to antioxidant and neuroprotective effects.

Rapid analysis of anthocyanin and its structural modifications in fresh tomato fruit

Anthocyanin is derived from a flavylium cation structure, and it promotes health in humans and functions in plants as protection against environmental stress. The rapid analysis of anthocyanin structure and content is a critical challenge for improving fruit quality. In this study, the tomato cultivar Indigo Rose, which is a popular purple cultivated tomato used for breeding, was taken as an example for anthocyanin analysis. A rapid analysis method was developed to minimize anthocyanin loss from the fresh fruit. Four new anthocyanins were discovered in the tomato, and the structures of a total of 12 anthocyanins were determined. Among these, petunidin-3-(trans-p-coumaroyl)-rutinoside-5-glucoside and malvidin-3-(trans-p-coumaroyl)-rutinoside-5-glucoside were the main anthocyanins in Indigo Rose. The structural modifications of these anthocyanins were mainly glycosylation and acylation, and there were also hydroxylation and methylation. Our findings provide new insight into the biosynthesis pathway in tomato fruit.

Black goji as a potential source of natural color in a wide pH range

Lycium ruthenicum Murr. is a traditional Chinese herb widely distributed in Tibet. The fruit, known as black goji, is popular in traditional Chinese medicine. The objective of this study was to investigate its anthocyanin profile (by HPLC coupled to PDA and MS detectors) and the colorimetric and spectrophotometric properties. Black goji extracts contained abundant petunidin derivatives, with cis and trans isomers of petunidin-3-p-coumaroyl-rutinoside-5-glucoside. The colorimetric and spectrophotometric traits of black goji anthocyanins were significantly impacted by solid-phase-extraction, pH, and acylation. MCX cartridge removed considerable polyphenolics from fruit extracts, but attenuated the saturation of color expression. Petunidin-3-trans-p-coumaroyl-rutinoside-5-glucoside contributed most of the color expression of the black goji extract, and showed superior stability compared to other extracts over time. Acylation strengthened the petunidin derivatives color retention, and enhanced the color intensity and stability. Black goji anthocyanins produced various vivid hues over wide ranges of pH, making them promising candidates for natural colorants.

Characterization of anthocyanins in the hybrid progenies derived from Iris dichotoma and I. domestica by HPLC-DAD-ESI/MS analysis

Iris dichotoma with different flower colors and I. domestica are beardless wild irises belonging to the family Iridaceae that bloom in the summer and have long flowering periods. In this study, we collected three accessions of I. dichotoma with violet, yellow, and white flowers, respectively, in China, and crossed them with I. domestica individuals. The flower color of the hybrids derived from these crosses was categorized into eight groups: violet, purple, brown, orange, red, pink, yellow, and white. From this population, 45 individuals were selected for analysis, and their fully expanded inner and outer perianths were harvested for extraction of anthocyanins. Using high-performance liquid chromatography-mass spectrometry (HPLC-MS) analysis, 29 anthocyanins were identified by comparing MS and UV-visible spectra and elution order based on published data and guidelines. The 29 anthocyanins were classified into six groups: non-acylated glycosides (3RG, 3RG5G), acetylglycosides (3acRG5G), p-coumaroylglycosides (3pCRG, 3pCRG5G), caffeoylglycosides (3CRG5G), feruloylglycosides (3feRG, 3feRG5G), and acetyl-(p-coumaroyl) glycosides (3ac-pCRG5G). Acylated anthocyanin contents were considerably higher than non-acylated anthocyanin contents in the individuals evaluated, regardless of flower color, except in the yellow-flowered I. dichotoma and its yellow-flowered progeny. We found ten anthocyanins derived from pelargonidin, including pelargonidin 3-O-(caffeoyl)rutinoside-5-O-glucoside (Pg3CRG5G), pelargonidin 3-O-(feruloyl)rutinoside-5-O-glucoside (Pg3feRG5G), and pelargonidin 3-O-(feruloyl)rutinoside (Pg3feRG), that have not yet been reported in other Iris species. Moreover, delphinidin 3-O-(feruloyl) rutinoside-5-O-glucoside (Dp3feRG5G), and delphinidin 3-O-(feruloyl)rutinoside (Dp3feRG) were also characterized for the first time in Iris. Two to five major anthocyanins were detected in the petals of the violet and purple groups, whereas those of the brown group contained three to six anthocyanins. Petals of the orange, red, and pink groups contained two to four major anthocyanins. The total variance explained by the first two principal components (PC) in a PC analysis of the intensities of the compound peaks detected in individuals representing the eight color groups was 44.7%. Individuals were classified into 10 types (A-I to A-X) according to their anthocyanidin composition in the flower petals. Knowledge of the types of anthocyanins determining flower petal color will aid comprehensive understanding of flower color characteristics in hybrid progeny and will contribute to the development of breeding Iris cultivars of diverse flower colors.

Cis-Trans Configuration of Coumaric Acid Acylation Affects the Spectral and Colorimetric Properties of Anthocyanins

The color expression of anthocyanins can be affected by a variety of environmental factors and structural characteristics. Anthocyanin acylation (type and number of acids) is known to be key, but the influence of acyl isomers (with unique stereochemistries) remains to be explored. The objective of this study was to investigate the effects of cis-trans configuration of the acylating group on the spectral and colorimetric properties of anthocyanins. Petunidin-3-rutinoside-5-glucoside (Pt-3-rut-5-glu) and Delphinidin-3-rutinoside-5-glucoside (Dp-3-rut-5-glu) and their cis and trans coumaroylated derivatives were isolated from black goji and eggplant, diluted in pH 1-9 buffers, and analyzed spectrophotometrically (380-700 nm) and colorimetrically (CIELAB) during 72 h of storage (25 °C, dark). The stereochemistry of the acylating group strongly impacted the spectra, color, and stability of the Dp and Pt anthocyanins. Cis acylated pigments exhibited the greatest λmax in all pH, as much as 66 nm greater than their trans counterparts, showing bluer hues. Cis acylation seemed to reduce hydration across pH, increasing color intensity, while trans acylation generally improved color retention over time. Dp-3-cis-p-cou-rut-5-glu exhibited blue hues even in pH 5 (C*ab = 10, hab = 256°) where anthocyanins are typically colorless. Cis or trans double bond configurations of the acylating group affected anthocyanin spectral and stability properties.

Molecular Structures of the Stem Tuber Anthocyanins of Colored Potatoes and Their Coloring Effects on the Tubers

This paper summarized the important achievements about the general characteristics of the molecular structures of the stem tuber anthocyanins of Colored potatoes and the basic coloring effects of the anthocyanins on the tubers. The various coloration patterns of the skins and/or flesh of Colored potato tubers result from the accumulation of the anthocyanins in the periderms, phelloderms and/or peripheral cortices of the tubers, and the tuber colors are fundamentally determined by the matching profiles of the six naturally occurring anthocyanidins, i.e., cyanidin, delphinidin, malvidin, pelargonidin, peonidin and petunidin. Generally, the tuber anthocyanidins hold an O-glycosidic bond-linked rutinosyl at the C3 site, and either a glucosyl linked by an O-glycosidic bond or no substituent group may exist at the C5 site simultaneously. Furthermore, an E-monoacyl frequently exists at the C3- rutinosyls or at the C5-glucosyls of most tuber anthocyanins, and the phenolic acids acylating the tuber anthocyanins are often p-coumaric, ferulic and caffeic acids. The popular names of the p-coumaric acid derivatives of the malvidin, pelargonidin, peonidin and petunidin of the tubers are Malvanin, Pelanin, Peonanin and Petanin, respectively. This review provides a reference for the exploration of the mechanism of the tuber coloration and the identification of the molecular structures of the stem tuber anthocyanins of Colored potatoes.

Identification and quantification of anthocyanins in Kyoho grape juice-making pomace, Cabernet Sauvignon grape winemaking pomace and their fresh skin

BACKGROUND

The anthocyanins of Kyoho grape juice-making pomace, Cabernet Sauvignon grape winemaking pomace and their fresh skin were identified and quantified by high-performance liquid chromatography-tandem mass spectrometry, and the influence of processing on the anthocyanin profiles was investigated.

RESULTS

Twenty-three and 16 anthocyanins were found in fresh skin of Kyoho and Cabernet Sauvignon grapes, respectively. Malvidin 3-(trans)-coumaroyl-5-diglucoside and malvidin 3-glucoside were the most abundant anthocyanin in fresh skin of Kyoho and Cabernet Sauvignon grapes, respectively. The cis and trans isomers of malvidin 3-coumaroyl-5-diglucoside are reported in Kyoho grape for the first time. In addition, the anthocyanin content of juice-making pomace of Kyoho grapes and winemaking pomace of Cabernet Sauvignon grapes was significantly lower than the fresh skin samples (p < 0.05). The percentage variation of non-acylated anthocyanins was lower than that of acylated anthocyanins in all pomace samples.

CONCLUSION

Kyoho grape and Cabernet Sauvignon grape showed distinctive anthocyanin profiles. Juice-making pomace is a better source of anthocyanins for use in functional foods than winemaking pomace.

Schizanthus grahamii and Schizanthus hookeri. Is there any relationship between their anthocyanin compositions and their different pollination syndromes?

Three different pollination syndromes (bee, hummingbird and moth-pollination syndromes) have been described for the different species of the genus Schizanthus Ruiz & Pav. (Solanaceae). Two closely related species from a phylogenetic point of view, Schizanthus grahamii and Schizanthus hookeri, show hummingbird and bee-pollination syndromes, respectively. One of the traits used to assign these pollination syndromes is the colour of the petals, which is red in S. grahamii and bluish-pink in S. hookeri. The objective of this work was to establish the differences in the anthocyanin composition of these two Schizanthus species that contribute to the different pollination syndrome. Identification of the pigments was carried out from the chromatographic and spectral data supplied by the HPLC-DAD-MS(n) analyses of the samples. Alkaline and acid hydrolyses were also performed in the extracts and in some isolated compounds in order to confirm the identities. First difference between these two species was found in the total anthocyanin content, which was about 13-fold higher in S. grahamii than in S. hookeri. Furthermore, the major peak was also different in both cases, thus explaining quantitative and qualitative colour differences between species. Delphinidin 3-O-rutinoside represented ca. 72% of the total area in S. grahamii and petanin (Petunidin 3-O-p-coumaroylrutinoside-5-O-glucoside) accounted for almost 62% of the total area in S. hookeri. The presence of the p-coumaroylrutinosyl moiety in the petanin makes the intramolecular copigmentation possible, thus conferring the bluish-pink hue to the petals of S. hookeri. Delphinidin 3-O-rutinoside is in turn responsible for the red colour exhibited by the petals of S. grahamii and along with other floral traits, responsible for the attraction of hummingbirds to the plant. Pigments structurally related to petanin, which have been often detected in other genus of Solanaceae, were detected in both species and in similar contents, supporting results from previous studies that pointed to a bee-pollinated common ancestor for both species that further specialised acquiring traits attractive to hummingbirds and among them, red colour of the petals which is mainly supplied by delphinidin 3-O-rutinoside.

Anthocyanins and their variation in red wines I. Monomeric anthocyanins and their color expression

Originating in the grapes, monomeric anthocyanins in young red wines contribute the majority of color and the supposed beneficial health effects related to their consumption, and as such they are recognized as one of the most important groups of phenolic metabolites in red wines. In recent years, our increasing knowledge of the chemical complexity of the monomeric anthocyanins, their stability, together with the phenomena such as self-association and copigmentation that can stabilize and enhance their color has helped to explain their color representation in red wine making and aging. A series of new enological practices were developed to improve the anthocyanin extraction, as well as their color expression and maintenance. This paper summarizes the most recent advances in the studies of the monomeric anthocyanins in red wines, emphasizing their origin, occurrence, color enhancing effects, their degradation and the effect of various enological practices on them.

Principal component regression analysis of the relation between CIELAB color and monomeric anthocyanins in young Cabernet Sauvignon wines

Color is one of the key characteristics used to evaluate the sensory quality of red wine, and anthocyanins are the main contributors to color. Monomeric anthocyanins and CIELAB color values were investigated by HPLC-MS and spectrophotometry during fermentation of Cabernet Sauvignon red wine, and principal component regression (PCR), a statistical tool, was used to establish a linkage between the detected anthocyanins and wine coloring. The results showed that 14 monomeric anthocyanins could be identified in wine samples, and all of these anthocyanins were negatively correlated with the L*, b* and H*ab values, but positively correlated with a* and C*ab values. On an equal concentration basis for each detected anthocyanin, cyanidin-3-O-glucoside (Cy3-glu) had the most influence on CIELAB color value, while malvidin 3-O-glucoside (Mv3-glu) had the least. The color values of various monomeric anthocyanins were influenced by their structures, substituents on the B-ring, acyl groups on the glucoside and the molecular steric structure. This work develops a statistical method for evaluating correlation between wine color and monomeric anthocyanins, and also provides a basis for elucidating the effect of intramolecular copigmentation on wine coloring.

Simultaneous separation by reversed-phase high-performance liquid chromatography and mass spectral identification of anthocyanins and flavonols in Shiraz grape skin

A limitation of large-scale viticultural trials is the time and cost of comprehensive compositional analysis of the fruit by high-performance liquid chromatography (HPLC). In addition, separate methods have generally been required to identify and quantify different classes of metabolites. To address these shortcomings a reversed-phase HPLC method was developed to simultaneously separate the anthocyanins and flavonols present in grape skins. The method employs a methanol and water gradient acidified with 10% formic acid with a run-time of 48 min including re-equilibration. Identity of anthocyanins and flavonols in Shiraz (Vitis vinifera L.) skin was confirmed by mass spectral analysis.

Antioxidant activity, polyphenol content, and related compounds in different fruit juices and homogenates prepared from 29 different pomegranate accessions

Pomegranate juice is well known for its health beneficial compounds, which can be attributed to its high level of antioxidant activity and total polyphenol content. Our objective was to study the relationships between antioxidant activity, total polyphenol content, total anthocyanins content, and the levels of four major hydrolyzable tannins in four different juices/homogenates prepared from different sections of the fruit. To this end, 29 different accessions were tested. The results showed that the antioxidant activity in aril juice correlated significantly to the total polyphenol and anthocyanin contents. However, the homogenates prepared from the whole fruit exhibited an approximately 20-fold higher antioxidant activity than the level found in the aril juice. Unlike the arils, the antioxidant level in the homogenates correlated significantly to the content of the four hydrolyzable tannins in which punicalagin is predominant, while no correlation was found to the level of anthocyanins.

Characterisation of betalain patterns of differently coloured inflorescences from Gomphrena globosa L. and Bougainvillea sp. by HPLC-DAD-ESI-MSn

In the present study, the betaxanthin (bx) and betacyanin patterns of differently coloured inflorescences from Gomphrena globosa L. and Bougainvillea sp. have been investigated in detail by applying reversed phase high-performance liquid chromatography-diode array detection (HPLC-DAD) coupled with positive ion electrospray mass spectrometry. Histidine-bx was found to be the predominant betaxanthin of Gomphrena globosa inflorescences. Furthermore, arginine-bx was detected as a novel betaxanthin, which to the best of our knowledge has not been reported as a pigment that occurs naturally so far. Dopa-bx was the major betaxanthin of Bougainvillea sp., although several minor betaxanthins were also present, including lysine-bx and putrescine-bx, novel betaxanthins hitherto not observed naturally. Remarkable differences in the betacyanin patterns between the purple, red and orange varieties were observed for both Gomphrena and Bougainvillea inflorescences. Hence, both the betacyanin profiles and the relative betaxanthin:betacyanin ratios determine the broad colour palette of Gomphrena petals and Bougainvillea bracts.

Influence of different phenolic copigments on the color of malvidin 3-glucoside

The effectiveness of seven phenolic compounds (catechin, epicatechin, procyanidin B2, caffeic acid, p-coumaric acid, myricitrin, and quercitrin) as copigments of malvidin 3-glucoside, the major anthocyanin in red wines from Vitis vinifera, using a copigment/pigment molar ratio of 1:1 was assayed in model wine solutions under the same conditions (pH=3.6, 12% ethanol). The stability of the copigment-pigment complexes formed was studied during a storage period of 60 days at 25 degrees C. Tristimulus colorimetry was applied for color characterization of the copigmentation process, and HPLC-DAD-MS was used to monitor changes in the composition of the samples. Copigmentation has been found to occur in all cases despite the low copigment/pigment molar ratio used, although the effect was different depending on the compound. Flavan-3-ols appeared as the less effective copigments, procyanidin B2 being even worse than monomeric flavanols, whereas flavonols behaved as the best ones. These latter copigments also induced the most statistically significant bathochromic shift in lambdamax. In the colorimetric analysis, it was observed that the lightness L* of the copigmented solutions increased with time, chroma C*ab decreased, and the hue hab increased. The copigments that produced a greater increase in the hue angle were the monomeric flavan-3-ols, which therefore showed to be the least protective cofactors against browning of the anthocyanin solution during the storage. With the time of storage, the formation of new pigments was observed in the solutions containing flavanols (xanthylium structures) and hydroxycinnamic acids (pyranoanthocyanins), which explains some of the color modifications produced in these solutions. Another relevant observation was that the stability of the anthocyanin was not much improved by most of the assayed copigments, since quite similar degradation rates were observed in the presence and absence of those cofactors.

Electronic and infrared vibrational analysis of cyanidin-quercetin copigment complex

Copigment complex formation between cyanidin and quercetin, in aqueous buffered solutions, was studied by electronic absorption and infrared vibrational spectroscopies. It was found that the association of cyanidin with quercetin occurred at pH 3.0 and pH 5.0 including cyanidin flavylium ion and anhydrobase transformation forms, respectively. Obtained copigmentation constant values of K=2726.7 (pH 3.0) and K=1093.1 (pH 5.0) indicated good association ability of the investigated molecules. Infrared spectra revealed the existence of hydrogen bonds in the copigment complexes structures. The analysis of the deconvoluted infrared spectra indicated several types of hydrogen bonds, differently formed: the H--O...H bonds with the corresponding bands around 3500 cm(-1) and bonds formed via H(3)O(+), oxonium, ion of the molecules with the corresponding bands below 3000 cm(-1).

The copigmentation effect of sinapic acid on malvin: a spectroscopic investigation on colour enhancement

The present paper reports on spectroscopic investigation of copigmentation effect of sinapic acid on the malvin molecule. A reaction of copigmentation was investigated by the use of UV-Vis absorption spectra in the whole range of acidic and moderately acidic buffered aqueous solutions (pH range 1.0-6.0). It was observed that the ratio (A-A0)/A0, as a good measure of the copigment effect, has its maximum value at pH 3.6. The influences of the pH of the medium, molecular concentration, and temperature were investigated. The reaction was thermodynamically defined in terms of deltaH0, deltaG0 and deltaS0 values.

Why are grape/fresh wine anthocyanins so simple and why is it that red wine color lasts so long?

Vitis vinifera red berries are characterized by anthocyanins whose chemical structures are among the simplest encountered in higher plants. On the contrary, many plants, including orchids, petunias, red cabbage, elderberries, potatoes for instance, have developed very complicated anthocyanins featuring side-chains at the available positions of the aglycone skeleton. Such pigments were shown to possess bio-physico-chemical properties not to be seen with the grape common anthocyanins. Among beverages (water, tea, beer, wine, coffee, juices, milk), red wine is the only one whose organoleptic properties improve with time and this is called ageing. The grape/fresh red wine pigments, after a few months, disappear from the wine giving birth to new pigments resulting from the wine spontaneous chemistry allowing it to remain red for many years. What are the wine pigments and why are they so stable is the purpose of this mini-review. The structural simplicity of grape anthocyanins and the long lasting colour of red wine is another French paradox; we call it French paradox II.