Copigmentation Effect Research Articles

Color and stability of anthocyanins in strawberry nectars containing various co-pigment sources and sweeteners

Effects of various co-pigment sources [gallic acid (GA) and the extracts of rose leaf (RLE), cherry stem (CSE), pomegranate rind (PRE) and sour cherry stem (SCSE)] on anthocyanins and colour in strawberry nectars (SNs), sweetened with sucrose (SNS), maltose syrup (SNM) and honey (SNH), were investigated during storage at 20 °C. Honey elicited the highest stabilities of anthocyanins, hyperchromic and bathochromic effects in SNs containing all co-pigment sources, except for PRE. PRE co-pigments were composed of mainly tannins which could interact with SNs proteins and honey proline. As a result of these interactions, PRE co-pigments could not show significant contribution to protection of SN anthocyanins and colour. Among co-pigment sources, SCSE caused the highest stabilities of anthocyanins, hyperchromic effect and colour density, regardless of sweetener used. Interactions between SCSE phenolic acids, and pelargonidin-3-glucoside and pelargonidin-3-rutinoside resulted in the most stable co-pigmentation effect. Thus, SCSE should be preferred in beverages containing pelargonidin-based anthocyanins.

Combined use of hydrocolloids in pomegranate juice and their effects on clarification and copigmentation

SummaryPomegranate juices (PJs) were clarified using hydrocolloids [albumin (A), casein (C), chitosan (CH) and xanthan gum (XG)] and in combination with each other. The lowest turbidity was observed in PJs clarified with ‘CH+XG’ and ‘A+C+CH’. Unlike ‘CH+XG’, effects of albumin and its combinations on clarity were mainly related with the contents of ellagic acid (r = −0.861), α‐punicalagin (r = −0.761), rutin (r = −0.734), β‐punicalagin (r = −0.730) and total punicalagin (r = −0.713). ‘CH+XG’ caused the highest phenolic (602 mg L−1) and anthocyanin (449 mg L−1) contents, and the second highest Amax (0.811 ABS), resulting from copigmentation of delphinidin‐3‐glucoside and delphinidin‐3,5‐diglucoside with CH. Since A showed moderate copigmentation effect, A had lower hyperchromic effect than CH. Moreover, C reduced Amax, anthocyanin content and colour density when combined with other hydrocolloids. As a result, ‘CH+XG’ would be the best combination to obtain high clarity, maintain phenolics and anthocyanins and provide high copigmentation effect in PJ.

Effect of Caffeine Copigmentation of Anthocyanin Dyes on DSSC Efficiency.

Caffeine is known to influence the absorbance spectrum of anthocyanin dyes. Such dyes are often used as sensitizers in dye-sensitized solar cells (DSSCs). Natural dyes, like anthocyanins, yield only small DSSC efficiencies, but are of high interest since they are usually non-toxic and inexpensive. Here we report on the influence of copigmentation of anthocyanins, taken from commercially available tea, with caffeine. In this way, the efficiencies were increased for measurements with a solar simulator as well as with ambient light. In addition, the well-known pH dependence of the efficiency of DSSCs dyed with anthocyanins was shifted—while a pH value of 1–2 was ideal for pure anthocyanins used as dyes, a higher pH value of 2–3 was sufficient to reach the maximum efficiencies for caffeine-copigmented dyes. This means that instead of reducing the pH value by adding an acid, adding caffeine can also be used to increase the efficiency of DSSCs prepared with anthocyanins. Finally, a comparison of several literature sources dealing with anthocyanin-based DSSCs allows for evaluation of our results with respect to the work of other groups.

Potential of Cooperage Byproducts Rich in Ellagitannins to Improve the Antioxidant Activity and Color Expression of Red Wine Anthocyanins.

Cooperage byproducts are an important source of phenolic compounds that could be used for wine technology applications. The effects of the addition of two types of oak wood shavings (American, AOW, and Ukrainian, UOW) on the antioxidant activity and color of red wine anthocyanins, in a wine model solution, were evaluated by spectrophotometric and colorimetric analyses. Phenolic compounds from shavings, mainly ellagitannins, were determined by ultra-high-performance liquid chromatography/mass spectrometry (UHPLC/MS). Antioxidant and copigmentation effects varied depending on the type of shavings (AOW and UOW) and the phenolic concentration (100, 400, and 500 mg/L). Phenolic compounds from shavings improved the color characteristics (darker and more bluish color) and the copigmentation effect of red wine anthocyanins, being UOW a better source of copigments than AOW shavings. The best antioxidant activity was found for the 400 and 500 mg/L model solutions for both types of shavings. Results show a winemaking technological application based on the repurposing of cooperage byproducts, which could improve color and antioxidant characteristics of red wines.

Copigmentation potential of overripe seeds from sun‐dried white grapes on anthocyanins colour and stability by differential colorimetry

SummaryOverripe seeds are wine by‐products from grapes submitted to postharvest sun drying, which induce phenolic biosynthesis and polymerisation. Overripe seeds from Pedro Ximénez (PX) and Moscatel (MO) sun‐dried grapes were compared as copigments sources to modulate grape anthocyanin (GA) colour and stability in simulated wine conditions. RRLC/MS analysis proved that overripe seeds contain specific phenolic mixtures capable of inducing positive quantitative and qualitative colour changes in GAs, evidenced by differential colorimetry. Copigmentation effects significantly varied depending on the overripe seed variety, related to their qualitative phenolic composition and content. MO extracts richer in gallic acid, catechin and procyanidin B1 led to the stronger colour intensification and perceptible qualitative changes. PX extracts richer in epicatechin, procyanidins B2, B2‐GAL and B7 behaved as weak copigments. Overripe seed copigments preserved better GAs colour stability during storage leading to the formation of new anthocyanin‐derived pigments, being the stabilising effect stronger with those of MO variety.

Stabilization of Black Rice (Oryza Sativa, L. Indica) Anthocyanins Using Plant Extracts for Copigmentation and Maltodextrin for Encapsulation.

Black rice (Oryza sativa L. indica) is one of the cereal commodities considered to be a source of anthocyanin. One of the obstacles of using anthocyanins as natural food colorants is their low stability. The objective of this study was to determine the effect of natural plants extracts on anthocyanin copigmentation and to study the stability of the encapsulated copigmented anthocyanin during storage under different temperatures and light exposure. Dried bilimbi leaves (BL) and sow thistle leaves (STL) were extracted using ethanol to obtain the crude flavonoid extract that was subsequently purified using solid phase extraction. Both crude (CBL, CSTL) and purified (PBL, PSTL) extract were used as copigment agents with the molar ratio of 1:0.1 to 1:10 at pH 1 and pH 3. The copigmentation effect was evaluated by measuring the wavelength and absorbance shifts at wavelengths of 500 to 600 nm. The stability of the dried anthocyanin powder was evaluated under different temperatures and light exposure for up to 4 weeks. Anthocyanin was successfully copigmented with BL and STL extracts showing a wavelength shift and absorbance increase at pH 1 and pH 3. Purification of BL enhanced the hyperchromic effect more than that of the crude form, in contrast to the STL. Meanwhile, the retention of absorbance (%) for encapsulated copigmented anthocyanin samples was within 74% to 83% at the end of the storage period. PRACTICAL APPLICATION: Natural food pigment such as anthocyanin obtained from plant extract usually shows very limited stability under various processing conditions. This study shows that color stability of anthocyanin extracted from black rice can be improved by copigmentation with flavonoids extracted from particular plants. Encapsulation of the copigmented anthocyanin could further enhance its color stability. The availability of encapsulated and copigmented anthocyanins with improved color stability is expected to provide more alternatives for especially the beverage industry to choose suitable natural colorant for their products.

Anthocyanin copigmentation and color attributes of bog bilberry syrup wine during bottle aging: Effect of tannic acid and gallic acid extracted from Chinese gallnut

Tannic and gallic acids, extracted from Chinese gallnut, were applied as copigments to bog bilberry syrup wine with two different mass ratios of 1:2.5 and 1:6 of anthocyanin to copigment. The effect of copigmentation on anthocyanins and the changes in non-anthocyanin compounds and color characters during 6 months of aging were studied. Addition of copigment significantly helped to retain redness while reduced increase in the yellow shade and lightness. After 6 months of aging, the syrup wines with added copigments had 1.4–1.8 times higher total anthocyanin content compared to the control. The percentage of polymeric anthocyanins in copigment treated wines was lower than in control wine. Oppositely, the copigment treated wines possessed a higher percentage of copigmented anthocyanins than the control. The highest value of redness, the lowest percentage of polymeric anthocyanins and the highest percent of copigmented anthocyanins were presented in the wines treated with a high dosage of gallic acid. Practical applications Bottle aging shows a negative effect on the appearance of bog bilberry syrup wine. Copigmentation between anthocyanins and copigments is an alternative approach to prevent the loss of color during aging. However, the high expense of pure copigments limits the application of this protocol in wine industry. The cheaper copigments of tannic acid and gallic acid, extracted from Chinese gallnut, were used in the present study and presented positive effects on remaining red hub of bog bilberry fermented products through the enhancement of anthocyanin copigmentation. The current study provides new insights on exploiting somewhat poorly utilized bog bilberry byproduct in wine industry. The findings also verify the practicable of the economical copigments of Chinese gallnut extracted tannic and gallic acids in bog bilberry fermented products. On the other hand, observations made with bog bilberry in this study may be exploited with other berry materials, as well.

Copigmentation of cyanidin 3-O-glucoside with phenolics: Thermodynamic data and thermal stability

The intermolecular copigmentation of cyanidin-3-O-glucoside (C3G) with three colorless phenolic compounds and its thermal stability were investigated. The influence of the copigment (ferulic acid, dopamine, or (+)-catechin), the pigment-to-copigment molar ratio (1 : 1, 1 : 10, and 1 : 100), the pH value (pH 3–7), and the temperature (20, 30, 40, and 50 °C) on the copigmentation effect, stoichiometric ratio (n), the equilibrium constant (K), and thermodynamic parameters (ΔG°, ΔH°, and ΔS°) were obtained. The strongest immediate copigmentation reactions were observed at pH 3 and 1 : 100 molar ratio, being significantly higher with (+)-catechin, followed by ferulic acid and then dopamine. The greatest hyperchromic shift was found in the complex of C3G/(+)-catechin, which was reasonable for its n and K values of 0.7 and 17.1, respectively. Moreover, the reactions were favored at low temperature. The thermodynamic data indicated that all these complexes were formed by spontaneous exothermic reactions. The C3G/(+)-catechin complex at the molar ratio 1 : 100 exhibited the greatest thermodynamic properties, with negative values of ΔG° (−6.92 kJ/mol), ΔH° (−38.7 kJ/mol), and ΔS° (−108.0 J/K/mol). The C3G/(+)-catechin complex exhibited a low Ea value (78 J/mol), indicating greater thermal stability against temperature change compared with those with the other phenolic pigments. In addition, copigmentation of anthocyanins in mulberry juice with (+)-catechin significantly reduced the loss of anthocyanins during pasteurization (80 °C for 15 min).

Identification and Functional Analysis of a Flavonol Synthase Gene from Grape Hyacinth.

Flavonols are important copigments that affect flower petal coloration. Flavonol synthase (FLS) catalyzes the conversion of dihydroflavonols to flavonols. In this study, we identified a FLS gene, MaFLS, expressed in petals of the ornamental monocot Muscari aucheri (grape hyacinth) and analyzed its spatial and temporal expression patterns. qRT-PCR analysis showed that MaFLS was predominantly expressed in the early stages of flower development. We next analyzed the in planta functions of MaFLS. Heterologous expression of MaFLS in Nicotiana tabacum (tobacco) resulted in a reduction in pigmentation in the petals, substantially inhibiting the expression of endogenous tobacco genes involved in anthocyanin biosynthesis (i.e., NtDFR, NtANS, and NtAN2) and upregulating the expression of NtFLS. The total anthocyanin content in the petals of the transformed tobacco plants was dramatically reduced, whereas the total flavonol content was increased. Our study suggests that MaFLS plays a key role in flavonol biosynthesis and flower coloration in grape hyacinth. Moreover, MaFLS may represent a new potential gene for molecular breeding of flower color modification and provide a basis for analyzing the effects of copigmentation on flower coloration in grape hyacinth.

New insight about the functionality of oenological tannins; Main results of the working group on oenological tannins

This communication synthetize all the results obtained by the OIV working group on oenological tannins to the current date. The obtained results confirm that oenological tannins really exert a protection effect against grape juice and wine oxidation because they have antioxidant activity, they consume directly oxygen and they exert an inhibitory effect on the laccase activity. Moreover, oenological tannins also exert a copigmentation effect which can improve and protect de color of red wines.

Effects of sucrose and copigment sources on the major anthocyanins isolated from sour cherries

Cyanidin-3-O-glucosylrutinoside and cyanidin-3-O-rutinoside were isolated from sour cherry juice concentrate (SCJC). Sucrose and copigments [gallic acid (GA), cherry stem extract (CSE) and pomegranate rind extract (PRE)] were added to these anthocyanins. Effects of sucrose and copigments on the isolated anthocyanins were studied during storage at 20 °C for 140 days. All copigment sources provided protection against degradation effect of sucrose on the isolated anthocyanins before storage. Although GA increased the stabilities of both isolated anthocyanins, only CSE had copigmentation effect on both isolated anthocyanins. Copigmentation effect on cyanidin-3-O-glucosylrutinoside continued throughout storage. However, this effect on cyanidin-3-O-rutinoside continued for only 56 days of storage. Cyanidin-3-O-glucosylrutinoside containing three sugar moieties was more prone to copigmentation than cyanidine-3-rutinoside containing two sugar moieties. Results showed that the presence of more than one anthocyanin in a media changed stability of copigmentation. We recommend CSE for enhancement in colour density, but GA for enhancement in anthocyanin stability.

Co-pigmentation of black chokeberry (Aronia melanocarpa) anthocyanins with phenolic co-pigments and herbal extracts

The co-pigmentation of black chokeberry (Aronia melanocarpa) anthocyanins with ten phenolic co-pigments was studied. Tested compounds provoked different co-pigmentation effect, manifested by hyperchromic and batochromic shifts. The co-pigmentation was accompanied by a magnification of color intensity and decrease of color hue, both related to a more pleasant color. The hyperchromic effect was the most significant for rosmarinic acid (51.02%), syringic acid (43.24%) and catechin (39.73%). However, it was observed at the highest pigment/co-pigment ratio (1:50), not achievable in plant matter. Targeting the potential practical application of co-pigmentation, we tested eight herbal extracts for their co-pigmentation ability with aronia anthocyanins. The use of herbal extracts led to a significant hyperchromic effect at much lower pigment/co-pigment ratios, compared to pure compounds. The use of selected herbal extracts as co-pigments opens realistic prospects for development of aronia functional foods with improved sensory properties and biological effects, due to enhanced color and anthocyanin stability.

Study of the Interaction of Anthocyanins with Phenolic Aldehydes in a Model Wine Solution.

Aldehydes may be present in wines as a result of metabolic processes during wine fermentation or through oxidation and extraction from wood during wine aging in oak barrels. Apart from acetaldehyde, the most abundant aldehyde in wine, other aldehydes such as furfural and more recently vanillin have shown to contribute to the formation of more stable pigments. The copigmentation effect of phenolic molecules, including flavanols and anthocyanins themselves, has been previously evaluated in wine and model solutions, and even the effect of aldehydes related to wine aging has been documented at different pHs and molar ratios. The copigmentation phenomenon is observed by hyperchromic effects and bathochromic shifts of λmax, and, in the same time, the presence of larger molecular weight pigments, potentially less susceptible to degradation, was followed up. This experimental work intended to evaluate the potential of five different aldehydes, all of which are safe for human consumption and are used in the food industry, to the formation of pyranoanthocyanin-like and polymeric pigments in the model solution.

Copigmentation effects of phenolics on color enhancement and stability of blackberry wine residue anthocyanins: Chromaticity, kinetics and structural simulation

To expound the copigmentation effects of phenolics on blackberry wine residue anthocyanins (BWRA), the color and stability of BWRA with storage, thermal, light and oxidation treatments were evaluated by chromaticity, kinetics and structural simulation analysis. Results indicated that phenolic acids showed preferable copigmetation on BWRA solutions with the enhanced color, thermostability at 50–70 °C and light stability, whereas the degradation was accelerated at 90 °C. Meanwhile, flavonoids promoted the oxidation stability of BWRA. Of all the phenolic acids, ferulic acid presented the best copigmentation effect, and among the flavonoids rutin was the most active. Structural simulation suggested rutin and ferulic acid had the largest volume, potential energy (164.8 and 32.8 kcal/mol), minimized energy (39.2 and 11.3 kal/mol) and van der Waals energy (81.6 and 28.1 kcal/mol), respectively, which were favorable to the stabilization of the flavylium ion. The hydrogen bonding, π-π stacking and solvent effects were together involved in the copigmentation mechanism.

Understanding the shielding effects of whey protein on mulberry anthocyanins: Insights from multispectral and molecular modelling investigations

Assembling between polyphenols and proteins has been recently spotlighted and this binding is of specific importance in food chemistry since these complexes are typically used in different foodstuffs. A study on the copigmentation among three encapsulation wall-materials, including maltodextrin, gum Arabic, and whey proteins, with mulberry anthocyanins (AC) proved that whey protein (WP) is an outstanding wall-material due to its wrapping and hyperchromicity effects. Additionally, high binding ability of WP with AC was shown to be responsible for its superior copigmentation effects. Accordingly, the underlying shielding mechanism of WP on AC based on their non-covalent assembling was deeply studied using multispectral and computational assays. The fluorometric results demonstrated that a static and heat-stable binding between WP and AC occurred, leading to modification in size, hydrophobicity, and secondary structures of WP. The docking results explained that WP-AC complex was mainly molded via hydrophobic effects of WP surface and subsequently be stabilized by H-bonding and van der Waals forces. These results may contribute to a better understanding on the enhanced colouring proprieties of anthocyanins by using whey proteins.

Effects of high hydrostatic pressure-assisted organic acids on the copigmentation of Vitis amurensis Rupr anthocyanins

Natural anthocyanins are safer and nutritious as compared to synthetic pigments; however, their stability is poor. They can produce spontaneous copigmentation with organic acids, leading to the improvement of colour stability, albeit slowly. Box–Behnken experimental design was used to elucidate the mechanism of copigmentation between Vitis amurensis Rupr anthocyanins (0.1 mg/mL) and organic acids (0.87 mg/mL, ferulic acid:d-gluconic acid:caffeic acid:vanillic acid = 1.5:2.5:2.5:0.5, w/w/w/w) promoted by high hydrostatic pressure (HHP; 300 MPa, 2 min). The copigmentation effect and antioxidant activity of anthocyanins were also evaluated. The structure of anthocyanins was analysed using ultraviolet–visible spectroscopy, Fourier-transform infrared spectroscopy, high-performance liquid chromatography, and mass spectrometry. The results of HHP copigmentation showed that the following anthocyanins were newly formed—delphinidin-3-O-catechol, petunidin-3-O-catechol, delphinidin-4-vinyl-catechol, petunidin-3-O-guaiacol, malvidin-4-vinyl-guaiacol, cyanidin-3-O-(6″-O-caffeoyl)-glucoside, peonidin-3-O-(6″-O-caffeoyl)-glucoside, delphinidin-3-O-(6″-O-caffeoyl)-glucoside, malvidin-3-O-glucoside-4-vinyl-guaiacol, and malvidin-3-O-(6″-O-feruloyl)-glucoside—owing to appropriate modifications that increased the copigmentation rate (R = 42.12%), photo-thermal stability (R > 45%), and potential antioxidant activities expressed in vivo (p < 0.01 vs. Model Group).

Application of Anthocyanins from Blackcurrant ( Ribes nigrum L.) Fruit Waste as Renewable Hair Dyes.

There is much concern about the toxicological effects of synthetic hair dyes. As an alternative approach, renewable waste blackcurrant ( Ribes nigrum L.) fruit skins from the fruit pressing industry were extracted using acidified water with a solid-phase purification stage. Anthocyanin colorants were isolated in good yields (2-3% w/ w) and characterized by HPLC. Sorption of anthocyanins onto hair followed a Freundlich isotherm; anthocyanin-anthocyanin aggregation interactions enabled high buildup on the substrate. Sorption energy of cyanidin-3- O-glucoside (monosaccharide) > cyanidin-3- O-rutinoside (disaccharide), but sorption properties of different anthocyanin glucosides were very similar. Intense blue-colored dyeing on hair could be achieved with λmax-vis at 580 nm, typical of the anionic quinonoid base; it is suggested that hair provides an environment that enables the stabilization of the anionic quinonoid base on adsorption through association with cations in the hair and copigmentation effects. Dyeings were stable to multiple washes.

Copigment-polyelectrolyte complexes (PECs) composite systems for anthocyanin stabilization

This study aimed to explore copigment-polyelectrolyte complexes (PECs) composite systems for simultaneous color intensification and stabilization of anthocyanins. The polysaccharide-based PECs consisting of chitosan and chondroitin sulfate were fabricated at different pHs (3.3, 4.0, and 5.0) and incorporated various copigments, including catechol (CAT), gallic acid (GA), gallic acid ethyl ester (GAEE), and (-)-epigallocatechin gallate (EGCG). We found that copigments could modulate anthocyanin loading into PECs and color quality of formulations, depending on the formulated pH and types of copigments. At pH 3.3 and 4.0, the incorporation of copigments simultaneously improved the red color and encapsulation efficiency of PECs, whereas these effects were not pronounced at pH 5.0. Stability assay demonstrated the synergistic effect of copigmentation and PECs encapsulation at pH 3.3 on protection of anthocyanin against nucleophilic attack of ascorbic acid. This phenomenon was attributed to the additional dense network created by hydrogen bonding between copigments and polysaccharides as well as the formation of hydrophobic environments inside PECs. The strongest copigmentation effect was observed for GAEE, followed by CAT, GA, and EGCG. However, the stabilizing effect of copigments was negligible or even opposite at pH 4.0 and 5.0. Our findings on pH- and copigment-dependent modulating effects should guide the design of copigment-PECs composite systems as carriers for natural colorants, such as anthocyanin, in nutraceuticals and functional foods.

Hibiscus sabdariffa anthocyanins-rich extract: Chemical stability, in vitro antioxidant and antiproliferative activities

Hibiscus sabdariffa calyx is a rich source of anthocyanins and other bioactive compounds but no study reported the effects of experimental conditions on the extraction of these chemical compounds. Therefore, the effects of time and extraction temperature on the bioactive compounds and antioxidant activity of Hibiscus sabdariffa calyx were evaluated. In addition, the effects of copigmentation and pH on the stability of anthocyanins were assessed and the cytotoxic effects (LC50, IC50, and GC50) of the extracts were determined in relation to tumor cell lines - Caco-2, HepG-2, HCT8, and A549. The temperature significantly influenced the total anthocyanins and flavonoids contents. The interaction between time/temperature influenced the total phenolic content and ascorbic acid. The t1/2 and the percentage of colour retention decreased markedly at temperatures above 80 °C. Variations in pH conserved the antioxidant activity of the anthocyanins, and the protonation-deprotonation process of the extract was reversible. The treatment of cells with purified anthocyanin extract or crude extracts at 5–800 μg mL−1 did not show significant cytotoxic effects on the cell lines, corroborating the chemical antioxidant effect of the extracts (DPPH assay). Cyanidin-3-glucoside, delphinidin-3-sambubioside, delphinidin-3-glucoside, and cyanidin-3-sambubioside were identified in the extracts by LC-ESI-MS.

The effect of prefermentative addition of gallic acid and ellagic acid on the red wine color, copigmentation and phenolic profiles during wine aging

Though non-anthocyanin phenolics normally do not have red color, they affect the red color expression in the copigmentation of red wines. In this study, the influence of prefermentative addition of 300mg/L gallic acid and ellagic acid, as cofactors, on aging dry red wines had been systematically evaluated at the industrial scales from the perspectives of color, phenolic profiles and copigmentation effects of anthocyanins. Red wines made with these two compounds exhibited better color properties than the control, having better CIELAB chromatic parameters. Additionally, significantly higher levels of detectable anthocyanins and copigmented anthocyanin ratio had been observed. Wines with ellagic acid showed better chromatic properties and phenolic profiles than wines with gallic acid, as shown in previous theoretical results. Anti-copigmentation phenomenon was noticed and elucidated. These practical results confirmed that ellagic acid was the better cofactor, and would give more additional guidance for the production of high quality wine. Chemical compoundsMalvidin-3-O-glucoside (PubChem CID: 443,652); Petunidin-3-O-glucoside (PubChem CID: 443,651); Delphinidin-3-O-glucoside (PubChem CID: 443,650); Peonidin-3-O-glucoside (PubChem CID: 443,654); Ellagic acid (PubChem CID: 5,281,855); Gallic acid (PubChem CID: 370); Quercetin (PubChem CID: 443,654); Caffeic acid (PubChem CID: 689,043); (+)-catechin (PubChem CID: 9064); Vanillic acid (PubChem CID: 8468).