Color and antioxidant properties of cyanidin-based anthocyanin pigments

Phenolic compounds, carotenoids, anthocyanins, and antioxidant capacity of colored maize (Zea mays L.) kernels

In this study, the contents of total phenolics, flavonoids, anthocyanins, β-carotene, and lutein as well as free, conjugated, and insoluble bound phenolic acids were determined in whole kernels of 10 different colored maize genotypes. In addition, the antioxidant activity was evaluated as radical scavenging activity with ABTS (2,2-azino-bis/3-ethil-benothiazoline-6-sulfonic acid) and DPPH (2,2-diphenyl-1-picrylhydrazyl) reagents. Generally, considerable differences in phytochemical contents and antioxidant capacity were observed between the genotypes. The β-carotene and lutein contents ranged from 0 to 2.42 mg/kg d.m. and from 0 to 13.89 mg/kg d.m., respectively, whereas the total anthocyanin contents of anthocyanin-rich colored maize genotypes ranged from 2.50 to 696.07 mg CGE/kg d.m. (cyanidin 3-glucoside equivalent) with cyanidin 3-glucoside (Cy-3-Glu) as the most dominant form. The light blue ZPP-2 selfed maize genotype has a higher content of total phenolics, flavonoids, and ferulic acid as compared to other tested maize and the highest ABTS radical scavenging activity.

Inhibition or enhancement by 4 Pacific Island food plants against cancers induced by 2 amino-3-methylimidazo[4,5-f]quinoline in male Fischer 344 rats

A 1-yr carcinogenicity bioassay was conducted in rats fed 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), simultaneously with AIN-76/ high-fat (HF) diet alone, or with 10% starch replaced with kumara, pineapple, coconut, or taro, prepared as for a human diet. All of the non-IQ treated control, kumara, pineapple, or taro but not coconut-fed rats survived to 1 yr. None of the IQ-fed animals survived to 1 yr and although there were minor survival time differences among the groups, none was statistically significant. At sacrifice, IQ/HF controls had tumors in the skin, Zymbal's gland, ear canal, oral cavity, liver, and small intestine, totaling 32 among 20 animals. Kumara-fed rats had a similar tumor distribution but no tumors in the ear or oral cavity, and a total of 27 tumors among 20 animals, whereas pineapple-fed rats showed a somewhat lower tumor incidence (23/20 animals), including no small intestine lesions. Unexpectedly, a higher tumor incidence, especially of skin tumors, was seen in coconut and taro-fed animals (35/20 and 41/20 animals, respectively). In particular, the incidence of malignant liver tumors and gastrointestinal tumors were significantly increased in the taro-fed group in comparison with the kumara group.

Cyanidin-3-glucoside suppresses TNF-α-induced cell proliferation through the repression of Nox activator 1 in mouse vascular smooth muscle cells: involvement of the STAT3 signaling

Cyanidin-3-glucoside (C3G) is a member of the anthocyanin family which belongs to the flavonoid class and possesses antiatherogenic properties. Many studies have demonstrated the protective effects of C3G on vascular endothelial cells and monocytes, however, the precise effects on vascular smooth muscle cells (VSMCs) have been less thoroughly studied. Hence, we investigated the role of C3G in TNF-α-induced VSMCs proliferation and explored the possible mechanisms. TNF-α stimulated VSMCs proliferation, and pretreatment with C3G inhibited the proliferation in dose- and time-dependent manners. Then, we found that C3G attenuated TNF-α-induced ROS over generation by Dihydroethidium staining. The combination of 50 μM C3G and 100 μM apocynin significantly reduced ROS generation. Moreover, C3G pretreatment significantly suppressed the expression of Nox activator 1, a subunit of NADPH oxidase in mouse VSMCs. C3G also inhibited TNF-α-induced signal transducer and activator of transcription (STAT3) phosphorylation, and the inhibitory effect was more prominent in C3G and apocynin co-pretreated cells than that pretreated with C3G or apocynin alone. Administration of the ROS scavenger catalase (2,000 U/ml) remarkably inhibited TNF-α-induced cell proliferation and STAT3 activation. These data suggest that C3G exerts its antiproliferative effect on TNF-α-induced VSMCs proliferation through inhibiting STAT3 activation by attenuating NoxA1-derived ROS over production.

Thermal degradation of anthocyanins from purple potato (cv. Purple Majesty) and impact on antioxidant capacity

Degradation parameters of purified anthocyanins from purple-fleshed potato (cv. Purple Majesty) heated at high temperatures (100-150 °C) were determined. Purified anthocyanins, prepared by removing salts, sugars, and colorless nonanthocyanin phenolics from the crude extract, were monitored and quantified using HPLC and spectrophotometry for heat-induced degradation products. Separation of colorless phenolics from the anthocyanins was confirmed using HPLC at two wavelengths, 280 and 520 nm. The degradation kinetics of purified anthocyanins followed a first-order reaction with reaction rate constants (k values) of 0.0262-0.2855 min(-1), an activation energy of 72.89 kJ/mol, thermal death times (D values) of 8.06-8789 min, and a z value of 47.84 °C over the temperature range of 100-150 °C. The enthalpy and entropy of activation were 59.97 kJ/mol and -116.46 J/mol·K, respectively. The antioxidant capacity in the purified anthocyanins, measured by DPPH and ABTS assays, was increased after the thermal treatment, indicating antioxidant activities of degradation products in the samples.

Chemopreventive effect of cactus Opuntia ficus indica on oxidative stress and genotoxicity of aflatoxin B1

BACKGROUND

Aflatoxin B1 (AFB1) is potent hepatotoxic and hepatocarcinogenic agent. In aflatoxicosis, oxidative stress is a common mechanism contributing to initiation and progression of hepatic damage. The aim of this work was to evaluate the hepatoprotective effect of cactus cladode extract (CCE) on aflatoxin B1-induced liver damage in mice by measuring malondialdehyde (MDA) level, the protein carbonyls generation and the heat shock proteins Hsp 70 and Hsp 27 expressions in liver. We also looked for an eventual protective effect against AFB1-induced genotoxicity as determined by chromosome aberrations test, SOS Chromotest and DNA fragmentation assay. We further evaluated the modulation of p53, bax and bcl2 protein expressions in liver.

METHODS

Adult, healthy balbC (20-25 g) male mice were pre-treated by intraperitonial administration of CCE (50 mg/Kg.b.w) for 2 weeks. Control animals were treated 3 days a week for 4 weeks by intraperitonial administration of 250 μg/Kg.b.w AFB1. Animals treated by AFB1 and CCE were divided into two groups: the first group was administrated CCE 2 hours before each treatment with AFB1 3 days a week for 4 weeks. The second group was administrated without pre-treatment with CCE but this extract was administrated 24 hours after each treatment with AFB1 3 days a week for 4 weeks.

RESULTS

Our results clearly showed that AFB1 induced significant alterations in oxidative stress markers. In addition, it has a genotoxic potential and it increased the expression of pro apoptotic proteins p53 and bax and decreased the expression of bcl2. The treatment of CCE before or after treatment with AFB1, showed (i) a total reduction of AFB1 induced oxidative damage markers, (ii) an anti-genotoxic effect resulting in an efficient prevention of chromosomal aberrations and DNA fragmentation compared to the group treated with AFB1 alone (iii) restriction of the effect of AFB1 by differential modulation of the expression of p53 which decreased as well as its associated genes such as bax and bcl2.

CONCLUSION

We concluded that CCE might have a hepatoprotective effect against aflatoxicosis in mice, probably acting by promoting the antioxidant defence systems.

Phytochemical composition and biological activity of 8 varieties of radish (Raphanus sativus L.) sprouts and mature taproots

Radishes (Raphanus sativus L.) are members of the cruciferous vegetable family that contain many classes of biologically active phytochemicals. This study determined the phytochemical composition of the sprouts and mature taproots of 8 radish varieties. Radish sprouts contained significantly greater concentrations of glucosinolates (3.8-fold) and isothiocyanates (8.2-fold) than the mature radish taproot and also contained significantly greater concentrations of phenolics (on average 6.9-fold). The anthocyanin concentrations of the mature radish taproot were significantly greater than in the sprouts of red, pink, and purple varieties. The primary anthocyanidins present in the red and pink radish varieties were pelargonidin and delphinidin, while the primary anthocyanidin in the purple radish variety was cyanidin. Radish sprouts were between 9- and 59-fold more potent than the corresponding mature taproot at activating the antioxidant response element (ARE) in a stably transfected hepatoma cell line. The ARE activity of the radish sprouts and mature taproots was significantly correlated with the total isothiocyanate concentration of the radishes. Practical Application: Understanding the influence variety and developmental stage has on the biological activity of cruciferous vegetables provides important information for further studies examining the in vivo effects of radish treatment and foundation for providing recommendations to reduce the risk of chronic disease through dietary intervention.

Red cabbage anthocyanins may protect blood plasma proteins and lipids

The present in vitro study was designed to examine the antioxidative activity of red cabbage anthocyanins (ATH) in the protection of blood plasma proteins and lipids against damage induced by oxidative stress. Fresh leaves of red cabbage were extracted with a mixture of methanol/distilled water/0.01% HCl (MeOH/H2O/HCl, 50/50/1, v/v/w). Total ATH concentration [µM] was determined with cyanidin 3-glucoside as a standard. Phenolic profiles in the crude red cabbage extract were determined using the HPLC method. Plasma samples were exposed to 100 µM peroxynitrite (ONOO−) or 2 mM hydrogen peroxide (H2O2) in the presence/absence of ATH extract (5–15 µM); oxidative alterations were then assessed. Pre-incubation of plasma with ATH extract partly reduced oxidative stress in plasma proteins and lipids. Dose-dependent reduction of both ONOO− and H2O2-mediated plasma protein carbonylation was observed. ATH extract partly inhibited the nitrative action of ONOO−, and significantly decreased plasma lipid peroxidation caused by ONOO− or H2O2. Our results demonstrate that anthocyanins present in red cabbage have inhibitory effects on ONOO− and H2O2-induced oxidative stress in blood plasma components. We suggest that red cabbage ATH, as dietary antioxidants, should be considered as potentially usable nutraceuticals in the prevention of oxidative stress-related diseases.

Composition and stability of anthocyanins from purple Solanum tuberosum and their protective influence on Cr(VI) targeted to bovine serum albumin

Anthocyanins from the purple Solanum tuberosum newly cultivated by the Taian Academy of Agricultural Sciences were extracted and analyzed using high-performance liquid chromatography (HPLC) and UV-vis spectroscopy. Four individual anthocyanins were detected as the major components, and the total anthocyanin content was 273.5 ± 14.3 mg of cyanidin-3-glucoside equiv/100 g of dry seeds. Results of color stability showed that the purple S. tuberosum anthocyanins (PSTAs) are more stable under low pH and temperatures. Heat and general food additives have fine compatibility with PSTAs; however, they are very sensitive with oxidant and reduction. The influence of PSTAs on Cr(VI) targeted to bovine serum albumin (BSA) was also studied. The quenching of BSA fluorescence caused by Cr(VI) could be delayed by PSTAs. UV-vis and circular dichroism (CD) data suggested that PSTAs can protect the secondary and tertiary structures of BSA by probably interacting with Cr(VI) in advance.

Anthocyanin composition of black carrot (Daucus carota ssp. sativus var. atrorubens Alef.) cultivars Antonina, Beta Sweet, Deep Purple, and Purple Haze

This study aimed to identify the pigment composition of black carrot (Daucus carota ssp. sativus var. atrorubens Alef.) cultivars Antonina, Beta Sweet, Deep Purple, and Purple Haze. Cyanidin 3-xylosyl(glucosyl)galactosides acylated with sinapic acid, ferulic acid, and coumaric acid were detected as major anthocyanins by high-performance liquid chromatography with diode array detection (HPLC-DAD) and with electrospray ionization multiple mass spectrometry (HPLC-ESI-MS(n)) analyses. The preparative isolation of these pigments was carried out by means of high-speed countercurrent chromatography (HSCCC). The color activity concept was applied to the isolated anthocyanins at three pH values. Cyanidin 3-xylosyl(sinapoylglucosyl)galactoside was found to exhibit a lower visual detection threshold and a higher pH stability than cyanidin 3-xylosyl(feruloylglucosyl)galactoside and cyanidin 3-xylosyl(coumaroylglucosyl)galactoside. The color parameters of the fresh roots of the four cultivars were described by the CIELab coordinates L* (lightness), C* (chroma), and h(ab) (hue angles). Total phenolics varied among the cultivars and ranged from 17.9 to 97.9 mg gallic acid equivalents (GAE)/100 g fresh weight (fw). For the content of monomeric anthocyanins, values between 1.5 and 17.7 mg/100 g fw were determined.

Global gene expression of Poncirus trifoliata, Citrus sunki and their hybrids under infection of Phytophthora parasitica

Background

Gummosis and root rot caused by Phytophthora are among the most economically important diseases in citrus. Four F₁ resistant hybrids (Pool R), and four F₁ susceptible hybrids (Pool S) to P. parasitica, were selected from a cross between susceptible Citrus sunki and resistant Poncirus trifoliata cv. Rubidoux. We investigated gene expression in pools of four resistant and four susceptible hybrids in comparison with their parents 48 hours after P. parasitica inoculation. We proposed that genes differentially expressed between resistant and susceptible parents and between their resistant and susceptible hybrids provide promising candidates for identifying transcripts involved in disease resistance. A microarray containing 62,876 UniGene transcripts selected from the CitEST database and prepared by NimbleGen Systems was used for analyzing global gene expression 48 hours after infection with P. parasitica.

Results

Three pairs of data comparisons (P. trifoliata/C. sunki, Pool R/C. sunki and Pool R/Pool S) were performed. With a filter of false-discovery rate less than 0.05 and fold change greater than 3.0, 21 UniGene transcripts common to the three pairwise comparative were found to be up-regulated, and 3 UniGene transcripts were down-regulated. Among them, our results indicated that the selected transcripts were probably involved in the whole process of plant defense responses to pathogen attack, including transcriptional regulation, signaling, activation of defense genes participating in HR, single dominant genes (R gene) such as TIR-NBS-LRR and RPS4 and switch of defense-related metabolism pathway. Differentially expressed genes were validated by RT-qPCR in susceptible and resistant plants and between inoculated and uninoculated control plants

Conclusions

Twenty four UniGene transcripts were identified as candidate genes for Citrus response to P. parasitica. UniGene transcripts were likely to be involved in disease resistance, such as genes potentially involved in secondary metabolite synthesis, intracellular osmotic adjustment, signal transduction pathways of cell death, oxidative burst and defense gene expression. Furthermore, our microarray data suggest another type of resistance in Citrus-Phytophthora interaction conferred by single dominant genes (R gene) since we encountered two previously reported R genes (TIR-NBS-LRR and RPS4) upregulated in the resistant genotypes relative to susceptible. We identified 7 transcripts with homology in other plants but yet unclear functional characterization which are an interesting pool for further analyses and 3 transcripts where no significant similarity was found. This is the first microarray study addressing an evaluation of transcriptional changes in response to P. parasitica in Citrus.

Identification and characterisation of F3GT1 and F3GGT1, two glycosyltransferases responsible for anthocyanin biosynthesis in red-fleshed kiwifruit (Actinidia chinensis)

Much of the diversity of anthocyanins is due to the action of glycosyltransferases, which add sugar moieties to anthocyanidins. We identified two glycosyltransferases, F3GT1 and F3GGT1, from red-fleshed kiwifruit (Actinidia chinensis) that perform sequential glycosylation steps. Red-fleshed genotypes of kiwifruit accumulate anthocyanins mainly in the form of cyanidin 3-O-xylo-galactoside. Genes in the anthocyanin and flavonoid biosynthetic pathway were identified and shown to be expressed in fruit tissue. However, only the expression of the glycosyltransferase F3GT1 was correlated with anthocyanin accumulation in red tissues. Recombinant enzyme assays in vitro and in vivo RNA interference (RNAi) demonstrated the role of F3GT1 in the production of cyanidin 3-O-galactoside. F3GGT1 was shown to further glycosylate the sugar moiety of the anthocyanins. This second glycosylation can affect the solubility and stability of the pigments and modify their colour. We show that recombinant F3GGT1 can catalyse the addition of UDP-xylose to cyanidin 3-galactoside. While F3GGT1 is responsible for the end-product of the pathway, F3GT1 is likely to be the key enzyme regulating the accumulation of anthocyanin in red-fleshed kiwifruit varieties.

Cyanidin-3-O-glucoside protection against TNF-α-induced endothelial dysfunction: involvement of nuclear factor-κB signaling

Oxidative stress and inflammation are considered to play a pivotal role in vascular endothelial dysfunction by triggering activation of transcription factors, such as NF-κB, functionally dependent on cellular redox status. The anthocyanin cyanidin-3-O-glucoside (C3G), as well as other phytochemicals recognized as potent antioxidants and free radical scavengers, may act as modulators of gene regulation and signal transduction pathways. This study demonstrates that C3G is able to protect human endothelial cells against alterations induced by TNF-α, including the activation of NF-κB, increased gene expression of adhesion molecules, leukocyte adhesion to endothelium, and intracellular accumulation of H2O2 and lipid peroxidation byproducts. These observations contribute to provide a conceptual background for the understanding of the mechanisms underlying the role of C3G, as well as other dietary plant polyphenols, in the prevention of diseases associated with inflammation and oxidative stress, including atherosclerosis.

Effects of concentration prior to cold-stabilization on anthocyanin stability in concord grape juice

The color of Concord grape juice produced by concentration before cold-stabilization and detartration (direct-to-concentrate, DTC) was compared to juice produced via cold-stabilization prior to concentration (standard concentrate, SC) and evaluated by several metrics. Using the Boulton copigmentation assay, the majority of the absorbance at 520 nm in bottled SC juice (72%) was due to monomeric anthocyanins. Following reconstitution, DTC juice had a 63% greater absorbance at 520 nm than SC juice. A significant loss of anthocyanins was observed using a paired t test during cold-stabilization of single-strength juice during SC processing (mean loss: 79 mg/L as cyanidin-3-glucoside, 23% of total anthocyanins), while no significant loss of anthocyanins or change in other color metrics was observed during cold-stabilization of DTC concentrate. The concentration of anthocyanins in the SC bitartrate crystals was 0.80% w/w compared to 0.13% w/w in the DTC bitartrate crystals. Between DTC and SC, no difference in copigmentation was observed in cold-stabilized concentrate or reconstituted juice, indicating that the increased stability of anthocyanins could not be credited to greater copigmentation in DTC during detartration. HPLC analyses indicated that anthocyanin species with higher pKh and thus proportionally greater flavylium ion concentration at juice pH are preferentially lost during SC processing. The proportional changes in color metrics during shelf life stability testing (0-16 weeks, 2-30 °C) were not significantly different between SC and DTC juices.

Drinking water with red beetroot food color antagonizes esophageal carcinogenesis in N-nitrosomethylbenzylamine-treated rats

This study was undertaken to determine if the oral consumption of red beetroot food color would result in an inhibition of N-nitrosomethylbenzylamine (NMBA)-induced tumors in the rat esophagus. Rats were treated with NMBA and given either regular water ad libitum or water containing 78 microg/mL commercial red beetroot dye, E162. The number of NMBA-induced esophageal papillomas was reduced by 45% (P < .001) in animals that received the food color compared to controls. The treatment also resulted in reduced rates of cell proliferation in both precancerous esophageal lesions and in papillomas of NMBA-treated rats, as measured by immunohistochemical staining of Ki-67 in esophageal tissue specimens. The effects of beetroot food color on angiogenesis (microvessel density by CD34 immunostaining), inflammation (by CD45 immunostaining), and apoptosis (by terminal deoxynucleotidyl transferase dUTP nick end-labeling staining) in esophageal tissue specimens were also determined. Compared to rats treated with NMBA only, the levels of angiogenesis and inflammation in the beetroot color-consuming animals were reduced, and the apoptotic rate was increased. Thus, the mechanism(s) of chemoprevention by the active constituents of red beetroot color include reducing cell proliferation, angiogenesis, and inflammation and stimulating apoptosis. Importantly, consumption of the dye in the drinking water for a period of 35 weeks did not appear to induce any overt toxicity. Based on the fact that red beetroot color contains betanins, which have strong antioxidant activity, it is postulated that these effects are mediated through inhibition of oxygen radical-induced signal transduction. However, the sum of constituents of E162 has not been determined, and other components with other mechanisms may also be involved in antagonizing cancer development.

Modeling relationships among active components in black raspberry (Rubus occidentalis L.) fruit extracts using high-resolution (1)H nuclear magnetic resonance (NMR) spectroscopy and multivariate statistical analysis

A process was developed to ascertain the bioactive components of black raspberry (Rubus occidentalis L.) fruit extracts by relating chemical constituents determined by high-field nuclear magnetic resonance (NMR) spectroscopy to biological responses using partial least-squares regression analysis. To validate our approach, we outlined relationships between phenolic signals in NMR spectra and chemical data for total monomeric anthocyanin (TMA) content and antioxidant capacity by the ferric-reducing antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays. Anthocyanins, cyanidin 3-O-rutinoside (Cy 3-rut), cyanidin 3-O-(2(G))-xylosylrutinoside (Cy 3-xylrut), and cyanidin 3-O-glucoside (Cy 3-glc), were significant contributors to the variability in assay results, with the two most important NMR bins corresponding to the methyl peaks in Cy 3-rut (6''') and/or Cy 3-xylrut (6(IV)). Many statistically important bins were common among assay models, but differences in structure-activity relationships resulted in changes in bin ranking. The specificity of these results supported the application of the process to investigate relationships among health-beneficial natural products and potential biological activity.

Spectral alteration and degradation of cyanidin-3-glucoside exposed to pulsed electric field

Anthocyanins are polyphenol antioxidants that have been shown to prevent many chronic diseases. The compounds are not stable, so they tend to be decolorized or degraded during processing and storage. In this study, the spectral characteristics alteration and degradation products of cyanidin-3-glucoside (Cyd-3-glc) exposed to pulsed electric field (PEF) were investigated, and the reaction kinetics was discussed. The intensity of the UV-vis spectra decreased noticeably upon PEF treatment without modification of the spectral pattern. Protocatechuic acid and 2,4,6-trihydroxybenzoic acid were identified as degradation products of both PEF and thermally treated Cyd-3-glc, but cyanidin present in thermally treated Cyd-3-glc was absent in PEF-treated Cyd-3-glc, indicating that the first step of Cyd-3-glc degradation induced by PEF was not the hydrolysis of glycosidic bonds, which was different from that of thermal degradation. With increased electric field intensity or treatment time, the degradation of Cyd-3-glc and the formation of protocatechuic acid were enhanced; their kinetics (except 7 kV/cm for protocatechuic acid formation) were well fitted to a first-order reaction. Meanwhile, a good correlation was present between Cyd-3-glc degradation and protocatechuic acid formation.

Characterization and quantification of anthocyanins in red kiwifruit ( Actinidia spp.)

Red-fleshed fruit occur in a small number of distantly related taxa in different sections of the genus Actinidia (kiwifruit). We describe and identify the anthocyanin profile of fruit of several Actinidia species. Differences in the relative amounts of cyanidin- and delphinidin-based anthocyanins determine whether the fruit appear red or purple. Cyanidin derivatives have been found in all Actinidia species that contain anthocyanins, whereas delphinidin derivatives are limited to two taxa: A. melanandra and A. arguta var. purpurea . The fruit of these not only contain a wider range of anthocyanins, but they also have greater concentrations. Anthocyanins of most Actinidia species are usually conjugated with either xylosyl-galactose or galactose, whereas A. deliciosa anthocyanins are conjugated with glucose and galactose.

Reducing Sugar Production in Sweet Potatoes Heated by Electromagnetic Radiation

The apparent reaction rate constant needed to generate reducing sugar was determined by heating a thin slice of sweet potato using thermal conductive heating. This value was used to predict reducing sugar production in sweet potatoes cooked by electromagnetic irradiation. The generation of reducing sugar in the thin slice was not observed at temperatures <65°C or >85°C, but it increased linearly during the early stage of heating. The Arrhenius plot had a peak of approximately 83°C, allowing determination of the values for activation energy and frequency factor. Then, using the values obtained for apparent reaction rate constant, the yields of reducing sugar in sweet potatoes cooked by infrared (IR) and microwave (MW) heating were calculated and compared with experimental data. Although the calculated values exceeded the experimental values in the early stages of electromagnetic irradiative heating, the calculated amounts of reducing sugar generally agreed with the experimental values. Moreover, when the time needed to heat the sweet potato from 65°C to 85 °C was longer than approximately 8 min, the yield of reducing sugar was maximized for both MW and IR heating. These results indicated that the yield of reducing sugar did not depend on the heat transfer mechanism and that the amount of reducing sugar produced in heat-treated sweet potatoes could be predicted.

Effect of glucuronosylation on anthocyanin color stability

The effect of glucuronosylation on the color stability of anthocyanins was investigated using glucuronosylated anthocyanins isolated from the flower petals of the red daisy (Bellis perennis) or obtained by enzymatic in vitro synthesis using heterologously expressed red daisy glucuronosyltransferase BpUGT94B1. Color stability toward light and heat stress was assessed by monitoring CIELAB color coordinates and stability at pH 7.0 by A(550). Cyanidin-3-O-2''-O-glucuronosylglucoside showed improved color stability in response to light compared to both cyanidin 3-O-glucoside and cyanidin 3-O-2''-O-diglucoside. A similar increase in color stability was not observed following heat treatment. Glucuronosylation did not increase the stability of anthocyanins at pH 7.0 as determined by A(550). To test for a possible effect of glucuronosylation on the color stability of anthocyanins in plant extracts used for food coloration, an elderberry (Sambucus nigra) extract was glucuronosylated in vitro. Glucuronosylation of approximately 50% of total anthocyanins proceeded fast and resulted in increased color stability in response to both heat and light. The data show that glucuronosylation may be used to stabilize industrially used extracts of natural colorants.

Antioxidant enzymes activity and phenolic compounds content in red cabbage seedlings exposed to copper stress

The phenolics: anthocyanin (ATH), sinapoyl esters and activity of antioxidant enzymes: superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (POX), ascorbate peroxidase (APX), glutathione peroxidase (GPX) and glutathione reductase (GR), in red cabbage seedlings subjected to Cu2+ stress were investigated. Cu2+ at low doses (0.5 mM), increased the levels of ATH and sinapoyl derivatives in red cabbage. High Cu2+ concentration (2.5 mM) provoked oxidative stress and enhanced thiobarbituric acid reactive substances (TBARS) content in tissues. A lower level of TBARS was correlated with high ATH content. It seems that synthesis of these isoflavonoids is an effective strategy against reactive oxygen species (ROS). The analysis of the antioxidant enzymes activity suggested that peroxidases were the most active enzymes in red cabbage seedlings exposed to Cu2+ stress. It could results from the fact that phenolic compounds (PhC), which could be also substrates for different peroxidases, were the first line of defence against metal stress.

Fractionation of blue wheat anthocyanin compounds and their contribution to antioxidant properties

Demands for anthocyanin-rich foods and supplements are steadily increasing due to their significant roles in human health and food coloration. In the development of blue wheat as a functional food ingredient, dry milling was employed to separate the bran fraction where anthocyanins are concentrated 2.3-fold as compared to whole grain (13.9 mg/100 g). Anthocyanins were then extracted with aqueous ethanol and partially purified into a highly concentrated powder. The total anthocyanin content in the isolated powder as analyzed by high-performance liquid chromatography (HPLC) averaged 3378 mg/100 g and afforded a 243-fold increase in concentration relative to the whole grain product. Four main anthocyanins, delphinidin-3-glucoside (45%), cyanidin-3-glucoside (28%), delphinidin-3-rutinoside (22%), and cyanidin-3-rutinoside (2%), were isolated from the powder using preparative HPLC. Anthocyanin products and compounds were assessed against scavenging of 2,2-diphenyl-1-picryl-hydrazyl and 2,2'-azino-di-(3-ethylbenzthiazoline sulfonate) radicals and inhibition of human low-density lipoprotein cholesterol oxidation. Significant differences in antioxidant capacity were observed with anthocyanin powder and compounds exceeding that of butylated hydroxytoluene, indicating a potential for the development of blue wheat-based natural antioxidants and colorants.

Structure-function relationships of anthocyanins from various anthocyanin-rich extracts on the inhibition of colon cancer cell growth

Anthocyanins are potent antioxidants and may be chemoprotective. However, the structure-function relationships are not well understood. The objectives of this study were to compare the chemoprotective properties of anthocyanin-rich extracts (AREs) with variable anthocyanin profiles to understand the relationship between anthocyanin chemical structure and chemoprotective activity, measured as inhibition of colon cancer cell proliferation. Additionally, the chemoprotective interaction of anthocyanins and other phenolics was investigated. AREs with different anthocyanin profiles from purple corn, chokeberry, bilberry, purple carrot, grape, radish, and elderberry were tested for growth inhibition (GI 50) using a human colorectal adenocarcinoma (HT29) cell line. All AREs suppressed HT29 cell growth to various degrees as follows: purple corn (GI 50 approximately 14 microg of cy-3-glu equiv/mL) > chokeberry and bilberry > purple carrot and grape > radish and elderberry (GI 50 > 100 microg of cy-3-glu equiv/mL). Anthocyanins played a major role in AREs' chemoprotection and exerted an additive interaction with the other phenolics present. Statistical analyses suggested that anthocyanin chemical structure affected chemoprotection, with nonacylated monoglycosylated anthocyanins having greater inhibitory effect on HT-29 cell proliferation, whereas anthocyanins with pelargonidin, triglycoside, and/or acylation with cinnamic acid exerted the least effect. These findings should be considered for crop selection and the development of anthocyanin-rich functional foods.

Analysis of anthocyanins in red onion using capillary electrophoresis-time of flight-mass spectrometry

For the first time, a capillary electrophoresis-time of flight-mass spectrometry analysis method for detecting anthocyanins in red onion was developed. The analysis method included the use of silica capillaries coated with poly-LA 313 (polycationic amine-containing polymer) and an MS-compatible volatile background electrolyte (BGE). The method was environmentally friendly and sensitive; and its rapidness combined with an acidic BGE helped in preventing anthocyanin degradation. By using high-resolution TOF-MS with pre-run tuning of masses, low mass errors were achieved in the determination of conjugated anthocyanins in red onion, and a simultaneous up-front fragmentation provided confirmation of the aglycon backbone for their secure identification. Most anthocyanins (at least seven out of ten) known in red onion from the literature were found, as well as one new for this matrix.

Major anthocyanins from purple asparagus (Asparagus officinalis)

Two major anthocyanins (A1 and A2) were isolated from peels of the spears of Asparagus officinalis cv. Purple Passion. They were purified by column, paper and high-performance liquid chromatographic separations, and their structures were elucidated by high-resolution Fourier transform ion cyclotron resonance mass spectrometry (HR-FT-ICR MS), 1H, 13C and two-dimensional NMR spectroscopic analyses and either acid or alkaline hydrolysis, respectively. A1 was identified as cyanidin 3-[3''-(O-beta-d-glucopyranosyl)-6''-(O-alpha-l-rhamnopyranosyl)-O-beta-d-glucopyranoside], whereas A2 was cyanidin 3-rutinoside, which is widely distributed in higher plants. Oxygen radical absorbance capacity (ORAC) assays proved their high antioxidant activities.

Thermal degradation of anthocyanins and its impact on color and in vitro antioxidant capacity

The aim of the current study was to thoroughly investigate the structural changes of anthocyanins at pH 3.5 in purified fractions from black carrot, elderberry and strawberry heated over 6 h at 95 degrees C. Degradation products were monitored by HPLC-DAD-MS(3 )to elucidate the prevailing degradation pathways. In addition, alterations of color and antioxidant properties observed upon heating were scrutinized. Most interestingly, the degradation pathways at pH 3.5 were found to differ from those at pH 1. Among others, chalcone glycosides were detected at 320 nm in heat-treated elderberry and strawberry pigment isolates, and opening of the pyrylium ring initiated anthocyanin degradation. In the case of acylated anthocyanins, acyl-glycoside moieties were split off from the flavylium backbone, first. Finally, for all pigment isolates, phenolic acids and phloroglucinaldehyde were the terminal degradation products as remainders of the B- and A-ring, respectively. Maximum and minimum antioxidant stabilizing capacities were found in black carrot and strawberry, respectively, which was explained by the high degree of acylation in the former. After heating, decline of trolox equivalent antioxidant capacity (TEAC) was observed in all samples, which was attributed to both anthocyanins and their colorless degradation products following thermal exposure. As deduced from the ratio of TEAC value and anthocyanin content, the loss of anthocyanin bioactivity could not be compensated by the antioxidant capacity of newly formed colorless phenolics upon heating.

Molar absorptivities and reducing capacity of pyranoanthocyanins and other anthocyanins

To improve accuracy in the determination of anthocyanin purity and succeeding antioxidant capacity, 1H and 13C nuclear magnetic resonance spectroscopy have been combined with high-performance liquid chromatography (HPLC) equipped with a diode array detector and UV-vis spectroscopy in the analysis of anthocyanidin 3-glycosides and 5-carboxypyranoanthocyanidin 3-glycosides. The molar absoptivity (epsilon) values were found to be relatively similar, in contrast to previously reported literature values, and the average epsilon values for both anthocyanidin 3-monoglycosides and 5-carboxypyranoanthocyanidin 3-glycosides were proposed to be 22,000 and 23,000 in acidified aqueous and methanolic solutions, respectively. To assess the influence of structure on the potential antioxidant capacity of anthocyanins, the 3-glucosides of pelargonidin (1), cyanidin (2), peonidin (3), delphinidin (4), petunidin (5), malvidin (6), 5-carboxypyranopelargonidin (8), 5-carboxypyranocyanidin (9), 5-carboxypyranodelphinidin (11), 5-carboxypyranopetunidin (12), and 5-carboxypyranomalvidin (13) and the 3-galactosides of cyanidin (7) and 5-carboxypyranocyanidin (14) were examined by a ferric ion reducing antioxidant power (FRAP) assay. The reducing capacities of the individual anthocyanins were in the range of 0.9-5.2 micromol of Trolox equivalents/micromol. The two 5-carboxypyranoanthocyanins 11 and 9 and the four common anthocyanins 2, 4, 7, and 14, all possessing pyrogallol or catechol type of B rings, showed the highest antioxidant capacity measured by FRAP. However, the inclusion of the 5-hydroxyl in the D ring and just one oxygen substituent on the B ring in 8 diminished the reducing capacity considerably. Correspondingly, electrochemical behavior of 5-carboxypyranoanthocyanidin 3-glucosides and anthocyanidin 3-glucosides was derived using HPLC coupled to a coulometric array detector set from 100 to 800 mV in increments of 100 mV. The relative order of the reducing capacity of the various 5-carboxypyranoanthocyanidin 3-glucosides and anthocyanidin 3-glucosides were nearly alike, whether determined by coulometric array detection or FRAP.