Mixture Of Anthocyanins Research Articles

Role of aluminum in red-to-blue color changes in Hydrangea macrophylla sepals

Red, purple, and blue sepals on selected cultivars of Hydrangea macrophylla were analyzed for their aluminum content. This content was determined to be a function of the sepal color with red sepals possessing 0-10μg Al/g fresh sepal, purple sepals having 10-40μg Al/g fresh sepal, and blue sepals containing greater than 40μg Al/g fresh sepal. Accordingly, the threshold aluminum content needed to change H. macrophylla sepals from red to blue was about 40μg Al/g fresh sepal. Higher aluminum concentrations were incorporated into the sepals, but this additional aluminum did not affect the intensity or hue of the blue color. These observations agreed with a chemical model proposing that the concentration of the blue Al(3+)-anthocyanin complex reached a maximum when a sufficient excess of aluminum was present. In addition, the visible absorbance spectra of harvested red, purple, and blue sepals were duplicated by Al(3+) and anthocyanin (delphinidin-3-glucoside) mixtures in this model chemical system.

Investigation of the pH effect and UV radiation on kinetic degradation of anthocyanin mixtures extracted from Hibiscus acetosella

The major anthocyanin pigments extracted from Hibiscus acetosella flower were investigated by UV–Vis spectroscopy and multivariate curve resolution-alternating least squares (MCR-ALS). Pure spectra and kinetic of the species present at different pH values were recovered for anthocyanins transformation and degradation products, found with and without UV radiation exposure. In the absence of UV radiation, up to seven different species were detected and by UV radiation exposure, this number increased to up to nine. The species detected in the absence of radiation were also detected when pigments samples were exposed to UV radiation, where degradation occurred faster and two new species appear. The kinetic profiles obtained at different pH values allowed the proposal of a reaction mechanism and pathway.

The clinical effectiveness of chokeberry: a systematic review

Products derived from the black chokeberry, Aronia melanocarpa, are claimed to be beneficial in disorders or diseases associated with oxidative stress. The claims are based on evidence from in vitro studies and animal experiments. The active principle--a mixture of procyanidins, anthocyanins and phenolic acids--constitutes one of the most potent natural antioxidants. A systematic review was carried out of the quality of the clinical trials on chokeberry products that had been published up to December 2009, and conventionally established criteria were used to assess the strength of the evidence for their clinical effectiveness. Thirteen studies were identified. The quality of most of the trials and, correspondingly, the evidence of effectiveness for Aronia products is poor. Though laboratory and clinical data indicate that chokeberry products may well be useful as 'functional food' for disorders or diseases related to oxidative stress, these promising indications need to be confirmed in more rigorous studies before putative therapeutic uses can be confidently recommended for chokeberry products.

Additive Inhibitory Effects of Tart Cherry Anthocyanins and Atorvastatin on Interleukin‐6 Production in Adipose Stem Cells

Studies have shown positive correlations between inflammatory cytokines interleukin‐6 (IL‐6) and the development of chronic diseases including cardiovascular disease. The objective of our study was to investigate effects of tart cherry extract, a mixture of tart cherry anthocyanins, and an isolated tart cherry anthocyanin in reducing IL‐6. Since we have previously shown that adipose tissue stem cells secrete higher levels of IL‐6 when compared to adipocytes and macrophages, we investigated the effect of tart cherry extract in primary adipose stem cells isolated from obese, leptin deficient ob/ob mice. Since atorvastatin calcium (lipitor) has been independently shown to reduce inflammatory responses, using in vitro stem cell cultures, we also tested the additive effects of tart cherry and lipitor on IL‐6 secretion. Results showed that LPS‐induced adipose stem cell secretion of IL‐6 is reduced with the tart cherry extract, a mixture of tart cherry anthocyanins, and tart cherry cyanidin‐3‐O‐glucoside (C3G) in a dose‐dependent manner. In addition, lipitor added together with tart cherry extract and tart cherry anthocyanins mixture exhibited additive inhibitory effects. These results support potential benefits of using dietary phytochemicals in conjunction with pharmacological therapies to decrease adipose inflammation, drug doses, and ultimately, drug‐induced adverse effects.

Pomegranate ( Punica granatum) supplements: Authenticity, antioxidant and polyphenol composition

Pomegranates contain a complex mixture of gallotannins, ellagitannins, ellagic acid and anthocyanins. However, label claims on pomegranate supplements (PS) may not correlate with actual content of antioxidants, polyphenols or tannins. Nineteen PS were evaluated for their authenticity by determining ellagitannin composition by RP-HPLC and studying the relationship between total polyphenols as measured by the Folin–Ciocalteau assay and antioxidant capacity by oxygen radical absorbing capacity (ORAC), free radical scavenging properties by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and ferric reducing antioxidant power (FRAP). Only a limited number of pomegranate supplements were authentic. Product labels were inconsistent with polyphenol composition and antioxidant content. A majority of the samples ( n = 13) contained disproportionately high amounts of ellagic acid and low or no detectable pomegranate tannins. Only six products had tannin composition that resembled pomegranates (punicalagin, punicalin, ellagitannins and gallotannins). PS-01 (natural pomegranate extract) was the most representative of pomegranate fruit polyphenols with 99% total pomegranate polyphenol and the highest antioxidant capacity across all measures. Correlations between total polyphenols and antioxidant content were high ( R 2 > 0.87) in products that had polyphenol composition resembling pomegranates. Products that contained high amounts of ellagic acid and low or no detectable pomegranate tannins had poor correlations between total polyphenols and antioxidant content. The results indicate that reliable labeling information, better standardization, improved manufacturing practices and regulation of the market is required to assure consumers of the quality of pomegranate supplements.

Effect of Vaccinium myrtillus and Its Polyphenols on Angiotensin-Converting Enzyme Activity in Human Endothelial Cells

This study investigates if the connection between Vaccinium myrtillus and angiotensin-converting enzyme (ACE) might be an explanation of the pharmacological effects on circulation. Cultured endothelial cells from human umbilical veins were incubated with bilberry 25E extract. The main anthocyanidins combined in myrtillin chloride and separately in cyanidin, delphinidin, and malvidin, respectively, were examined concerning their effects on ACE. After 10 min of incubation with bilberry 25E, a significant, dose-dependent inhibition of ACE activity was seen, and after incubation with myrtillin chloride a significant inhibition was seen. No effect was seen with the anthocyanidins. The effect seems to be dependent on this specific mixture of anthocyanins in the bilberry. V. myrtillus may thus have the potential to prevent and protect against cardiovascular diseases.

Effects of Anthocyanins on Psychological Stress-Induced Oxidative Stress and Neurotransmitter Status

There is strong evidence that oxidative stress participates in the etiology of neurodegenerative diseases such as Parkinson's, and Alzheimer's diseases. Moreover, emotional stress effects in the central nervous system play a vital role in homeostasis. The protective effect of anthocyanins on the cerebral oxidative stress was studied using the whiskers cut model. In mice, such treatment causes psychological or emotional distress leading to oxidative stress in tissues. To investigate the in vivo antioxidant activity of anthocyanins, an extract of Vaccinium myrtillis L., an anthocyanin mixture, was orally administered (100 mg/kg of body weight.) to mice for 7 days, and then psychological stress was assessed by cutting off their whiskers. Whisker removal increased both protein carbonyl formation and lipid peroxidation in the brain, heart, kidney, and liver. Further, the levels of oxidative markers showed regional differences in the brain. Concomitantly, dopamine neurotransmitter levels were altered in both the midbrain and the brain cortex. Orally administered anthocyanins were also active in the brain, suppressing stress-induced cerebral oxidative stress and dopamine abnormalities in distressed mice. These effects of anthocyanin treatment suggest their possible usefulness for the treatment of cerebral disorders related to oxidative stress.

Colored and White Sectors From Star-Patterned Petunia Flowers Display Differential Resistance to Corn Earworm and Cabbage Looper Larvae

Anthocyanins are likely a visual aid that attract pollinators. However, there is also the possibility that anthocyanins are present in some flowers as defensive molecules that protect them from excess light, pathogens, or herbivores. In this study, resistance due to anthocyanins from commercial petunia flowers (Petunia hybrida) was examined for insecticide/antifeedant activity against corn earworm (CEW, Helicoverpa zea) and cabbage looper (CL, Trichoplusia ni). The petunia flowers studied contained a star pattern, with colored and white sectors. CEW larvae ate significantly less colored sectors than white sectors in no-choice bioassays in most cases. All CEW larvae feeding on blue sectors weighed significantly less after 2 days than larvae feeding on white sectors, which was negatively correlated with total anthocyanin levels. CL larvae ate less of blue sectors than white sectors, and blue sectors from one petunia cultivar caused significantly higher CL mortality than white sectors. Partially purified anthocyanin mixtures isolated from petunia flowers, when added to insect diet discs at approximately natural concentrations, reduced both CEW and CL larva weights compared to the controls. These studies demonstrate that the colored sectors of these petunia cultivars slow the development of these lepidopteran larvae and indicate that anthocyanins play some part in flower defense in petunia.

Oral administration of purple passion fruit peel extract attenuates blood pressure in female spontaneously hypertensive rats and humans

Abstract Hypertension is one of the most important modifiable risk factors for cardiovascular and cerebrovascular diseases. We investigated the potential antihypertensive effect of the purple passion fruit peel (PFP) extract, a mixture of bioflavonoids, phenolic acids, and anthocyanins, in spontaneously hypertensive rats and human. A high-performance liquid chromatography analysis was performed to identify the active ingredients of the PFP extract. In a rat liver toxicity assay, no hepatotoxicity was observed after 9 hours incubation in the presence of PFP extract (20 μ g/mL). The PFP extract also revealed hepatoprotection against chloroform (1 mmol/L)-induced liver injury. In the experimental model, 24 spontaneously hypertensive rats were divided into 3 treatment groups for a period of 8weeks: control group and groups fed diet supplemented with either 10 or 50 mg/kg PFP extract. The diet supplemented with PFP extract at 50 mg/kg significantly lowered systolic blood pressure by 12.3mm Hg ( P P P

Novel transgenic rice overexpressing anthocyanidin synthase accumulates a mixture of flavonoids leading to an increased antioxidant potential

In addition to their plant-associated functions, flavonoids act as antioxidants against harmful free radicals in animals. Genetic engineering of food crops for a mix of antioxidant flavonoids is highly beneficial in promoting human health. Anthocyanidin synthase (ANS) is one of the four dioxygenases (DOX) of the flavonoid biosynthetic pathway that catalyzes the formation of anthocyanidins from leucoanthocyanidins. To investigate whether ANS mediates different DOX reactions of the pathway and produces a mix of flavonoids, the rice ANS cDNA was cloned and overexpressed in a rice mutant Nootripathu (NP). This mutant accumulates proanthocyanidins exclusively in pericarp and absolutely no anthocyanins in any tissue. In silico sequence analysis revealed that ANS contains a double-stranded beta helix and shows high sequence similarity with other DOXs of the pathway including flavonol synthase, flavonone 3 β-hydroxylase and flavone synthase I. Bacterially expressed ANS protein converted dihydroquercetin to quercetin and Pro 35S:ANS complemented the maize a2 mutant in producing anthocyanins in aleurone, suggesting that ANS functions as a DOX with different flavonoid substrates. Similarly, transgenic NP plants overexpressing Pro MAS:ANS channeled the proanthocaynidin precursors to the production of anthocyanins in pericarp. Transgenics showed approximately ten and four-fold increase in the ANS transcripts and enzyme activity, respectively. As a result, these plants showed an increased accumulation of a mixture of flavonoids and anthocyanins, with a concomitant decrease in proanthocyanidins, suggesting that ANS may act directly on different flavonoid substrates of DOX reactions. Thus, overexpression of ANS in a rice mutant resulted in novel transgenic rice with a mixture of flavonoids and an enhanced antioxidant potential.

Bioavailability and Tissue Distribution of Anthocyanins in Bilberry (Vaccinium myrtillus L.) Extract in Rats

To clarify how structural diversity of anthocyanins relates to their in vivo function, bioavailability was precisely studied in rats using bilberry (Vaccinium myrtillus L.) extract (Bilberon 25) as an anthocyanin source that contains 15 different anthocyanins. The bilberry extract was orally or intravenously administered to rats, and the plasma levels of each anthocyanin were determined by high-performance liquid chromatography. As the result, all anthocyanins except peonidin 3-O-alpha-L-arabinoside were detectable in the blood plasma. The plasma concentration of anthocyanins as a whole reached the maximum level of 1.2 microM at 15 min after oral administration of 400 mg/kg bilberry extract (153.2 mg/kg as anthocyanins) and then decreased with time. Uptake and decay profiles of each anthocyanin in the plasma were almost the same for all anthocyanins except a few with their maximum after 30 min. Among the anthocyanins carrying the same aglycone, the plasma level after 15 min of oral administration was as follows: galactoside > glucoside > arabinoside. Plasma clearance of anthocyanins after intravenous administration clearly showed that arabinoside disappeared more rapidly than glucoside and galactoside. On the other hand, when anthocyanins carrying the same sugar moiety were compared, the half disappearance time of plasma anthocyanins was in the following order: delphinidin > cyanidin > petunidin = peonidin > malvidin. The bioavailability of anthocyanins was in the range of 0.61-1.82% and was 0.93% as the anthocyanin mixture. The bioavailability of anthocyanins carrying the same aglycone was in the following order: Galactoside showed the highest followed by glucoside and arabinoside for cyanidin and delphinidin, but arabinoside and galactoside showed a higher bioavailability than glucoside for petunidin and malvidin. Anthocyanins recovered in urine and bile during the first 4 h after intravenous administration were only 30.8 and 13.4%, respectively. Anthocyanin profiles in tissues were quite different from those in blood plasma. The major anthocyanins distributed in liver and kidney were the O-methyl anthocyanins such as peonidin, malvidin, and other O-methyl anthocyanins derived from delphinidin, cyanidin, and petunidin-glycosides.

Effect of cyanidin‐3‐glucoside and an anthocyanin mixture from bilberry on adenoma development in the ApcMin mouse model of intestinal carcinogenesis—Relationship with tissue anthocyanin levels

AbstractAnthocyanins are dietary flavonoids, which can prevent carcinogen‐induced colorectal cancer in rats. Here, the hypotheses were tested that Mirtoselect, an anthocyanin mixture from bilberry, or isolated cyanidin‐3‐glucoside (C3G), the most abundant anthocyanin in diet, interfere with intestinal adenoma formation in the ApcMin mouse, a genetic model of human familial adenomatous polyposis, and that consumption of C3G or Mirtoselect generates measurable levels of anthocyanins in the murine biophase. ApcMin mice ingested C3G or Mirtoselect at 0.03, 0.1 or 0.3% in the diet for 12 weeks, and intestinal adenomas were counted. Plasma, urine and intestinal mucosa were analyzed for presence of anthocyanins by high‐pressure liquid chromatography with detection by UV spectrophotometry (520 nm) or tandem mass spectrometry (multiple reaction monitoring). Ingestion of either C3G or Mirtoselect reduced adenoma load dose‐dependently. At the highest doses of C3G and Mirtoselect adenoma numbers were decreased by 45% (p < 0.001) or 30% (p < 0.05), respectively, compared to controls. Anthocyanins were found at the analytical detection limit in the plasma and at quantifiable levels in the intestinal mucosa and urine. Anthocyanin glucuronide and methyl metabolites were identified in intestine and urine. Total anthocyanin levels in mice on C3G or Mirtoselect were 43 ng and 8.1 μg/g tissue, respectively, in the intestinal mucosa, and 7.2 and 12.3 μg/ml in the urine. The efficacy of C3G and Mirtoselect in the ApcMin mouse renders the further development of anthocyanins as potential human colorectal cancer chemopreventive agents worthwhile. © 2006 Wiley‐Liss, Inc.

Antihypertensive effects of purple passion fruit peel extract in rats and humans

With an increasing number of patients suffering from hypertension and the frequent inability of conventional diet modification and therapy to effectively control the problem, alternative therapies are being sought after. These studies were undertaken to investigate the efficacy of the purple passion fruit peel (PFP) extract—a mixture of bioflavonoids, phenolic acids, and anthocyanins—in animals and patients with mild to severe hypertension. Spontaneously hypertensive rats were divided into 3 groups: basic diet, basic diet supplemented with the PFP extract at 10 mg/kg and 50 mg/kg; and serum nitric oxide and systolic blood pressure were analyzed. Studies were then extended to hypertensive subjects within a four-week randomized, double-blind, placebo-controlled trial through the administration of oral PFP extract (400 mg/day) or placebo pills. In spontaneously hypertensive rats, consumption of the PFP extract at 50 mg/kg lowered systolic blood pressure by 12.3 mm Hg on average (p<0.01) and markedly decreased the nitric oxide production by 65% on average (p<0.05). In hypertensive humans, the systolic and diastolic blood pressure of those supplemented with the PFP extract decreased significantly (p<0.001). Hypertensive patients given the PFP extract reported experiencing no significant adverse effects from it. The purple passion fruit peel extract may be safely offered to hypertensive patients as an alternative treatment option. This study was supported in part by Kemin Foods.

Color genes in the orchid Oncidium Gower Ramsey: identification, expression, and potential genetic instability in an interspecific cross

Orchids are one of the most unique and evolved of flowering plants, with many being valuable floricultural crops. Spatial localization of pigments within the flower of the commercially important bi-color Oncidium Gower Ramsey demonstrated a mixture of carotenoids and anthocyanins concentrated in the adaxial epidermis. Chromatography identified the predominant yellow pigment to be an equal mixture of all-trans and 9-cis isomers of violaxanthin, with esterification specific to the 9-cis isomer. Red ornamentation was comprised of the anthocyanins cyanidin and its methylated derivate, peonidin. Five key pigment biosynthesis genes encoding dihydroflavonol 4-reductase (DFR), phytoene synthase (PSY), phytoene desaturase, carotenoid isomerase, and the downstream 9-cis epoxycarotenoid dioxygenase were isolated and their expression profiles determined. Northern analyses showed both phytoene desaturase and carotenoid isomerase expression to be up-regulated in floral tissue relative to leaves whereas PSY was not. Three closely related DFR genes were isolated, including one with an insertion in the 3' coding region. DFR expression occurred throughout flower development in Oncidium, unlike in Dendrobium and Bromheadia orchids. A number of the isolated anthocyanin and carotenoid genes showed variations due to insertion events. These findings raise questions about the genetic stability in interspecific crosses in orchids, such as the tri-specific Oncidium Gower Ramsey.

Anthocyans from fruits and vegetables – Does bright colour signal cancer chemopreventive activity?

Consumption of fruits and berries has been associated with decreased risk of developing cancer. The most abundant flavonoid constituents of fruits and berries are anthocyans ( i.e. anthocyanins, glycosides, and their aglycons, anthocyanidins) that cause intense colouration. In this review, we describe epidemiological evidence hinting at the cancer preventive activity of anthocyan-containing foods in humans, results of chemoprevention studies in rodent models with anthocyans or anthocyan-containing fruit/vegetable extracts, and pharmacological properties of anthocyans. Anthocyanidins have been shown to inhibit malignant cell survival and confound many oncogenic signalling events in the 10 −6–10 −4 M concentration range. Studies of the pharmacokinetics of anthocyanins after their consumption as single agents, anthocyanin mixtures or berry extracts suggest that anthocyanins reach levels of 10 −8–10 −7 M in human blood. It is unclear whether such concentrations are sufficient to explain anticarcinogenic effects, and whether anthocyanins exert chemopreventive efficacy themselves, or if they need to undergo hydrolysis to their aglyconic counterparts. The currently available literature provides tantalising hints of the potential usefulness of anthocyans or anthocyan mixtures as cancer chemopreventive interventions. Nevertheless further studies are necessary to help adjudge the propitiousness of their clinical development.

Fast Access of Some Grape Pigments to the Brain

Anthocyanins represent the main flavonoid pigments in red grape and wine, in red berries, and in many other fruits and vegetables and are widespread in the human diet. After ingestion, these complex, hydrophilic compounds quickly appear as intact molecules in the plasma. This study investigated their presence in the brain of anesthetized rats that received 8 mg/kg of body weight of a pure anthocyanin mixture extracted from Vitis vinifera grapes. The mixture was maintained in the stomach for 10 min. After this time, intact anthocyanins were detected by HPLC-DAD-MS not only in the plasma (176.4 +/- 50.5 ng/mL, mean +/- SEM) but also in the brain (192.2 +/- 57.5 ng/g). These results demonstrate for the first time that grape pigments can reach the mammalian brain within minutes from their introduction into the stomach.

Probing Anthocyanin Profiles in Purple Sweet Potato Cell Line (Ipomoea batatas L. Cv. Ayamurasaki) by High-Performance Liquid Chromatography and Electrospray Ionization Tandem Mass Spectrometry

A purple line cell line (PL) generated from the storage root of purple-fleshed sweet potato (Ipomoea batatas L.) cv. Ayamurasaki produces a complex mixture of anthocyanins, and seven major anthocyanins have been isolated and identified to date. All these anthocyanins are exclusively cyanidin or peonidin 3-sophoroside-5-glucosides and their acylated derivatives. High-performance liquid chromatography (HPLC) coupled to photodiode array (PDA) detection and electrospray ionization tandem mass spectrometry (ESI-MS/MS) on a triple quadrupole instrument was employed to further investigate the anthocyanin composition of the PL extract. Precursor-ion analysis, product-ion analysis, and selected reaction monitoring (SRM) MS/MS experiments were conducted sequentially to screen and characterize anthocyanins in the aqueous extract of the PL cell line. Precursor-ion analysis specifically detected the molecular cations of each category of anthocyanins by scanning the precursors of anthocyanidins (cyanidin, peonidin, and pelargonidin). The detected molecular cation of each anthocyanin was fragmented using product-ion analysis by collisionally activated dissociation (CAD). MS/MS using SRM detection was conducted to further confirm the fragmentation observed during product-ion analysis. In comparison to the commonly used product-ion analysis technique, the combined use of precursor-ion analysis, product-ion analysis, and SRM is particularly useful for positive identification of anthocyanins in complex matrixes and provides important information to confirm the proposed structures. Twenty-six anthocyanins were detected and characterized in the aqueous extract of the PL cell line. Several anthocyanins, including two pelargonidin derivatives, were tentatively identified for the first time in these cells.

Quantification and characterisation of cyclo-oxygenase and lipid peroxidation inhibitory anthocyanins in fruits ofAmelanchier

The levels of bioactive anthocyanins in the fruits of Amelanchier alnifolia, A. arborea and A. canadensis have been determined by HPLC. Cyanidin 3-galactoside (1) was present in the fresh fruit of the three species at concentrations of 155, 390 and 165 mg/100 g, respectively. Cyanidin 3-glucoside (2) was present only in A. alnifolia and A. canadensis at concentrations of 54 and 48 mg/100 g, respectively. The anthocyanins were confirmed by LC-ESI/MS and NMR studies. At 100 ppm, anthocyanin mixtures from the three species inhibited cyclo-oxygenase (COX)-1 and -2 enzymes at 66 and 67%, 60 and 72%, and 51 and 76%, respectively. The positive controls used in the COX assays were aspirin, Celebrex and Vioxx at 180, 1.67 and 1.67 ppm, respectively, and showed 74 and 69%, 5 and 82% and 0 and 85% COX-1 and COX-2 inhibition, respectively. Anthocyanins 1 and 2 and cyanidin (3) inhibited COX-1 enzyme 50.5, 45.62 and 96.36%, respectively, at 100 ppm, whereas COX-2 inhibition was the highest for 3 at 75%. In the lipid peroxidation inhibitory assay, anthocyanin mixtures at 10 ppm from the three species showed activities of 72, 73 and 68%, respectively, compared with 89, 87 and 98% for commercial anti-oxidants butylated hydoxyanisole, butylated hydroxytoluene, and tert-butylhydroxyquinone at 1.67, 2.2 and 1.67 ppm, respectively. At 10 ppm, compounds 1-3 inhibited lipid peroxidation by 70, 75 and 78%, respectively.

In Vitro Inhibition of Human cGMP-Specific Phosphodiesterase-5 by Polyphenols from Red Grapes

A moderate consumption of red wine may reduce the risk of cardiovascular diseases via wine-derived phenolic compounds. A variety of biological mechanisms have been proposed for wine-derived phenolic compounds including nitric oxide-mediated vasorelaxation. This study examined whether the vasodilating effect of wine-derived phenolic compounds was associated with the inhibition of phosphodiesterases (PDEs) and, in particular, PDE5. For this purpose, human recombinant PDE5A1 isoform was prepared by expression of the full-length cDNA of PDE5A1 into COS-7 cells. Red wine and the extracts from grape skin inhibited PDE5A1 activity, whereas the seed extracts had a negligible effect. The mixture of anthocyanins inhibited the enzyme activity (IC50 = 11.6 microM), with malvidin-3-O-beta-glucoside (IC50 = 35.4 microM) and malvidin (IC50 = 24.9 microM) the most potent among the monoglucosides and aglycons, respectively. trans-Resveratrol and trans-piceid exhibited negligible effects, whereas hydroxycinnamates were completely inactive. These results indicate that polyphenols-induced vasorelaxation may also be sustained by smooth muscle PDE inhibition by anthocyanins present in red wines and grapes.

Thermal stability of Hibiscus sabdariffa L. anthocyanins in solution and in solid state: effects of copigmentation and glass transition

Kinetic studies on thermal stability of anthocyanins isolated from the dry calyces of Hibiscus sabdariffa L. (roselle) were carried out in aqueous solutions (55–98 °C), either as free or copigmented anthocyanins with chlorogenic acid, and in the dry state as free anthocyanins or co-lyophilized with an amorphous polysaccharide (pullulan) and stored in different relative humidity environments (water activities 0.33, 0.53, 0.75 and 0.84) at 40 °C. The rate constants for degradation were obtained from first-order reaction kinetic plots. The degradation kinetics of individual anthocyanin components in solution, as assessed by HPLC, followed an Arrhenius-type response with respect to temperature; activation energies, E a, varied between 13.3 and 15.1 kcal/mol. Copigmentation of anthocyanins with chlorogenic acid did not seem to improve their stability in solution. In the dry state, the degradation rate constants increased with the water activity, particularly above 0.53. In the freeze-dried pullulan–anthocyanin mixtures, the polysaccharide matrix delayed colour degradation compared to the free anthocyanin preparations by 1.5–1.8 times. The degradation kinetics of anthocyanins did not show any dependence on the molecular mobility of the system, as it relates to the glass–rubber transition ( T g) detectable by calorimetry. Anthocyanin degradation occurred, even at sub- T g temperatures of the amorphous matrices, whereas no changes in the rate constants were observed in the vicinity of the glass transition; the plot of (ln k) −1 against ( T− T g) was linear with all data fitting into a common line as predicted by the Williams–Landel–Ferry (WLF) equation. Both free and co-lyophilized with pullulan Hibiscus anthocyanins exhibited good antiradical activity throughout storage in all humidity environments studied, despite of a substantial loss in colour intensity.