Suppressive effect of carotenoid extract of Dunaliella salina alga on production of LPS-stimulated pro-inflammatory mediators in RAW264.7 cells via NF-κB and JNK inactivation

The carotenoid extract from Dunaliella salina was used to evaluate the suppressive effects on lipopolysaccharide (LPS)-induced pro-inflammatory mediators in RAW264.7 cells. The extract composed all-trans forms of α-carotene (28.8 mg/g extract), β-carotene (471.1 mg/g extract), lutein (7.1 mg/g extract) and zeaxanthin (7.2 mg/g extract), 13- or 13′-cis-β-carotene (12.1 mg/g extract), 9- or 9′-cis-α-carotene (19.1 mg/g extract) and 9- or 9′-cis-β-carotene (440.3 mg/g extract) dose-dependently reduced the production of interleukin (IL)-1β, IL-6 and tumor necrosis factor-α (TNF-α), the protein expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), and the secretion of nitric oxide (NO) and prostaglandin E₂ (PGE₂) in LPS-activated RAW264.7 cells. Its attenuation of LPS-induced inflammatory responses was closely related to inhibition of the nuclear NF-κB p50 subunit translocation by blocking inhibitor of κBα (IκB) phosphorylation and degradation correlated with suppressing IκB kinase (IKK) α/β phosphorylation, as well as down-regulation of the c-Jun NH₂-terminal kinase (JNK) activation.     

Soluble phenolics and antioxidant properties of soybean (Glycine max L.) cultivars with varying seed coat colours

This research was the first to investigate nutritional components, including soluble phenolics (isoflavones and anthocyanins), protein, oil, and fatty acid as well as antioxidant activities in different coloured seed coat soybeans (yellow, black, brown, and green) for two crop years. The soluble phenolics differed significantly with cultivars, crop years, and seed coat colours, while protein, oil, and fatty acid exhibited only slight variations. Especially, malonylgenistin and cyanidin-3-O-glucoside compositions had the most remarkable variations. Green soybeans had the highest average isoflavone content (3079.42 μg/g), followed by yellow (2393.41 μg/g), and black soybeans (2373.97 μg/g), with brown soybeans showing the lowest value (1821.82 μg/g). Anthocyanins showed only in black soybeans, with the average contents of the primary anthocyanins, cyanidin-3-O-glucoside, delphinidine-3-O-glucoside, and petunidin-3-O-glucoside, quantified at 11.046, 1.971, and 0.557 mg/g, respectively. Additionally, Nogchae of green soybean and Geomjeongkong 2 of black soybean may be recommended as potential cultivars owing to the highest average isoflavone (4411.10 μg/g) and anthocyanin (21.537 mg/g) contents. The scavenging activities of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radicals also differed remarkably, depending upon isoflavone and anthocyanin contents, with black soybeans exhibiting the highest antioxidant effects.     

Impact of various factors on the composition and stability of black currant anthocyanins

Nine black currant varieties cultivated in Lithuania were studied. The highest amount of ascorbic acid was established in fresh berries from cv Minaj Smyriov and Kupoliniai: these varieties contained 220.5 and 186.7 mg 100 g⁻¹ of ascorbic acid in berries. The highest amount of anthocyanins was found in cake produced from berries cv Kupoliniai and Kriviai: 14.65 and 15.42 mg g⁻¹, respectively. The major pigment determined in Kupoliniai variety was delphinidin-3-rutinoside; in Ben Lomond, Minaj Smyriov, Kriviai and Gagatai cultivars, cyanidin-3-rutinoside. The composition of the identified pigments was the following: cyanidin-3-rutinoside (33–38%), delphinidin-3-rutinoside (27–34%), cyanidin-3-glucoside (8–10%) and delphinidin-3-glucoside (8–10%). Impact of storage, thermal treatment and addition of sweeteners were studied. Cyanidin-3-rutinoside was the most stable to the effect of thermal treatment at 95 °C, while cyanidin and delphinidin rutinosides were the most stable during storage for 12 months at 8 °C. Fructose has a greater effect on anthocyanin degradation compared with glucose and aspartame.     

Studies on the anthocyanin profile and biological properties from the fruits of Acanthopanax senticosus (Siberian Ginseng)

The anthocyanin profile and biological activities, including antioxidant, xanthine oxidase inhibitory, angiotensin converting enzyme (ACE) inhibitory, and anticancer of Acanthopanax senticosus fruits were evaluated for the first time. The acidified 80% methanol extract of this species exhibited high biological properties at a concentration of 60 μg/ml. Moreover, cyanidin-3-O-(2″-O-xylosyl)-glucoside was identified using C₁₈ column chromatography, NMR spectroscopy, and HPLC-DAD-ESI/MS analysis. This compound was present at 5.2 mg/g, representing approximately 91% of the total peak area and possessed strong antioxidant effects against DPPH, ABTS, and hydroxyl radicals (IC₅₀ of 85.2, 43.7, and 126.6 μg/ml, respectively). Cyanidin-3-O-(2″-O-xylosyl)-glucoside also exhibited significant inhibitory activities against xanthine oxidase and ACE (IC₅₀: 55.5 and 47.1 μg/ml, respectively). Especially, LNCap (prostate), MOLT-4F (leukaemia), and ACHN (renal) cell lines exhibited potent anticancer effects, with IC₅₀ of 5.2, 11.2, and 22.5 μg/ml, respectively, in comparison with other cancer cell lines. Therefore, A. senticosus fruit may be utilised as an effective source for food and nutraceutical uses due to its high anthocyanin content as well as various biological properties.     

Inhibitory effect of polyphenol-rich extracts of jute leaf (Corchorus olitorius) on key enzyme linked to type 2 diabetes (α-amylase and α-glucosidase) and hypertension (angiotensin I converting) in vitro

Corchorus olitorius leaf is consumed in various parts of the world as leafy vegetable and folk remedy for the management of some degenerative diseases with dearth of information on its biochemical rationale. Therefore, this study sought to characterize the inhibitory action of polyphenol-rich extracts (free and bound) of C. olitorius on α-amylase, α-glucosidase and angiotensin I converting enzyme (ACE), as well as to identify the phenolic compound responsible for these activities. Our findings revealed that the extracts inhibited α-amylase and α-glucosidase (12.5–50.0 μg/mL), and ACE (10.0–50.0 μg/mL) in dose-dependently with free extracts having significantly (P < 0.05) higher α-amylase (17.5 μg/mL), α-glucosidase (11.4 μg/mL) and ACE (15.7 μg/mL) inhibitory activities as revealed by the IC₅₀. Reversed-phase HPLC analysis of the extracts revealed chlorogenic acid (7.5 mg/100 g) and isorhamnetin (51.1 mg/100 g) as the main phenolics in the free extract and caffeic acid (58.1 mg/100 g) in the bound extract. Therefore, the enzyme inhibitory activity of C. olitorius extracts may be attributed to the presence of caffeic acid, chlorogenic acid and isorhamnetin, thus justifying its use in folklore for the management of diabetes and hypertension.     

Carotenoid content,its stability during drying and the antioxidant activity of commercial coriander (Coriandrum sativum L.) varieties

Although populations of several tropical countries are under severe vitamin-A deficiency, traditional sources of pro-vitamin-A carotenoids have not been exploited due to the lack of relevant research data. In this study, ten commercial varieties of coriander (Coriandrum sativum L.), grown at identical conditions, were evaluated for carotenoids, their bio-efficacy and stability during drying, with the main emphasis on β-carotene (vitamin-A precursor) analysis by HPLC-MS. In all varieties, β-carotene content was higher in foliage at mature stage, than in seedlings and seeds. Variety GS4 Multicut produced highest biomass (6.18 ± 0.73 g/plant), total carotenoids (217.50 ± 5.6 mg/100 g DW) and β-carotene (73.64 ± 0.3 mg/100 g DW) at pre-flowering stage. Carotenoids extract showed a high antioxidant activity with IC₅₀ value of 14.29 ± 1.68 μg/ml, scavenging hydroxyl radicals and rendering higher protection to DNA than by standard gallic acid (IC₅₀ = 357.21 ± 4.29). Microwave drying of foliage was rapid with better retention of pigments, high intactness of trans-β-carotene and higher extractability of pigments when compared with oven drying.     

Saskatoon berries (Amelanchier alnifolia Nutt.) scavenge free radicals and inhibit intracellular oxidation

Two cultivars (Thiessen and Smoky) of Saskatoon berries (Amelanchier alnifolia Nutt.) possess free radical scavenging activities in a concentration-dependent manner, whereas Thiessen presented higher (p < 0.05) activity compared to Smoky due to its relatively abundant anthocyanin content. Total anthocyanin content significantly corresponded to free radical scavenging activities (p < 0.05). Solvent fractionation revealed that the free radical scavenging components, i.e., anthocyanin, predominantly occurred in the ethyl acetate and n-butanol extracted fractions, suggesting that active components are more likely to occur in glycoside forms. HPLC further confirmed the existence of cyanidin-3-O-galactoside and cyanidin-3-O-glucoside as leading anthocyanins in the Saskatoon berries. Furthermore, Saskatoon berries extracts from both cultivars suppressed peroxy-radical induced intracellular oxidation in a concentration-dependent manner without affecting cell viability. The obtained results provided useful information for the future application of Saskatoon berries in the nutraceutical industry.     

Identification of anthocyanins isolated from black rice (Oryza sativa L.) and their degradation kinetics

Black rice is rich in anthocyanins-plant pigments. The aim of this work was to identify anthocyanins in black rice using high-performance liquid chromatography (HPLC)-electrospray ionization — mass spectrometry with diode array detection. Four different anthocyanins (cyanidin-3-glucoside, peonidin-3-glucoside, cyanidin-3,5-diglucoside, cyanidin-3-rutinoside) were identified in black rice. Thermal stability of the four anthocyanins in black rice extract was studied at selected temperatures (80 °C, 90 °C and 100 °C) in the range of pH 1.0–pH 6.0. The results indicated that the thermal degradation of anthocyanins followed the first-order reaction kinetics. The temperature-dependent degradation was adequately modeled on the Arrhenius equation. The calculated values of activation energies (Ea), t_1/2 and k were different for the four anthocyanins. The degradation rate of monomeric anthocyanin increased with increasing heating temperature and pH values. Especially, as heating temperature increasing to 100 °C and pH value to 5.0.     

Citharexylum solanaceum fruit extracts: Profiles of phenolic compounds and carotenoids and their relation with ROS and RNS scavenging capacities

Citharexylum solanaceum is a native fruit from Brazil, which both bioactive compounds and antioxidant potential were not yet investigated. Thus, the freeze-dried extracts of seed and pulp + skin of C. solanaceum fruits were obtained after solid-liquid extraction with ethanol and their bioactive compounds composition, namely phenolic compounds and carotenoids, were determined. The antioxidant capacity of both extracts against physiologically relevant reactive oxygen species (ROS) and reactive nitrogen species (RNS) was further investigated. Both C. solanaceum extracts showed high contents of phenolic compounds; however, pulp + skin extract presented 2.4-times more phenolic compounds (33.54 mg/g) than the seed extract (14.09 mg/g). Verbascoside (phenylpropanoid) was the major compound identified in both extracts (11–25 mg/g). Regarding the carotenoid composition, all-trans-lutein (14–42 μg/g) and all-trans-β-carotene (13–44 μg/g) were the major compounds in both extracts. The high content of phenolic compounds and carotenoids in pulp + skin extract might explain its higher scavenging capacity against all the ROS/RNS as compared to seed extract. In general, both extracts showed better scavenging capacity for the RNS than for the ROS. Our results indicate that C. solanaceum fruits can be explored as an important natural source of antioxidant compounds.     

Pigment identification,nutritional composition,bioactivity, and in vitro cancer cell cytotoxicity of Rivina humilis L. berries,potential source of betalains

Ripened berries of Rivina humilis L. (pigeon berry) were investigated for pigment and nutritional composition, in vitro bioactivities, and cancer cell cytotoxicity of its extracts. Ten betalain pigments (total content–0.35 g/100 g fresh weight, and 1.7 g/100 g dry weight) with high level of betaxanthins were characterised. Carbohydrates (6.2 g), proteins (1.1 g), lipids (0.7 g), phenols (105.7 mg gallic acid equivalent), niacin (5.3 mg), and total tocopherols (0.77 mg) in 100 g fresh weight were observed. Antioxidant bioactivity of MeOH extract (maximum at 100 μg/mL) against OH and β-carotene oxidation was studied. The extract (1000 μg/mL) effectively protected kidney lipid peroxidation compared to butylated hydroxy anisole. Betalains rich extract, and purified betacyanins and betaxanthins revealed EC₅₀ against DPPH (51.0, 0.29, 0.11 μg/mL), and reducing power (39.3, 2.79, and 1.34 μg/mL) which was higher than that of gallic acid and ascorbic acid. In vitro cancer cell cytotoxicity was assessed through MTT assay on HepG2 cells after exposing to betalains rich extract, betacyanins and betaxanthins for 24 h; only betaxanthins exhibited cytotoxicity (EC₅₀ 12.0 μg/mL). After 48 h of exposure, betacyanins and betaxanthins showed elevated cytotoxicity.     

Characterization of antioxidant compounds in aqueous coriander extract (Coriandrum sativum L.)

An aqueous coriander extract obtained through a sequential extraction process, was analysed using chromatography and mass spectrometry in order to identify the phenolic compounds responsible for its antioxidant activity. Four fractions were identified from the crude extract using chromatography in a silica gel column. Their antioxidant activity, according to the β-carotene/linoleic acid model, was similar to one another but inferior to that of the crude extract and of butylated hydroxytoluene. Of the phenols identified through gas chromatography and mass spectrometry, it was noted that caffeic acid was present in high concentration (4.34 μg/ml in fraction I and 2.64 μg/ml in fraction III), whereas protocatechinic acid and glycitin were present in high concentration in fraction II (6.43 μg/ml) and fraction IV (3.27 μg/ml), respectively. These results, when considered with the recognized antioxidant ability of phenolic acids, suggest that they are principal components responsible for the antioxidant activity of the aqueous coriander extract.     

Lingonberry (Vaccinium vitis-idaea L.) grown in the Pacific Northwest of North America: Anthocyanin and free amino acid composition

Lingonberries and their products are popular and generally accessible in Europe, though in the US they are uncommon and considered a minor berry/fruit crop. The on-going interest in potential health benefits from berry consumption has heightened interest in broadening the selection of berry/fruit crops in the US. This study measured total phenolics, total tannins, complete anthocyanin content, and total (and individual) free amino acid composition for each of five lingonberry cultivars. Cultivars Ida, Koralle, Linnea, Sanna, and Sussi were grown in Oregon, USA, and had only been evaluated previously for their horticultural traits. All five cultivars contained the three anticipated anthocyanins (by HPLC): cyanidin-3-galactoside (main anthocyanin found in these berries), cyanidin-3-glucoside, and cyanidin-3-arabinoside. These lingonberries’ total anthocyanin content ranged from 27.4 (‘Linnea’) to 52.6 (‘Ida’) mg/100 g fw. They contained 22 free amino acids (FFAs) and total FAAs ranged from 28.92 (‘Sanna’) to 70.38 (‘Koralle’) mg/100 g fw. Asparagine (ASN) was the leading FAA (22–34% of the total FAAs) for all five cultivars. This is the first report on lingonberry FAA content.     

Encapsulation of carotenoids from sea buckthorn extracted by CO2 supercritical fluids method within whey proteins isolates matrices

Sea buckhorn (Hippophae rhamnoides L) carotenoids extracted by using CO₂ supercritical fluids (SC-CO₂) method were encapsulated with whey proteins isolate by coacervation and freeze drying. The SC-CO₂ yielded a 121.10 g oil/kg dried berries and 4517.54 mg carotenoids/kg dried berries. Two experimental stages were tested as follow: proteins-carotenoids and cross-linked proteins-carotenoids complex. The encapsulating efficiency was higher for the cross-linked complex. The HPLC analysis allowed the identification of carotenoid composition of sea buckthorn extract and powders, highlighting the fact that the variant obtained by crosslinking allowed entrapping a significantly higher amounts of esters and a lower amount of β-carotene. The laser confocal scanning microscopy revealed the distribution of bioactive compounds inside the coacervates, which exceed 30 μm in diameter, whereas larger spherosomes (50–80 μm size) were observed in cross-linked proteins-carotenoids complex. The scanning electron microscopy suggested the presence of the particles evenly distributed, with spherical dents corresponding to the homogeneous presence of sea buckthorn extract. No significant difference was observed in antioxidant activity, whereas the cross-linked sample showed significant higher antifungal activity for the Penicillium expansum MIUG M11.     

Phytochemical,antioxidant and pigment stability of açai (Euterpe oleracea Mart.) as affected by clarification,ascorbic acid fortification and storage

Açai juice at two clarity stages (semi-clarified and clarified) was compared to 100% açai pulp following ascorbic acid fortification to evaluate phytochemical and antioxidant changes during storage at 4 and 20 °C. Cyanidin-3-rutinoside (202 ± 5.8 mg/L) and cyanidin-3-glucoside (75 ± 4.8 mg/L) were the predominant anthocyanins in açai while 11 non-anthocyanin polyphenolics were detected in concentrations from 1.1 to 55 mg/L of açai pulp. Clarification of açai pulp resulted in a 27% loss in total polyphenolics (197 ± 6.9 mg gallic acid/100 mL) and in a 20% reduction in both total anthocyanins (729 ± 3.4 mg/L) and antioxidant capacity (54 ± 1.7 μmol Trolox equivalents/mL). Anthocyanin degradation followed first order kinetics, with half-lives ranging from 9.4 to 43 days for cyanidin-3-glucoside and from 18 to 82 days for cyanidin-3-rutinoside. Fortification with ascorbic acid accelerated anthocyanin degradation in clarified juice at both storage temperatures, likely due to the loss of polymeric anthocyanin forms (21%) during clarification. Although clarification enhanced the amount of monomeric anthocyanins present in açai juice which relates positively to the aesthetic quality, processing and handling regimes must be optimized to achieve maximum retention of their functional properties during storage.     

Characterization of in vitro anthocyanin-producing sour cherry (Prunus cerasus L.) callus cultures

Anthocyanin-producing callus cultures from in vitro sour cherry (Prunus cerasus L.) leaf tissues were established. As in the parent leaf tissues, the calli extracts showed the synthesis of a prevalent anthocyanin, cyanidin 3-glucoside. When the dark grown callus cultures were exposed to the light, cyanidin 3-glucoside content was increased from 0.1 to 4.5 mg 100 g⁻¹ fresh weight. Thus, of the available strategies for the enhancement of pigment production light resulted the triggering factor in this cell system. The addition of 50 μM jasmonic acid to the culture medium stimulated cyanidin 3-glucoside synthesis which resulted in an earlier appearance of pigment on the calli.     

Ameliorating effects of ethyl acetate fraction from onion (Allium cepa L.) flesh and peel in mice following trimethyltin-induced learning and memory impairment

The anti-amnesic effects of onion (Allium cepa L.) flesh (OF)¹ and peel (OP)² on trimethyltin (TMT)³-induced learning and memory dysfunction were investigated to confirm learning and memory function. The inhibitory effect against cellular acetylcholinesterase (AChE)⁴ showed that the EtOAc fraction of OP (EOP⁵, IC₅₀ value = 37.11 μg/mL) was higher than the EtOAc fraction of OF (EOF⁶, IC₅₀ value = 433.34 μg/mL). The cognitive effects in ICR mice were also evaluated using Y-maze, passive avoidance, and Morris water maze tests. After the behavioral tests, AChE activity (control = 100%, TMT = 128%, EOF 20 = 108%, EOP 10 = 104%, and EOP 20 = 98%), superoxide dismutase (SOD)⁷ activity, oxidized glutathione (GSSG)⁸/total glutathione (GSH)⁹ and malondialdehyde (MDA)¹⁰ production were examined. These results indicate that both EOF and EOP improved learning and memory function. The main compounds of the EOF and EOP were analyzed by Q-TOF UPLC/MS, and the results were as follows: The EOF (quercetin and quercetin-4′-glucoside) and the EOP (quercetin-4′-glucoside and isorhamnetin-4′-glucoside). Consequently, our results suggest that both EOF and EOP could be efficacious in improving cognitive function through AChE inhibition and antioxidant activity in mice brains.     

Analysis of antioxidant activity and antioxidant constituents of Chinese toon

Antioxidant activity of the methanol and water extracts of Chinese toon (Toona sinensis) leaf was evaluated using DPPH radical scavenging and lipid peroxidation assays. Contents of four major types of antioxidants including β-carotene, ascorbate, α-tocopherol and phenolics were also quantified. Open column chromatography followed by semi-preparative HPLC were applied to separate phenolic antioxidants whose contents were subsequently determined by HPLC. The methanol extract demonstrated much higher antioxidant activity than the water extract. Contents of β-carotene, ascorbate, α-tocopherol and phenolics were 1.23 μmol g^?1, 34.2 μmol g^?1, 2.40 μmol g^?1 and 872 μmol gallic acid equivalents g^?1, respectively. Six phenols were isolated. Their structures were characterized as 5-O-galloylquinic acid, gallic acid, methyl gallate, β-1,2,6-tri-O-galloyl-d-glucose, quercetin 3-O-β-d-glucopyranoside and quercetin 3-O-(2′′-O-galloyl)-β-d-glucopyranoside, respectively. The results indicate that phenolic compounds are the dominant antioxidants in Chinese toon. The compounds β-1,2,6-tri-O-galloyl-d-glucose and quercetin 3-O-(2′′-O-galloyl)-β-d-glucopyranoside were reported for the first time in Chinese toon.     

Evaluation of extraction method for the analysis of carotenoids in fruits and vegetables

This study evaluated a suitable extraction method for a wide range of sample matrices in carotenoid analysis. Using canned tomato juice as a representative sample, it is shown that two solvents of low biological hazard, ethanol and hexane are the most suitable for extracting carotenoids from the matrix. The use of double extraction, each with 35 ml of ethanol:hexane mixture (4:3, by volume), resulted in good recoveries of carotenoids (lycopene 96%, α-carotene 102% and β-carotene 93–100%). Coefficients of variation conducted on different days were: lycopene 5% and β-carotene 7%. An application of the established method to various kinds of fruit and vegetable matrices is also shown, using carrot and spinach as representative samples of root and leafy vegetables, for determining recoveries of added carotenoids. The average percent recoveries of added carotenoids from canned tomato juice, carrot and spinach were: 101, 99.8 and 101% for α-carotene (12.4, 24.8, 49.6 and 99.2 μg/10 ml of added α-carotene); and 98.1, 99.7 and 96.1 percent for β-carotene (25.5, 50.9, 101 and 201 μg/10 ml of added β-carotene). These similar recoveries over the explored concentration ranges confirm that the application of established extraction method is unaffected by differences in matrix composition of the samples.     

Anthocyanin profiles in south Patagonian wild berries by HPLC-DAD-ESI-MS/MS

Chilean Patagonia is one of the most beautiful natural scenarios, with a great diversity of habitats and vascular plants, including different berry fruits. There is no scientific information about the polyphenol profiles of most of these fruits, as well as about their potential use as functional food.Samples of 10 different berry species were collected in the Magallanes region in the extreme South of Chile. Their anthocyanin profiles were studied using liquid chromatography with photodiode array and mass spectrometry detection on the basis of retention times, UV and MS/MS spectra. In addition, total anthocyanin concentrations obtained by HPLC-DAD, antioxidant capacity estimated by TEAC (as trolox equivalent), and ascorbic acid contents were determined in these fruits. The studied species differed in their berry anthocyanin profiles and concentrations. In the berries of Berberis genus (Berberis microphylla, Berberis empetrifolia and Berberis ilicifolia), a predominance of delphinidin, petunidin and malvidin 3-glucoside was observed; they are the fruits with the highest total anthocyanin concentration (22.91–35.99, 16.11–21.40 and 13.70 μmol/g, respectively). In Ribes magellanicum and Ribes cucullatum, the 3-glucoside and 3-rutinoside derivates of cyanidins predominated, especially for R. cucullatum, showing intermediate total anthocyanin concentrations. The other studied berries (Gaultheria mucronata, Gaultheria antarctica, Rubus geoides, Myrteola nummularia and Fuchsia magellanica) presented as main anthocyanidin cyanidin and/or delphinidin derivates, with lower total concentrations in comparison with the other studied species. Antioxidant activity and especially the ascorbic acid concentration observed in these fruits were higher than those described for other widely consumed berries, reaching levels up to 75.1 μmol/g and 198.8 mg/100 g, respectively. These findings suggest that some of the berry species from Patagonia have an interesting potential to be used as functional food.     

Effect of cyclodextrins on the thermodynamic and kinetic properties of cyanidin-3-O-glucoside

In this study, the effect of α and β-cyclodextrin on cyanidin-3-O-glucoside color was investigated by UV–visible absorption techniques. The equilibrium and kinetic constants of the network of chemical reactions taking place in cyanidin-3-O-glucoside were also studied in water at 25 °C by UV–visible absorption techniques. The results showed that the addition of β-cyclodextrin resulted in the fading of anthocyanin solution, and this fading effect was greater at higher pH. This anti-copigmentation effect is caused by the selective inclusion and stabilization of the anthocyanin colorless forms into the β-cyclodextrin cavity. Oppositely, no changes were observed in the cyanidin-3-O-glucoside absorption spectra with the addition of α-cyclodextrin.Direct pH jump, from thermally equilibrated solutions at pH = 1.0 (flavylium cation, AH⁺), shows three kinetic processes: formation of the base A, hydration reaction to form the hemiketal B and the chalcone cis–trans isomerization (Cc–Ct). The results obtained clearly indicated that the equilibrium and kinetic constants of the network of chemical reactions taking place in cyanidin-3-O-glucoside were affected by the presence of β-cyclodextrin. Molecular inclusion in the β-cyclodextrin cavity resulted in the increase of the isomerization observed rate constant (k_obs) at pH 5.3 and in the increase of the hydration equilibrium constant K_h which is in agreement with the fading of the anthocyanin solution. For the macrocycle α-cyclodextrin, no significant changes were observed on the equilibrium and kinetic constants, which suggests that the inclusion of cyanidin-3-glucoside in the α-cyclodextrin's cavity is not favored.