Singlet oxygen quenching by anthocyanin's flavylium cations

The quenching of singlet molecular oxygen (¹O₂) by the flavylium cation form of six widespread anthocyanin derivatives: cyanidin 3-glucoside (CG), cyanidin 3-rutinoside (CR), cyanidin 3-galactoside (CGL), malvidin (M), malvidin 3-glucoside (MG) and malvidin 3,5-diglucoside (MDG) was studied in 1% HCl methanol solution by time-resolved phosphorescence detection (TRPD) of ¹O₂ and photostationary actinometry using perinaphthenone and methylene blue as sensitizers, respectively. The average value of the total (k₀) and chemical (k_c) quenching rate constants were ～ 4×10⁸ m^?1 s^?1 and 3×10⁶ m^?1 s^?1, respectively, indicating the good performance of the studied anthocyanins as catalytic quenchers of ¹O₂. The quenching efficiency was larger for malvidin than for cyanidin derivatives, probably by the extra electron-donating methoxy group in ring B of the malvidin derivatives; and it was also dependent on the number and type of glycosylated substitution. As observed for other phenolic-like derivatives, the quenching of ¹O₂ by anthocyanins was mediated by a charge-transfer mechanism, which was modulated by the total number of –OR substituents that increases the electron-donating ability of these compounds.     

Synergistic antioxidant effect of catechin and malvidin 3-glucoside on free radical-initiated peroxidation of linoleic acid in micelles

The inhibitory effect of anthocyanins has been investigated in the peroxidation of linoleic acid in micelles in the presence and in the absence of (+)-catechin. The peroxidation was initiated by thermal decomposition of 2,2(')-azobis[2-(2-imidazolin-2-yl)propane], and the kinetics of peroxidation were followed by measuring the rate of oxygen consumption and the rate of disappearance of the antioxidant. The analysis of the antioxidant effect of various anthocyanins, alone or in the presence of catechin, demonstrates that catechin, which is relatively inefficient at inhibiting linoleic acid oxidation, regenerates the highly efficient antioxidant malvidin 3-glucoside and, at a lower extent, peonidin 3-glucoside. The malvidin 3-glucoside recycling by catechin strongly increases the antioxidant efficiency of these two antioxidants. This protective mechanism appears specific for malvidin and peonidin 3-glucosides. The high unpaired spin density of the phenolic O atoms in the radicals generated by these anthocyanins, calculated by the semiempirical quantum chemical AM1 method, may explain the observed behavior.     

Kinetic study of the quenching reaction of singlet oxygen by tea catechins in ethanol solution

A kinetic study of the quenching reaction of singlet oxygen ((1)O(2)) with catechins (catechin (CA), epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECG), epigallocatechin gallate (EGCG)) and related compounds (5-methoxyresorcinol (MR), 4-methylcatechol (MC), and n-propyl gallate (PG)) was performed in ethanol at 35 degrees C. MR, MC, and PG are considered to be a model of resorcinol (A)-, catechol (B)-, and gallate (G)-rings in catechins, respectively. The overall rate constants, k(Q) (= k(q) + k(r), physical quenching + chemical reaction), for the reaction of catechins with (1)O(2) increased in the order of PG < MR < MC < CA < EC < EGC < ECG < EGCG. In a comparison of the rate constants, the relationship between quenching rates and chemical structures is discussed. The catechins which have lower peak oxidation potentials, E(P), show higher reactivities. It was observed that the chemical reaction (k(r)) is almost negligible in the quenching reaction of (1)O(2) by catechins. The k(Q) values of EGCG (1.47 x 10(8) M(-1) s(-1)) and ECG (7.81 x 10(7)) were found to be larger than those of lipids (1.3 x 10(5)-1.9 x 10(5) M(-1) s(-1)), amino acids (<3.7 x 10(7)), and DNA (5.1 x 10(5)). Further, these values are similar to those (1.15 x 10(8)-2.06 x 10(8) M(-1) s(-1)) of alpha- and gamma-tocopherol, ubiquinol-10, and gamma-tocopherol hydroquinone (plastoquinol model). The result suggests that catechins may contribute to the protection of oxidative damage in biological systems, by quenching (1)O(2).     

Anthocyanin composition of the fruit of Coriaria myrtifolia L

The anthocyanin composition of the fruit of Coriaria myrtifolia L. and the changes which occur during ripening were studied using HPLC-PAD and LC-MS. Ten anthocyanins were detected and identified by their absorption and mass spectra as the 3-glucoside and 3-galactoside derivatives of delphinidin, cyanidin, petunidin, peonidin and malvidin. Fruit ripening was accompanied by substantial changes in the anthocyanin profile, with methoxylated anthocyanins, i.e. malvidin and peonidin, predominating in the final stages of ripening, and the trihydroxylated anthocyanin, delphinidin, during the earlier stages. Furthermore, galactoside derivatives were more abundant than glucosides in the ripe fruit. At full maturity, the fruits of C. myrtifolia were very rich in anthocyanins with a content of 10.7% (on a dry weight basis), a level which is higher than that found in most fruits usually considered to be anthocyanin-rich. The ability to grow C. myrtifolia in damaged and nitrogen poor soils, together with the possibility of using this plant for the extraction of anthocyanin, makes it ideal for consolidating soils and repopulating semi-desert or fire-damaged areas.     

Anthocyanins of Cephaelis, Cynomorium, Euterpe, Lavatera and Pinanga

The two malonylated pigments, malonylmalvin and malvidin 3-malonylglucoside, were identified in petals of Lavatera maritima, which belongs to the Malvaceae, a family known to synthesise such pigments. Zwitterionic anthocyanins could not be detected in four other newly examined sources and common unacylated pigments were recorded. Thus, the fruits of the palms Euterpe edulis and Pinanga polymorpha have a mixture of cyanidin 3-glucoside and cyanidin 3-rutinoside, while the fruit of Cephaelis subcoriacea is coloured by cyanidin 3-glucoside. The latter pigment was also obtained from the reddish brown inflorescence of the parasitic plant Cynomorium coccineum.     

Black rice anthocyanins inhibit cancer cells invasion via repressions of MMPs and u-PA expression

Tumor metastasis is the most important cause of cancer death and various treatment strategies have targeted on preventing the occurrence of metastasis. Anthocyanins are natural colorants belonging to the flavonoid family, and are wildly used for their antioxidant properties. Here, we provided molecular evidence associated with the anti-metastatic effects of peonidin 3-glucoside and cyanidin 3-glucoside, major anthocyanins extracted from black rice (Oryza sativa L. indica), by showing a marked inhibition on the invasion and motility of SKHep-1 cells. This effect was associated with a reduced expression of matrix metalloproteinase (MMP)-9 and urokinase-type plasminogen activator (u-PA). Peonidin 3-glucoside and cyanidin 3-glucoside also exerted an inhibitory effect on the DNA binding activity and the nuclear translocation of AP-1. Furthermore, these compounds also exerted an inhibitory effect of cell invasion on various cancer cells (SCC-4, Huh-7, and HeLa). Finally, anthocyanins from O. sativa L. indica (OAs) were evidenced by its inhibition on the growth of SKHep-1 cells in vivo.     

Cyanidin glycosides in flowers of genus Corydalis (Fumariaceae)

Nine taxa of Corydalis were surveyed for their floral anthocyanins. Five cyanidin glycosides: cyanidin 3-glucoside, cyanidin 3-sambubioside, cyanidin 3-rutinoside, cyanidin 3-(2^G-xylosylrutinoside) and cyanidin 3-(2^G-xylosylrutinoside)-7-glucoside were isolated from these taxa and identified by chemical and spectroscopic techniques. A novel anthocyanin was found in the flowers of Corydalis elata and Corydalis flexuosa cultivars, and identified to be cyanidin 3-(2^G-xylosylrutinoside)-7-glucoside. Two anthocyanins, cyanidin 3-sambubioside and cyanidin 3-(2^G-xylosylrutinoside), were also found for the first time in Corydalis flowers. Furthermore, the major anthocyanin constituent of the flowers was cyanidin 3-sambubioside in the outer petals of Corydalis ambigua and Corydalis lineariloba, and cyanidin 3-rutinoside in those of Corydalis decumbens, Corydalis curvicalcarata and Corydalis speciosa. Similarly, Corydalis incisa contained cyanidin 3-(2^G-xylosylrutinoside), and C. flexuosa ‘China Blue’ and ‘Blue Panda’, and C. elata contained the most complex structural pigment, cyanidin 3-(2^G-xylosylrutinoside)-7-glucoside, as their dominant anthocyanin in their outer petals. According to the results of anthocyanin analyses, these nine plants were classified into four groups: groups A (three taxa), B (two taxa), C (one taxa) and D (three taxa). On the other hand, the anthocyanin constituent of their inner petals was composed of cyanidin 3-rutinoside as only one dominant anthocyanin.     

Cyanidin 3-[6-(p-coumaroyl)-2-(xylosyl)-glucoside]-5-glucoside and other anthocyanins from fruits of Sambucus canadensis.

From the fruits of Sambucus canadensis four anthocyanin glycosides have been isolated by successive application of an ion-exchange resin, droplet-counter chromatography and gel filtration. The structure of the novel, major (69.8%) pigment, cyanidin 3-O-[6-O-(E-p-coumaroyl-2-O-(beta-D-xylopyranosyl)-beta-D- glucopyranoside]-5-O-beta-D-glucopyranoside, was determined by means of chemical degradation, chromatography and spectroscopy, especially homo- and heteronuclear two-dimensional NMR techniques. The other anthocyanins were identified as cyanidin 3-sambubioside-5-glucoside (22.7%), cyanidin 3-sambubioside (2.3%) and cyanidin 3-glucoside (2.1%).     

Human tumor cell growth inhibition by nontoxic anthocyanidins, the pigments in fruits and vegetables

Anthocyanidins, the aglycones of anthocyanins, impart brilliant colors in many fruits and vegetables. The widespread consumption of diets rich in anthocyanin and anthocyanidins prompted us to determine their inhibitory effects on human cancer cell proliferation. Five anthocyanidins, cyanidin (1), delphinidin (2), pelargonidin (3), petunidin (4) and malvidin (5), and four anthocyanins, cyanidin-3-glucoside, cyanidin-3-galactoside, delphinidin-3-galactoside and pelargonidin-3-galactoside were tested for cell proliferation inhibitory activity against human cancer cell lines, AGS (stomach), HCT-116 (colon), MCF-7 (breast), NCI H460 (lung), and SF-268 (Central Nervous System, CNS) at 12.5-200 microg/mL concentrations. The viability of cells after exposure to anthocyanins and anthocyanidins was determined by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) colorimetric methods. The anthocyanins assayed did not inhibit cell proliferation of cell lines tested at 200 microg/mL. However, anthocyanidins showed cell proliferation inhibitory activity. Malvidin inhibited AGS, HCT-116, NCI-H460, MCF-7 and SF-268 cell growth by 69, 75.7, 67.7, 74.7 and 40.5%, respectively, at 200 microg/mL. Similarly, pelargonidin inhibited AGS, HCT-116, NCI H460, MCF-7 and SF-268 cell growth by 64, 63, 62, 63 and 34%, respectively, at 200 microg/mL. At 200 microg/mL, cyanidin, delphinidin and petunidin inhibited the breast cancer cell growth by 47, 66 and 53%, respectively. This is the first report of tumor cell proliferation inhibitory activity by anthocyanidins.     

Complex anthocyanins from Ipomoea congesta

Six acylated anthocyanins have been isolated from the flowers of Ipomoea congesta R. Brown. One has been previously described as an acylated peonidin derivative. Three others are isomers, derived from peonidin-3-(caffeylsophoroside)-5-glucoside. The fifth was characterised as peonidin-3-(p-coumarylcaffeylsophoroside)-5-glucoside and the last as peonidin-3-(coumarylsophoroside)-5-glucoside. It is noteworthy that the anthocyanins found in this species have the same glycosidic pattern, 3-sophoroside-5-glucoside, as those reported for the cyanidin derivatives in Ipomoea cairica flowers. Acylated anthocyanin occurrence in Tubiflorae order is of chemotaxonomical value.     

Covalent anthocyanin-flavonol complexes from flowers of chive, Allium schoenoprasum

The structures of eight anthocyanins have been determined in acidified methanolic extract of pale-purple flowers of chive, Allium schoenoprasum. Four of them have been identified as the anthocyanin-flavonol complexes (cyanidin 3-O-beta-glucosideAII) (kaempferol 3-O-(2-O-beta-glucosylFIII-beta-glucosideFII)-7-O-beta-gl ucosiduronic acidFIV) malonateAIII (AII-6-->AIII-1, FIV-2-->AIII-3), 1, (cyanidin 3-O-(3-O-acetyl-beta-glucosideAII) (kaempferol 3-O-(2-O-beta-glucosylFIII-beta-glucosideFII)-7-O-beta-gl ucosiduronic acidFIV) malonateAIII (AII-6-->AIII-1, FIV-2-->AIII-3), 2, and their 7-O-(methyl-O-beta-glucosiduronateFIV) analogous, 3 and 4. Pigments 1 and 2 are the first final identification of covalent complexes between an anthocyanin and a flavonol, while 3 and 4 are formed during the isolation process. The other four anthocyanins (5-8) were found to be the 3-acetylglucoside, 3-glucoside, 3-(6-malonylglucoside) and 3-(3,6-dimalonylglucoside) of cyanidin. The three latter pigments have earlier been identified as the major anthocyanins of the chive stem. The covalent anthocyanin-flavonol complexes show intramolecular association between the anthocyanidin (cyanidin) and flavonol (kaempferol) units, which influence the colour.     

Anthocyanins from red flowers of Camellia reticulata LINDL

Ten anthocyanins, cyanidin 3-sambubioside, 3-glucoside and their acylated derivatives, cyanidin 3-lathyroside and cyanidin 3-galactoside, were isolated from red flowers of Camellia reticulata. Their structures were determined on the basis of spectroscopic analyses, and the chemotaxonomic distribution of the accumulated anthocyanins in the petals of wild Camellia reticulata and C. pitardii var. yunnanica is discussed.     

Anthocyanins of grasses

The anthocyanin content of 23 grass species (Poaceae) belonging to five subfamilies has been determined. Altogether 11 anthocyanins were identified; the 3-(6″-malonylglucosides) and 3-glucosides of cyanidin, peonidin and delphinidin, the 3-(3″,6″-dimalonylglucoside), 3-(6″-rhamnosylglucoside) and 3-(6″-glucosylglucoside) of cyanidin, in addition to peonidin 3-(dimalonylglucoside) and delphinidin 3-(6″-rhamnosylglucoside). Anthocyanins acylated with one and/or two malonic acid moieties dominated the anthocyanin profiles of all the species in the subfamilies Pooideae and Panicoideae. On the other hand, the 3-glucoside and 3-rutinoside of cyanidin were the major anthocyanins in Sinarundinaria murielae (subfamily Bambusoideae) and Molinia caerulea (subfamily Arundinoideae), while the 3-glucosides of cyanidin and peonidin were the principal anthocyanins in rice, Oryza sativum (subfamily Oryzoideae). Pelargonidin derivatives and free anthocyanidins have previously been reported to occur in several Poaceae species, however, not identified in any of the species included in this survey.     

Acylated anthocyanidin 3-sophoroside-5-glucosides from Ajuga reptans flowers and the corresponding cell cultures

Four anthocyanins from Ajuga reptans flowers and its cell cultures were isolated, and a fifth was also characterized by HPLC-mass spectrometry. By means of chemical and spectroscopic analyses, their structures were identified as delphinidin 3-(p-coumaroyl-feruloyl)sophoroside-5-malonylglucoside, delphinidin 3-(diferuloyl)sophoroside-5-malonylglucoside, and cyanidin 3-(di-p-coumaroyl)sophoroside-5-glucoside, respectively. The other two were tentatively identified as delphinidin 3-(diferuloyl)sophoroside-5-glucoside and cyanidin 3-(feruloyl-p-coumaroyl)sophoroside-5-malonylglucoside. In neutral aqueous solution, the crude extract from A. reptans flower cell cultures and the major anthocyanin cyanidin 3-(di-p-coumaroyl)sophoroside-5-malonylglucoside were more stable than cyanidin 3-glucoside, and also prevented more efficiently peroxidation than did the latter. A. reptans flower cell culture anthocyanins may have a potential as natural colorants for food utilities or other purposes.     

Malonylated Anthocyanins from Bulbs of Red Onion,Allium cepa L.

Four cyanidin-based anthocyanins (1–4) were isolated from the red onion, Allium cepa L. Pigments 1 and 3 were identified as cyanidin 3-glucoside (Cy 3-Glc) and 3-malonylglucoside (Cy 3-MaGlc), respectively, by cochromatography with standard pigments. Anthocyanins 2 and 4 were respectively determined as cyanidin 3-laminaribioside (Cy 3-Lam) and 3-malonyllaminaribioside (Cy 3-MaLam), a new anthocyanin, mainly by NMR tech-niques. Malonylated anthocyanins 3 and 4 were found for the first time in red onions.     

Cyanidin 3-[6-(p-coumaroyl)-2-(xylosyl)-glucoside]-5-glucoside and other anthocyanins from fruits of sambucus canadensis

From the fruits of Sambucus canadensis four anthocyanin glycosides have been isolated by successive application of an ion-exchange resin, droplet-counter chromatography and gel filtration. The structure of the novel, major (69.8%) pigment, cyanidin 3-O-[6-O-(E-p-coumaroyl-2-O-(β- -xylopyranosyl)-β- -glucopyranoside]-5-O-β- -glucopyranoside, was determined by means of chemical degradation, chromatography and spectroscopy, especially homo- and heteronuclear two-dimensional NMR techniques. The other anthocyanins were identified as cyanidin 3-sambubioside-5-glucoside (22.7%), cyanidin 3-sambubioside (2.3 %) and cyanidin 3-glucoside (2.1 %).     

Superoxide radical- and peroxynitrite-scavenging activity of anthocyanins; structure-activity relationship and their synergism

Antioxidant activities of 15 purified bilberry anthocyanins together with pelargonidin 3-O-beta-D-glucopyranoside and 4'-O-methyl delphinidin 3-O-beta-D-glucopyranoside (MDp 3-glc), the major metabolite of delphinidin 3-O-beta-D-glucopyranoside (Dp 3-glc), were evaluated in order to study the structure-antioxidant activity relationship and any synergism among them in the mixture. Both aglycone structure and the attached sugar moiety affected the O*2- and ONOO- -scavenging activities, although the effect of the attached sugar moiety was smaller than that of the aglycone structure. The potency of activity toward the superoxide radical was in the following order: delphinidin > petunidin > malvidin =approximately cyanidin>(+)-catechin > peonidin > pelargonidin. The activity toward ONOO- was: delphinidin > cyanidin =approximately petunidin > malvidin =approximately (+)-catechin > peonidin > pelargonidin. It was confirmed that methylation of 4'-OH markedly reduced the antioxidant activity of anthocyanin. Further, it was revealed that synergism occurred in both - and ONOO- -scavenging activities among the anthocyanins in the mixture.     

On the antioxidant properties of therapeutic drugs: quenching of singlet molecular oxygen by aminosalicylic acids

The ability of the widely employed therapeutic drugs 4-aminosalicylic acid and 5-aminosalicylic acid to act as singlet molecular oxygen (O(2)((1)delta(g))) scavengers was investigated at pH 7 and pH 12. The isomer 3-aminosalicylic acid was also included in the study for comparative purposes. All three compounds quench photochemically generated O(2)((1)delta(g)) with rate constants in the range of 10(7)-10(8) x M(-1)s(-1), depending on the experimental conditions. No chemical reaction (oxidation of the aminosalicylic acids) was detected at the neutral pH, whereas at pH 12 both chemical and physical interactions with O(2)((1)delta(g)) operated. The physical process implies the de-activation of the oxidant species without destruction of the aminosalicylic acid. The quotients between the overall and reactive rate constants for O(2)((1)delta(g)) quenching at pH 12 (k(r)/k(t) ratios), which account for the actual effectiveness of photodegradation, were relatively low (0.22, 0.04, and 0.06 for 3-, 4- and 5-aminosalicylic acids, respectively). This indicates that the drugs, particularly the 4- and 5-amino derivatives, de-activate the excited oxygen species, at both pH values studied, mainly in a physical fashion, preventing its photodegradation and providing an antioxidative protection for possible photo-oxidizable biological targets in the surroundings.     

Triacylated cyanidin 3-(3X-glucosylsambubioside)-5-glucosides from the flowers of Malcolmia maritima

Three acylated cyanidin 3-(3(X)-glucosylsambubioside)-5-glucosides (1-3) and one non-acylated cyanidin 3-(3(X)-glucosylsambubioside)-5-glucoside (4) were isolated from the purple-violet or violet flowers and purple stems of Malcolmia maritima (L.) R. Br (the Cruciferae), and their structures were determined by chemical and spectroscopic methods. In the flowers of this plant, pigment 1 was determined to be cyanidin 3-O-[2-O-(2-O-(trans-sinapoyl)-3-O-(beta-D-glucopyranosyl)-beta-D-xylopyranosyl)-6-O-(trans-p-coumaroyl)-beta-D-glucopyranoside]-5-O-[6-O-(malonyl)-(beta-D-glucopyranoside) as a major pigment, and a minor pigment 2 was determined to be the cis-p-coumaroyl isomer of pigment 1. In the stems, pigment 3 was determined to be cyanidin 3-O-[2-O-(2-O-(trans-sinapoyl)-3-O-(beta-D-glucopyranosyl)-beta-D-xylopyranosyl)-6-O-(trans-p-coumaroyl)-beta-d-glucopyranoside]-5-O-(beta-D-glucopyranoside) as a major anthocyanin, and also a non-acylated anthocyanin, cyanidin 3-O-[2-O-(3-O-(beta-D-glucopyranosyl)-beta-D-xylopyranosyl)-beta-D-glucopyranoside]-5-O-(beta-D-glucopyranoside) was determined to be a minor pigment (pigment 4). In this study, it was established that the acylation-enzymes of malonic acid has important roles for the acylation of 5-glucose residues of these anthocyanins in the flower-tissues of M. maritima; however, the similar enzymatic reactions seemed to be inhibited or lacking in the stem-tissues.     

Survey of bioactive components in Western Canadian berries

Berries native to Western Canada were analyzed for total anthocyanins, total phenolics, and trolox equivalent antioxidant activity (TEAC). Values ranged from 1.60 to 9.55 mmol trolox equivalent per 100 g fresh mass. Anthocyanin content ranged from 41.6 (in red twinberries) to 1081 mg cyanidin-3-glucoside equivalents per 100 g fresh mass (in honeysuckle fruits). Honeysuckle fruits contained the highest amount of total polyphenols, 1111 mg gallic acid equivalents per 100 g, among analyzed fruits. Additionally, anthocyanins in the investigated berries were identified and characterized by HPLC - electrospray ionization - tandem mass spectrometric method coupled with diode array detection. The number of anthocyanins varied from 4 in saskatoon berries (Amelanchier alnifolia Nutt.) to 20 in bilberries (Vaccinum myrtilloides Michx.). In all the samples analyzed, 6 common anthocyanidins:, cyanidin, delphinidin, pelargonidin, petunidin, peonidin, and malvidin, were found. Half the analyzed berries contained acylated anthocyanins, but a significant amount was found only in bilberries. The analyzed berry seed oils contained high amounts of unsaturated fatty acids (over 90%), but only the golden currant seed oil contained gamma-linolenic acid.