Øyvind M. Andersen

Flavonoids : chemistry, biochemistry, and applications

【From the n-butanol fraction of the water extract of the seeds of Phaseolus radiatus, two flavonoid C-glycosides were isolated and identified as iso-vitexin (1) and vitexin (2) by spectroscopic methods.】

Anthocyanin-rich extract decreases indices of lipid peroxidation and DNA damage in vitamin E-depleted rats

Anthocyanins are secondary plant metabolites responsible for the blue, purple, and red color of many plant tissues. The phenolic structure of anthocyanins conveys marked antioxidant activity in model systems via donation of electrons or hydrogen atoms from hydroxyl moieties to free radicals. Dietary intakes of anthocyanins may exceed 200 mg/day, however, little is known about their antioxidant potency in vivo. Consequently, the aim of this study was to establish whether anthocyanins could act as putative antioxidant micronutrients. Rats were maintained on vitamin E-deficient diets for 12 weeks in order to enhance susceptibility to oxidative damage and then repleted with rations containing a highly purified anthocyanin-rich extract at a concentration of 1 g/kg diet. The extract consisted of the 3-glucopyranoside forms of delphinidin, cyanidin, petunidin, peonidin, and malvidin. Consumption of the anthocyanin-repleted diet significantly improved (p <.01) plasma antioxidant capacity and decreased (p <.001) the vitamin E deficiency-enhanced hydroperoxides and 8-Oxo-deoxyguanosine concentrations in liver. These compounds are indices of lipid peroxidation and DNA damage, respectively. Dietary consumption of anthocyanin-rich foods may contribute to overall antioxidant status, particularly in areas of habitually low vitamin E intake.

Colour and stability of pure anthocyanins influenced by pH including the alkaline region

This study on anthocyanin colour variation (intensity, λmax, e) over the pH range 1–9 during 60 days of storage, was conducted on petunidin 3-[6-O-(4-O-E-p-coumaroyl-O-α-l-rhamnopyranosyl)-β-d-glucopyranoside]-5-O-β-d-glucopyranoside (petanin) and cyanidin 3-O-β-d-glucopyranoside (cy3glc) at 10 and 23°C. Compared to cy3glc, petanin afforded higher colour intensity and higher or similar stability throughout the whole pH range. At pH 4.0, 84% of petanin was intact after 60 days storage at 10°C, while the corresponding solution of cy3glc was totally degraded. At pH 8.1 the colour intensity of petanin was even higher than at the lowest pH values. The visible λmax absorption of petanin after 5 days at pH 8.1 at 10°C was similar or higher than the corresponding absorptions of the fresh solutions of cy3glc at any pH. The use of anthocyanins like petanin as food colorants in slightly alkaline products (bakery, milk, egg, etc.) should therefore be considered—at least in products with limited storage time kept in a refrigerator..

Colour and stability of the six common anthocyanidin 3-glucosides in aqueous solutions

Abstract This study on anthocyanin stability and colour variation ( λ max , e ) in the pH range 1–12 during a period of 60 days storage at 10 and 23°C, was conducted on the 3-glucosides of the six common anthocyanidins. It was mostly in the alkaline region that differences in colour and stability became significant. Although it has been generally accepted that anthocyanins are stable only at low pH values, this study revealed that, for some of the anthocyanin 3-glucosides (e.g. malvidin 3-glucoside), the bluish colours were rather intense and stability relatively high in the alkaline region. Thus, they can be regarded as potential colorants for some slightly alkaline food products.

Flavonoids from red onion (Allium cepa)

Abstract Quercetin 3,7,4′-O-β-triglucopyranoside together with quercetin, quercetin 4′-O-β-glucopyranoside and quercetin 3,4′-O-β-diglucopyranoside were isolated from the pigmented scales of Allium cepa var. ‘Red Baron’. The former flavonol has previously been reported to be formed when cell cultures of a Vitis hybrid is fed with quercetin. Minor amount of taxifolin 4′-O-β-glucopyranoiside, a rare dihydroflavonol, was also detected. The structures were established on the basis of acid hydrolysis, chromatography (TLC and HPLC) and homo- and heteronuclear NMR spectroscopic techniques.

Flavonoids from blue flowers of Nymphaèa caerulea

Abstract Seven flavonols including the novel 3-(2″-acetylrhamnosides) of myricetin and quercetin ( 2 and 6 ), the rare kaempferol 3-(2″-acetylrhamnoside) and quercetin 3-(3″-acetylrhamnoside), in addition to the 3-rhamnosides of kaempferol, quercetin and were isolated from blue flowers of the African water lily Nymphaea caerulea (= Nymphaea capensis ). Their structures were elucidated by a combination of chromatography and homo- and heteronuclear two-dimensional NMR techniques and electrospray MS for compound 2 .

Syringetin 3-O-(6″-acetyl)-β-glucopyranoside and other flavonols from needles of norway spruce, Picea abies

Abstract The novel flavonol, syringetin 3- O -(6″-acetyl)- β -glucopyranoside, has been isolated from needles of Norway spruce ( Picea abies ) together with the 3- O -(6″-acetyl)- β -glucopyranosides of isorhamnetin and kaempferol, the 3- O -(6″- α -rhamnopyranosyl)- β -glucopyranosides of laricitrin, isorhamnetin, myricetin, quercetin and kaempferol and the 3- O - β -glucopyranosides of laricitrin, isorhamnetin, myricetin, quercetin and kaempferol. Most of the flavonols have been isolated for the first time from Norway spruce. Kaempferol 3- O -(6″-acetyl)- β -glucopyranoside has previously been isolated from Senecio aureus , but without determination of the binding site of the acetyl group. Structure determination of the flavonols was achieved from TLC, 1 H NMR and UV shift reagent data, and, in most cases, 13 C NMR and MS.

Combination of chromatographic techniques for the preparative isolation of anthocyanins — applied on blackcurrant (Ribes nigrum) fruits

A combination of column chromatography on Toyopearl HW-40F gel and reversed-phase high-performance liquid chromatography enabled us to preparatively separate anthocyanins, without any re-application of overlapping bands of the major (the 3-O-glucosides and 3-O-rutinosides of delphinidin and cyanidin) and minor (the 3-O-rutinosides of peonidin and malvidin) anthocyanins in a 0.81-g sample from blackcurrant (Ribes nigrum) fruits. Anthocyanins substituted with methoxyl groups on the aglycone have never been detected previously in the genus Ribes. By variation of sample loading, flow-rate and solvent strength, Toyopearl HW-40F gel gave rise to chromatograms with higher resolution between the anthocyanidin 3-rutinoside and anthocyanidin 3-glucoside bands than Sephadex LH-20 gel, in all cases.

Anthocyanins from a Norwegian potato cultivar

Abstract The main anthocyanins of purple sprouts of a Norwegian potato cultivar, Solanum tuberosum L., were isolated from a purified methanolic extract by preparative HPLC. Their structures were determined to be the novel anthocyanins, petunidin 3- O -[6- O -(4- O - E -caffeoyl- O -α-rhamnopyranosyl)-β-glucopyranoside]-5- O -β-glucopyranoside ( 1 ) (10%) and peonidin, 3- O -[6- O -(4- O - E -caffeoy1- O -α-rhamnopyranosyl)-β-glucopyranoside]-5- O -β-glucopyranoside ( 2 ) (6%) in addition to petunidin, 3- O -[6- O -(4- O-E -p- coumaroyl -O- α-rhamnopyranosyl)-β-glucopyranoside]-5- O -β-g1ucopyranoside, petanin ( 3 ) (37%) and peonidin, 3- O -[6- O -(4- O - E - p -coumaroyl- O -α-rhamnopyranosyl)-β-glucopyranoside]-5- O -β-glucopyranoside, peonanin ( 4 ) (25%). The same major anthocyanins, however, in other proportions (4, 54, and 32%, for 1 , 3 , and 4 , respectively), were also found in the thin violet zone located in the flesh 0.5–1 cm from the surface of the tubers. This is the first report on anthocyanins from S . tuberosum, which are acylated with caffeic acid.

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%).