Browsing by Author "Skaar, Irene"

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    Anthocyanin Profile and Antioxidant Activity of Edible Leaves of Dissotis brazzae Cogn (Melastomataceae)
    (Journal of Food and Nutrition Sciences, 2020) Adaku, Christopher; Skaar, Irene; Gumisiriza, Hannington; Byamukama, Robert; Jordheim, Monica; Andersen, JOyvind Moksheim
    Anthocyanins are colored bioactive phytochemicals in the class of flavonoids with high potential as dietary antioxidants. Demand for anthocyanins in functional food and nutraceutical industries has continued to increase over the past decades. However, sources of anthocyanins for commercial exploitation are currently limited. Tropical Africa and Uganda in particular, harbors many plant species with potential to serve as new sources of anthocyanins. In this study, the anthocyanin profile and antioxidant activity of edible leaves of Dissotis brazzae, a plant of tropical African origin, were investigated. Two known anthocyanins, (1) cyanidin 3-O-β-glucopyranoside (1.28±0.44 mg/g fr. wt.) and (2) cyanidin 3-O-α-rhamnopyranoside (1.89±0.42 mg/g fr. wt.), were isolated from D. brazzae purple leaves by a combination of chromatographic techniques. Their structures were elucidated mainly by homo- and heteronuclear NMR spectroscopy and online HPLC/UV-Vis spectroscopy. The isolated anthocyanins showed appreciable level of antioxidant activity against DPPH, with 1 (IC50=9.2±0.2 μg/ml) showing slightly higher antioxidant potency than 2 (IC50=14.0±0.6 μg/ml). However, quercetin (IC50=4.5±0.4 μg/ml) used as a reference showed a higher antioxidant activity than 1 and 2. The total anthocyanin content of D. brazzae leaves (317 mg/100g) was within the range (80 – 680 mg/100g) of anthocyanins content in most dietary sources. This is the first report of fully characterised anthocyanins from the genus Dissotis, which may be of taxonomic importance. A new dietary source of the rare cyanidin 3-O-α-rhamnopyranoside has been identified.
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    Anthocyanin Profile and Antioxidant Property of Anti-asthma Flowers of Cordyline terminalis (L.) Kunth (Agavaceae)
    (Natural Product Communications, 2020) Adaku, Christopher; Skaar, Irene; Byamukama, Robert; Jordheim, Monica; Øyvind, M. Andersen
    Cordyline terminalis flower is traditionally used to treat asthma and the purple color of the flower is suggestive of anthocyanins. Thepurpose of this study was to characterize and determine the antioxidant property of anthocyanins from C. terminalis purple flowers. five anthocyanins, cyanidin 3,5-di-O-β-glucopyranoside (2.6 ± 0.2 mg/g fr. wt) (1), peonidin 3,5-di- O- β-glucopyranoside (2.8 ± 0.3 mg/g fr. wt) (2), cyanidin 3-O- β-(6″-O- E- p- caffeoylglucopyranoside)- 5-O- β-glucopyranoside (3.2 ± 0.2 mg/g fr. wt) (3), cyanidin 3-O- β-(6″-O- E- p- coumaroylglucopyranoside)- 5-O- β-glucopyranoside (6.2 ± 0.4 mg/g fr. wt) (4), and peonidin 3-O- β-(6″-O- E- p- c oumaroylglucopyranoside)-5-O- β-glucopyranoside (9.8 ± 0.2 mg/g fr. wt) (5), were isolated from the flowers of C. terminalis by a combination of chromatographic techniques. Their structures were established by UV-visible, NMR, and ESI-MS. The extract exhibited appreciable antioxidant activity (IC50 ± SD = 13.1 ± 0.8 μg/mL) against quercetin (IC50 ± SD = 4.5 ± 0.4 μg/mL) compared to the individual anthocyanins (IC50 ± SD = 13.8 ± 0.5 to 16.4 ± 0.7 μg/mL) when measured using the 2,2-diphenyl- 1-picryl- hydrazyl method. Cordyline terminalis flowers extract may be justified for use and standardization as herbal remedy for asthma.
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    Anthocyanins from Mauve Flowers of Erlangea tomentosa (Bothriocline longipes) Based on erlangidin – The first Reported Natural Anthocyanidin with C-ring methoxylation
    (Phytochemistry Letters, 2019) Adaku, Christopher; Skaar, Irene; Berland, Helge; Byamukama, Robert; Jordheim, Monica; Andersen, Øyvind M.
    Above 700 different anthocyanins have been isolated from plants. These flavonoid pigments are grouped after the number and position of hydroxy- and methoxy-groups on their anthocyanidin A- and B-rings, which influence their properties. In this study two new anthocyanins, erlangidin 5-O-(4″-(E-caffeoyl)-6″-(malonyl)-β-glucopyranoside)- 3′-O-(6‴-(3II-(β-glucopyranosyl)-E-caffeoyl)-β-glucopyranoside) and erlangidin 5-O-(6″-(malonyl)- β-glucopyranoside)-3′-O-(6‴-(3II-(β-glucopyranosyl)-E-caffeoyl)-β-glucopyranoside) were isolated from purple flowers of Erlangea tomentosa (Bothriocline longipes) Oliv. & Hiern (Asteraceae) in amounts of ∼1.6 and 0.6 mg/g fr. wt., respectively. They were found to contain the first reported natural anthocyanidin with a methoxy-group on the heterocyclic C-ring, which we have given the name erlangidin.” During extraction, isolation and storage in acidified methanolic solvents the two anthocyanins were both partly converted to their demalonylated and methylmalonyl esterified forms. Spectroscopic and chromatographic characteristics for erlangidin in comparison with the common anthocyanidins, which it might be mistaken for, are included.
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    Anthocyanins with Unusual Furanose Sugar (Apiose) from Leaves of Synadenium Grantii (Euphorbiaceae)
    (Elsevier, 2010) Andersen, Øyvind M.; Jordheim, Monica; Byamukama, Robert; Mbabazi, Angella; Ogweng, George; Skaar, Irene; Kiremire, Bernard
    Four anthocyanins, cyanidin 3-O-(200-(5000-(E-p-coumaroyl)-b-apiofuranosyl)-b-xylopyranoside)-5-O-bglucopyranoside, cyanidin 3-O-(200-(5000-(E-p-coumaroyl)-b-apiofuranosyl)-b-xylopyranoside), cyanidin 3-O-(200-(5000-(E-caffeoyl)-b-apiofuranosyl)-b-xylopyranoside) and cyanidin 3-O-(200-(5000-(E-feroyl)-bapiofuranosyl)- b-xylopyranoside) were isolated from leaves of African milk bush, (Synadenium grantii Hook, Euphorbiaceae) together with the known cyanidin 3-O-b-xylopyranoside-5-O-b-glucopyranoside and cyanidin 3-O-b-xyloside. The four former pigments are the first reported anthocyanins containing the monosaccharide apiose, and the three 5000-cinnamoyl derivative-200-(b-apiosyl)-b-xyloside subunits have previously not been reported for any compound.
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    New Anthocyanidin and Anthocyanin Pigments from Blue Plumbago
    (Journal of agricultural and food chemistry, 2012) Skaar, Irene; Jordheim, Monica; Byamukama, Robert; Mbabazi, Angella; Wubshet, Sileshi G.; Kiremire, Bernard; Andersen, Øyvind M.
    Phytochemical investigations of blue plumbago (Plumbago auriculata Poir. syn. Plumbago capensis Thunb.) flowers have led to the isolation of six new anthocyanins based on three new anthocyanidins with 5,7-dimethoxylated A-rings. Their structures were identified by 2D nuclear magnetic resonance and high-resolution mass spectrometry as the 3-O-β- galactopyranosides (1,2,4) and 3-O-α-rhamnopyranosides (3,5,6) of 5,7-dimethyldelphinidin, 5,7-dimethylpetunidin, and 5,7- dimethylmalvidin. Identification of 1−6 implies new structures for the previously reported anthocyanidins pulchellidin, europinidin, and capensinidin to be 5,7-dimethoxy-3,3′,4′,5′-tetrahydroxyflavylium, 5,7,3′-trimethoxy-3,4′,5′-trihydroxyflavylium, and 5,7,3′,5′-tetramethoxy-3,4′-dihydroxyflavylium cations, respectively. The anthocyanins (0.4 mg/g flowers) were accompanied by the dihydroflavonol taxifolin 3′-O-β-glucopyranoside (1.4 mg/g) and the flavonols 5-methylquercetin 3-O-α-rhamnopyranoside (8.8 mg/g) and 5-methylquercetin (0.4 mg/g). The anthocyanins 1−6 are the first reported natural anthocyanins with no free hydroxyl groups in their 5- and 7-positions on their A-rings. They have thus no possibility of forming the tautomeric quinonoidal bases (anhydrobases), which are related to the free hydroxyl groups in the 5- and 7-positions of previously reported anthocyanins. The genes behind the 5,7-dimethoxylated anthocyanins might be useful for making anthocyanins with special properties (colors, etc.).
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    Purple anthocyanin colouration on lower (abaxial) leaf surface of Hemigraphis colorata (Acanthaceae)
    (Phytochemistry, 2014) Skaar, Irene; Adaku, Christopher; Jordheim, Monica; Byamukama, Robert; Kiremire, Bernard; Andersen, Øyvind M.
    The functional significance of anthocyanin colouration of lower (abaxial) leaf surfaces is not clear. Two anthocyanins, 5-O-methylcyanidin 3-O-(300-(b-glucuronopyranosyl)-b-glucopyranoside) (1) and 5-O-methylcyanidin 3-O-b-glucopyranoside (2), were isolated from Hemigraphis colorata (Blume) (Acanthaceae) leaves with strong purple abaxial colouration (2.2 and 0.6 mg/g fr. wt., respectively). The glycosyl moiety of 1, the disaccharide 300-(b-glucuronopyranosyl)-b-glucopyranoside), has previously been reported to occur only in a triterpenoid saponin, lindernioside A. The structural assignment of the aglycone of 1 and 2 is the first complete characterisation of a natural 7-hydroxy-5-methoxyanthocyanidin. Compared to nearly all naturally occurring anthocyanidins, the 5-O-methylation of this anthocyanidin limits the type of possible quinoidal forms of 1 and 2 to be those forms with keto-function in only their 7- and 40-positions