Departmental Bulletin Paper Distribution and Composition of Flavonols in the Flowers of Rhododendron oldhamii Maxim.

Huyen, Dao Thi Thanh  ,  Van, Dao Thanh  ,  Huang, KuangLiang  ,  Miyajima, Ikuo

61 ( 1 )  , pp.37 - 40 , 2016-02-29 , Faculty of Agriculture, Kyushu University
Rhododendron oldhamii Maxim. is an endemic evergreen azalea in Taiwan and recently planted in Japan. This species is distributed from 150 m to 2,700 m above sea level. Red–flowered species with petal color ranging from orange to red normally contain only cyanidin series anthocyanins and no flavonols in their petals. However, the color of blotches on the upper lobe of the petals or at the base of the funnel is slightly reddish–purple that suggested the presence of flavonols. In R. oldhamii, cyanidin 3–arabinoside and cyanidin 3–galactoside are two major anthocyanins in both upper and lower petals but flavonols were only detected in the upper petals, specifically in the blotches areas, by HPLC analysis. Two major flavonols were identified as quercetin glycosides. The pH value of reddish–purple blotches was slightly higher than that of surrounding areas and lower petals. These results indicated that co–pigmentation between cyaniding glycosides and quercetin glycosides pigments associated with higher pH condition, causing reddish–purple color for blotches in R. oldhamii flowers.

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