Chemical studies on different color development in blue- and red-colored sepal cells of Hydrangea macrophylla

To clarify the cause of the difference in blue and red color development of hydrangea sepals, Hydrangea macrophylla, we analyzed the organic and inorganic components in the colored cells. To obtain colored protoplasts, each blue and red sepal tissue was treated with a combination of cellulase and pectinase, and then from the suspension of the olored and colorless protoplast mixture colored cells of the same hue were collected with a micro-pipette. The content of organic components (delphinidin 3-glucoside, chlorogenic acid, neochlorogenic acid and 5-O-p-coumaroylquinic acid) and Al(3+) in each colored cell was quantified respectively by semimicro-HPLC and graphite furnace atomic absorption spectroscopy (GFAAS). In the blue cells 13 eq. of 5-O-acylquinic acids and 1.2 eq. of Al(3+) to anthocyanin were contained. Contrary to this result, in the red cells, only 3.6 eq. of 5-O-acylquinic acids and 0.03 eq. of Al(3+) were detected. A reproduction experiment of each blue and red sepal color by mixing those components concluded that, for blue coloration, both 5-O-acylquinic acids and Al(3+) were essential.