Quantitative analysis of taxiphyllin, a cyanogenic glycoside, in the leaves of Hydrangea macrophylla var. thunbergii

The dried and fermented leaves of Hydrangea macrophylla var. thunbergii are currently used as crude drugs (Sweet Hydrangea Leaf) with a sweet taste for patients with diabetes. In recent years, cases of food poisoning with symptoms of vomiting etc. have been reported after drinking a decoction of this crude drug. Cyanogenic glycosides have been suggested as potential causative agents. However, cyanogenic glycosides from H. macrophylla var. thunbergii was ambiguous. In the present study, we found that the leaves contained the cyanogenic glycoside taxiphillin (1). Next, the content of 1 in leaves of different sizes, colors, parts, and growth periods was quantified. In addition, we prepared the leaves of plants grown in five types of soils with different pH values (pH 5.0–7.5). The content of 1 in the leaves of the plants grown in these soils was quantified. The content of 1 varied greatly, with more than a three-fold difference, depending on when the leaves were collected from the plants. Furthermore, we compared the content of 1 in the crude drug obtained under different processing conditions for H. macrophylla var. thunbergii. The results showed that 1 was mostly hydrolyzed during plant processing. It has been suggested that cyanogenic glycosides are not the causative constituents of food poisoning.

Graphical abstract