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.

Production of Dihydroisocoumarins by Callus Induction from Hydrangea macrophylla var. thunbergii Leaves

Dihydroisocoumarins, hydrangenol 8-O-β-D-glucopyranoside (1), phyllodulcin 8-O-β-D-glucopyranoside (2), hydrangenol (3), and phyllodulcin (4), are well-known as the major secondary metabolites in the leaves of Hydrangea macrophylla var. thunbergii. Dihydroisocoumarins are pharmaceutical compounds with diverse bioactivity. Although dihydroisocoumarins are commonly isolated from Hydrangea plants or via organic chemical synthesis, their production via callus induction is considered a promising alternative. In the present study, callus induction and proliferation of H. macrophylla var. thunbergii, and constituents 1-4 were quantified in calluses cultured in 17 different media. We found that the combination of the phytohormones 2,4-dichlorophenoxyacetic acid (2,4-D) and 6-benzylaminopurine (BA) was useful for callus proliferation in H. macrophylla var. thunbergii. The balance and concentrations of indole-3-acetic acid (IAA) and BA greatly affected the contents of 1-4. Particularly, 1 (2.03-3.46% yield from the dry callus) was successfully produced from the callus induced by IAA (0.5 mg/L) and BA (1.0 mg/L) at yields comparable to isolated yields from plants. To the best of our knowledge, this is the first study to show that the calluses of H. macrophylla var. thunbergii contained 1. These findings may be useful for producing bioactive dihydroisocoumarins.

Comparison of Growth in Hydrangea macrophylla var. thunbergii Grown in Different Soil pH and Quantitative Analysis of Its Sweetness-Related Constituents

Dried and fermented (processed) leaves of Hydrangea macrophylla Seringe var. thunbergii Makino (Hydrangeae Dulcis Folium) are currently used as a crude drug with a sweet taste for diabetic patients and as an oral refrigerant. The sweet taste of this crude drug is primarily attributed to phyllodulcin. However, there are currently no standards for the cultivation of H. macrophylla var. thunbergii and the isolation and production of the primary constituents of this crude drug. In the present study, we prepared five types of soils with different pH values (pH 7.5-5.0) and investigated the effects of these soils on the growth of this plant. The contents of phyllodulcin and its glycoside, phyllodulcin 8-O-β-D-glucopyranoside, in the leaves of plants grown in these soils were quantified. Furthermore, the correlation between the sweetness of Hydrangeae Dulcis Folium and phyllodulcin was investigated. The results showed that soils with pH ranging from 7.0 to 5.5 was not only suitable for plant growth but also increased the content of phyllodulcin and phyllodulcin 8-O-β-D-glucopyranoside in the leaves. Altogether, these findings could be useful for the development of high-quality Hydrangeae Dulcis Folium.

Fluorescence from abnormally sterile pollen of the Japanese apricot

We observed trees of the Japanese apricot, Prunus mume 'Nanko' (Rosaceae), bearing two types of flowers: 34% had blue fluorescent pollen under UV irradiation, and 66% had non-fluorescent pollen. The fluorescent pollen grains were abnormally crushed, sterile, and devoid of intine and pollenkitt. The development of microspores within anthers was investigated: in the abnormally developed anthers, tapetal cells were vacuolated at the unicellular microspore stage, and fluorescent pollen was produced. Compounds responsible for the blue fluorescence of pollen were identified as chlorogenic acid and 1-O-feruloyl-β-D-glucose. The anthers with fluorescent pollen contained 6.7-fold higher and 3.8-fold lower amounts of chlorogenic acid and N ¹,N ⁵,N ¹⁰-tri-p-coumaroylspermidine, respectively, compared to those with non-fluorescent pollen. The tapetal vacuolization, highly accumulated chlorogenic acid, and deficiency of N ¹,N ⁵,N ¹⁰-tri-p-coumaroylspermidine imply that low-temperature stress during the early unicellular microspore stage caused a failure in microsporogenesis. Furthermore, potential effects of the visual difference on the bee behavior were also discussed through the colorimetry. The sterility, likely induced by low-temperature stress, and the preference of honeybees for fluorescence may reduce the pollination efficiency of P. mume.

Neolignan and megastigmane glucosides from the aerial parts of Isodon japonicus with cell protective effects on BaP-induced cytotoxicity

Six neolignan glucosides, named isodonosides I-VI, and a megastigmane glucoside named isodonmegastigmane I, were isolated together with 15 known compounds from the methanolic extract of aerial parts of Isodon japonicus cultivated in Tokushima, Japan. The chemical structures of the compounds were elucidated based on their MS and NMR spectroscopic analysis. The absolute configurations of the neolignan and megastigmane glucosides were determined by derivatizations, by ECD (electronic circular dicroism) Cotton effect approximation, and by the modified Mosher's method. In addition, a significant cell protective effects of neolignan glucosides on benzo[a]pyrene-induced cytotoxicity was found.

Toxicity of tannins towards the free-living nematode Caenorhabditis elegans and the brine shrimp Artemia salina

Toxicities of gallo- and condensed tannins towards the free-living nematode Caenorhabditis elegans is dependent on the tannins' molecular sizes. In the present paper we investigate the toxicity of ellagitannins to C elegans and the toxicity of ellagi-, gallo-, and condensed tannins to the brine shrimpArtemia salina. Ellagitannins 1 and 2 were isolated from Euphorbia supina and identified as tellimagrandin I and rugosin A methyl ester, respectively. An ellagitannin preparation from Cornus officinalis was chromatographically fractionated into ellagitannins A through H, having different molecular weights and specific rotations. Three of the ten ellagitannins, 2, G, and H produced significant toxicity towards C. elegans, showing the presence of an activity-structure relationship, as opposed to the results from tests of gallo- and condensed tannins. Ellagi-, gallo-, and condensed tannins also produced toxicity in A. salina.