[Development of bioactive functions in hydrangeae dulcis folium. II. Antiulcer, antiallergy, and cholagoic effects of the extract from hydrangeae dulcis folium]

VIS-NIR Modeling of Hydrangenol and Phyllodulcin Contents in Tea-Hortensia (Hydrangea macrophylla subsp. serrata)

Hyperspectral data are commonly used for the fast and inexpensive quantification of plant constituent estimation and quality control as well as in research and development applications. Based on chemical analysis, different models for dihydroisocoumarins (DHCs), namely hydrangenol (HG) and phyllodulcin (PD), were built using a partial least squares regression (PLSR). While HG is common in Hydrangea macrophylla, PD only occurs in cultivars of Hydrangea macrophylla subsp. serrata, also known as ‘tea-hortensia’. PD content varies significantly over the course of the growing period. For maximizing yield, a targeted estimation of PD content is needed. Nowadays, DHC contents are determined via UPLC, a time-consuming and a destructive method. In this research article we investigated PLSR-based models for HG and PD using three different spectrometers. Two separate trials were conducted to test for model quality. Measurement conditions, namely fresh or dried leaves and black or white background, did not influence model quality. While highly accurate modeling of HG and PD for single plants was not possible, the determination of the mean content on a larger scale was successful. The results of this study show that hyperspectral modeling as a decision support for farmers is feasible and provides accurate results on a field scale.

Natural Phenyldihydroisocoumarins: Sources, Chemistry and Bioactivity

The present review gives an overview about naturally occurring phenyldihydroisocoumarins, their sources, and bioactivities. In total, 54 compounds are covered, including eight substances which are in fact alkaloids or protoalkaloids. These nitrogen containing compounds were exclusively found in the Papaveraceae family. The remaining 46 compounds have been reported from twelve different source families, ranging from mosses to angiosperms. Six of the nitrogen free compounds feature additional rings, while 40 are simple phenyldihydroisocoumarins with substituents in all possible positions, except 3, 2’, and 6’. Common substituents of these simple phenyldihydroisocoumarins are hydroxy groups, methoxy groups, and glucosyloxy groups; on the other hand, acuminosyloxy and rutinosyloxy groups have so far been found only in one and two naturally occurring phenyldihydroisocoumarins, respectively. Though a number of bioactivities have been proven for phenyldihydroisocoumarins, ranging from anticancer and antidiabetic to antimicrobial and anti-inflammatory activities, so far only one taxon, Hydrangea macrophylla var. thunbergii, is widely used. Moreover, the usage of this taxon is mainly due to the sweet taste properties of the contained phenyldihydroisocoumarin phyllodulcin and less based on the alleged health-promoting effects of its constituents.

Relative sweetness and sweetness quality of phyllodulcin [(3R)-8-Hydroxy-3-(3-hydroxy-4-methoxyphenyl)-3,4-dihydro-1H-isochromen-1-one]

Phyllodulcin, a sweet-tasting compound extracted from Hydrangea macrophylla var. thunbergii, has recently received attention as a natural intense alternative sweetener with beneficial health effects. This study was conducted to determine the sweetness potency of phyllodulcin, relative to that of sucrose and to elucidate its sensory profile. Phyllodulcin solution was prepared by dissolving it in 1% ethanol (v/v) at 50°C. Relative sweetness to that of 3% sucrose in 1% ethanol solution was determined using the two-alternative forced-choice test. The sensory profile was obtained based on the descriptive analysis of 10 trained panelists. The relative sweetness of phyllodulcin was 434.8. Phyllodulcin was characterized by its bitterness, alcohol flavor, cooling sensation, and astringent aftertaste, but the persistence and onset of the sweetness of phyllodulcin were similar to those of sucrose. Further studies are required to improve the sweetness quality of phyllodulcin for facilitating its use in industrial applications by reducing its unfavorable flavor attributes.

The establishment of efficient bioconversion, extraction, and isolation processes for the production of phyllodulcin, a potential high intensity sweetener, from sweet hydrangea leaves (Hydrangea macrophylla Thunbergii)

INTRODUCTION

Hydrangea leaf tea has been traditionally consumed in the far-east Asian countries and is favoured for its distinct minty-sweet taste. Phyllodulcin is identified as a key sweet-tasting compound; it is 400-800 times sweeter than sucrose. However, its extraction has not been well-documented. In an effort to optimise phyllodulcin production, pretreatment processes to accumulate phyllodulcin as a final metabolite in leaf tissue were studied, and an efficient process was established for the extraction and purification of phyllodulcin.

METHODS

Phyllodulcin was structurally identified using an LC/MS system. Hydrangea leaves were processed by either hand rolling or mechanical blending, by exposing them at different drying temperatures (25 and 70°C), and even by inducing bioconversion in leaf tissue. The leaf powder was extracted with various solvents (methanol, ethanol, and water) by soaking at 25°C for 12 h, ultrasonication at 35°C for 1 h or accelerated solvent extraction (ASE). Extracts were purified with ion exchange resins and purified using preparative HPLC.

RESULTS

Traditional hand rolling and drying at 70°C significantly increased phyllodulcin accumulation in the leaves. Meanwhile, more phyllodulcin was obtained from the leaves blended mechanically or converted enzymatically compared to traditionally processed ones (P < 0.05). Methanol and ethanol were superior to water as extraction media, and the greatest phyllodulcin yields obtained by ASE, soaking and ultrasonication were 21.28, 21.20 and 19.33 mg/g, respectively, when methanol was used. Highly pure phyllodulcin powder was obtained with a yield of 2.12%.

CONCLUSIONS

This promising result would be beneficial to the industrial utilisation of phyllodulcin as a potential high-intensity sweetener.

Suppression by Hydrangeae Dulcis Folium of D-galactosamine-induced liver injury in vitro and in vivo

Hydrangeae Dulcis Folium, the fermented and dried leaves of Hydrangea macrophylla SER. var. thunbergii MAKINO, suppressed D-galactosamine-induced liver injury by 85.2% when added to the diet at 1% and fed to rats for fifteen days. The hepatoprotective effect is more potent than that of a milk thistle extract and turmeric powder. Some fractionated extracts showed hepatoprotective activity in the D-galactosamine-induced in vitro liver injury model.

Metabolic fate of orally administered phyllodulcin in rats

Naturally occurring phyllodulcin (1) was orally administered to rats to investigate its metabolic fate. Urinary metabolites were analyzed by three-dimensional HPLC. Phyllodulcin-3'-O-sulfate (2), phyllodulcin-3'-O-beta-glucuronide (3), 2-[2-(3,4-dihydroxyphenyl)ethyl]-6-hydroxybenzoic acid (4), and one novel bibenzyl derivative, 2-[2-(3-hydroxy-4-methoxyphenyl)ethyl]-6-hydroxybenzoic acid (5), together with thunberginol G (6) and hydrangenol (7) were isolated from the phyllodulcin-treated urine. 1 was extensively metabolized to 4-6 by a rat fecal suspension after incubation for 24 h. Urinary excretion of 4-6 in rats administered phyllodulcin orally was substantially reduced when the rats were treated with antibiotics to suppress their intestinal flora. On the other hand, the incubation of 1 with rat liver S-9 mix showed the presence of 7 together with 4 and 5.

Bioactive constituents of Chinese natural medicines. VII. Inhibitors of degranulation in RBL-2H3 cells and absolute stereostructures of three new diarylheptanoid glycosides from the bark of Myrica rubra

Three new diarylheptanoid glycosides, named (+)-S-myricanol 5-0-beta-D-glucopyranoside, myricanene A 5-O-alpha-L-arabinofuranosyl(1-->6)-beta-D-glucopyranoside, and myricanene B 5-0-alpha-L-arabinofuranosyl(1-->6)-beta-D-glucopyranoside, were isolated from the bark of Chinese Myrica rubra, together with twenty known compounds. The absolute stereostructures of the new diarylheptanoid glycosides were elucidated on the basis of chemical and physicochemical evidence, including the application of the modified Mosher's method. The inhibitory effects of isolated constituents on the release of beta-hexosaminidase from RBL-2H3 cells were examined, and several diarylheptanoids, myricanol, (+)-S-myricanol, myricanone, and myricanenes A and B, and a flavonol, myricetin, were found to show the inhibitory activity.

Structure-requirements of isocoumarins, phthalides, and stilbenes from Hydrangeae Dulcis Folium for inhibitory activity on histamine release from rat peritoneal mast cells

We examined the structure-activity relationships of isocoumarins, phthalides and stilbenes isolated from Hydrangeae Dulcis Folium and related compounds for the inhibition of histamine release in rat peritoneal mast cells. The activities of isocoumarins such as thunberginols A and B were more potent than those of dihydroisocoumarins such as hydrangenol and thunberginol G. The double bond at the 3-position seemed to be essential to potentiate the activity. The hydroxyl groups at the 8-, 3'- and 4'-positions of isocoumarin were essential for the activity, while the hydroxyl group at the 6-position was scarcely needed. Since the activities of benzylidenephthalides such as thunberginol F were more potent than those of hydramacrophyllols A and B, the presence of a double bond at the 3-position was needed to increase the activity. Moreover, the hydroxyl group at the 8-position was essential for the activity. On the time course study, thunberginols A, B and F completely inhibited histamine release by pretreatment at 100 microM for 1 to 15 min, whereas DSCG inhibited histamine release only following 1-min pretreatment at 1000 microM. These results suggested that the mechanisms of the inhibitory effect of thunberginols are different from that of DSCG.

Immunomodulatory activity of thunberginol A and related compounds isolated from Hydrangeae Dulcis Folium on splenocyte proliferation activated by mitogens

We investigated the immunomodulatory effects of antiallergic constituents from Hydrangeae Dulcis Folium, the processed leaves of Hydrangea macrophylla SERINGE var. thunbergii MAKINO, on splenocyte proliferation in mice. Thunberginol A and hydrangenol significantly suppressed T lymphocyte proliferation induced by concanavalin A. Thunberginol A also suppressed B lymphocyte proliferation induced by lipopolysaccharide, but other constituents induced significant increases. These inhibitory effects of thunberginol A on splenocyte proliferation seemed to contribute to the suppressive effect on type IV allergy.