Escins-Ia, Ib, IIa, IIb, and IIIa, bioactive triterpene oligoglycosides from the seeds of Aesculus hippocastanum L.: their inhibitory effects on ethanol absorption and hypoglycemic activity on glucose tolerance test

Horse Chestnut Saponins-Escins, Isoescins, Transescins, and Desacylescins

Escins constitute an abundant family of saponins (saponosides) and are the most active components in Aesculum hippocastanum (horse chestnut-HC) seeds. They are of great pharmaceutical interest as a short-term treatment for venous insufficiency. Numerous escin congeners (slightly different compositions), as well as numerous regio-and stereo-isomers, are extractable from HC seeds, making quality control trials mandatory, especially since the structure-activity relationship (SAR) of the escin molecules remains poorly described. In the present study, mass spectrometry, microwave activation, and hemolytic activity assays were used to characterize escin extracts (including a complete quantitative description of the escin congeners and isomers), modify the natural saponins (hydrolysis and transesterification) and measure their cytotoxicity (natural vs. modified escins). The aglycone ester groups characterizing the escin isomers were targeted. A complete quantitative analysis, isomer per isomer, of the weight content in the saponin extracts as well as in the seed dry powder is reported for the first time. An impressive 13% in weight of escins in the dry seeds was measured, confirming that the HC escins must be absolutely considered for high-added value applications, provided that their SAR is established. One of the objectives of this study was to contribute to this development by demonstrating that the aglycone ester functions are mandatory for the toxicity of the escin derivative, and that the cytotoxicity also depends on the relative position of the ester functions on the aglycone.

Escin's Multifaceted Therapeutic Profile in Treatment and Post-Treatment of Various Cancers: A Comprehensive Review

Although modern medicine is advancing at an unprecedented rate, basic challenges in cancer treatment and drug resistance remain. Exploiting natural-product-based drugs is a strategy that has been proven over time to provide diverse and efficient approaches in patient care during treatment and post-treatment periods of various diseases, including cancer. Escin-a plant-derived triterpenoid saponin-is one example of natural products with a broad therapeutic scope. Initially, escin was proven to manifest potent anti-inflammatory and anti-oedematous effects. However, in the last two decades, other novel activities of escin relevant to cancer treatment have been reported. Recent studies demonstrated escin's efficacy in compositions with other approved drugs to accomplish synergy and increased bioavailability to broaden their apoptotic, anti-metastasis, and anti-angiogenetic effects. Here, we comprehensively discuss and present an overview of escin's chemistry and bioavailability, and highlight its biological activities against various cancer types. We conclude the review by presenting possible future directions of research involving escin for medical and pharmaceutical applications as well as for basic research.

Impact of the Hydrolysis and Methanolysis of Bidesmosidic Chenopodium quinoa Saponins on Their Hemolytic Activity

Saponins are specific metabolites abundantly present in plants and several marine animals. Their high cytotoxicity is associated with their membranolytic properties, i.e., their propensity to disrupt cell membranes upon incorporation. As such, saponins are highly attractive for numerous applications, provided the relation between their molecular structures and their biological activities is understood at the molecular level. In the present investigation, we focused on the bidesmosidic saponins extracted from the quinoa husk, whose saccharidic chains are appended on the aglycone via two different linkages, a glycosidic bond, and an ester function. The later position is sensitive to chemical modifications, such as hydrolysis and methanolysis. We prepared and characterized three sets of saponins using mass spectrometry: (i) bidesmosidic saponins directly extracted from the ground husk, (ii) monodesmosidic saponins with a carboxylic acid group, and (iii) monodesmosidic saponins with a methyl ester function. The impact of the structural modifications on the membranolytic activity of the saponins was assayed based on the determination of their hemolytic activity. The natural bidesmosidic saponins do not present any hemolytic activity even at the highest tested concentration (500 µg·mL⁻¹). Hydrolyzed saponins already degrade erythrocytes at 20 µg·mL⁻¹, whereas 100 µg·mL⁻¹ of transesterified saponins is needed to induce detectable activity. The observation that monodesmosidic saponins, hydrolyzed or transesterified, are much more active against erythrocytes than the bidesmosidic ones confirms that bidesmosidic saponins are likely to be the dormant form of saponins in plants. Additionally, the observation that negatively charged saponins, i.e., the hydrolyzed ones, are more hemolytic than the neutral ones could be related to the red blood cell membrane structure.

Microwave-Assisted Desulfation of the Hemolytic Saponins Extracted from Holothuria scabra Viscera

Saponins are plant and marine animal specific metabolites that are commonly considered as molecular vectors for chemical defenses against unicellular and pluricellular organisms. Their toxicity is attributed to their membranolytic properties. Modifying the molecular structures of saponins by quantitative and selective chemical reactions is increasingly considered to tune the biological properties of these molecules (i) to prepare congeners with specific activities for biomedical applications and (ii) to afford experimental data related to their structure-activity relationship. In the present study, we focused on the sulfated saponins contained in the viscera of Holothuria scabra, a sea cucumber present in the Indian Ocean and abundantly consumed on the Asian food market. Using mass spectrometry, we first qualitatively and quantitatively assessed the saponin content within the viscera of H. scabra. We detected 26 sulfated saponins presenting 5 different elemental compositions. Microwave activation under alkaline conditions in aqueous solutions was developed and optimized to quantitatively and specifically induce the desulfation of the natural saponins, by a specific loss of H₂SO₄. By comparing the hemolytic activities of the natural and desulfated extracts, we clearly identified the sulfate function as highly responsible for the saponin toxicity.

Hypoglycemic and Anti-Inflammatory Effects of Triterpene Glycoside Fractions from Aeculus hippocastanum Seeds

Horse chestnut (Aesculus hippocastanum L.)-derived drugs have shown their potential in biomedical applications. The seed of A. hippocastanum contains various kinds of chemical compounds including phenolics, flavonoids, coumarins, and triterpene saponins. Here, we investigated the chemical components in A. hippocastanum L. grown in Uzbekistan, which has not yet been studied in detail. We identified 30 kinds of triterpene saponins in an extract of A. hippocastanum L. Classifying extracted saponins into eight fractions, we next studied the hypoglycemic and the anti-inflammatory activities of escin and its derivatives through in vivo experiments. We came by data indicating the highest (SF-1 and SF-2) and the lowest (SF-5 and SF-8) antidiabetic and anti-inflammatory effects of those eight fractions. These results imply the prospective use of A. hippocastanum L. grown in Uzbekistan in the production of pharmaceutical drugs to treat diabetes and inflammation.

Enhancing the Membranolytic Activity of Chenopodium quinoa Saponins by Fast Microwave Hydrolysis

Saponins are plant secondary metabolites. There are associated with defensive roles due to their cytotoxicity and are active against microorganisms. Saponins are frequently targeted to develop efficient drugs. Plant biomass containing saponins deserves sustained interest to develop high-added value applications. A key issue when considering the use of saponins for human healthcare is their toxicity that must be modulated before envisaging any biomedical application. This can only go through understanding the saponin-membrane interactions. Quinoa is abundantly consumed worldwide, but the quinoa husk is discarded due to its astringent taste associated with its saponin content. Here, we focus on the saponins of the quinoa husk extract (QE). We qualitatively and quantitively characterized the QE saponins using mass spectrometry. They are bidesmosidic molecules, with two oligosaccharidic chains appended on the aglycone with two different linkages; a glycosidic bond and an ester function. The latter can be hydrolyzed to prepare monodesmosidic molecules. The microwave-assisted hydrolysis reaction was optimized to produce monodesmosidic saponins. The membranolytic activity of the saponins was assayed based on their hemolytic activity that was shown to be drastically increased upon hydrolysis. In silico investigations confirmed that the monodesmosidic saponins interact preferentially with a model phospholipid bilayer, explaining the measured increased hemolytic activity.

Discrimination of Regioisomeric and Stereoisomeric Saponins from Aesculus hippocastanum Seeds by Ion Mobility Mass Spectrometry

Modern mass spectrometry methods provide a huge benefit to saponin structural characterization, especially when combined with collision-induced dissociation experiments to obtain a partial description of the saponin (ion) structure. However, the complete description of the structures of these ubiquitous secondary metabolites remain challenging, especially since isomeric saponins presenting small differences are often present in a single extract. As a typical example, the horse chestnut triterpene glycosides, the so-called escins, comprise isomeric saponins containing subtle differences such as cis-trans ethylenic configuration (stereoisomers) of a side chain or distinct positions of an acetyl group (regioisomers) on the aglycone. In the present paper, the coupling of liquid chromatography and ion mobility mass spectrometry has been used to distinguish regioisomeric and stereoisomeric saponins. Ion mobility arrival time distributions (ATDs) were recorded for the stereoisomeric and regioisomeric saponin ions demonstrating that isomeric saponins can be partially separated using ion mobility on a commercially available traveling wave ion mobility (TWIMS) mass spectrometer. Small differences in the ATD can only be monitored when the isomeric saponins are separated with liquid chromatography prior to the IM-MS analysis. However, gas phase separation between stereoisomeric and regioisomeric saponin ions can be successfully realized, without any LC separation, on a cyclic ion mobility-enabled quadrupole time-of-flight (Q-cIM-oaToF) mass spectrometer. The main outcome of the present paper is that the structural analysis of regioisomeric and stereoisomeric natural compounds that represents a real challenge can take huge advantages of ion mobility experiments but only if increased ion mobility resolution is attainable.

Nutraceuticals and Diet-based Phytochemicals in Type 2 Diabetes Mellitus: From Whole Food to Components with Defined Roles and Mechanisms

BACKGROUND

Over the past decades, the development and use of an array of prescription medications have considerably improved the clinical management of type 2 diabetes mellitus and the quality of life of patients. However, as our knowledge of the associated risk factors and approaches to its management increases, the increasing roles of diet and the composition of the diet in the etiology and successful management of diabetes mellitus are being illuminated. Presently, a lot of attention is being given to nutraceuticals and certain phytochemicals that are integral parts of the human diet. It is believed that a clearer understanding of their roles may be crucial to 'non-invasive' or minimallyintrusive management, with regards to daily living of patients. In this review, an overview of nutraceutical components and phytochemicals that may be of benefit, or had been known to be beneficial in diabetes mellitus is given. Also, how the roles of such dietary components are evolving in the management of this disorder is highlighted. Lastly, the obstacles that need to be overcome before nutraceuticals can be considered as options for the clinical management of diabetes mellitus areconsidered.

CONCLUSION

Despite studies that demonstrate their efficacy, no nutraceutical or food-derived compound has been formally adopted as a direct replacement for any class of antidiabetic drugs.

Triterpenoid Saponins from the Seeds of Aesculus chinensis and Their Cytotoxicities

Six new triterpenoid saponins, aesculusosides A-F (1-6), together with 19 known ones, were isolated from the seeds of Aesculus chinensis. The new structures were elucidated through extensive spectroscopic analyses and by comparison with previously reported data. Some of the isolates were evaluated for their cytotoxic activities against MCF-7 cell line by an MTT assay, and compounds 15, 16, 19, and 23-25 exhibited inhibitory activities against MCF-7 with IC₅₀ values ranging from 7.1 to 31.3 μM.

Congmujingnosides B-G, triterpene saponins from the stem of Aralia chinensis and their protective effects against H2O2-induced myocardial cell injury

Phytochemical investigation of the stem of Aralia chinensis yielded six new oleanane-type triterpene saponins named as congmujingnosides B-G (1-6). The new ones were elucidated on the basis of the chemical and spectroscopic analysis. Protective effects of compounds 1-6 were tested against H₂O₂-induced H9c2 cardiomyocyte injury, and the data showed that compounds 1 and 5 had significant cell-protective effects. No significant DPPH radical scavenging activity was observed for compounds 1-6.

Influence of Hydrophilic Polymers on theβFactor in Weibull Equation Applied to the Release Kinetics of a Biologically Active Complex ofAesculus hippocastanum

Triterpenoid saponins complex of biological origin, escin, exhibits significant clinical activity in chronic venous insufficiency, skin inflammation, epidermal abrasions, allergic dermatitis, and acute impact injuries, especially in topical application. The aim of the study is the comparison of various hydrogel formulations, as carriers for a horse chestnut seed extract (EH). Methylcellulose (MC), two polyacrylic acid derivatives (PA1 and PA2), and polyacrylate crosspolymer 11 (PC-11) were employed. The release rates of EH were examined and a comparison with the Weibull model equation was performed. Application of MC as the carrier in the hydrogel preparation resulted in fast release rate of EH, whereas in the case of the hydrogel composed with PC-11 the release was rather prolonged. Applied Weibull function adhered best to the experimental data. Due to the evaluated shape parameterβ, in the Weibull equation, the systems under study released the active compound according to the Fickian diffusion.

Natural Triterpenoids for the Treatment of Diabetes Mellitus: A Review

Triterpenoids, an important group of secondary metabolites, are widely distributed in nature. Many triterpenoids have been found with potential therapeutic effect against diabetes mellitus. However, the use of triterpenoids for the treatment of diabetes has not been systematically discussed previously. This review summarized the anti-diabetic activity of natural triterpenoids reported since the late 1980s with the emphasis on the molecular mechanisms.

Determination of Four Major Saponins in Skin and Endosperm of Seeds of Horse Chestnut (Aesculus Hippocastanum L.) Using High Performance Liquid Chromatography with Positive Confirmation by Thin Layer Chromatography

PURPOSE

To separate and quantify four major saponins in the extracts of the skin and the endosperm of seeds of horse chestnut (Aesculus hippocastanum L.) using ultrasonic solvent extraction followed by a high performance liquid chromatography-diode array detector (HPLC-DAD) with positive confirmation by thin layer chromatography (TLC).

METHODS

The saponins: escin Ia, escin Ib, isoescin Ia and isoescin Ib were extracted using ultrasonic extraction method. The optimized extraction conditions were: 70% methanol as extraction solvent, 80 °C as extraction temperature, and the extraction time was achieved in 4 hours. The HPLC conditions used: Zorbax SB-ODS-(150 mm × 2.1 mm, 3 μm) column, acetonitrile and 0.10% phosphoric acid solution (39:61 v/v) as mobile phase, flow rate was 0.5 mL min(-1) at 210 nm and 230 nm detection. The injection volume was 10 μL, and the separation was carried out isothermally at 30 °C in a heated chamber.

RESULTS

The results indicated that the developed HPLC method is simple, sensitive and reliable. Moreover, the content of escins in seeds decreased by more than 30% in endosperm and by more than 40% in skin upon storage for two years.

CONCLUSION

This assay can be readily utilized as a quality control method for horse chestnut and other related medicinal plants.

Pharmacokinetics of escin Ia in rats after intravenous administration

ETHNOPHARMACOLOGICAL RELEVANCE

Escin, a natural mixture of triterpene saponins, is commonly utilized for the treatment of chronic venous insufficiency, hemorrhoids, inflammation and edema. Escin Ia is the chief active ingredient in escin and plays key role in mediating its pharmacological effects. Adequate pharmacokinetic data are essential for proper application of escin agent in clinical practice. However, pharmacokinetic properties of escin Ia are still poorly understood and this conflicts with the growing use of escin agent over the years. The goal of this study is to investigate the pharmacokinetic behavior of escin Ia in rats after low, medium and high-dose intravenous administration.

MATERIALS AND METHODS

Wistar rats were divided into 3 groups (n=6 per group) and escin Ia was administered via the caudal vein at doses of 0.5, 1.0 and 2.0 mg/kg, respectively. Subsequently, the concentrations of escin Ia and its metabolite isoescin Ia, a positional isomer of escin Ia, in rats׳ plasma were measured by an established liquid chromatography tandem mass spectrometry (LC-MS/MS) method at various time points following the administration of the drug. Main pharmacokinetic parameters were calculated by non-compartmental analysis using the TopFit 2.0 software package (Thomae GmbH, Germany).

RESULTS

After intravenous administration, the Cmax and AUC of escin Ia increased in a dose-proportional manner at the dose of 0.5 mg/kg and 1.0 mg/kg, while increased in a more than dose-proportional manner at the doses of 1.0 mg/kg and 2.0 mg/kg. The t₁/₂ was significantly longer with increased intravenous doses, while other parameters such as CL and Vd also exhibit disagreement among three doses. Taken together, our data showed dose-dependent pharmacokinetic profile of escin Ia in rats after intravenous administration at the doses of 0.5-2.0 mg/kg. After intravenous administration, escin Ia was rapidly and extensively converted to isoescin Ia.

CONCLUSIONS

The results suggested dose-dependent pharmacokinetics of escin Ia at the doses of 0.5-2.0 mg/kg after intravenous administration. Escin Ia is isomerized to isoescin Ia rapidly and extensively regardless of the doses.

A rapid method for total Β-escin analysis in dry, hydroalcoholic and hydroglycolic extracts of Aesculus hippocastanum L. by capillary zone electrophoresis

INTRODUCTION

Seeds of Aesculus hippocastanum L. are used in European phytotherapy to treat inflammatory and vascular problems, and also to help in the regulation of the microcirculation. Thus, the quality control of herbal medicines using this species is important.

OBJECTIVE

To develop and to optimise a capillary zone electrophoresis method to determine total β-escin in different extracts of A. hippocastanum L.

METHODS

The optimal condition found through chemometric approach was: 25 mmol/L of bicarbonate-carbonate buffer, pH 10.3; +20 kV of voltage; 20°C of cartridge temperature; direct ultraviolet detection at 226 nm; 13 mbar injection for 5 s and analysis time within 6 min.

RESULTS

Repeatability, coefficient of variation (CV; %) = 3.19, 3.07 and 1.89 (n = 12), and intermediate precision, CV (%) = 3.05, 3.53 and 2.99 (n = 24) for dry, hydroalcoholic and hydroglycolic extracts, respectively were achieved. The accuracy was evaluated through recovery tests in concentration levels of 100, 150 and 200 g/L, ranging from 98.17 to 104.68%. The proposed method exhibited linearity (r = 0.9983) in the concentration range from 101.4 to 907.2 g/L and limits of detection and quantification equal to 11.63 and 38.76 g/L respectively.

CONCLUSION

A fast and reliable methodology for determination of total β-escin was successfully validated and applied on extracts of A. hippocastanum L. demonstrating its usefulness to quality control of medicines containing this plant species.

Cytotoxic triterpenoid saponins from Aesculus glabra Willd

Twenty-four acylated polyhydroxyoleanene saponins were isolated from the seeds of Aesculus glabra. Sixteen of them, namely aesculiosides G1-G16 (1-16), were determined as compounds by spectroscopic and chemical analysis. The structural features of all 24 saponins are: (1) arabinofuranosyl units affixed to C-3 of the glucuronopyranosyl unit in the trisaccharide chain; (2) no 24-OH substitution; (3) C-2 sugar moiety substitution of the 3-O-glucuronopyranosyl unit is either glucopyranosyl or galactopyranosyl. The features of these isolated saponin structures provide more evidence for chemical taxonomy within the genus Aesculus. The cytotoxicity of the aesculiosides (1-16) were tested against A549 and PC-3 cancer cell lines with GI₅₀ from 5.4 to >25 μM.

Effects of escin mixture from the seeds of Aesculus hippocastanum on obesity in mice fed a high fat diet

Escins, a triterpene glycoside mixture obtained from the ethanol extract of Aesculus hippocastanum L. (Hippocastanaceae) seed, was evaluated for its in vivo effects on the plasma levels of some hormones (leptin, insulin, FT(3), FT(4)) and biochemical parameters (glucose, triglyceride, total cholesterol, HDL-C, LDL-C concentrations) in mice fed with a high fat diet for 5 weeks. A high fat diet induced a remarkable increment in the plasma leptin (p <0.01), total cholesterol (p <0.01) and LDL-C (p <0.001) concentrations compared to control group animals. Combined administration of a high-fat diet with escins decreased leptin (31.6%) (p<0.05) and FT(4) (36.0%) (p<0.05) levels, increased HDL-C concentration (17.0%), while remained ineffective on LDL-C concentration in mice. Results have shown that escins may have beneficial effects in the understanding of obesity.

Antiobese effects of novel saponins from edible seeds of Japanese horse chestnut (Aesculus turbinata BLUME) after treatment with wood ashes

Recently, we have identified novel saponins from edible seeds of Japanese horse chestnut ( Aesculus turbinata BLUME) after processing the natural seeds with wood ashes to remove bitterness. We attempted to determine anti-obesity effects of those saponins from edible seeds as well as natural seeds. The purified individual components of saponins from natural and edible seeds inhibited pancreatic lipase in vitro. The potency was in the order of escins > desacylescins > deacetylescins. Escins Ib and IIb as well as deacetylescins Ib and IIb with the angeloyl moiety were more potent than the corresponding Ia and IIa series with the tigloyl moiety. Moreover, in vivo anti-obesity effects of the saponin fractions were monitored for 8 weeks in mice fed high-fat diets. Saponin fractions from both seeds significantly attenuated the elevation in body weight, the mass of peritoneal adipose tissues, and plasma triacylglycerol, which was accompanied by higher contents of undigested fats in feces without changes in food intake, indicating the effective inhibition of fat digestion in vivo. Taken together, saponin fractions including desacylescins and deacetylescins from edible seeds are potentially useful for the development of nutraceutical foods with anti-obesity effects and more attenuated bitter taste.

Identification of novel saponins from edible seeds of Japanese horse chestnut (Aesculus turbinata Blume) after treatment with wooden ashes and their nutraceutical activity

Natural seeds of Japanese horse chestnut (Aesculus turbinata Blume) contain large amounts of mixed triterpenoidal saponins called escins. Recent studies have shown that escins have several biological activities including anti-inflammatory action and inhibitory effects on the absorption of ethanol and glucose. For the edible utilization of the seeds, natural seeds are usually treated with wooden ashes to remove harshness. Here, we found the novel compounds derived from escins in the edible seeds after the food processing with wooden ashes. The instrumental analyses revealed the chemical structures of escins and the derivatives. These compounds are identified as four types of deacetylescins Ia, IIa, Ib, and IIb as well as two types of desacylescins I and II. To determine their biological activity, the purified compounds were tested for their potential nutraceutical activity. The oral glucose tolerance test in mice revealed that a single oral administration of the isolated components of deacetylescins at a dose of 100 mg/kg was clearly effective in attenuating the elevation of blood glucose levels. The inhibitory effects of escins and their derivatives were in the order of escins>deacetylescins>desacylescins. Moreover, we found the inhibitory activity of those compounds on pancreatic lipase. Escins were the most potent in inhibiting the enzyme activity, and followed by desacylescins and then deacetylescins. Taken together, our results suggest the potential usefulness of novel saponins including deacetylescins and desacylescins from edible seeds as novel sources for nutraceutical foods with anti-obese effects.

Two New Triterpenoid Glycosides Isolated from Aesculus assamica GRIFF

Phytochemical study of the ethanol extract of the seeds of Aesculus assamica led to the isolation of two new triterpenoid saponins. The structure of the new compounds were elucidated on the basis of spectral data to be 28-O-acetyl-21-O-(4-O-angeloyl)-6-deoxy-beta-glucopyranosyl-3-O-[beta-glucopyranosyl(1-2)-O-[beta-glucopyranosyl(1-4)]-beta-glucuronopyranosyl]protoaescigenin (1), and 21-O-(4-O-angeloyl)-6-deoxy-beta-glucopyranosyl-3-O-[beta-glucopyranosyl(1-2)-O-[beta-glucopyranosyl(1-4)]-beta-glucuronopyranosyl]protoaescigenin (2). Their in vitro bioactivity against plant pathogenic fungus Pyricularia oryzae and cytotoxicity against K562 and HCT-15 cell lines were evaluated.

Assamicin I and II, novel triterpenoid saponins with insulin-like activity from Aesculus assamica Griff

Two novel triterpenoid saponins with insulin-like activity, termed assamicin I and II, were isolated from the roots of Aesculus assamica Griff. and their structures were characterized as 1 and 2, respectively. They inhibited release of free fatty acids from epinephrine-treated rat adipocytes and enhanced glucose uptake into 3T3-L1 adipocytes.

The bioactivity of saponins: triterpenoid and steroidal glycosides

Triterpenoid and steroidal glycosides, referred to collectively as saponins, are bioactive compounds present naturally in many plants. They have considerable potential as pharmaceutical and/or nutraceutical agents in natural or synthetic form. Saponins, from a variety of sources, have been shown to have hypocholesterolemic, anti-coagulant, anticarcinogenic, hepatoprotective, hypoglycemic, immunomodulatory, neuroprotective, anti-inflammatory and anti-oxidant activity. This paper reviews saponin research of the last decade, focussing on developments in understanding their mechanism of action and structure-activity relationships. Virtually all of this work has used animal and in vitro models. To date there are very few human data.

Enhancement by escins Ib and IIb of Mg(2+) absorption from digestive tract in mice: role of nitric oxide

The effects of escins Ib and IIb isolated from horse chestnuts on Mg(2+) absorption from the digestive tract and the role of endogenous nitric oxide (NO) were investigated in mice. Test samples were given orally to fasted mice 30, 120, 180, 240 and 300 min before administration of 0.5 M MgSO(4) (10 ml/kg, p.o.). The serum Mg(2+) levels were determined 30, 60, 120 and 180 min after administration of MgSO(4). Escins Ib and IIb (12.5 and 25 mg/kg) significantly increased the serum Mg(2+) by 10.0-27.3%, 30, 120 and 180 min after administration of the samples, and 30, 60, 120 and 180 min after administration of MgSO(4). Escins Ib and IIb (12.5 mg/kg) significantly decreased the Mg(2+) content in the small intestinal fluid in MgSO(4)-loaded mice, but did not increase the serum Mg(2+) levels in normal mice. The effects of escins Ib and IIb (12.5 mg/kg) on serum Mg(2+) levels were attenuated in a dose-related manner by the pretreatment with N(G)-nitro-L-arginine methyl ester (L-NAME, 3-20 mg/kg, i.p., an inhibitor of constitutive and inducible NO synthase), but not with D-NAME (10 mg/kg, i.p., the inactive enantiomer of L-NAME) or dexamethasone (0.05 and 0.5 mg/kg, s.c., an inhibitor of inducible NO synthase). The effect of L-NAME was reversed by L-arginine (600 mg/kg, i.p., a substrate of NO synthase), but not by D-arginine (900 mg/kg, i.p., the enantiomer of L-arginine). These results suggest that escins Ib and IIb enhance Mg(2+) absorption from the digestive tract in mice, in which the constitutive, but not the inducible, NO synthase plays an important role.

Effects of escins Ia, Ib, IIa, and IIb from horse chestnuts on gastrointestinal transit and ileus in mice

The effects of saponin fraction and its principal constituents escins Ia (1), Ib (2), IIa (3), and IIb (4) from horse chestnuts on gastrointestinal transit (GIT) and ileus were investigated in mice. Ileus was induced by acetic acid peritoneal irritation or by laparotomy with manipulation. One hour after the oral administration, the saponin fraction (12.5-100 mg/kg) and 14 (12.5-50 mg/ kg, except for 3 at 12.5 mg/kg) dose-dependently accelerated GIT. The optimal effects of the saponin fraction (25 mg/kg) occurred 5-240 min (applied intervals between the fraction and the charcoal meal) after the oral administration. The fraction (12.5-100 mg/ kg) and 1-4 (12.5-50 mg/kg, except for 1 and 2 at 12.5 mg/kg) dose-dependently prevented the inhibition of GIT induced by the acetic acid peritoneal irritation. They (12.5-100mg/kg) also dose-dependently prevented the inhibition of GIT induced by the laparotomy with manipulation. Desacylescins I (5) and II (6) (50 mg/kg) showed no such effects. These results demonstrated that the saponin fraction and 1-4 accelerated GIT and prevented the experimental ileus, and indicate that the 21, 22-acyl groups are essential for the accelerative effects of 1-4. The accelerations of GIT by 1-4 were completely abolished by the pretreatment with streptozotocin (100 mg/kg, iv), but not by the pretreatment with capsaicin (75 mg/kg in total, sc) or atropine (10 mg/kg, sc). These results imply that the sympathetic nervous system may be, but neither capsaicin-sensitive sensory nerves nor the cholinergic mechanism, involved in the accelerations of GIT by escins 1-4.

Gastroprotections of escins Ia, Ib, IIa, and IIb on ethanol-induced gastric mucosal lesions in rats

Effects of escins Ia, Ib, IIa, and IIb isolated from horse chestnuts on ethanol-induced gastric mucosal lesions and the roles of capsaicin-sensitive afferent neurons, endogenous nitric oxide (NO), sulfhydryls, prostaglandins, as well as gastric secretion and the sympathetic nervous system, were investigated in rats. Test samples were given orally to fasted rats 1 h before ethanol (1.5 ml/rat, p.o.) treatment or ligation of the pylorus. Escins Ia-IIb (10-50 mg/kg) potently inhibited ethanol-induced gastric mucosal lesions, whereas desacylescins I and II (50 mg/kg) showed no such effect. These active saponins (10 and 20 mg/kg) did not decrease the gastric secretion. The gastroprotections of escins Ia-IIb were attenuated by the pretreatment with capsaicin, N(G)-nitro-L-arginine methyl ester, and indomethacin, but not by N-ethylmaleimide. The effects of escins Ia-IIb were also attenuated in streptozotocin-induced diabetic rats, in which the activity of the sympathetic nervous system was abnormal. These results suggest that the gastroprotections of escins Ia-IIb on ethanol-induced gastric mucosal lesions are acid-independent, whereas endogenous prostaglandins, NO, capsaicin-sensitive afferent neurons, and the sympathetic nervous system participate.

Effects of escins Ia, Ib, IIa, and IIb from horse chestnuts on gastric emptying in mice

Inhibitory effects of the saponin fraction and its principal constituents, escins Ia, Ib, IIa, and IIb, from horse chestnuts on gastric emptying were investigated in mice loaded with a non-nutrient or nutrient meal. The saponin fraction and escins Ia-IIb inhibited gastric emptying of a 1.5% carboxymethyl cellulose sodium salt (CMC-Na) meal by 11.1-54.2% (12.5-200 mg/kg). Escins Ia-IIb (50 mg/kg) also inhibited gastric emptying of a 40% glucose meal by 21.1-23.5% except for escin Ia, a milk meal by 18.4-33.1%, and a 30% ethanol meal by 13.5-15.9%. The effects of escins Ia-IIb on gastric emptying of the CMC-Na meal were attenuated by pretreatment with streptozotocin (100 mg/kg, i.v.), capsaicin (75 mg/kg in total, s.c.), or insulin (1 U/kg, s.c.). The effect of insulin was reduced by glucose (2 g/kg, i.v.) which can directly nourish the brain, but not by fructose (2 g/kg, i.v.) which cannot be utilized by the brain. The effects of escins Ia-IIb (50 mg/kg) were overridden in 60% ethanol-loaded mice, in which the central nervous system was suppressed by ethanol. These results suggest that capsaicin-sensitive sensory nerves and central nervous system partly participate in the effects of escins Ia-IIb.

Structure-related inhibitory activity of oleanolic acid glycosides on gastric emptying in mice

We examined the effects of various oleanolic acid oligoglycosides obtained from traditional herbs on gastric emptying in non-nutrient meal- or nutrient meal-loaded mice. Test samples were given orally to fasted mice 0.5 h before loading of test meals. Oleanolic acid 3-O-monodesmosides [oleanolic acid 3-O-glucuronide (3, 12.5-50 mg/kg), momordin Ic (4, 25 and 50 mg/kg), momordin I (6, 12.5-50 mg/kg), and 28-O-deglucosyl-chikusetsusaponins IV (8, 12.5-50 mg/kg) and V (10, 50 mg/kg)] were found to show inhibitory effects on gastric emptying in 1.5% CMC-Na test meal-loaded mice. 4, 6, and 8 also inhibited gastric emptying in mice given 40% glucose test meal, milk test meal, and 60% ethanol test meal. 3 inhibited gastric emptying in mice given milk test meal or 60% ethanol test meal, but lacked significant inhibition in 40% glucose test meal-loaded mice. 10 (50 mg/kg) also slightly inhibited gastric emptying in milk test meal-loaded mice, but lacked the significant inhibition in mice given 40% glucose or 60% ethanol test meal. Whereas oleanolic acid 3,28-0-bisdesmosides [momordin IIc (5), chikusetsusaponins IV (7) and V (9)], oleanolic acid 28-O-monodesmoside [compound O (2)], and their common aglycon [oleanolic acid (1)] showed no such effects at dose of 50 mg/kg. 28-O-Deglucosyl-chikusetsusaponin V (10) showed a little inhibition in these experiments. These results indicate that both the 3-O-monodesmoside structure and 28-carboxyl group were confirmed to be essential for such activity, and the 28-ester glucoside moiety and 2'-O-beta-D-glucopyranoside moiety reduce the activity.

Separation of a triterpenoid saponin mixture from Maesa lanceolata: semipreparative reversed-phase wide pore high performance liquid chromatography with temperature control

A mixture of triterpenoid saponins derived from the dried leaves of Maesa lanceolata was separated, without structure deterioration, in its components. Seven fractions (I-VII) of high molecular weight (1234-1358) saponins were obtained on a semipreparative scale using wide pore reversed-phase high performance liquid chromatography with an acetonitrile trifluoroacetic acid (500:0.3 w/w)-water-trifluoroacetic acid (391:0.3, w/w) gradient from 35 to 56% in 30 min. The mobile phase was cooled in an ice bath (0 degrees C) during chromatography in order to prevent bubble formation and to improve the quality of the separation. Freeze-dried fractions IV, V, VI and VII were further separated using solvent systems developed for each of the fractions. Fourteen pure triterpenoid saponins were isolated in this way and their molar weight determined.

Mode of action of escins Ia and IIa and E,Z-senegin II on glucose absorption in gastrointestinal tract

We examined the mode of action of escins Ia (1) and IIa (2) and E,Z-senegin II (3) for the inhibitory effect on the increase in serum glucose levels in oral glucose-loaded rats. Although 1-3 inhibited the increase in serum glucose levels in oral glucose-loaded rats, these compounds did not lower serum glucose levels in normal or intraperitoneal glucose-loaded rats, or alloxan-induced diabetic mice. Furthermore, 1-3 suppressed gastric emptying in rats, and also inhibited glucose uptake in the rat small intestine in vitro. These results indicated that 1-3 given orally have neither insulin-like activity nor insulin-releasing activity. Compounds 1-3 inhibited glucose absorption by suppressing the transfer of glucose from the stomach to the small intestine and by inhibiting the glucose transport system at the small intestinal brush border.