Elatosides A and B, potent inhibitors of ethanol absorption in rats from the bark of Aralia elata Seem: the structure-activity relationships of oleanolic acid oligoglycosides

Natural Deep Eutectic Solvents for the Extraction of Triterpene Saponins from Aralia elata var. mandshurica (Rupr. & Maxim.) J. Wen

The roots of the medicinal plant Aralia elata are rich in biologically active natural products, with triterpene saponins constituting one of their major groups. These metabolites can be efficiently extracted by methanol and ethanol. Due to their low toxicity, natural deep eutectic solvents (NADES) were recently proposed as promising alternative extractants for the isolation of natural products from medicinal plants. However, although NADES-based extraction protocols are becoming common in routine phytochemical work, their application in the isolation of triterpene saponins has not yet been addressed. Therefore, here, we address the potential of NADES in the extraction of triterpene saponins from the roots of A. elata. For this purpose, the previously reported recoveries of Araliacea triterpene saponins in extraction experiments with seven different acid-based NADES were addressed by a targeted LC-MS-based quantitative approach for, to the best of our knowledge, the first time. Thereby, 20 triterpene saponins were annotated by their exact mass and characteristic fragmentation patterns in the total root material, root bark and root core of A. elata by RP-UHPLC-ESI-QqTOF-MS, with 9 of them being identified in the roots of this plant for the first time. Triterpene saponins were successfully extracted from all tested NADES, with the highest efficiency (both in terms of the numbers and recoveries of individual analytes) achieved using a 1:1 mixture of choline chloride and malic acid, as well as a 1:3 mixture of choline chloride and lactic acid. Thereby, for 13 metabolites, NADES were more efficient extractants in comparison with water and ethanol. Our results indicate that new, efficient NADES-based extraction protocols, giving access to high recoveries of triterpene saponins, might be efficiently employed in laboratory practice. Thus, our data open the prospect of replacing alcohols with NADES in the extraction of A. elata roots.

Traditional uses, phytochemistry, pharmacology, toxicity and quality control of medicinal genus Aralia: A review

ETHNOPHARMACOLOGICAL RELEVANCE

Aralia, which belongs to Araliaceae family, is mainly distributed in Asia, such as China, Japan and South Korea. It has a long medicinal history and is widely used in the treatment of various diseases, such as hepatitis, rheumatoid arthritis, bruises, lumps and carbuncles.

AIM OF THE STUDY

The purpose of this review is to systematically evaluate the traditional uses, phytochemistry, pharmacology, toxicity and quality control of main medicinal plants of Aralia, discusses the application of ethnic medicine, modern scientific research and the relationship between them, and put forward some suggestions to promote the further development and utilization of Aralia.

MATERIALS AND METHODS

The relevant information on Aralia was collected through electronic databases (PubMed, Web of Science, Science Direct, Springer, CNKI and Wanfang), Chinese herbal classics, Ph.D. and M.Sc. dissertations, Chinese Pharmacopoeia. Plant names were verified by "The Plant List" (http://www.theplantlist.org). The literature cited in this review can be traced back to 1878 to 2021.

RESULTS

More than 290 chemical constituents have been isolated from the genus Aralia, including triterpenoid saponins, terpenoids, organic acids, flavonoids, polyacetylenes, phenylpropanoids and other constituents. Pharmacological studies have shown that the extracts and compounds of Aralia have a wide range of pharmacological activities, including anti-inflammation, analgesic, anti-tumor, liver protection, protection of cardiovascular and nervous system, regulating substance metabolism, antibacterial, antiviral and antioxidation.

CONCLUSIONS

The genus Aralia is not only an excellent traditional herbal medicine, but also a source of bioactive molecules with good application prospects. However, the structure-activity relationship, in vivo activity and action mechanism of its bioactive components need to be further studied. In addition, more toxicological and quality control studies are essential to evaluate the efficacy and safety of Aralia as medicine.

Identification and comparison of triterpene saponins in Aralia elata leaves and buds by the energy-resolved MSAll technique on a liquid chromatography/quadrupole time-of-flight mass spectrometry

In this study, we identify the triterpene saponins (TSs) extracted from the leaves and buds of Aralia elata (Miq.) Seems using ultra-performance liquid chromatography and positive ionization electrospray quadrupole time-of-flight mass spectrometry (UPLC-ESI⁺-QTOF). The energy-resolved MS^All (erMS^all) technique is applied in order to simultaneously collect the diverse precursors attributed to [M+H]⁺, [M + NH₄]⁺ and [M + Na]⁺ ions. A practical and effective erMS^all workflow is established to rapidly identify and compare the saponins in the analyzed samples. In total, 111 TSs of structure are estimated, including 44 new compounds that had not been identified previously in A. elata. Of the five aglycones detected in the samples, a sapogenin 3β, 16α, 23-trihydroxyoleana-11,13-dien-28-oic acid (A5) that is identified for the first time in A. elata leaves. Compared to the buds, the leaves number twice as many hederagenin-type (A2) compounds. Although the number of other aglycones does not vary significantly between the buds and the leaves, A5 compounds are exclusively detected in the latter. Moreover, the C-3 sugar chains of TSs in A. elata leaves are mainly neutral (e.g., Hex+Hex, Hex+Hex+Hex and Hex+Hex+Hex+Hex), whereas those of bud TS compounds are primarily acidic (e.g., Pen+HexA, Hex+HexA and Hex+Pen+HexA). Some of the identified TS compounds, e.g., 27, 28, 32, 46, 54, 57, 71 and 105 can be used as indices to evaluate the quality of the plant leaves and buds. Overall, this study is of great significance for the comparative study of triterpenoid saponins in the leaves and buds of Aralia elata.

Ethnopharmacological Applications Targeting Alcohol Abuse: Overview and Outlook

Excessive alcohol consumption is the cause of several diseases and thus is of a major concern for society. Worldwide alcohol consumption has increased by many folds over the past decades. This urgently calls for intervention and relapse counteract measures. Modern pharmacological solutions induce complete alcohol self-restraint and prevent relapse, but they have many side effects. Natural products are most promising as they cause fewer adverse effects. Here we discuss in detail the medicinal plants used in various traditional/folklore medicine systems for targeting alcohol abuse. We also comprehensively describe preclinical and clinical studies done on some of these plants along with the possible mechanisms of action.

Effect of alcohol tincture of Aralia elata on the organism of rats and their gut microbiota against the background of excessive fat diet

Pharmacological effects of the medicinal plant Aralia elata (Miq.) Seem. 1868 (Araliaceae) are related to presence of over 150 secondary metabolites, including flavonoids, sterols, polysaccharides, terpenoid saponins and terpenoid acids, though the main biologically active substances of A. elata are saponins and flavonoids. Some clinical tests and experimental studies have proved the influence of A. elata on the organism through increase in physical work capacity, exerting an anti-stress effect against a broad range of harmful factors, including stress from cold, immobilization, ultraviolet radiation and low pressure. The literature also reports the anti-ulcer, anti-secretory, antifungal, anti-tumour, and antimicrobial activity of preparations from this plant. In our laboratory experiment, we determined that ethanolic tincture of A. elata has no effect on the intensity of growth of body weight of young rats against the background of excessive content of fat in their diet. Excessive fat-feeding of male rats leads mostly to disorders in the functioning of the liver and development of steatosis. This was accompanied by reduction in relative mass of the liver, increase in activity of hepatic enzymes, dysproteinemia, increase in the level of bilirubin and decrease in the level of urea. Additional use of 0.1% ethanol led to impaired functioning of the kidneys, reduction of their relative mass, signs of dehydration, increase in the level of creatinine and total calcium in the blood. Use of ethanolic tincture of A. elata mitigates negative excess of fat, is accompanied by normalization of indices of mass of the organs, less notable dysproteinemia, impairment in the level of creatinine, glucose, urea, cholesterol, bilirubin and total calcium. Ethanolic tincture of A. elata has a low immunosuppressive action, against the background of a high fat diet it leads to increase in the amount of typical Escherichia сoli, decrease in Еnterococcus spp. and Enterobacter spp., significant decrease and in high concentrations (0.1% ethanolic tincture of A. elata) elimination of bacteria of Clostridium and Klebsiella genera, and also various yeast fungi in the intestine. In the examined male rats, against the background of excess of fat in the diet, no serious changes in the composition of the normal gut microbiota (Bifidobacterium spp., Lactobacillus spp., Proteus spp., Staphylococcus spp., Candida spp.) was observed, nor were any lactose-negative enterobacteria (Citrobacter genus) found. Perspectives of further research include determining histological, histochemical and immune-histological changes in the organs of laboratory animals under the effect of ethanolic tincture of A. elata following excessive accumulation of fat.

Anti-Inflammatory and anti-proliferative oleanane-type triterpene glycosides from the vine of Momordica cochinchinensis

This research isolated two new oleanane-type triterpene glycosides, named mocochinosides A (1) and B (2), together with ten known compounds as chikusetsusaponin IVa ethyl ester (3), momordin Ib (4), momordin IIb (5), momordin II (6), calenduloside G (7), calenduloside H (8), elatoside A (9), elatoside C (10), calendulaglycoside C 6'-O-7-butyl ester (11), and hederagenin 3-O-β-D-glucuronopyranoside (12) and characterized them from the vines of Momordica cochinchinensis. The new structures of both glycosides 1-2 were elucidated by spectroscopic analysis including 2 D NMR and MS, followed by an analysis of their anti-inflammatory and cytotoxic activities. Compounds 1, 4, and 11 showed moderate inhibitions for NO production on RAW264.7 macrophages induced by LPS at IC₅₀ 5.41 ∼ 11.28 μM. Compounds 3, 4, and 7 (IC₅₀ 8.42 ∼ 19.74 μM) exhibited potential anti-proliferative activities against both of WiDr and MCF-7 human tumor cell lines.

Aralia elata var. mandshurica (Rupr. & Maxim.) J.Wen: An overview of pharmacological studies

PURPOSE

Aralia elata var. mandshurica (Rupr. & Maxim.) J.Wen syn. A. mandshurica Rupr. & Maxim is evaluated for its medicinal application. The aim of this study is to analyze pharmacological studies on A. elata var. mandshurica published until December 2015.

METHODS

The information regarding the chemistry, safety, effectiveness, and pharmacological and clinical effects of A. elata was systematically collected from the scientific literature through library catalogs; online services such as E-library.ru, Medline/PubMed, Scopus, Web of Science, and Google Scholar.

RESULTS

A. elata is often considered an example of a medicinal plant used in Chinese, Korean, and Japanese traditional medicine. However, the contemporary applications of Aralia in officinal medicine result primarily from a large number of pharmacological and clinical investigations carried out in the former USSR in the mid-20th century. Since the 1950s, medicinal preparations from radices of A. elata and radices of A. mandshurica have secured an established position within Russian/USSR medicine as evidenced by the inclusion of the drug in recent editions of the National Pharmacopoeia of the USSR and in the Register of Medicinal Preparations of Russia. Pharmacological studies on animals have shown that Aralia increases physical working capacity and affords a stress-protective effect against a broad spectrum of harmful factors including cold stress, immobilization, UV irradiation, and low air pressure. The phytoadaptogen exerts an effect on the central nervous, reproductive, immune, respiratory, and gastrointestinal systems; the metabolic syndrome including hypolipidemic and antidiabetic effects; and blood coagulation. Together with general properties of adaptogens, Aralia has its own specificity, which manifests in cardioprotective and antiarrhythmic activities. Studies on isolated organs, cells, and enzymes have revealed that Aralia preparations exhibit antioxidant activities and enhance sarcoplasmic reticulum Ca²⁺-ATPase activity, inhibit endoplasmic reticulum stress-associated apoptosis markers (GRP78, CHOP, Caspase-12, and JNK), and increase phosphorylation of STAT3 and Bcl2/Bax ratio; they also show cytotoxic activities against some tumor cell lines; affect NF-κB and PPARs activities; and regulate biosynthesis of pro-inflammatory cytokines and inflammation-related protein expression, tissue respiration, and oxygen consumption. In healthy subjects, Aralia increases mental performance, working capacity, and endurance of movement. Numerous clinical trials have shown the efficiency of Aralia preparations in patients with traumatic brain injury (accompanied with asthenic syndrome and neurotic reactions, depression, neurasthenia, and psychasthenia), neurological diseases (accompanied with astheno-depressive and astheno-hypochondriasis syndromes), myasthenia syndrome (accompanied with chronic post-influenza arachnoiditis), and arterial hypotension. Aralia tincture and "Saparal" are useful as antiviral remedies. Radioprotective properties of Aralia have been reported in pregnant women. Synergistic antiobesity effect was reported for the combination of A. mandshurica and Engelhardtia chrysolepis extracts and antidiabetic effect for the combination of Aralia and glipizide. Promising stress-relieving effects of Aralia are reported for professionals whose work requires a high level of attention. Its proposed ability to moderate stress-induced damage and dysfunction in the cardiovascular tissue might make Aralia the adaptogen of choice among patients with higher risk for cardiovascular diseases. Because Aralia extract administration appears to affect plasma glucose level and hepatic lipid accumulation and ameliorate hyperinsulinemia, it might also provide benefits and be the adaptogen of choice for patients with obesity and diabetes.

CONCLUSION

This review describes the considerable diversity of pharmacological effects of A. elata reported in numerous studies carried out in the former USSR and other countries, which have been confirmed over >47 years of use of the plant as an official medicinal remedy. The knowledge discussed in this review can be applied to the expansion of the use of this high-value plant in the pharmacotherapy of European and other countries and for the further discovery of new drugs based on the secondary metabolites of this plant. Modern approaches in mechanisms of action, including a study of gene expression profiling, suggest the most up-to-date challenges for the future research of Aralia.

Phytotherapy of Alcoholism

Alcoholism is a medical, social, and economic problem where treatment methods mostly include difficult and long-lasting psychotherapy and, in some cases, quite controversial pharmacological approaches. A number of medicinal plants and pure natural compounds are reported to have preventive and therapeutic effects on alcoholism and alcohol dependency, but their constituents, efficacy and mechanism of action are mostly unknown so far. Recently, kudzu [ Pueraria lobata (Willd.) Ohwi], St. John's wort ( Hypericum perforatum L.), danshen ( Salvia miltiorrhiza Bge.), ginseng ( Panax ginseng C.A. Mey.), Japanese raisin tree ( Hovenia dulcis Thunb.), ibogaine ( Tabernanthe iboga H. Bn.), evening primrose ( Oenothera biennis L.), prickly pear fruit ( Opuntia ficus indica (L.) Mill.), purple passionflower ( Passiflora incarnata L.), thyme ( Thymus vulgaris L.), fenugreek seed ( Trigonella foenum-graecum L.), ginger ( Zingiber officinale Roscoe) and many others drew the attention of researchers. Can, therefore, drugs of natural origin be helpful in the treatment of alcoholism or in decreasing alcohol consumption?

Suppressive effects on the biosynthesis of inflammatory mediators by Aralia elata extract fractions in macrophage cells

The aim of this study is to elucidate the anti-inflammatory effects of Aralia elata extract fractions (AEEFs). A. elata-ethyl acetate fraction (AEEF) had the strongest antioxidant activity. A. elata-chloroform fraction (AECF) and A. elata-butanol fraction (AEBF) inhibited potently LPS-induced nitrite production from RAW 264.7 macrophage cells. The inhibition of nitric oxide (NO) production by AEEFs was partially due to chemical scavenge of NO and the suppression of inducible NOS (iNOS) transcription level in LPS-induced macrophage cells. In addition, AEEFs inhibited significantly the biosynthesis of Prostaglandin E(2) (PGE(2)), and cyclooxygenase-2, which regulates the synthesis of PGE(2), was attenuated partially by the treatment of AEEFs in LPS-induced macrophage cells. Also, A. elata-methanolic extract (AEME) suppressed remarkably IL-1β and IL-6 level to the basal (more than 99% inhibition) in concentration-dependant manners. Its anti-inflammatory actions might be related with inhibition of NF-κB activation in LPS-stimulated macrophage cells. It is concluded that AEEFs may be useful as a functional food material and an alternative medicine for the relief and retardation of immunological inflammatory responses.

Isolation and tandem mass fragmentations of an anti-inflammatory compound from Aralia elata

One-step isolation of a saponin from Aralia elata was undertaken using high-speed countercurrent chromatography coupled with evaporative light scattering detection. A triterpenoid saponin, elatoside F, was purified with 96.8% purity using a two-phase-system comprising chloroform-methanol-water-isopropanol. The yield was 35.0 mg from 348.2 mg of the enriched saponin fraction. In vitro anti-inflammatory study demonstrated that elatoside F inhibited lipopolysaccharide-induced nitric oxide production, as well as nuclear factor kappaB activation, in a dose-dependent manner. Two types of mass ionization technique were compared on elatoside F to investigate characteristic fragmentation patterns. MALDI-TOF tandem mass spectrometric fragmentation patterns of sodiated ions provided structural information on glycosidic cleavages and on extensive cross-ring cleavages. Electrospray ionization multiple-stage tandem mass fragmentation of both sodiated and lithiated ions could provide information on glycosidic cleavages. All observed tandem mass fragmentation spectra provided valuable elatoside F structural information when unknown samples from crude extracts are under screening by mass spectrometry.

Oleanolic acid and related derivatives as medicinally important compounds

Oleanolic acid has been isolated from chloroform extract of Olea ferruginea Royle after removal of organic bases and free acids. The literature survey revealed it to be biologically very important. In this review the biological significance of oleanolic acid and its derivatives has been discussed. The aim of this review is to update current knowledge on oleanolic acid and its natural and semisynthetic analogs, focussing on its cytotoxic, antitumer, antioxidant, anti-inflamatory, anti-HIV, acetyl cholinesterase, alpha-glucosidase, antimicrobial, hepatoprotective, anti-inflammatory, antipruritic, spasmolytic activity, anti-angiogenic, antiallergic, antiviral and immunomodulatory activities. We present in this review, for the first time, a compilation of the most relevant scientific papers and technical reports of the chemical, pre-clinical and clinical research on the properties of oleanolic acid and its derivatives.

Triterpenoid saponin, oleanolic acid 3-O-β-d-glucopyranosyl(1→3)-α-l-rhamnopyranosyl(1→2)-α-l-arabinopyranoside (OA) from Aralia elata inhibits LPS-induced nitric oxide production by down-regulated NF-κB in raw 264.7 cells

It is well known that the pro-inflammatory mediators such as nitric oxide (NO) and prostaglandin (PG)E(2) are involved in several inflammatory diseases and lipopolysaccharide (LPS) can stimulate these inflammatory responses. Oleanolic acid 3-O-beta-d-glucopyranosyl(1-->3)-alpha-l-rhamnopyranosyl(1-->2)-alpha-l-arabinopyranoside (OA) was purified from edible plant Aralia elata. OA inhibited LPS-induced NO and PGE(2) production in raw 264.7 murine macrophages in a dose-dependent manner and RT-PCR analysis indicated OA inhibited mRNA transcriptions of iNOS and COX-2 genes in LPS-induced cells. EMSA and Western blot analysis revealed that OA drastically reduced NF-kappaB translocation by the inhibition effects of LPS-induced phosphorylation of IkappaBalpha. In addition, it was found that OA inhibited the phosphorylation of ERK1/2, p38 and JNK MAPK, and the treatment of U0126 in LPS-induced raw 264.7 cells showed significant inhibition activity on the NO production and the phosphorylation of IkappaBalpha. Taken together, it is suggested that OA from A. elata has an anti-inflammatory activity via down-regulation of NF-kappaB.

Natural medicines for alcoholism treatment: a review

Alcoholism is a serious problem throughout the world. The development of alcoholism remedies have medical, social and economical significance. In view of the pitfalls of psychological dependence and adverse behavioural effects of synthetic drugs, the development of low toxicity and high efficiency medicines derived from natural products exhibits expansive market prospects. Based on these considerations, we summarize briefly folk application of traditional hangover remedies and clinical application of herbal complex and patent medicines for alcoholism treatment. We have reviewed the effects of natural medicines on intake, absorption and metabolism of alcohol, as well as the protective effects on alcohol-induced acute and chronic tissue injury.

Araloside A, an Antiulcer Constituent from the Root Bark of Aralia elata

Araloside A, a potent inhibitor of gastric lesion and ulcer formation in rats, was isolated from the root bark of Aralia elata through a bioassay-guided separation procedure. The compound exhibited significant reduction of HCl.ethanol-induced gastric lesions and aspirin-induced gastric ulcers at oral doses of 50 and 100 mg/kg, respectively. These activities are comparable to those of cimetidine.

Effects of Saponins from the Root Bark of Aralia elata on the Transport of Chondroitin Sulfate in Caco-2 Cell Monolayers and Rats

We investigated the intestinal absorption enhancing effect of the saponins from the root bark of Aralia elata (SRBAE) in Caco-2 cell monolayers and rats. SRBAE at concentrations of 0.04% and 0.08% (w/v) decreased the transepithelial electrical resistance (TEER) values and increased the paracellular uptake of chondroitin sulfates (CSs) having different molecular weights (MW 500, 4500, and 18000) in a dose-dependent manner. We also evaluated the cytotoxicity of SRBAE to determine its proper concentration as an absorption enhancer. MTT assay and trypan blue exclusion test indicated that the cytotoxicity of SRBAE at concentrations of 0.04% and 0.08% was negligible. CS (MW 18000) was orally administered with or without SRBAE to rats. The oral administration of SRBAE (250 mg/kg) in 1 h increased the intestinal absorption of CS, by 4.9-fold versus the control (CS alone). Histological examination of the gastrointestinal tissues showed that SRBAE did not cause any damage to tissues. In conclusion, our results suggest that SRBAE acts as an efficient absorption enhancer and makes it easier for hydrophilic molecules to penetrate the intestinal epithelium.

Saponins and Other Constituents from the Leaves of Aralia elata

A new triterpenoid saponin, together with five known saponins, were isolated from the nonpolar n-hexane fraction of the leaves of Aralia elata. The structure of the new saponin, durupcoside C, was elucidated as hederagenin 3-O-beta-D-glucopyranosyl(1-->3)-beta-D-glucopyranosyl(1-->3)-alpha-L-arabinopyranoside on the basis of spectroscopic analysis. The known saponins were characterized as 3-O-alpha-L-rhamnopyranosyl(1-->2)-alpha-L-arabinopyranosyl hederagenin 28-O-beta-D-xylopyranosyl(1-->6)-beta-D-glucopyranosyl ester, hederagenin 3-O-beta-D-glucopyranosyl(1-->3)-alpha-L-rhamnopyranosyl(1-->2)-alpha-L-arabinopyranoside, oleanolic acid 3-O-beta-D-glucopyranosyl(1-->3)-alpha-L-rhamnopyranosyl(1-->2)-alpha-L-arabinopyranoside, hederagenin 3-O-alpha-L-rhamnopyranosyl(1-->2)-alpha-L-arabinopyranoside (alpha-hederin), and hederagenin 3-O-beta-D-glucopyranosyl(1-->3)-alpha-L-arabinopyranoside (collinsonidin). In addition, two known lipids, Arisaema glyceride 3 and ceramide mixtures were also isolated and characterized. Collinsonidin and two known lipids were isolated for the first time from this plant.

Bioactive oleanolic acid saponins and other constituents from the roots of Viguiera decurrens

The bisdesmoside oleanolic acid saponin, 3-0-(methyl-beta-D-glucuronopyranosiduronoate)-28-0-beta-D-glucopyranosyl-oleanolate along with nine known compounds (two diterpenic acids, one chromene, three triterpenes, one steroidal glycoside, and two monodesmoside oleanolic acid saponins), were obtained from Viguiera decurrens roots. The chemical structure of the bisdesmoside oleanolic saponin was determined by chemical and NMR spectral evidence. A mixture of monodesmoside saponins displayed cytotoxic activity against P388 and COLON cell lines (ED50= 2.3 and 3.6 microg/ml, respectively). Two of the known compounds showed insecticidal activity against the Mexican bean beetle larvae (Epilachna varivestis).

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.

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.

Cholesterol-independent membrane disruption caused by triterpenoid saponins

The membrane-disrupting activity of 15 triterpenoid saponins, obtained from Chinese plants of the genus Aralia, was investigated using phosphatidylcholine liposomes with and without cholesterol. The permeability of the membrane was examined by monitoring the induced fluorescent dye release from the liposome. On the basis of the obtained results, the structure-activity relationship among glucuronides of oleanolic acid was discussed. This takes into account particularly the variation in the carboxyl function. Namely, the saponins could induce a permeability change on liposomal membrane without cholesterol when they are glycosylated at both C-3 and C-28 of the oleanolic acid. There also exists a great similarity in the time-course curves for dye-release within such saponins, reflecting their similar action with the lipid bilayer membrane. The saponins glycosylated only at C-3 could also exhibit the same activity with somewhat different action profiles when the glucuronic acid is esterified, while those with the free glucuronic acid required cholesterol in the liposomes to induce permeability change thereof.