Medicinal foodstuffs. VII. On the saponin constituents with glucose and alcohol absorption-inhibitory activity from a food garnish "Tonburi", the fruit of Japanese Kochia scoparia (L.) Schrad.: structures of scoparianosides A, B, and C

Hypoglycemic effects of mountain caviar extract and inhibitory mechanism of saponins, including momordin Ic, on glucose absorption

Mountain caviar is a fruit of Kochia scoparia that contains momordin Ic as a major saponin constituent. Its extract (MCE) has been shown to suppress blood glucose elevations in the human oral glucose tolerance test (OGTT) as well as increases in blood glucose in OGTT, gastric emptying (GE), and glucose incorporation in the small intestine in rats. However, the effects of MCE and momordin Ic on glucose absorption in mice and these action mechanisms have not been examined for more than 2 decades. Therefore, we herein investigated the effects of MCE, its saponin fraction, and momordin Ic on blood glucose elevations in mice. Mouse blood glucose elevation tests were performed on carbohydrate-loaded mice. The mountain caviar saponin fraction significantly delayed blood glucose elevations in glucose-, sucrose-, and soluble starch-loaded mice. In glucose-loaded mice, the saponin fraction, MCE, and momordin Ic significantly suppressed rapid glucose elevations after glucose loading, but not sucrose loading. A mouse GE study was performed by loading with glucose and phenolphthalein solution. Momordin Ic and MCE strongly suppressed mouse GE. Intestinal glucose absorption was evaluated by the incorporation of 2-deoxyglucose (2-DG) into Caco-2 cell layers and mouse duodenum wall vesicles. The results obtained showed that momordin Ic inhibited the incorporation of 2-DG into Caco-2 cells and mouse duodenum vesicles. Collectively, these results suggest that MCE, particularly the principal saponin, momordin Ic, preferably suppressed glucose-induced blood glucose elevations and delayed carbohydrate-induced glucose elevations in mice. The underlying mechanism was found to involve the suppression of GE and intestinal glucose absorption.

New biofunctional effects of oleanane-type triterpene saponins

In the current review, we describe the novel biofunctional effects of oleanane-type triterpene saponins, including elatosides, momordins, senegasaponins, camelliasaponins, and escins, obtained from Aralia elata (bark, root cortex, young shoot), Kochia scoparia (fruit), Polygala senega var. latifolia (roots), Camellia japonica (seeds), and Aesculus hippocastanum (seeds), considering the following biofunctional activities: (1) inhibitory effects on elevated levels of blood alcohol and glucose in alcohol and glucose-loaded rats, respectively, (2) inhibitory effects on gastric emptying in rats and mice, (3) accelerative effects on gastrointestinal transit in mice, and (4) protective effects against gastric mucosal lesions in rats. In addition, we describe (5) suppressive effects of the extract and chakasaponins from Camellia sinensis (flower buds) on obesity based on inhibition of food intake in mice. The active saponins were classified into the following three types: (1) olean-12-en-28-oic acid 3-O-monodesmoside, (2) olean-12-ene 3,28-O-acylated bisdesmoside, and (3) acylated polyhydroxyolean-12-ene 3-O-monodesmoside. Furthermore, common modes of action, such as involvements of capsaicin-sensitive nerves, endogenous NO and PGs, and possibly sympathetic nerves, as well as common structural requirements, were observed. Based on our findings, a common mechanism of action might mediate the pharmacological effects of active saponins. It should be noted that the gastrointestinal tract is an important action site of saponins, and the role of the saponins in the gastrointestinal tract should be carefully considered.

Pharmaceutical Food Science: Search for Bio-Functional Molecules Obtained from Natural Resources to Prevent and Ameliorate Lifestyle Diseases

In this review, our resent pharmaceutical food science research for bio-functional molecules obtained from natural resources that contribute to i) suppression of postprandial blood glucose elevation and/or improvement of glucose tolerance and ii) reduction of visceral fat accumulation and improvement of lipid metabolism were summarized. Based on studies using MONOTORI science, salacinol (1), neokotalanol (4), and trans-tiliroside (20) have been approved or notified by the Consumer Affairs Agency in Japan as functional substances in food with health claims, Food for Specified Health Use and Food with Functional Claims.

Recurvataside, a new saponin from aerial parts of Mussaenda recurvata

A new glycoside, recurvataside (1) and six known compounds, quinovic acid (2), quinovic acid 28-O-β-D-glucopyranosyl ester (3), 3-O-β-D-glucopyranosylquinovic acid (4), 3-O-β-D-glucopyranosylquinovic acid 28-O-β-D-glucopyranosyl ester (5), pomolic acid (6), and ursolic acid (7) were isolated from aerial parts of Mussaenda recurvata. The structure of compound 1 was identified from its spectroscopic data and by comparison with the literature. Recurvataside represents the first occurrence of δ-oleanolic acid saponin bearing two D-glucose units at C-3 and C-28 in nature. This is the first time δ-oleanane-type saponin reported in the genus Mussaenda. Compounds 1-7 were evaluated the cytotoxicity against two cancer cell lines MCF-7 and HepG2. Among them, only compound 7 exhibited moderate activity against MCF-7 and HepG2 cell lines with IC₅₀ value of 16.97 ± 1.55 and 20.28 ± 1.00 μM, respectively. Compounds 1-7 were also tested for their inhibitory NO production in LPS-stimulated RAW264.7 cells. Compounds 3, 5, and 7 showed significant reduction of nitrite accumulation in LPS-stimulated RAW 264.7 cells with the IC₅₀ values of 8.81 ± 0.48, 13.42 ± 0.84, and 18.37 ± 0.67 μM, respectively.

A review of antidiabetic active thiosugar sulfoniums, salacinol and neokotalanol, from plants of the genus Salacia

During our studies characterizing functional substances from food resources for the prevention and treatment of lifestyle-related diseases, we isolated the active constituents, salacinol (1) and neokotalanol (4), and related thiosugar sulfoniums, from the roots and stems of the genus Salacia plants [Celastraceae (Hippocrateaceae)] such as Salacia reticulata Wight, S. oblonga Wall., and S. chinensis L., and observed their antidiabetic effects. These plant materials have been used traditionally in Ayurvedic medicine as a specific remedy at the early stage of diabetes, and have been extensively consumed in Japan, the United States, and other countries as a food supplement for the prevention of obesity and diabetes. Here, we review our studies on the antidiabetic effects of plants from the genus Salacia, from basic chemical and pharmacological research to their application and development as new functional food ingredients.

Synthesis and anti-inflammatory activity of saponin derivatives of δ-oleanolic acid

Pentacyclic triterpenes (PTs) are the active ingredients of many medicinal herbs and pharmaceutical formulations, and are well-known for their anti-inflammatory activity. On the other hand, anti-inflammatory effects of AMP-activated protein kinase (AMPK) have recently drawn much attention. In this study, we found that a variety of naturally occurring PTs sapogenins and saponins could stimulate the phosphorylation of AMPK, and identified δ-oleanolic acid (10) as a potent AMPK activator. Based on these findings, 23 saponin derivatives of δ-oleanolic acid were synthesized in order to find more potent anti-inflammatory agents with improved pharmacokinetic properties. The results of cellular assays showed that saponin 29 significantly inhibited LPS-induced secretion of pro-inflammatory factors TNF-α and IL-6 in THP1-derived macrophages. Preliminary mechanistic studies showed that 29 stimulated the phosphorylation of AMPK and acetyl-CoA carboxylase (ACC). The bioavailability of 29 was significantly improved in comparison with its aglycon. More importantly, 29 showed significant anti-inflammatory and liver-protective effects in LPS/D-GalN-induced fulminant hepatic failure mice. Taken together, PTs saponins hold promise as therapeutic agents for inflammatory diseases.

A Review of Biologically Active Natural Products from a Desert Plant Cistanche tubulosa

An Orobanchaceae plant Cistanche tubulosa (SCHENK) WIGHT (Kanka-nikujuyou in Japanese), which is one of the authorized plant resources as Cistanches Herba in both Japanese and Chinese Pharmacopoeias, is a perennial parasitic plant growing on roots of sand-fixing plants. The stems of C. tubulosa have traditionally been used for treatment of impotence, sterility, lumbago, and body weakness as well as a promoting agent of blood circulation. In recent years, Cistanches Herba has also been widely used as a health food supplement in Japan, China, and Southeast Asian countries. Here we review our recent studies on chemical constituents from the stems of C. tubulosa as well as their bioactivities such as vasorelaxtant, hepatoprotective, and glucose tolerance improving effects.

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.

Protonated montmorillonite-mediated highly specific isomerization of oleanolic acid esters: application to the synthesis of Δ13(18)-CDDO-Me

A one-pot highly specific isomerization of oleanolic acid esters (5a–g) to δ-oleanolic acid esters (6a–g) was achieved in the presence of proton-exchanged montmorillonite (H-mont) under mild reaction conditions.

Studies on the flavone glycosides from Fructus Kochiae

A series of flavone glycosides were isolated from Fructus Kochiae for the first time, including two new flavone glycosides. The structures were established by interpretation of their spectroscopic data. Two new flavone glycosides are quercetin 3-O-β-d-apiofuranosyl-(1 → 2)-β-d-galactopyranosyl-7-O-β-d-glucopyranoside (1) and quercetin 3-O-α-l-rhamnopyranosyl-(1 → 6)-β-d-galactopyranosyl-7-O-β-d-sophoroside (2). The others are quercetin 7-O-β-d-glucopyranoside (3), quercetin 3-O-β-d-apiofuranosyl-(1 → 2)-β-d-galactopyranoside (4), quercetin 3-O-β-d-galactopyranosyl-7-O-β-d-glucopyranoside (5), and quercetin 7-O-β-d-sophoroside (6).

Inhibition of human renin activity by saponins

Renin is the most important enzyme in the renin-angiotensin system. Our previous study led to the identification of soyasaponin I, the first renin inhibitor isolated from soybean. In the present study, the effects of saponins and sapogenols on human renin activities were investigated. Soyasaponins I and II, glycyrrhizin, monoglucuronyl glycyrrhetic acid (MGGA), chikusetsusaponin IV, and Kochia scoparia fruit saponins (momordins) were found to inhibit renin activity. On the other hand, sapogenols (soyasapogenol B and glycyrrhetic acid), saikosaponins b2 and c, and ginsenoside Rb(1) had no effect on renin activity. These results clearly indicate that the 3-O-beta-dglucopyranosiduronic moiety in saponins (glucuronide saponin) is essential for renin inhibition.

Bioactive constituents from chinese natural medicines. XXIV. Hypoglycemic effects of Sinocrassula indica in sugar-loaded rats and genetically diabetic KK-A(y) mice and structures of new acylated flavonol glycosides, sinocrassosides A(1), A(2), B(1), and B(2)

The methanolic extract from the whole plant of Sinocrassula indica (Crassulaceae) was found to inhibit the increase in serum glucose levels in oral administration of sucrose and glucose in rats at a dose of 250 mg/kg (p.o.). However, the extract did not inhibit the increase in serum glucose levels after intraperitoneal administration of glucose in these animals but did partly inhibit the gastric emptying. On the other hand, this extract significantly inhibited the increase in serum glucose levels after administration for 2 weeks in KK-A(y) mice, a genetically type II diabetic mice, at a dose of 250 mg/kg/d (p.o.) without significant changes of the weights of body, liver, and visceral fat. From the extract, four new acylated flavonol glycosides, sinocrassosides A(1), A(2), B(1), and B(2), were isolated together with 11 flavonoids and 2 megastigmanes. The absolute stereostructures of the four new compounds were elucidated on the basis of chemical and physicochemical evidence.

Reduction of fat storage in mice fed a high-fat diet long term by treatment with saponins prepared from Kochia scoparia fruit

The fresh fruit (Japanese name, Tonburi) of Kochia scoparia has been used as a food garnish in Japanese-style dishes from ancient times, and may prevent metabolic syndromes such as hyperlipidemia, hypertension, obesity and atherosclerosis. This study was performed to clarify whether an ethanol extract of K. scoparia fruit prevented obesity induced in mice by a high-fat diet for 9 weeks. The ethanol extract of K. scoparia fruit prevented the increases in body weight and parametrial adipose tissue weight induced by the high-fat diet. Furthermore, consumption of a high-fat diet containing 1% or 3% K. scoparia extract significantly increased the fecal content and the fecal triacylglycerol level at day 3 compared with those in the high-fat diet group. The ethanol extract (250 mg/kg) and total saponins (100 mg/kg) of K. scoparia inhibited the elevation of the plasma triacylglyccerol level 2 or 3 h after the oral administration of the lipid emulsion. Total saponins, momordin Ic, 2'-O-beta-d-glucopyranosyl momordin Ic and 2'-O-beta-d-glucopyranosyl momordin IIc isolated from K. scoparia fruit inhibited the pancreatic lipase activity (in vitro). These findings suggest that the anti-obesity actions of K. scoparia extract in mice fed a high-fat diet may be partly mediated through delaying the intestinal absorption of dietary fat by inhibiting pancreatic lipase activity.

Medicinal Flowers. XII.1) New Spirostane-Type Steroid Saponins with Antidiabetogenic Activity from Borassus flabellifer

The methanolic extract from the male flowers of Borassus flabellifer was found to inhibit the increase of serum glucose levels in sucrose-loaded rats at a dose of 250 mg/kg, p.o. From the methanolic extract, six new spirostane-type steroid saponins, borassosides A-F (1-6), were isolated together with 23 known constituents. The structures of borassosides (1-6) were elucidated on the basis of chemical and physicochemical evidences. In addition, the principal steroid saponin, dioscin (13), inhibited the increase of serum glucose levels in sucrose-loaded rats at a dose of 50 mg/kg, p.o.

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.

Momordin Ic and oleanolic acid from Kochiae Fructus reduce carbon tetrachloride-induced hepatotoxicity in rats

Hepatoprotective effects of momordin Ic and oleanolic acid obtained from Kochiae Fructus (KF), the fruit of a traditional Oriental medicinal plant, were evaluated against carbon tetrachloride (CCl4)-induced liver damage in rats. Male Sprague-Dawley rats were divided into four groups: control, CCl4-treated, CCl4 plus momordin Ic-treated (MMDIc-CCl4), and CCl4 plus oleanolic acid-treated (OAA-CCl4). Momordin Ic (30 mg/kg of body weight) and oleanolic acid (30 mg/kg of body weight) were orally administered once a day for 14 days. A mixture of 0.2 mL/100 g of body weight of CCl4 in olive oil (1:1, vol/vol) was injected 30 minutes after the final administration of momordin Ic and oleanolic acid. The momordin Ic and oleanolic acid pretreatments resulted in significantly lower serum transaminase, lactic dehydrogenase, and gamma-glutamyltransferase levels in the CCl4-treated rats. The CCl4-treated rats had significantly lower activities of glutathione, glutathione reductase, glutathione S-transferase, superoxide dismutase, catalase, and glutathione peroxidase. However, pretreatment with momordin Ic and oleanolic acid reduced the effect of CCl4 and helped maintain levels of the enzymes. Pretreatment with momordin Ic and oleanolic acid resulted in significantly lower production of aminopyrine N-demethylase and aniline hydroxylase in the CCl4-treated rats. Pretreatment with momordin Ic resulted in lower catalase and aminopyrine N-demethylase activity induction by CCl4, towards normalization. Momordin Ic and oleanolic acid obtained from KF appear to contribute to alleviating the adverse effects of CCl4 treatment by enhancing the hepatic antioxidant defense system.

Anti-inflammatory and Antitumor-Promoting Effects of the Triterpene Acids from the Leaves of Eriobotrya japonica

Sixteen triterpene acids, viz., five of the oleanane-type (1-5), nine of the ursane-type (6-14), and two of the lupane-type (15, 16), were isolated and identified from the ethyl acetate-soluble fraction of the methanol extract of the leaves of loquat, Eriobotrya japonica LINDL. (Rosaceae). Twelve of these compounds, 1-4, 6, 8-13, and 15, were evaluated for their inhibitory effects on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced inflammation (1 microg/ear) in mice. All the compounds tested showed a marked anti-inflammatory effect, with a 50% inhibitory dose (ID50) of 0.03-0.43 mg per ear. In addition, an evaluation against the Epstein-Barr virus early antigen (EBV-EA) activation induced by TPA for all of the compounds, 12 and 13 showed potent inhibitory effects on EBV-EA induction. Furthermore, euscaphic acid (12) exhibited marked antitumor-promoting activity in an in vivo two-stage carcinogenesis test of mouse tumor by using 7,12-dimethylbenz[a]anthracene (DMBA) as an initiator and TPA as a promoter.

Acetylated glucuronide triterpene bidesmosidic saponins from Symplocos glomerata

Nine new bidesmosidic 3-O-glucuronide oleanane triterpenoid saponins were isolated from the stem bark of Symplocos glomerata King along with two known saponins, salsoloside C and copteroside E, and two major lignans, (-)-pinoresinol and (-)-pinoresinol-4'-O-beta-D-glucopyranoside. The structures of the new saponins were established using one- and two-dimensional NMR spectroscopy and mass spectrometry as, 3-O-[beta-D-xylopyranosyl(1-->4)-[2-O-acetyl]-beta-D-glucuronopyranosyl]-28-O-[beta-D-glucopyranosyl]-oleanolic acid, 3-O-[beta-D-xylopyranosyl(1-->4)-[3-O-acetyl]-beta-D-glucuronopyranosyl]-28-O-[beta-D-glucopyranosyl]-oleanolic acid, 3-O-[beta-D-xylopyranosyl (1-->4)-[2,3-O-diacetyl]-beta-D-glucuronopyranosyl]-28-O-[beta-D-glucopyranosyl]-oleanolic acid, 3-O-[alpha-L-arabinopyranosyl(1-->4)-beta-D-glucuronopyranosyl]-28-O-[beta-D-glucopyranosyl]-oleanolic acid, 3-O-[alpha-L-arabinopyranosyl (1-->4)-[2-O-acetyl]-beta-D-glucuronopyranosyl]-28-O-[beta-D-glucopyranosyl]-oleanolic acid, 3-O-[[beta-D-xylopyranosyl (1-->2)]-[beta-D-xylopyranosyl (1-->4)]-[3-O-acetyl]-beta-D-glucuronopyranosyl]-28-O-[beta-D-glucopyranosyl]-oleanolic acid, 3-O-[[beta-D-glucopyranosyl (1-->2)]-[beta-D-xylopyranosyl (1-->4)]-[3-O-acetyl]-beta-D-glucuronopyranosyl]-28-O-[beta-D-glucopyranosyl]-oleanolic acid, 3-O-[[beta-D-glucopyranosyl (1-->2)]-[alpha-L-arabinofuranosyl (1-->4)]-[3-O-acetyl]-beta-D-glucuronopyranosyl]-28-O-[beta-D-glucopyranosyl]-oleanolic acid, and 3beta-O-[beta-D-xylopyranosyl(1-->4)-[2-O-acetyl]-beta-D-glucuronopyranosyl]-28-O-[beta-D-glucopyranosyl]-morolic acid. The EtOH and EtOAc extracts of the stem bark showed no cytotoxic activity. At a concentration of 370 microg/ml, the saponin mixture showed haemolytic activity and caused 50% haemolysis of a 10% suspension of sheep erythrocytes.

Anti-rheumatoid arthritis effect of the Kochia scoparia fruits and activity comparison of momordin lc, its prosapogenin and sapogenin

MeOH extract of Kochia scoparia was fractionated into CHCl3-, EtOAc- and BuOH extracts and the last fraction were hydrolyzed by 3%-NaOH (MeOH-H2O) to compare the bioactivities on antinociceptive and anti-inflammatory effects. Silica gel column chromatography of BuOH fraction afforded a large amount of 3-O-beta-D-xylopyranosyl (1-->3)-beta-D-glucuronopyranosyl oleanolic acid (momordin lc, 4) and that of acid hydrolysate of BuOH fraction gave 3-O-beta-D-glucuronopyranosyl oleanolic acid (momordin lb, 3), its 6'-O-methyl ester (2) and oleanolic acid (1). Silica gel column chromatography of alkaline hydrolysate afforded a large amount of 4. MeOH extract and both EtOAc- and BuOH fractions were active in the rheumatoidal rat induced Freund's complete adjuvant reagent (FCA) whereas CHCl3 fraction was inactive. Compound 1 and 4 showed significant activities in the same assay but oleanolic acid 3-O-glucuronopyranoside (3) showed no activity. These fashions were also observed in carrageenan-induced edema of the rat and in the antinociceptive activity tests undertaken in hot plate- and writhing methods. These results suggest that momordin lc and its aglycone, oleanolic acid, could be active principles for rheumatoid arthritis.

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.

Alcohol absorption inhibitors from bay leaf (Laurus nobilis): structure-requirements of sesquiterpenes for the activity

Through a bioassay-guided separation using inhibitory activity on blood ethanol elevation in oral ethanol-loaded rat, various sesquiterpenes having an alpha-methylene-gamma-butyrolactone moiety, costunolide (1), dehydrocostus lactone (2), zaluzanin D (3), reynosin (4), santamarine (5), 3alpha-acetoxyeudesma-1,4(15),11(13)-trien-12,6alpha-+ ++olide (6) and 3-oxoeudesma-1,4,11(13)-trien-12,6alpha-olide (7), were isolated as the active principle from the leaves of Laurus nobilis (bay leaf, laurel). In order to characterize the structure requirement for the activity, several reduction products (2a-2d) and amino acid adducts (2e, 2f) of the alpha-methylene-gamma-butyrolactone moiety were synthesized from 2 and the inhibitory activities of these sesquiterpenes, together with alpha-methylene-gamma-butyrolactone (12) and its related compounds (13-16), were examined. These results indicated that the gamma-butyrolactone or gamma-butyrolactol moiety having alpha-methylene or alpha-methyl group was essential for the inhibitory activity on ethanol absorption. Since 1, 2 and 12 showed no significant effect on glucose absorption, these sesquiterpenes appeared to selectively inhibit ethanol absorption. In addition, the acute toxicities of 1 and 2 in a single oral administration were found to be lower than that of 12.

Acceleration of gastrointestinal transit by momordin Ic in mice: possible involvement of 5-hydroxytryptamine, 5-HT(2) receptors and prostaglandins

Possible involvement of 5-hydroxytryptamine (5-HT), 5-HT receptors and prostaglandins in the acceleration of gastrointestinal transit by momordin Ic was investigated in mice. Accelerative effect of momordin Ic (25 mg/kg, p.o.) on gastrointestinal transit was attenuated by pretreatment with a bolus of DL-p-chlorophenylalanine methyl ester (an inhibitor of 5-HT synthesizing enzyme), but not repeated pretreatment with DL-p-chlorophenylalanine methyl ester. Furthermore, cyproheptadine (a nonselective 5-HT(2) receptor antagonist), ritanserin (a 5-HT(2A/2B/2C) receptor antagonist) and clozapine (a 5-HT(2A/2C) receptor antagonist) also attenuated the effect of momordin Ic, but methiothepin (a 5-HT(1) receptor antagonist), MDL 72222 (3-tropanyl-3,5-dichlorobenzoate) and metoclopramide (5-HT(3) receptor antagonists), tropisetron (a 5-HT(3/4) receptor antagonist), ketanserin and haloperidol (5-HT(2A) receptor antagonists) did not. These results suggested a possible involvement of endogenous 5-HT and 5-HT(2B/2C) over 5-HT(2A) receptors. Attenuation by pretreatment with indomethacin (an inhibitor of prostaglandins synthesis) suggested involvement of prostaglandins. It is postulated that momordin Ic accelerates gastrointestinal transit partially by stimulating synthesis of 5-HT to act through 5-HT(2), possibly 5-HT(2C) and/or 5-HT(2B) receptors, which, in turn, increases synthesis of prostaglandins.

Adjuvant and haemolytic activities of 47 saponins derived from medicinal and food plants

Adjuvant and haemolytic activities of 47 saponins purified from medicinal and food plants were examined. The compounds showed various levels of both adjuvant and haemolytic activities. Soyasaponins and lablabosides showed strong adjuvant activity but little haemolytic activity. Jujubosides showed strong adjuvant and haemolytic activities. Escins showed weaker adjuvant activity than the adjuvant-control, but strong haemolytic activity. Comparison of the functional groups of each saponin revealed that the acyl residue in saponin, the aldehyde group at carbon 4 in aglycone, and branched sugar chains attached to aglycone, were not essential for adjuvant activity. Furthermore, saponins with an acyl residue or oxide-ring moiety tended to show haemolytic activity. These results suggest that the adjuvant activity of saponins does not relate with haemolytic activity. It is considered that not only the functional groups themselves, but the overall conformation harmoniously consisting of such functional groups, affects adjuvant activity of saponins.

Preventive effect of sesquiterpenes from bay leaf on blood ethanol elevation in ethanol-loaded rat: structure requirement and suppression of gastric emptying

The methanolic extract from the leaves of Laurus nobilis (bay leaf, laurel) potently inhibited the elevation of blood ethanol level in ethanol-loaded rat. Through bioassay-guided separation, costunolide, dehydrocostus lactone, and santamarine were isolated as the active constituents and the alpha-methylene-gamma-butyrolactone structure was found to be essential for the preventive effect on ethanol absorption. In addition, the retardation of gastric emptying seemed to be partially involved in the preventive effects.

Roles of capsaicin-sensitive sensory nerves, endogenous nitric oxide, sulfhydryls, and prostaglandins in gastroprotection by momordin Ic, an oleanolic acid oligoglycoside, on ethanol-induced gastric mucosal lesions in rats

The roles of capsaicin-sensitive sensory nerves (CPSN), endogenous nitric oxide (NO), sulfhydryls (SHs), prostaglandins (PGs) in the gastroprotection by momordin Ic, an oleanolic acid oligoglycoside isolated from the fruit of Kochia scoparia (L.) SCHRAD., on ethanol-induced gastric mucosal lesions were investigated in rats. Momordin Ic (10 mg/kg, p.o.) potentially inhibited ethanol-induced gastric mucosal lesions. The effect of momordin Ic was markedly attenuated by the pretreatment with capsaicin (125 mg/kg in total, s.c., an ablater of CPSN), N(G)-nitro-L-arginine methyl ester (L-NAME, 70 mg/kg, i.p., an inhibitor of NO synthase), N-ethylmaleimide (NEM, 10 mg/kg, s.c., a blocker of SHs), or indomethacin (10 mg/kg, s.c., an inhibitor of PGs biosynthesis). The attenuation of L-NAME was abolished by L-arginine (300 mg/kg, i.v., a substrate of NO synthase), but not by D-arginine (300 mg/kg, i.v., the enatiomer of L-arginine). The effect of the combination of capsaicin with indomethacin, NEM, or L-NAME was not more potent than that of capsaicin alone. The combination of indomethacin and NEM, indomethacin and L-NAME, or indomethacin and NEM and L-NAME increased the attenuation of each alone. These results suggest that CPSN play an important role in the gastroprotection by momordin Ic on ethanol-induced gastric mucosal lesions, and endogenous PGs, NO, and SHs interactively participate, in rats.

Effects of oleanolic acid glycosides on gastrointestinal transit and ileus in mice

The effects of various oleanolic acid glycosides obtained from medicinal herbs on gastrointestinal transit (GIT) and ileus were investigated in fasted mice. Ileus was induced by the peritoneal-irritation or by the laparotomy with manipulation. One hour after the oral administration, three oleanolic acid 3-O-monodesmosides (oleanolic acid 3-O-glucuronide (3, 50 mg/kg), momordin Ic (4, 25 and 50 mg/kg), and momordin I (6, 25 mg/kg)) significantly accelerated GIT, but two oleanolic acid 3-O-monodesmosides (28-deglucosyl-chikusetsusaponins IV (8) and V (10)), oleanolic acid 3,28-O-bisdesmosides (momordin IIc (5), chikusetsusaponins IV (7) and V (9)), and their common aglycon (oleanolic acid (1)) (50 mg/kg) showed no significant effect. On the other hand, oleanolic acid 28-O-monodesmoside (compound O (2, 50 mg/kg)) significantly inhibited GIT. 4 (5-25 mg/kg) and 6 (12.5 and 25 mg/kg) also significantly prevented the inhibition of GIT induced by the peritoneal injection of acetic acid. 2 and 9 (50 mg/kg) significantly potentiated the inhibition of GIT, whereas 1, 3, 5, 7, 8, and 10 (50 mg/kg) showed no significant effect. 3, 4, 6, and 10 (50 mg/kg) significantly prevented the inhibition of GIT induced by laparotomy with manipulation, while 1, 2, 5, 7, 8, and 9 (50 mg/kg) showed no significant effect. These results indicate that the 3-O-glycoside moiety seems to be essential to show the GIT accelerating activity, and the 28-O-glucoside moiety reduce the activity. The accelerations of GIT by 3, 4, and 6 were completely abolished by the pretreatment with streptozotocin (100 mg/kg, i.v.), but not by the pretreatment with capsaicin (75 mg/kg in total, s.c.). These results suggest that sympathetic nervous system, but not capsaicin-sensitive sensory nerves, be involved in the enhancements of GIT by 3, 4, and 6. It is worthy to study their therapeutical effect in the prevention of the inhibition of GIT, including ileus, in clinic.

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.

Protective effects of oleanolic acid oligoglycosides on ethanol- or indomethacin-induced gastric mucosal lesions in rats

We examined the effects of various oleanolic acid oligoglycosides obtained from traditional herbs on ethanol- or indomethacin-induced gastric mucosal lesions in rats and on gastric secretion in pylorus-ligated rats. Test samples were given orally to fasted rats 1 h before absolute ethanol (1.5 ml/rat, p.o.) or indomethacin (30 mg/kg, s.c.) treatment, or ligation of the pylorus. Oleanolic acid 3-O-monodesmosides [oleanolic acid 3-O-glucuronide (1, 20-50 mg/kg), momordin Ic (2, 5-50 mg/kg), and 28-O-deglucosyl-chikusetsusaponins IV (5, 10-50 mg/kg) and V (7, 10-50 mg/kg)] were found to show protective effects on ethanol-induced gastric mucosal lesions, whereas oleanolic acid 3,28-O-bisdesmosides [momordin IIc (3), chikusetsusaponins IV (4) and V (6)], oleanolic acid 28-O-monodesmoside [compound O (8)], and their common aglycon [oleanolic acid (9)] showed no such effects. Oleanolic acid 3-O-monodesmosides (1, 2, and 5) also showed protective effects on indomethacin-induced gastric mucosal lesions. 28-O-Deglucosyl-chikusetsusaponin V (7) did not inhibit the indomethacin-induced lesions, while chikusetsusaponins V (6, 50 mg/kg) had the gastroprotective effect. These active saponins (1, 2, 4-7, 10-50 mg/kg) did not decrease the gastric secretion by oral administration in pylorus-ligated rats.

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.