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The 70% ethanol extract of the rhizome of Alisma orientale (Alismatis rhizome) (AOE) was prepared and found to significantly inhibit 5-lipoxygenase (5-LOX)-catalyzed leukotriene (LT) production from rat basophilic leukemia (RBL)-1 cells and β-hexosaminidase release by antigen-stimulated RBL-2H3 cells. It also attenuated delayed-type hypersensitivity (DTH) reaction in mice. Among the three major triterpene constituents isolated (i.e., alisol B, alisol B 23-acetate, alisol C 23-acetate) as active principles, alisol B and its 23-acetate strongly and significantly inhibited LT production and β-hexosaminidase release between 1-10 µM. On the other hand, all these alisol derivatives significantly and strongly inhibited DTH response after oral administration. In addition, AOE (200 mg/kg/d) was for the first time found to considerably alleviate hapten-induced dermatitis symptoms in NC/Nga mice, an animal model of atopic dermatitis. These results indicate that alisol derivatives possess inhibitory activities on immediate-type as well as delayed-type hypersensitivity reactions and may contribute to the anti-allergic action of AOE.

New protostane-type triterpenes termed alisols H, 1, J-23-acetate, K-23-acetate, L-23-acetate, M-23-acetate, and N-23-acetate were isolated from Alismatis Rhizoma, the rhizome of Alisma orientale JUZEP. Their stereostructures were determined on the basis of physicochemical evidence.

From the water-soluble portion of Chinese Alismatis Rhizoma, four bioactive sesquiterpenes, sulfoorientalols a, b, c, and d, were isolated and their structures having a sulfonic acid function were established on the basis of chemical and physicochemical evidence. In addition, two sulfoorientalol congeners were derived from alismol by sulfonation of the exo-methylene moiety. Sulfoorientalols and the synthetic congeners were found to inhibit the carbachol-induced contraction of isolated bladder smooth muscle of guinea pig.

An acidic polysaccharide, called alisman PII, was isolated from the tuber of Alisma orientale Juzepcz. It was homogeneous on electrophoresis and gel chromatography, and its molecular mass was estimated to be 5.25 x 10(4). It is composed of L-arabinose:D-galactose:D-glucuronic acid in the molar ratio of 4:9:2, in addition to some of O-acetyl groups. Reduction of carboxyl groups, methylation analysis, nuclear magnetic resonance and controlled Smith degradation indicated that the core structural features include a backbone chain composed of beta-1,3-linked D-galactose units. Some of the galactose units in the backbone carry beta-D-galactosyl side chains at position 6. Both alpha-1,5-linked L-arabinosyl side chains and terminal beta-D-glucuronic acid residues are linked to the core galactan units. Alisman PII showed significant potentiation of the reticuloendothelial system using a carbon clearance test and also potent anti-complementary activity.

Following the characterization of the triterpene constituents in Chinese Alismatis Rhizoma, we investigated the chemical structures of orientalols A, B, and C, isolated from the less polar fraction of the crude drug together with two known sesquiterpenes, alismol and alismoxide. On the basis of the chemical and physicochemical evidence, the structures of orientalols A, B, and C have been determined and those of alismol and alismoxide were revised. All five sesquiterpenes were found to show an inhibitory effect on the contraction of isolated bladder smooth muscle induced by carbachol.

Two new protostane-type triterpenes named 11-deoxyalisols B and B 23-acetate were isolated from the fresh rhizome of Alisma orientale JUZEP. originating from Japan, Taiwan, and China, together with known triterpenes and sesquiterpenes. The absolute stereostructures of 11-deoxyalisols B and B 23-acetate have been determined on the basis of chemical and physicochemical evidence. Sesquiterpene compositions in fresh rhizomes of Alisma orientale of the three different origins were examined and it was found that Japanese rhizome contained germacrene D as a major constituent, while fresh rhizomes from plants of Taiwanese and Chinese origin contained germacrene C and small amounts of alismol and alismoxide.

From the less polar fraction of Chinese Alismatis Rhizoma [the dried rhizome of the aquatic plant Alisma orientale JUZEP. collected in Szechwan Province, China (Sentaku in Japanese)], three new protostane-type triterpenes named alisols E 23-acetate, F, and G were isolated together with four guaiane-type sesquiterpenes and several known triterpenes including 13, 17-epoxyalisol A. The absolute stereostructures of alisols E 23-acetate, F, and G have been determined on the basis of chemical and physicochemical evidence, which included the chemical correlations of alisols E 23-acetate, F, and G with the known triterpenes alisols A and A 24-acetate, and the application of the modified Mosher's method.

New bioactive seco-protostane and protostane-type triterpenes, alismalactone 23-acetate and alismaketone-A 23-acetate, were isolated from Chinese Alismatis Rhizoma originating from Fukien province, the dried rhizoma of Alisma orientale JUZEP. Absolute stereostructures of the new triterpenes were determined on the basis of chemical and physicochemical evidence, which included chemical correlations with the known triterpene alisol B monoacetate. Alismalactone 23-acetate and alismaketone-A 23 acetate were found to show inhibitory activity on the contractions induced by a high concentration of K+ in isolated aortic strips from rats.

A glucan, called alisman SI, was isolated from the tuber of Alisma orientale Juzepcz. It was homogeneous on electrophoresis and gel chromatography, and its molecular mass was 1.1 x 10(4). It is composed solely of D-glucose. Methylation analysis, nuclear magnetic resonance and enzymic degradation studies indicated that it has a high-branched glucan type structure mainly composed of alpha-1,4-linked D-glucopyranosyl residues with partially alpha-1,6-linked units and both 3,4- and 4,6-branching points. The polysaccharide exhibited significant reticuloendothelial system-potentiating activity in a carbon clearance test, as well as a pronounced anti-complementary activity.

Four new sesquiterpenes, sulfoorientalols a, b, c, and d, having a sulfonic acid function were isolated from Chinese Alismatis Rhizoma. Their structures were determined on the basis of chemical and physicochemical evidence. Sulfoorientalols inhibited the contraction of isolated bladder smooth muscle induced by carbachol.

Three new sesquiterpenes named orientalols A, B, and C were isolated from Chinese Alismatis Rhizoma, the dried rhizome of Alisma orientale JUZEPCZUK, together with two known sesquiterpenes, alismol and alismoxide. On the basis of the chemical and physiconhemical evidence, the structures of orientalols A (3), B (4), and C(5) were determined and those of alismol and alismoxide were revised from 1' and 2' to 1 and 2, respectively.