Kazuko Yoshikawa

Structure studies of new antisweet constituents from Gymnema sylvestre

Abstract Gymnemic acid I , II , III and IV have been isolated from hot water extract of leaves of Gymnema sylvestre R. Br. as antisweet principles. The whole structures were determined by chemical and spectroscopic means.

Saponins from Albizia lebbeck

Three main saponins named albiziasaponins A, B, and C were isolated from the barks of Albizia lebbeck. Their structures were established through spectral analyses as acacic acid lactone 3-O-beta-D-xylopyranosyl-(1-->2)-alpha-L-arabinopyranosyl-(1-->6)- beta-D-glucopyranoside, 3-O-beta-D-glucopyranosyl-(1-->2)-O-[alpha-L-arabinopyranosyl-(1-- >6)]- beta-D-glucopyranoside and 3-O-beta-D-xylopyranosyl-(1-->2)-alpha-L-arabinopyranosyl-(1-->6)- O- [beta-D-glucopyranosyl-(1-->2)]-beta-D-glucopyranoside.

Inhibitory effect of lignans from the rhizomes ofCoptis japonica var.dissecta on tumor necrosis factor-α production in lipopolysaccharide-stimulated RAW264.7 cells

The inhibitory effect of 10 lignan constituents isolated from the rhizomes ofCoptis japonica var.dissecta on tumor necrosis factor (TNF)-α production in lipopolysaccharide (LPS)-stimulated macrophage cell line (RAW264.7 cells) has been studied. Among them, pinoresinol, vvoorenoside-V and lariciresinol glycoside showed significant inhibitory activities in the range from 37% to 55% at the concentration of 25 µg/ml. The results are first report that the lignans isolated fromCoptis japonica inhibit TNF-α production, and suggest that the lignan components may partly participate in antiinflammatory and antiallergic effect ofCoptis japonica through the inhibition of TNF-α production.

Four cycloartane triterpenoids and six related saponins from Passiflora edulis.

Four cycloartane triterpenes, cyclopassifloic acids A (1), B (2), C (3), and D (4), and six related saponins, cyclopassiflosides I (5), II (6), III (7), IV (8), V (9), and VI (10), were isolated from the leaves and stems of Passiflora edulis, and their structures were elucidated on the base of extensive NMR experiments and chemical methods. Cyclopassifloic acids A-D were assigned as 22(R), 24(S)-1alpha,3beta,22,24,31-pentahydroxy-24-methylcycloartan -28-oic acid; 24(S)-1alpha,3beta,24, 31-tetrahydroxy-24-methylcycloartan-28-oic acid; 20(S),24(S)-1alpha, 3beta,21,24,31-pentahydroxy-24-methylcycloartan-28-oic acid; and 22(R)-1alpha,3beta,22-trihydroxy-24-oxocycloartan-28-oic acid, respectively. Cyclopassiflosides I-VI, in turn, were established as the 28-O-beta-D-glucopyranosides of cyclopassifloic acids A-D. Finally, cyclopassiflosides III and V were demonstrated as the 28, 31-bis-O-beta-D-glucopyranosides of cyclopassifloic acids B and C, respectively. Also obtained in this investigation were the known compounds passiflorin (11) and passifloric acid (12).

Triterpenes and triterpene glycosides from the leaves of Ilex rotunda

Abstract Two new triterpenes, ilexolic acid A and B, and seven new saponins, ilexosides XXXIII–XXXIX, together with the known saponin rotungenoside were isolated from the fresh leaves of Ilex rotunda , and their structures elucidated on the basis of chemical and physicochemical evidence. The structures of ilexolic acid A and B were elucidated as 3β,19α,21β,23-tetrahydroxyurs-12-en-28-oic acid and 3β,19α-dihydroxyolean-12-ene-18,23-dioic acid, respectively. Ilexoside XXXIII was the 3- O -glucuronide of 23-oxosiaresinolic acid, ilexoside XXXIV was the 3- O -sulphate of pedunculoside. Ilexoside XXXV and XXXVI were the 28-glucosyl 3-sulphate and 3,28-bisglucoside of rotungenic acid, respectively. Ilexosides XXXVII–XXXIX were bisdesmosides of rotundic acid.

A new type of antisweet principles occurring in Gymnema sylvestre

A New type of antisweet principles, gymnemasaponins I–V has been isolated from Gymnema sylvestre. Their structures were established as novel D-glucosides of 3β, 16β,23,28-tetrahydroxyolean-12-ene on the basis of spectroscopic analysis. The antisweet activity of these compounds is discussed in relation to another type of active components, gymnemic acids I–VI.

Phenylpropanoids and other secondary metabolites from fresh fruits of Picrasma quassioides

Four new constituents; two benzofuran glucosides (picraquassiosides A and B), a neolignan (picraquassioside C) and a phenol (picraquassioside D) were isolated from fresh fruits of Picrasma quassioides, together with seven known compounds. The structures of the new compounds were elucidated as 6-hydroxy-4-methoxy-5-benzofuran-propionic acid 6-O-β-d-glucopyranoside, 6-hydroxy-4,7-dimethoxy-5-benzofuranpropionic acid 6-O-β-d-glucopyranoside, 1-(4′-O-glucopyranosyl-4′-hydroxy-3′,5′-dimethoxyphenyl)-2{2″,6″-dimethoxy-4″-[1-(E) propen-3-ol]-phenoxy}- propan-1,3-diol(threo), and methylphloroglucinol β-d-glucopyranoside by spectroscopic means.

Steroidal Glycosides from the Fresh Stem of Stephanotis lutchuensis var.japonica (Asclepiadaceae). Chemical Structures of Stephanosides K-Q

The structural elucidation of seven related oxypregnane-oligoglycosides stephanosides K (1), L (2), M (3), N (4), O (5), P (6), and Q (7) from the fresh stem of Stephanotis lutchuensis var. japonica (Asclepiadaceae) was achieved through on a detailed study of their high-field 1H- and 13C-NMR spectra. The results show that all the sugars are beta (1-->4)-linked. The aglycones of stephanosides K, M, and O, and stephanosides L, N, and P were identified as 12-O-cinnamoyl-20-O-(E)-2-methyl-2-butenoyl, and 12-O-cinnamoyl-20-O-nicotinoyl derivatives of (20S)-pregn-6-ene-3 beta,5 alpha,8 beta,12 beta,14 beta,17 beta,20-heptaol, respectively. The aglycone of stephanoside Q was 12-O-cinnamoyldeacetylmetaplexigenin (kidjoranin).

Limonoids and protolimonoids from the fruits of Phellodendron amurense

Abstract Two novel limonoids, named kihadalactone A and B, have been isolated from the fresh fruits of Phellodendron amurense, along with seven tirucallanes triterpenoids, niloticin, dihydroniloticin, niloticin acetate, piscidinol A, hispidol B, bourjotinolone A, and hispidone. Their structures were established on the basis of spectral and chemical evidence. Further NMR spectral analysis of the tirucallanes showed that the reported shifts of C-13 and C-14 should be revised.

Antisweet substances, jujubasaponins I–III from zizyphus jujuba revised structure of ziziphin

The structures of jujubasaponins I–III (1–3, new jujubogenin glycosides, isolated from the fresh leaves of Zizyphus jujuba have been determined and the structure of ziziphin known as active substance of the title plant has been revised as 4 from their chemical and spectral evidence. Acylated saponins, compound 2 and 3 showed antisweet activity.