Hiroshi Kohda

New sweet diterpene glucosides from Stevia rebaudiana

Abstract From the leaves of Stevia rebaudiana, two new sweet glucosides, rebaudiosides A and B, were isolated besides the known glucosides, stevioside and steviolbioside. On the basis of IR, MS, 1H and 13C NMR as well as chemical evidences, the structure of rebaudioside B was assigned as 13-O-[β-glucosyl(1-2)-β-glucosyl(1-3)]-β-glucosyl-steviol and rebaudioside A was formulated as its β-glucosyl ester.

Aromatic glycosides from Berchemia racemosa

Two new aromatic glucosides have been isolated from the stems of Berchemia racemosa together with the known glycosides, nudiposide, (−)-secoisolariciresinol-O-β-d-glucopyranoside and methoxyhydroquinone-1-O-β-d-glucopyranoside (isotachioside). The structures of the new glucosides were found to be β-d-glucopyranosyl syringate, and methoxyhydroquinone-4-O-β-d-glucopyranoside on the basis of chemical and spectral evidences.

Benzoxazinones from Coix lachryma-jobi var. ma-yuen

Abstract The absolute configurations of 2- O -β- D -glucopyranosyl-7-methoxy-1,4(2H)-benzoxazin-3-one and three congeners isolated from Coix lachryma-jobi var. ma-yuen were determined by X-ray analysis and chemical correlation as the 2 R type. 13 C NMR spectra of all congeners and coixol were fully assigned.

A triterpene and saponin from roots of Ilex pubescens

Abstract A new triterpene and its glycoside have been isolated from methanol extract of roots of Ilex pubescens. Their structures were established as 3β, 19α-dihydroxyurs-12-en-24,28-dioic acid and its 28-β- d -glucopyranosyl ester, based on chemical and spectral evidence.

Eurycomanone and eurycomanol, quassinoids from the roots of Eurycoma longifolia

Abstract From the roots of Eurycoma longifolia , used as an Indonesian folk medicine, two highly oxygenated quassinoids, named eurycomanone and eurycomanol were isolated. The structures of both new bitter principles were elucidated by NMR, MS, UV and IR.

The active principles of the branchlet and hook of Uncaria sinensis Oliv. examined with a 5-hydroxytryptamine receptor binding assay

Of the alkaloids obtained from Uncaria sinensis Oliv., geissoschizine methyl ether, corynantheine and dihydrocorynantheine decreased specific [3H]5‐HT binding to membrane preparations from rat brain and from in‐vitro experiments on guinea‐pig ileum, these alkaloids were found to be partial agonists for 5‐HT receptors. Therefore, they might be useful in the treatment of diseases resulting from disorders of 5‐HT metabolism.

ent-labdane-type diterpene glucosides from leaves of Rubus chingii

Abstract Previously, a sweet steviol bisglucoside named rubusoside was isolated from leaves of a Chinese Rubus spp. which was tentatively assigned as R. chingii. From leaves of Japanese Rubus chingii (Japanese name Gosho-Ichigo) which are not sweet, five ent-labdane-type diterpene glucosides named goshonosidies F1-5 were isolated instead of rubusoside and their structures were elucidated. The name ‘R. suavissimus’ has been proposed for the Chinese plant.

Dammarane and oleanane saponins from callus tissue of Panax japonicus

Abstract From tissue callus of Panax japonicus grown in South Kyushu, two ginseng dammarane saponins, ginsenosides Rg1 and Re, and an oleanane saponin (desglucosylchikusetsusaponin-IV) together with chikusetsusapon-in-IV were isolated.

Revision of configuration of the 12-hydroxyl group of eurycomanone and eurycomanol, quassinoids from eurycoma longifolia

Abstract As a result of the recent structural revision of ailanthone, the configuration of the 12-hydroxyl group of eurycomanone and eruycomanol has been amended to be α.

Monoterpene glucosides from Berchemia racemosa

Abstract Two monoterpene glycosides isolated from the stem of Berchemia racemosa , have been characterized as (+)-angelicoidenol-2- O -β- d -glucopyranoside and (−)-angelicoidenol-2- O -β- d -glucopyranoside on the basis of chemical and spectral evidence. Isoarborinol was also isolated from the plant.