Diterpene glycosides from Stevia rebaudiana

Three novel diterpene glycosides were isolated for the first time from the commercial extract of the leaves of Stevia rebaudiana, along with several known steviol glycosides, namely stevioside, rebaudiosides A-F, rubusoside and dulcoside A. The new compounds were identified as 13-[(2-O-β-D-glucopyranosyl-3-O-β-D-glucopyranosyl-β-D-glucopyranosyl)oxy] ent-kaur-15-en-19-oic acid, 13-[(2-O-β-D-glucopyranosyl-3-O-β-D-glucopyranosyl-β-D-glucopyranosyl)oxy]-16β-hydroxy-ent-kauran-19-oic acid and 13-methyl-16-oxo-17-nor-ent-kauran-19-oic acid-β-D-glucopyranosyl ester on the basis of extensive 2D NMR and MS spectroscopic data as well as chemical studies.     

A new diterpene glycoside from Stevia rebaudiana

From the commercial extract of the leaves of Stevia rebaudiana, a new diterpene glycoside was isolated besides the known steviol glycosides including stevioside, rebaudiosides A-F, rubusoside and dulcoside A. The new compound was identified as 13-[(2-O-β-D-glucopyranosyl-3-O-β-D-glucopyranosyl-β-D-glucopyranosyl)oxy] ent-kaur-16-en-19-oic acid-(2-O-α-L-rhamnopyranosyl-β-D-glucopyranosyl) ester (1) on the basis of extensive spectroscopic (NMR and MS) and chemical studies.     

A silica gel orthogonal high-performance liquid chromatography method for the analyses of steviol glycosides: novel tetra-glucopyranosyl steviol

A silica gel orthogonal method using acetonitrile: water was developed for the analyses of fractions rich in very polar steviol glycosides and resolve regions of co-elution of these compounds in reversed-phase. Additionally, we also used this normal phase analytical method to scale up the purification process of steviol glycosides. Using these approaches, one novel minor tetra-glucopyranosyl diterpene glycosides together with three known compounds were purified from a commercial Stevia rebaudiana leaf extract. Compound 1 was unambiguously elucidated as 13-[(2-O-β-D-glucopyranosyl-β-D-glucopyranosyl)oxy]ent-kaur-16-en-19-oic acid-(6-O-β-D-glucopyranosyl-β-D-glucopyranosyl) ester (rebaudioside Y) based on high-performance liquid chromatography retention times, tandem mass spectrometry dissociation pattern and 1D and 2D NMR experiments. Known compounds were isolated in gram quantities and identified as rebaudioside D, E and M.     

Two minor diterpene glycosides from the leaves of Stevia rebaudiana

Two new new diterpene glycosides, 13-[(2-O-(6-O-beta-D-glucopyranosyl)-beta-D-glucopyranosyl-beta-D-glucopyranosyl)oxy] kaur-16-en-18-oic acid beta-D-glucopyranosyl ester (1) and 13-[(2-O-beta-D-glucopyranosyl-3-O-beta-D-fructofuranosyl-beta-D-glucopyranosyl)oxy] kaur-16-en-18-oic acid beta-D-glucopyranosyl ester (2) were isolated from the leaves of Stevia rebaudiana, along with the known steviol glycosides stevioside, rebaudiosides A-F and dulcoside A. The structures of the two new compounds were established on the basis of extensive 2D NMR (COSY, HSQC, and HMBC), MS and chemical studies.     

Two new triterpenoid saponins from Rhaponticum uniflorum

Two new triterpenoid saponins were isolated from the roots of Rhaponticum uniflorum.Their structures were elucidated as 3-O-[β-D-glucopyranosyl] -ilexolic acid-28-O-[β-D-glucopyranosyl]ester 1 and 3-O-[β-D-glucopyranosyl]-urs-12,19(29)-dien-oic acid-28-O-[β-D-glucopyranosyl]ester 2 mainly by 1D,2D NMR techniques and chemical methods.     

Microbial hydroxylation and glycosidation of oleanolic acid by Circinella muscae and their anti-inflammatory activities

Biotransformation of oleanolic acid (OA) by Circinella muscae AS 3.2695 was investigated. Nine hydroxylated and glycosylated metabolites (1–9) were obtained. Their structures were elucidated as 3β,7β-dihydroxyolean-12-en-28-oic acid (1), 3β,7β,21β-trihydroxyolean-12-en-28-oic acid (2), 3β,7α,21β-trihydroxyolean-12-en- 28-oic acid (3), 3β,7β,15α-trihydroxyolean-12-en-28-oic acid (4), 7β,15α-dihydroxy- 3-oxo-olean-12-en-28-oic acid (5), 7β-hydroxy-3-oxo-olean-12-en-28-oic acid (6), oleanolic acid-28-O-β-D-glucopyranosyl ester (7), 3β,21β-dihydroxyolean-12-en-28- oic acid-28-O-β-D-glucopyranosyl ester (8), and 3β,7β,15α-trihydroxyolean-12-en- 28-oic acid-28-O-β-D-glucopyranosyl ester (9) by spectroscopic analysis. Among them, compounds 4 and 9 were new compounds. In addition, anti-inflammatory activities were assayed and evaluated for the isolated metabolites. Most of the metabolites exhibited significant inhibitory activities on lipopolysaccharides-induced NO production in RAW 264.7 cells.     

Regioselective Enzyme-Mediated Glycosylation of Natural Polyhydroxy Compounds. Part 1. Galactosylation of stevioside and steviolbioside

Bovine β-1,4-galactosyltransierase is an efficient catalyst for the regioselective transfer of galactose from UPD-galactose, generated in situ with the UDP-glucose/UDP-glucose-4-epimerase system, to the kaurane glycosides stevioside ( 1 ) and Steviolbioside ( 2 ), affording the corresponding galactosyl derivatives 3 and 4 in high yields. By a combination of 2D NMR techniques (COSY, TOCSY, ROESY, HMQC, and HMBC), the structure of the products is established as 13-[(β -D -galactopyranosyl-(1 → 4)-β-D -glucopyranosyl-(1 → 2)- β -D -glucopyranosyl)oxy]kaur-16-en-19-oic acid β -D -glucopyranosyl ester ( 3 ) and 13-[(β-D -galactopyranosyl-(1 → 4)- β-D -glu-copyranosyl-(1 → 2)- β-D -glucopyranosyl)oxy]kaur-16-en-19-oic acid ( 4 ).     

Additional minor diterpene glycosides from Stevia rebaudiana

From the commercial extract of the leaves of Stevia rebaudiana, two additional new diterpenoid glycosides were isolated and their structures were characterized as 13-[(2-O-beta-glucopyranosyl-3-O-beta-D-xylopyranosyl-beta-D-glucopyranosyl)oxy] ent-kaur-16-en-19-oic acid beta-D-glucopyranosyl ester (1) and 13-[(2-O-beta-D-xylopyranosyl-beta-D-glucopyranosyl)oxy] ent-kaur-16-en-19-oic acid beta-D-glucopyranosyl ester (2) on the basis of extensive spectral data (NMR and MS) and chemical studies.     

A new triterpene from the plant of uncaria macrophylla

Our ongoing investigations on the stem bark of Uncaria macrophylla afforded a new ursolic triterpene, 3β,6β,19α-trihydroxy-urs-12-en-28-oic acid-24-carboxylic acid methyl ester (1), named uncariursanic acid, and three known ursolic triterpenes including 3β,6β,19α-trihydroxy-23-oxo-urs-12-en-28-oic acid (2), 3β,6β,19α-trihydroxy-urs-12-en-28-oic acid (3) and ursolic acid (4). Their structures were elucidated by extensive spectral methods, including 1D and 2D NMR and HR-ESI-MS. The cytotoxicities of the four compounds were evaluated against two cancer cell lines (MCF-7 and HepG2) by the MTT method, and only compound 4 exhibited potent activity.     

Synthesis and Sensory Evaluation of <em>ent</em>-Kaurane Diterpene Glycosides

Catalytic hydrogenation of the three ent-kaurane diterpene glycosides isolated from Stevia rebaudiana, namely rubusoside, stevioside, and rebaudioside-A has been carried out using Pd(OH)₂ and their corresponding dihydro derivatives have been isolated as the products. Synthesis of reduced steviol glycosides was performed using straightforward chemistry and their structures were characterized on the basis of 1D and 2D NMR spectral data and chemical studies. Also, we report herewith the sensory evaluation of all the reduced compounds against their corresponding original steviol glycosides and sucrose for the sweetness property of these molecules.     

New triterpenoid saponins from Stelmatocrypton khasianum

Four new triterpenoid saponins, designated as stelmatotriterpenosides E-H (1-4), together with three known compounds, asterbatanoside B (5), 2alpha,3beta,19alpha,23-tetrahydroxy-olean-12-en-28-oic acid-3-O-beta-D-glucopyranosyl-28-O-beta-D-glucopyranosyl ester (6) and 2alpha,3beta,19alpha,23-tetrahydroxy-urs-12-en-28-oic acid-3-O-beta-D-glucopyranosyl-28-O-beta-D-glucopyranosyl ester (7), were isolated from the stems of Stelmatocrypton khasianum. On the basis of chemical and spectral evidence, the structures of 1-4 were established as 2alpha,3beta,23-trihydroxy-olean-12-en-28-oic acid-3-O-beta-D-glucopyranosyl-28-O-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl ester (1), 2alpha,3beta,23-trihydroxy-urs-12-en-28-oic acid-3-O-beta-D-glucopyranosyl-28-O-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl ester (2), 2alpha,3beta,19alpha-trihydroxy-urs-12-en-28-oic acid-3-O-beta-D-glucopyranosyl-28-O-beta-D-glucopyranosyl-(1-->2)-beta-D-glucopyranosyl ester (3), and 2beta,3beta,19alpha-trihydroxy-urs-12-en-24,28-dioic acid-24-O-beta-D-glucopyranosyl-28-O-beta-D-glucopyranosyl diester (4).     

Triterpenoids from the roots of Sanguisorba tenuifolia var. Alba

The ethyl acetate soluble fraction from the roots of Sanguisorba tenuifolia was found to have a hypoglucemic effect in alloxan-induced diabetic rats. Two new triterpenoids, identified as 2-oxo-3β,19α-dihydroxyolean-12-en-28-oic acid β-D-gluco-pyranosyl ester (1) and 2α,19α-dihydroxy-3-oxo-12-ursen-28-oic acid β-D-glucopyranosyl ester (4) were isolated from this fraction, along with thirteen known triterpenoids. Their structures were elucidated by chemical and spectroscopic methods. All these compounds demonstrated inhibitory activities against α-glucosidase with IC?? values in the 0.62-3.62 mM range.     

A New 24, 30-Dinortriterpenoid from Paeonia delavayi

We reported some constituents from the plant of Paeonia delavayi Franch1. Further investigation on the chemical constituents of the same plant resulted in the isolation and determination of a new triterpenoid, 3(, 4(, 23-trihydroxy-24, 30-dinorolean-12, 20(29)-dien-28-oic acid 1, in addition to five known compounds, 2(, 3(, 23-trihydroxy-12-oleanen-28-oic acid-(-D-glucopyranosyl ester2, palbinone3, 2-hydroxy-benzoic acid4, vanillic acid4, syringic acid5. In this paper we describe the structur…     

27-Nor-triterpenoid saponins from Adina rubella

Three new 27-nor-triterpenoid saponias named rubenorside A (1),rubenorside B(2) and rubenorside C (3) were isolated from the roots of Adina rubella.Their structures were characienzed as pyrocincholic acid 3β-O-α-L-rhamnopyranosyl(28→1 )-β-D-glucopyranosyl ester (1),pyrocinchohe acid 3β-O-β-D-glucopyranosyl(1→2)-β-D-fucopyranosyl(28→1)-β-D-glucopyranosyl(1→6)-β-D-glico-pyranosyl ester (2) and pyrocincholic acid 3β-O-β-D-glucopyranosyl(1→2)-β-D-glucopyranosyl(28→1)β-D-glucopyranosyl(1→6)-β-D-glucopyranosyl ester () by spectral methods,especially 2D NMR experiments.     

Development of a high‐performance liquid chromatography procedure to identify known and detect novel C‐13 oligosaccharide moieties in diterpene glycosides from Stevia rebaudiana (Bertoni) Bertoni (Asteraceae): Structure elucidation of rebaudiosides V and W

As an aid for structure elucidation of new steviol glycosides, reversed‐phase C18 high‐performance liquid chromatography method was developed with several previously characterized diterpene glycosides, to identify known and detect novel aglycone‐C13 oligosaccharide moieties and indirectly identify C‐19 interlinkages. Elution order of several diterpene glycosides and their aglycone‐C13 oligosaccharide substituted with different sugar arrangements were also summarized. Comparison of the retention time of a product obtained after alkaline hydrolysis with the aglycone‐C‐13 portions of known compounds reported herein allowed us to deduce the exact positions of the sugars in the C‐13 oligosaccharide portion. The elution position of several steviol glycosides with an ent‐kaurene skeleton was helpful to describe an identification key. Two previously uncharacterized diterpene glycosides together with two known compounds were isolated from a commercial Stevia rebaudiana leaf extract. One was found to be 13‐[(2‐O‐β‐d ‐xylopyranosyl‐ 3‐O‐β‐d ‐glucopyranosyl‐β‐d ‐glucopyranosyl)oxy]ent‐kaur‐16‐en‐19‐oic acid‐(2‐O‐β‐d ‐glucopyranosyl‐β‐d ‐glucopyranosyl) ester (rebaudioside V), whereas the other was determined to be 13‐[(2‐O‐β‐d ‐xylopyranosyl‐ 3‐O‐β‐d ‐glucopyranosyl‐β‐d‐ glucopyranosyl)oxy]ent‐kaur‐16‐en‐19‐oic acid‐(2‐O‐α‐l ‐rhamnopyranosyl‐3‐O‐β‐d ‐glucopyranosyl‐β‐d ‐glucopyranosyl) ester (rebaudioside W). Previously reported compounds were isolated in gram quantities and identified as rebaudioside J and rebaudioside H. In addition, a C‐19 sugar‐free derivative was also prepared from rebaudioside H to afford rebaudioside H₁. Chemical structures were partially determined by the high‐performance liquid chromatography method and unambiguously characterized by using one‐dimensional and two‐dimensional nuclear magnetic resonance experiments.     

Cytotoxic lupane-, secolupane-, and oleanane-type triterpenes from Viburnum awabuki

Bioassay-guided fractionation of the methanolic extract of Viburnum awabuki afforded two new lupane triterpene derivatives; 6 beta-hydroxyl-3,20-dioxo-30 norlupane-28-oic acid (1) and 3,4-secolup-4,20-dihydroxy-3,28-dioic acid-3-oic acid methyl ester (2), along with seven known lupane and oleanane-type triterpenes (3-9). The structure of the isolated compounds was assigned using different spectroscopic techniques including 1D and 2D NMR. The 13CNMR data of compounds 5 and 9 is reported for the first time. Triterpenes 1, 2, and 7-9 showed in vitro cytotoxic activity against several tumor cell lines.     

Chemical constituents isolated from Zygophyllum melongena Bunge growing in Mongolia

We report the first investigation of the chemical constituents of Zygophyllum melongena Bunge, a species growing in Mongolia. The quinovic acid glycosides 3-O-(β-D-glucopyranosyl)quinovic acid and 3-O-(β-D-glucopyranosyl)quinovic acid (28→1)-(β-D-glucopyranosyl) ester were identified in the chloroform fraction along with the flavonoid glycoside astragalin. The n-butanol fraction contained (+)-D-pinitol as the major component, a cyclitol with anti-diabetic properties. The structures of the isolated natural products were confirmed using ESI-MS and NMR spectroscopy (¹H, ¹³C, COSY, HSQC, HMBC, NOESY and ROESY). This is the first report of the isolation of (+)-D-pinitol from the genus Zygophyllum.     

An unusual diterpene glycoside from the nuts of almond (Prunus amygdalus Batsch)

A new unusual kauranoid diterpene glycoside, named amygdaloside, was isolated from the nuts of almond (Prunus amygdalus). It's structure was established as 17-O-β-D-glucopyranoside ent-6,7-epoxy-6-hydroxyl-6,7-secokaur-19-oic acid, 6,19-lactone 16β17-diol on the basis of high-resolution 1D and 2D NMR spectral studies.     

Asymmetric synthesis of methyl (-)-13-oxo-15,16-dinorlabda-8(17),11E-dien-19-oate, methyl ester of a potent suppressor toward carcinogenic promotor

Asymmetric synthesis of methyl ester (4) of (-)-13-oxo-15,16-dinorlabda-8(17),11E-dien-19-oic acid (1), which exhibited the most potent activity for the prevention of incipient carcinogenesis among the isolated diterpenes from Thuja standishii and its related plants, was achieved by using methyl (-)-1,4a-dimethyl-5-oxodecahydronaphthalene-1-carboxylate (5) as a strating material, which was easily prepared on gram scale by baker's yeast-catalyzed asymmetric reduction.     

A new pentacyclic triterpenoid glucoside from Prunus serrulata var. spontanea

A new triterpenoid, 2alpha,3alpha,24-trihydroxyurs-12-en-28-oic acid-28-O-beta-D-glucopyranosyl ester (4) along with four known triterpenoids, ursolic acid (1), 2alpha-hydroxyursolic acid (2), 2alpha,3alpha,24-trihydroxyurs-12-en-28-oic acid (3), and 2alpha,3alpha,19alpha,24-tetrahydroxyurs-12-en-28-oic acid-28-O-beta-D-glucopyranosyl ester (5), were isolated from the leaves of Prunus serrulata var. spontanea (Rosaceae). Compounds 3-5 showed ONOO(-) scavenging activity, whereas compounds 1 and 2 were virtually inactive.