Triterpene glycosides from Astragalus icmadophilus

Six cycloartane-type triterpene glycosides were isolated from Astragalus icmadophilus along with two known cycloartane-type glycosides, five known oleanane-type triterpene glycosides and one known flavonol glycoside. The structures of the six compounds were established as 3-O-[α-L-arabinopyranosyl-(1 → 2)-O-3-acetoxy-α-L-arabinopyranosyl]-6-O-β-D-glucopyranosyl-3β,6α,16β,24(S),25-pentahydroxycycloartane, 3-O-[α-L-rhamnopyranosyl-(1 → 2)-O-α-L-arabinopyranosyl-(1 → 2)-O-β-D-xylopyranosyl]-6-O-β-D-glucopyranosyl-3β,6α,16β,24(S),25-pentahydroxy cycloartane, 3-O-[α-L-arabinopyranosyl-(1 → 2)-O-3,4-diacetoxy-α-L-arabinopyranosyl]-6-O-β-D-glucopyranosyl-3β,6α,16β,24(S),25-pentahydroxycycloartane, 3-O-[α-L-arabinopyranosyl-(1 → 2)-O-3-acetoxy-α-L-arabinopyranosyl]-6-O-β-D-glucopyranosyl-3β,6α,16β,25-tetrahydroxy-20(R),24(S)-epoxycycloartane, 3-O-[α-L-arabinopyranosyl-(1 → 2)-O-β-D-xylopyranosyl]-6-O-β-D-glucopyranosyl-3β,6α,16β,24α-tetrahydroxy-20(R),25-epoxycycloartane, 3-O-[α-L-rhamnopyranosyl-(1 → 2)-O-α-L-arabinopyranosyl-(1 → 2)-O-β-D-xylopyranosyl]-6-O-β-D-glucopyranosyl-3β,6α,16β,24α-tetrahydroxy-20(R),25-epoxycycloartane by the extensive use of 1D- and 2D-NMR experiments along with ESIMS and HRMS analysis.The first four compounds are cyclocanthogenin and cycloastragenol glycosides, whereas the last two are based on cyclocephalogenin as aglycone, more unusual in the plant kingdom, so far reported only from Astragalus spp.     

Cycloartane-type glycosides from Astragalus amblolepis

Five cycloartane-type triterpene glycosides were isolated from the methanol extract of the roots of Astragalus amblolepis Fischer along with one known saponin, 3-O-β-D-xylopyranosyl-16-O-β-D-glucopyranosyl-3β,6α,16β,24(S),25-pentahydroxy-cycloartane. Structures of the compounds were established as 3-O-β-D-xylopyranosyl-25-O-β-D-glucopyranosyl-3β,6α,16β,24(S),25-pentahydroxy-cycloartane, 3-O-[β-D-glucuronopyranosyl-(1 → 2)-β-D-xylopyranosyl]-25-O-β-D-glucopyranosyl-3β,6α,16β,24(S),25-pentahydroxy-cycloartane, 3-O-β-D-xylopyranosyl-24,25-di-O-β-D-glucopyranosyl-3β,6α,16β,24(S),25-pentahydroxy-cycloartane, 6-O-α-L-rhamnopyranosyl-16,24-di-O-β-D-glucopyranosyl-3β,6α,16β,24(S),25-pentahydroxy-cycloartane, 6-O-α-L-rhamnopyranosyl-16,25-di-O-β-D-glucopyranosyl-3β,6α,16β,24(S),25-pentahydroxy-cycloartane by using 1D and 2D-NMR techniques and mass spectrometry. To the best of our knowledge, the glucuronic acid moiety in cycloartanes is reported for the first time.     

Cycloartane glycosides from Astragalus gombo

Six new cycloartane-type triterpene glycosides named 3-O-[β-d-glucopyranosyl(1 → 2)-β-d-xylopyranosyl]-3β,16β,23(R),24(R),25-pentahydroxycycloartane (1), 3-O-[β-d-glucopyranosyl(1 → 2)-β-d-xylopyranosyl]-3β,16β,23(R),24(R)-tetrahydroxy-25-dehydrocycloartane (2), 3-O-[β-d-xylopyranosyl]-6α-acetoxy-23α-methoxy-16β,23(R)-epoxy-24,25,26,27-tetranorcycloartane (3), 3-O-[β-d-xylopyranosyl]-6α-acetoxy-23α-butoxy-16β,23(R)-epoxy-24,25,26,27-tetranorcycloartane (4), 3-O-[β-d-glucopyranosyl(1 → 2)]-β-d-xylopyranosyl]-6α-acetoxy-23α-methoxy-16β,23(R)-epoxy-24,25,26,27-tetranorcycloartane (5), 3-O-[β-d-glucopyranosyl(1 → 2)]-β-d-xylopyranosyl]-23α-methoxy-16β,23(R)-epoxy-4,25,26,27-tetranorcycloartane (6), in addition to three known secondary metabolites consisting of another cycloartane triterpene glycoside and two flavonol glycosides, were isolated from the aerial parts of Astragalus gombo Coss. & Dur. (Fabaceae). The structures of the isolated compounds were established by spectroscopic methods, including 1D and 2D-NMR, mass spectrometry and comparison with literature data.     

Triterpenoid saponins from Aesculus sylvatica W. Bartram

16 triterpenoid saponins including two new compounds were isolated from the seeds of A esculus sylvatica W. Bartram. The two new saponins were assigned as 3-O-[β-D-glucopyranosyl-(1 → 2)]-α-L-arabinofuranosyl-(1 → 3)-β-D-glucuronopyranosyl-21,22-O-ditigloyl-3β,16α,21β,22α,24,28 hexahydroxyolean-12-ene (aesculioside S1, 1) and 3-O-[β-D-glucopyranosyl-(1 → 2)]-α-L-arabinofuranosyl-(1 → 3)-β-D-glucuronopyranosyl-21-O-tigloyl-22-O-angeloyl 3β,16α,21β,22α,24,28-hexahydroxyolean-12-ene (aesculioside S2, 2). Aesculioside S1 and S2 displayed moderate cytotoxicity against human non-small cell lung cancer cells (A549) and prostate cancer cells (PC3) (GI₅₀ ranged from 8.7 to 18.2 μM). The structural analysis of the saponins isolated from Aesculus supports the taxonomic placement of A. sylvatica under the section Pavia of Aesculus genus.     

Saponins in aerial parts of Helleborus viridis L.

In the search of natural compounds inhibiting methane production in ruminants three novel steroidal saponins have been isolated from the aerial parts of Helleborus viridis L. Their structures have been established based on spectral analyses as: (25R)-26-O-β-d-glucopyranosyl-5β-furostan-3β,22α,26-triol 3-O-β-d-glucopyranosyl-(1 → 6)-O-β-d-glucopyranoside, (25R)-26-O-β-d-glucopyranosyl-5α-furostan-3β,22α,26-triol 3-O-β-d-glucopyranosyl-(1 → 6)-O-β-d-glucopyranoside and (25R)-26-O-β-d-glucopyranosyl-furost-5-ene-1β,3β,22α,26-tetraol 1-O-{α-l-rhamnopyranosyl-(1 → 2)-O-[β-d-glucopyranosyl-(1 → 3)]-6-O-acetoxy-β-d-glucopyranoside}.     

Steroidal saponins from Tribulus terrestris

Five new steroidal saponins were isolated from the fruits of Tribulus terrestris. Their structures were fully established by spectroscopic and chemical analysis as (23S,25S)-5α-spirostane-24-one-3β,23-diol-3-O-{α-l-rhamnopyranosyl-(1 → 2)-O-[β-d-glucopyranosyl-(1 → 4)]-β-d-galactopyranoside} (1), (24S,25S)-5α-spirostane-3β,24-diol-3-O-{α-l-rhamnopyranosyl-(1 → 2)-O-[β-d-glucopyranosyl-(1 → 4)]-β-d-galactopyranoside} (2), 26-O-β-d-glucopyranosyl-(25R)-5α-furostan-2α,3β,22α,26-tetraol-3-O-{β-d-glucopyranosyl-(1 → 2)-O-β-d-glucopyranosyl-(1 → 4)-β-d-galactopyranoside} (3), 26-O-β-d-glucopyranosyl-(25R)-5α-furostan-20(22)-en-2α,3β,26-triol-3-O-{β-d-glucopyranosyl-(1 → 2)-O-β-d-glucopyranosyl-(1 → 4)-β-d-galactopyranoside} (4), and 26-O-β-d-glucopyranosyl-(25S)-5α-furostan-12-one-22-methoxy-3β,26-diol-3-O-{α-l-rhamnopyranosyl-(1 → 2)-O-[β-d-glucopyranosyl-(1 → 4)]-β-d-galactopyranoside} (5). The isolated compounds were evaluated for cytostatic activity against HL-60 cells.     

New cytotoxic dihydrochalcone and steroidal saponins from the aerial parts of Sansevieria cylindrica Bojer ex Hook

A new dihydrochalcone, 2‘,4‘-dihydroxy-3‘-methoxy-3,4-methylenedioxy-8-hydroxymethylene dihydrochalcone 1 and two new steroidal saponins, (25S)-ruscogenin-1-O-α-l-rhamnopyranosyl-(1 → 2)-β-d-glucopyranoside 2, (25S)-ruscogenin-3-O-α-l-rhamnopyranosyl-(1 → 4)-β-d-glucopyranoside 3, together with three known steroidal saponins (25S)-ruscogenin-3-O-β-d-glucopyranoside 4, (25S)-ruscogenin-1-O-α-l-rhamnopyranosyl-(1 → 2)-[β-d-xylopyranosyl-(1 → 3)]-α-l-arabinopyranoside 5 and (25R)-26-O-β-d-glucopyranosyl-furost-5-ene-1β,3β,22α,26-tetrol-1-O-α-L-rhamnopyranosyl-(1 → 2)-[β-d-xylopyranosyl-(1 → 3)]-α-l-arabinopyranoside 6 were isolated from the aerial parts of Sansevieria cylindrica. The structures of the new compounds were established by UV, IR, EI-MS, HR-ESI–MS as well as 1D (¹H,¹³C and DEPT-135) and 2D (HSQC, HMBC and TOCSY) NMR spectral analysis. The isolated compounds 1-6 were assayed for in vitro cytotoxicities against the three human tumor cell lines HT116, MCF7 and HepG2. Compound 1 showed a moderate cytotoxicity against MCF7. Compounds 2, 3 and 6 exhibited moderate cytotoxicities against the three used cell lines and compound 5 showed marked cytotoxicities against all used cell lines.     

Echinocystic acid 3,16-O-bisglycosides from Albizia procera

Three triterpene glycosides and two known ones were isolated from the bark of Albizia procera by using chromatographic techniques. The structures of the compounds were determined to be 3-O-β-d-xylopyranosyl-(1 → 2)-β-d-galactopyranosyl-(1 → 6)-2-acetamido-2-deoxy-β-d-glucopyranosyl echinocystic acid 16-O-β-d-glucopyranoside, 3-O-β-d-xylopyranosyl-(1 → 2)-α-l-arabinopyranosyl-(1 → 6)-2-acetamido-2-deoxy-β-d-glucopyranosyl echinocystic acid 16-O-β-d-glucopyranoside and 3-O-α-l-arabinopyranosyl-(1 → 2)-α-l-arabinopyranosyl-(1 → 6)-2-acetamido-2-deoxy-β-d-glucopyranosyl echinocystic acid 16-O-β-d-glucopyranoside. Their structures were determined by NMR techniques including HOHAHA, ¹H-¹H COSY, ROE, HMQC and HMBC experiments together with FABMS as well as acid hydrolysis. To the best of our knowledge, the new compounds are considered the first examples of echinocystic acid 3,16-O-bisglycosides. In contrast to other cytotoxic echinocystic acid glycosides with N-acetyl glucosamine unit, the new glycosides were found inactive when assayed by MTT method for their cytotoxicities against the human tumor cell lines HEPG2, A549, HT29 and MCF7. The results showed the importance of the free hydroxyl group at the aglycone C-16 for exhibiting cytotoxic properties.     

The synthesis of cholestane and furostan saponin analogues and the determination of sapogenin's absolute configuration at C-22

A facile and efficient way for the synthesis of cholestane and furostan saponin analogues was established and adopted for the first time. Following this strategy, starting from diosgenin, three novel cholestane saponin analogues: (22S,25R)-3β,22,26-trihydroxy-cholest-5-ene-16-one 22-O-[O-α-l-rhamnopyranosyl-(1 → 2)-β-d-glucopyranoside] 11, (25R)-3β,16β,26-trihydroxy-cholest-5-ene-22-one 16-O-[O-α-l-rhamnopyranosyl-(1 → 2)-α-d-glucopyranoside] 14 and (25R)-3β,16β,26-trihydroxy-cholest-5-ene-22-one 16-O-[O-α-l-rhamnopyranosyl-(1 → 2)-β-d-glucopyranoside] 17, three novel furostan saponin analogues: (22S,25R)-furost-5-ene-3β,22,26-triol 22-O-(α-d-glucopyranoside) 23, (22R,25R)-furost-5-ene-3β,22,26-triol 22-O-(α-d-glucopyranoside) 24 and (22S,25R)-furost-5-ene-3β,22,26-triol 22-O-[O-α-l-rhamnopyranosyl-(1 → 2)-α-d-glucopyranoside] 26, were synthesized ultimately. The structures of all the synthesized analogues were confirmed by spectroscopic methods. The S-chirality at C-22 of cholestane was confirmed by Mosher's method. The absolute configuration at C-22 of furostan saponin analogues was distinguished by conformational analysis combined with the NMR spectroscopy. The cytotoxicities of the synthetic analogues toward four types of tumor cells were shown also.     

Enzymatically derived aldouronic acids from Eucalyptus globulus glucuronoxylan

A glucuronoxylan was extracted from the holocellulose of Eucalyputus globulus wood with 10% KOH and subjected to hydrolysis by a commercial cellulase preparation “Meicelase”. Neutral xylooligosaccharides liberated were analyzed by size exclusion chromatography. Aldouronic acids liberated were purified by preparative anion exchange chromatography. Their structures were studied by monosaccharide analysis, comparison of volume distribution coefficients (Dvs) in anion exchange chromatography with those of the authentic samples, and ¹H and ¹³C NMR spectroscopy, resulting in the characterization of seven aldouronic acids including a novel one containing galactose residue.O-β-d-Xylp-(1 → 4)-[O-(4-O-Me-α-d-GlcAp)-(1 → 2)]-O-β-d-Xylp-(1 → 4)-O-β-d-Xylp-(1 → 4)-d-XylO-(4-O-Me-α-d-GlcAp)-(1 → 2)-O-β-d-Xylp-(1 → 4)-O-β-d-Xylp-(1 → 4)-d-XylO-(4-O-Me-α-d-GlcAp)-(1 → 2)-O-β-d-Xylp-(1 → 4)-d-XylO-β-d-Xylp-(1 → 4)-O-β-d-Xylp-(1→3)-O-α-l-Rhap-(1 → 2)-O-α-l-GalAp-(1 → 4)-d-XylO-β-d-Xylp-(1 → 4)-O-β-d-Xylp-(1 → 3)-O-α-l-Rhap-(1 → 2)-d-GalAO-β-d-Xylp-(1 → 3)-O-α-l-Rhap-(1 → 2)-O-α-d-GalAp-(1 → 4)-d-XylO-β-d-Galp-(1 → 2)-O-(4-O-Me-α-d-GlcAp)-(1 → 2)-O-β-d-Xylp-(1 → 4)-O-β-d-Xylp-(1 → 4)-d-Xyl.The oligosaccharides liberated provide information on multiplicity of xylanases secreted by Trichoderma viride. The presence of the last aldouronic acid shows a structural feature of E. globulus xylan.     

New oleanane-type saponins: Leptocarposide B-D,from Ludwigia leptocarpa (Onagraceae)

Three new oleanane-type saponins, leptocarposide B-D (1–3), were isolated from the whole plant of Ludwigia leptocarpa (Nutt.) Hara, together with ten known compounds 4–13.The structures of these compounds were determined by interpretation of their spectral data, mainly HR-TOFESIMS, 1D-NMR (¹H, ¹³C) and 2D-NMR (¹H–¹H COSY, HSQC, HMBC, and NOESY), and by comparison with the literature data. The structures of the new compounds were established as 28-O-β-d-xylopyranosyl-(1 → 4)-α-l-rhamnopyranosyl-(1 → 2)-[α-l-arabinopyranosyl-(1 → 3)]-4-O-(3′-hydroxybutanoyloxy-3-hydroxybutanoyloxy)-β-d-fucopyranosyl zanhic acid (1); 3-O-β-d-glucopyranosyl-28-O-β-d-xylopyranosyl-(1 → 4)-α-l-rhamnopyranosyl-(1 → 2)-4-O-(3′-hydroxybutanoyloxy-3-hydroxybutanoyloxy)-β-d-fucopyranosyl medicagenic acid (2); 3-O-β-d-glucopyranosyl-(1 → 4)-β-d-glucopyranosyl-28-O-β-d-xylopyranosyl-(1 → 4)-α-l-rhamnopyranosyl-(1 → 2)-[α-l- arabinopyranosyl-(1 → 3)]-4-O-(3′-hydroxybutanoyloxy-3-hydroxybutanoyloxy)-β-d-fucopyranosyl zanhic acid (3).     

Three new flavonoid glycosides from the aerial parts of Graptophyllum grandulosum Turril (Acanthaceae)

Grandulosides A-C, three new flavonoid glycosides, were isolated from the aerial parts of Graptophyllum grandulosum Turill and identified as chrysoeriol-7-O-β-d-apiofuranosyl-(1 → 2)-β-d-xylopyranoside (1), chrysoeriol-7-O-[4′′′-O-acetyl-β-d-apiofuranosyl-(1 → 2)]-β-d-xylopyranoside (2) and 7-O-α-l-rhamnopyranosyl-(1 → 6)-β-d-(4′′-Sodium hydrogeno sulfate) glucopyranoside (3). Four known compounds, chrysoeriol-7-O-β-d-xyloside (4), isorhamnetin-3-O-α-l-rhamnopyranosyl-(1 → 6)-β-d-glucopyranoside (5), luteolin-7-O-β-d-apiofuranosyl-(1 → 2)-β-d-xylopyranoside (6) and sucrose (7) were also obtained. The structures of these compounds were established by interpretation of their spectral data, mainly HR-TOFESIMS, 1D-NMR (¹H, ¹³C) and 2D-NMR (COSY, NOESY, HSQC and HMBC) and by comparison with the literature data.     

Acylated flavonol pentaglycosides from Baphia nitida leaves

Two new acylated flavonol pentaglycosides were isolated from the butanolic extract of Baphia nitida leaves by Sephadex LH-20 and preparative HPLC. Structural elucidation of kaempferol 3-O-β-d-xylopyranosyl(1 → 3)-(4-O-E-p-coumaroyl-α-l-rhamnopyranosyl(1 → 2))[β-d-glucopyranosyl(1 → 6)]-β-d-galactopyranoside-7-O-α-l-rhamnopyranoside (1) and kaempferol 3-O-β-d-xylopyranosyl(1 → 3)-(4-O-Z-p-coumaroyl-α-l-rhamnopyranosyl(1 → 2))[β-d-glucopyranosyl(1 → 6)]-β-d-galactopyranoside-7-O-α-l-rhamnopyranoside (2) was achieved using UV, NMR, and mass spectrometry, indicating the presence of trans or cis isomers of p-coumaric acid moiety in these novel structures. The antioxidant activity of the two compounds was assessed in the peroxynitrite assay.     

Rheediinosides A and B,two antiproliferative and antioxidant triterpene saponins from Entada rheedii

Two triterpenoid saponins have been isolated from the seed kernels of Entada rheedii. Their structures have been established using 1D- and 2D-NMR and mass spectrometry as 3-O-β-d-xylopyranosyl-(1 → 3)-O-α-l-arabinopyranosyl-(1 → 6)-2-acetylamino-2-deoxy-β-d-glucopyranosylentagenic acid 28-O-β-apiofuranosyl-(1 → 3)-β-d-xylopyranosyl-(1 → 2)-β-d-glucopyranoside (Rheediinoside A, 1) and 3-O-β-d-glucopyranosyl-(1 → 3)-O-[β-d-xylopyranosyl-(1 → 3)-α-l-arabinopyranosyl-(1 → 6)]-2-acetylamino-2-deoxy-β-d-glucopyranosylentagenic acid 28-O-β-apiofuranosyl-(1 → 3)-β-d-xylopyranosyl-(1 → 2)-β-d-glucopyranoside (Rheediinoside B, 2). Compounds 1 and 2 were tested for their antiproliferative activity against T98G, A431, PC3 and B16-F1 cell lines, and further for their antioxidant properties. Moderate cytotoxic potency and antioxidant properties were found for these compounds whereas Rheediinoside B was in all assays more active than Rheediinoside A.     

A new complex triterpenoid saponin from Samanea saman with haemolytic activity and adjuvant effect

A new complex triterpenoid saponin was isolated from the stem bark of Samanea saman by using chromatographic methods. Its structure was established as 3-[(2-O-β-d-glucopyranosyl-β-d-glucopyranosyl)oxy]-2,23-dihydroxy-(2β,3β,4α)-olean-12-en-28-oic acid O-β-d-glucopyranosyl-(1 → 3)-O-[O-β-d-glucopyranosyl-(1 → 4)]-O-6-deoxy-α-l-mannopyranosyl-(1 → 2)-6-O-[4-O-[(2E,6S)-2,6-dimethyl-1-oxo-2,7-octadienyl]-6-deoxy-α-l-mannopyranosyl)oxy]-β-d-glucopyranosyl ester (1). Structural elucidation was performed using detailed analyses of ¹H and ¹³C NMR spectra including 2D NMR spectroscopic techniques and chemical conversions. The haemolytic activity of the saponin was evaluated using in vitro assays, and its adjuvant potential on the cellular immune response against ovalbumin antigen was investigated using in vivo models.     

Cycloartane-type glycosides from Astragalus schottianus

Three new cycloartane-type triterpene glycosides were isolated from the roots of Astragalus schottianus Boiss. Their structures were established as 20(R),25-epoxy-3-O-β-d-xylopyranosyl-24-O-β-d-glucopyranosyl-3β,6α,16β,24α-tetrahydroxycycloartane (1), 20(R),25-epoxy-3-O-[β-d-glucopyranosyl(1 → 2)]-β-d-xylopyranosyl-24-O-β-d-glucopyranosyl-3β,6α,16β,24α-tetrahydroxycycloartane (2), 3-O-β-d-xylopyranosyl-3β,6α,16β,20(S),24(S),25-hexahydroxycycloartane (3) by the extensive use of 1D and 2D-NMR techniques and mass spectrometry.     

Two new penterpenoid saponins and a new diterpenoid glycoside from Hemsleya chinensis

Two new penterpenoid saponins, hemsloside-Ma4 (1) hemsloside-Ma5 (2), and a new diterpenoid glycoside, hemsloside-Ma6 (3), were isolated from the rhizomes of Hemsleya chinensis. By detailed analysis of the NMR spectra and chemical methods, the structures of new compounds were determined to be 3-O-β-l-arabinopyranosyl-(1 → 3)-O-(6′-methyl ester)-β-d-glucuropyranosyl-oleanolic acid-28-O-β-d-glucopyranosyl-(1 → 6)-O-β-d-glucopyranoside (1), 3-O-β-l-arabinopyranosyl-(1 → 3)-O-(6′-methyl ester)-β-d-glucuropyranosyl-oleanolic acid-28-O-β-d-xylopyranosyl-(1 → 6)-O-β-d-glucopy-ranoside (2), and 13ϵ-hydroxylabda-8(17), 14-dien-18-oic acid-18-O-α-l-rhamnopyranosyl-(1 → 2)-O-β-d-glucopyranosyl-(1 → 4)-O-α-l-rhamnopyranoside (3). Diterpenoid-type compound (3) was isolated from Hemsleya genus for the first time.     

Highly glycosylated flavonols with an O-linked branched pentasaccharide from Iberis saxatilis (Brassicaceae)

Four flavonol glycosides isolated from non-flowering leafy shoots of Iberis saxatilis (Brassicaceae) were characterised by spectroscopic and chemical methods as saxatilisins A–D, the 3-O-β-d-glucopyranosyl-(1 → 3)-α-l-rhamnopyranosyl-(1 → 2)[β-d-glucopyranosyl-(1 → 2)-α-l-rhamnopyranosyl-(1 → 6)]-β-d-glucopyranoside, 3-O-β-d-glucopyranosyl-(1 → 3)-α-l-rhamnopyranosyl-(1 → 2)[α-l-rhamnopyranosyl-(1 → 6)]-β-d-glucopyranoside, 3-O-(6-O-E-sinapoyl)-β-d-glucopyranosyl-(1 → 3)-α-l-rhamnopyranosyl-(1 → 2)[β-d-glucopyranosyl-(1 → 2)-α-l-rhamnopyranosyl-(1 → 6)]-β-d-glucopyranoside, and 3-O-(6-O-E-feruloyl)-β-d-glucopyranosyl-(1 → 3)-α-l-rhamnopyranosyl-(1 → 2)[β-d-glucopyranosyl-(1 → 2)-α-l-rhamnopyranosyl-(1 → 6)]-β-d-glucopyranoside of isorhamnetin (3,5,7,4′-tetrahydroxy-3′-methoxyflavone), respectively. Analysis of ²J_HC correlations detected with the H2BC (heteronuclear two-bond correlation) pulse sequence aided the unambiguous assignment of glycosidic resonances in the ¹H and ¹³C NMR spectra of these compounds. Saxatilisins A, C, and D, are the first flavonol glycosides to be described with a pentasaccharide chain at a single glycosylation site. Several pentaglycosides of kaempferol and quercetin, tentatively assigned as saxatilisin analogues from LC–MS/MS analyses, were present as minor constituents of the extracts.     

Flavonol triglycosides of leaves from Maytenus robusta with acetylcholinesterase inhibition

Although Maytenus robusta aqueous infusions of leaves are used in Brazilian traditional medicine for stomach disease treatment, only a few chemical studies of this species are found in literature. The phytochemical investigation of methanol extract from M. robusta leaves yielded the known compound kaempferol (3) and two new flavonol glycosides: kaempferol-3-O-β-d-glucopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-β-d-glucopyranoside (1) and quercetin-3-O-β-d-glucopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-β-d-glucopyranoside (2). The chemical structures of 1 and 2 were elucidated by 1D/2D NMR, ESI–MS and ESI–MS² spectral data. It is the first time flavonoids have been reported from M. robusta. Flavonols 1 and 2 showed 66% and 80% acetylcholinesterase (AChE) inhibition, compared to 93% of the standard eserine, by the Ellman’s method. These substances are one of the few active flavonols linked to a trisaccharide chain in the literature presenting this activity, and contribute to the screening for new types of natural AChE inhibitors.     

Triterpene glycosides from Agrostemma gracilis

Four triterpene saponins, agrostemmosides A–D were isolated from the methanol extract of Agrostemma gracilis. The structures of the compounds were determined as 3-O-β-d-xylopyranosyloleanolic acid 28-O-β-d-glucopyranosyl-(1 → 2)-[β-d-xylopyranosyl-(1 → 6)]-β-d-glucopyranosyl-(1 → 6)-β-d-glucopyranosyl ester, 3-O-α-l-rhamnopyranosyl-(1 → 2)-β-d-xylopyranosyloleanolic acid 28-O-β-d-glucopyranosyl-(1 → 2)-[β-d-xylopyranosyl-(1 → 6)]-β-d-glucopyranosyl-(1 → 6)-β-d-glucopyranosyl ester, 3-O-β-d-xylopyranosylechinocystic acid 28-O-β-d-glucopyranosyl-(1 → 2)-β-d-glucopyranosyl-(1 → 6)-β-d-glucopyranosyl ester, 3-O-β-d-xylopyranosylechinocystic acid 28-O-β-d-glucopyranosyl-(1 → 2)-[β-d-xylopyranosyl-(1 → 6)]-β-d-glucopyranosyl-(1 → 6)-β-d-glucopyranosyl ester by a combination of one- and two-dimensional NMR techniques, and mass spectrometry. To the best of our knowledge this is the first phytochemical report on A. gracilis, and echinocystic acid saponins were encountered for the first time in Caryophyllaceae family.