Cytotoxic and antioxidant triterpene saponins from Butyrospermum parkii (Sapotaceae)

Three new triterpenoid saponins, elucidated as 3-O-β-d-glucopyranosyloleanolic acid 28-O-β-d-xylopyranosyl-(1→4)-α-l-rhamnopyranosyl-(1→2)-β-d-xylopyranoside (parkioside A, 1), 3-O-[β-d-apifuranosyl-(1→3)-β-d-glucopyranosyl]oleanolic acid 28-O-[β-d-apifuranosyl-(1→3)-β-d-xylopyranosyl-(1→4)-[α-l-rhamnopyranosyl-(1→3)]-α-l-rhamnopyranosyl-(1→2)β-d-xylopyranoside (parkioside B, 2) and 3-O-β-d-glucuronopyranosyl-16α-hydroxyprotobassic acid 28-O-α-l-rhamnopyranosyl-(1→3)-β-d-xylopyranosyl-(1→4)-α-l-rhamnopyranosyl-(1→2)-β-d-xylopyranoside (parkioside C, 3), were isolated from the n-BuOH extract of the root bark of Butyrospermum parkii, along with the known 3-O-β-d-glucopyranosyloleanolic acid (androseptoside A). The structures of the isolated compounds were established on the basis of chemical and spectroscopic methods, mainly 1D and 2D NMR data and mass spectrometry. The new compounds were tested for both radical scavenging and cytotoxic activities. Compound 2 showed cytotoxic activity against A375 and T98G cell lines, with IC₅₀ values of 2.74 and 2.93 μM, respectively. Furthermore, it showed an antioxidant activity comparable to that of Trolox or butylated hydroxytoluene (BHT), used as controls, against 2,2-diphenyl-1-picryl hydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), oxygen and nitric oxide radicals.     

Novel steroidal saponins from Liriope graminifolia (Linn.) Baker with anti-tumor activities

Phytochemical investigation of the underground parts of Liriope graminifolia (Linn.) Baker resulted in the isolation of two new steroidal saponins lirigramosides A (1) and B (2) along with four known compounds. The structures were determined by extensive spectral analysis, including two-dimensional (2D) NMR spectroscopy and chemical methods, to be 3-O-{β-d-xylopyranosyl-(1→3)-α-l-arabinopyranosyl-(1→2)-[α-l-rhamnopyranosyl-(1→4)]-β-d-glucopyranosyl-(25S)-spirost-5-ene-3β,17α-diol (1), 1-O-[α-l-rhamnopyranosyl-(1→2)-β-d-xylopyranosyl]-(25R)-ruscogenin (2), 1-O-β-d-xylopyranosyl-3-O-α-l-rhamnopyranosyl-(25S)-ruscogenin (3), 3-O-α-l-rhamnopyranosyl-1-O-sulfo-(25S)-ruscogenin (4), methylophiopogonanone B (5), and 5,7-dihydroxy-3-(4-methoxybenzyl)-6-methyl-chroman-4-one, (ophiopogonanone B, 6), respectively. Compound 1 has a new (25S)-spirost-5-ene-3β,17α-diol ((25S)-pennogenin) aglycone moiety. The isolated compounds were evaluated for their cytotoxic activities against Hela and SMMC-7721 cells.     

New triterpenoid saponins from Patrinia scabiosaefolia

Phytochemical investigation of the methanol extract from the whole plants of Patrinia scabiosaefolia Fisch. resulted in the isolation of four new triterpenoid saponins (1–4) along with six known compounds (5–10). On the basis of spectroscopic and chemical methods, the structures of the new compounds were established as 3-O-β-d-xylopyranosyl-(1→3)-α-l-rhamnopyranosyl-(1→2)-β-d-xylopyranosyl-12β,30-dihydroxy-olean-28,13β-olide (1), 3-O-α-l-rhamnopyranosyl-(1→2)-β-d-xylopyranosyl-12β,30-dihydroxy-olean-28,13β-olide (2), 3-O-β-d-xylopyranosyl-(1→2)-β-d-glucopyranosyl-12β, 30-dihydroxy-olean-28,13β-olide (3), and 3-O-β-d-glucopyranosyl-(1→4)-β-d-xylopyranosyl-(1→3)-α-l-rhamnopyranosyl-(1→2)-β-d-xylopyranosyl-oleanolic acid 28-O-β-d-glucopyranoside (4), respectively. Compounds 1–3 possess a novel 12β,30-dihydroxy-olean-28,13β-lactone aglycone and a 12β-hydroxy substituent that is rarely found in this kind of triterpenoid saponin.     

Flavonoids and other constituents of Hymenostegia afzelii (Caesalpiniaceae)

Phytochemical investigation of the stem bark and leaves of Hymenostegia afzelii resulted in the isolation of three new flavonoids, named afzelin A-C (1–3), together with five known compounds: 7,6-(2″,2″-dimethylpyrano)-3,5,4′-trihydroxyflavone, apigenin, 3-O-α-l-rhamnopyranosylcincholic acid, 3-O-β-d-glucopyranosylcincholic acid, and dodecanoic acid 1,1′-[(1S)-1-(hydroxymethyl)-1,2-ethanediyl] ester. The structures of 1–3 were determined by means of spectroscopic methods. Compounds 1–3 were tested in vitro for their preliminary cytotoxicity using the Artemia salina assay.     

Two new steroidal saponins from Dioscorea panthaica

Two new furostanol saponins, 3-O-[α-l-rhamnopyranosyl-(1→4)-β-d-glucopyranosyl]-26-O-β-d-glucopyranosyl-25(R)-furosta-5,22(23)-dien-3β,20α,26-triol (1), 3-O-[β-d-glucopyranosyl-(1→3)-O-α-l-rhamnopyranosyl-(1→2)-β-d-glucopyranosyl]-26-O-β-d-glucopyranosyl-20(R)-methoxyl-25(R)-furosta-5,22(23)-dien-3β,26-diol (2) were isolated from the Dioscorea panthaica along with five known steroidal saponins (3–7). The structures of the new saponins were determined by detailed analysis of spectral data (including 2D NMR spectroscopy). The inhibitory activities of the saponins against α-glucosidase were investigated, gracillin (4) and 3-O-[α-l-rhamnopyranosyl-(1→2)-β-d-glucopyranosyl]-26-O-β-d-glucopyranosyl-25(R)-furosta-5,20(22)-dien-3β,26-diol (5) were found to exhibit potent activities with IC₅₀ values of 0.11 ± 0.04 mM and 0.09 ± 0.01 mM.     

Synthesis of the conjugation ready, downstream disaccharide fragment of the O-PS of Vibrio cholerae O:139

The linker-equipped disaccharide, 8-amino-3,6-dioxaoctyl 2,6-dideoxy-2-acetamido-3-O-β-d-galactopyranosyluronate-β-d-glucopyranoside (10), was synthesized in eight steps from acetobromogalactose and ethyl 4,6-O-benzylidene-2-deoxy-2-trichloroacetamido-1-thio-β-d-glucopyranoside. The hydroxyl group present at C-4^II in the last intermediate, 8-azido-3,6-dioxaoctyl 4-O-benzyl-6-bromo-2,6-dideoxy-2-trichloroacetamido-3-O-(benzyl 2,3-di-O-benzyl-β-d-galactopyranosyluronate)-β-d-glucopyranoside (9), is positioned to allow further build-up of the molecule and, eventually, construction of the complete hexasaccharide. Global deprotection (9→10) was done in one step by catalytic hydrogenolysis over palladium-on-charcoal.     

Efficient synthesis of exomethylene- and keto-exomethylene-d-glucopyranosyl nucleoside analogs as potential cytotoxic agents

A novel series of exomethylene- and keto-exomethylene-d-glucopyranonucleosides with thymine, uracil, and 5-fluorouracil as heterocyclic bases have been designed and synthesized. Wittig condensation of the 3-keto glucoside 1 gave the corresponding 1,2:5,6-di-O-isopropylidene-3-deoxy-3-methylene-d-glucofuranose (2), which after hydrolysis and acetylation led to the precursor 1,2,4,6-tetra-O-acetyl-3-deoxy-3-methylene-d-glucopyranose (4).Compound 4 was condensed with silylated thymine, uracil, and 5-fluorouracil, respectively, deacetylated and acetalated to afford 1-(3′-deoxy-4′,6′-O-isopropylidene-3′-methylene-β-d-glucopyranosyl)pyrimidines 7a–c. Oxidation of the free hydroxyl group in the 2′-position of the sugar moiety led to the formation of the labile 1-(3′-deoxy-4′,6′-O-isopropylidene-3′-methylene-β-d-glucopyranosyl-2′-ulose)pyrimidines 8a–c. Finally, deisopropylidenation of the resulted derivatives 8a–c afforded the diol nucleosides 9a–c. The target keto-exomethylene analogs 9a–c were more cytostatic against a variety of tumor cell lines than the corresponding saturated-hydroxy-exomethylene derivatives 6. In particular, the 5-fluorouracil derivative 9c was highly cytostatic at an IC₅₀ (50% inhibitory concentration) ranging between 0.56 and 9.4 μg/mL, which was comparable to the free parental 5-fluorouracil base.     

Keto-fluorothiopyranosyl nucleosides: a convenient synthesis of 2- and 4-keto-3-fluoro-5-thioxylopyranosyl thymine analogs

A novel series of fluorinated keto-β-d-5-thioxylopyranonucleosides bearing thymine as the heterocyclic base have been designed and synthesized. Deprotection of 3-deoxy-3-fluoro-5-S-acetyl-5-thio-d-xylofuranose (1) and selective acetalation gave the desired isopropylidene 5-thioxylopyranose precursor 3. Acetylation and isopropylidene removal followed by benzoylation led to 3-deoxy-3-fluoro-1,2-di-Ο-benzoyl-4-O-acetyl-5′-thio-d-xylopyranose (6). This was condensed with silylated thymine and selectively deacetylated to afford 1-(2′-Ο-benzoyl-3′-deoxy-3′-fluoro-5′-thio-β-d-xylopyranosyl)thymine (8). Oxidation of the free hydroxyl group in the 4′-position of the sugar led to the formation of the target 4′-keto compound together with the concomitant displacement of the benzoyl group by an acetyl affording, 1-(2′-O-acetyl-3′-deoxy-3′-fluoro-β-d-xylopyranosyl-4′-ulose)thymine (9). Benzoylation of 3 and removal of the isopropylidene group followed by acetylation, furnished 3-deoxy-3-fluoro-1,2-di-Ο-acetyl-4-O-benzoyl-5′-thio-d-xylopyranose (12). Condensation of thiosugar 12 with silylated thymine followed by selective deacetylation led to the 1-(4′-Ο-benzoyl-3′-fluoro-5′-thio-β-d-xylopyranosyl)thymine (14). Oxidation of the free hydroxyl group in the 2′-position and concomitant displacement of the benzoyl group by an acetyl gave target 1-(4′-O-acetyl-3′-deoxy-3′-fluoro-β-d-xylopyranosyl-2′-ulose)thymine (15).     

Activity-guided isolation of antileishmanial compounds from Piper hispidum

The bioassay-guided purification of the ethanolic extract from the leaves of Piper hispidum led to the isolation of one new amide, N-2-(3′,4′,5′-trimethoxyphenyl)ethyl-2-hydroxybenzamide (1) as well as two known chalcones 2′-hydroxy-3′,4′,6′-trimethoxychalcone (2); 2′,4′-dihydroxy-6′-methoxychalcone (cardamonin, 3) and one known flavanone, 5,7-dihydroxyflavanone (Pinocembrin, 4). Their structures were elucidated on the basis of spectroscopic data, including homo- and heteronuclear correlation NMR experiments (COSY, HSQC and HMBC) and comparison with data reported in the literature. The isolated compounds were tested against Leishmania amazonensis axenic amastigotes. The results showed that the known chalcone 2 exhibited the most potent antileishmanial activity with an IC₅₀ of 0.8 μM (amphotericin B: IC₅₀ = 0.2 μM) but was shown to exhibit mild cytotoxicity.     

Phenolic metabolites from Pyruscalleryana and evaluation of its free radical scavenging activity

Investigation of the aqueous alcoholic extract of Pyruscalleryana Decne. leaves led to the isolation of two new phenolic acids glycosides, namely protocatechuoylcalleryanin-3-O-β-glucopyranoside (1) and 3′-hydroxybenzyl-4-hydroxybenzoate-4′-O-β-glucopyranoside (2), together with nine known compounds among them lanceoloside A and methylgallate, which have been isolated for the first time from the genus Pyrus. Structures of the isolated compounds were established by spectroscopic analysis, including UV, IR, HRESI-MS, and 1D/2D NMR. The total extract and some isolated compounds were determined against DPPH (2,2-diphenyl-1-(2,4,6-trinitrophenyl) hydrazinyl radical, for their free radical scavenging activity, the total alcoholic extract showed strong antioxidant activity while the two new compounds showed weak antioxidant activity.     

Structure and absolute configuration of a secolignan from Peperomia blanda

A secolignan, (−)-2-methyl-3-[bis(3′,4′-methylenedioxy-5′-methoxyphenyl) methyl]butyrolactone (1), with a rare cis configuration was isolated from the aerial parts of Peperomia blanda (Piperaceae). The structure of this compound was elucidated by a combination of spectroscopic methods, including ultraviolet, infrared, 1D- and 2D- nuclear magnetic resonance as well as high resolution mass spectrometry data. The absolute configuration of (−)-1 was determined as (2R,3S) by the comparison of experimental electronic circular dichroism (ECD) spectroscopy and time-dependent density functional theory (TDDFT) calculations.     

Minor diterpenoid glycosides from the leaves of Stevia rebaudiana

From the commercial extract of the leaves of Stevia rebaudiana, three new diterpenoid glycosides were isolated besides eight known steviol glycosides including stevioside, rebaudiosides A–F and dulcoside A. The structures of the three compounds were identified as 13-[(2-O-β-d-glucopyranosyl-β-d-glucopyranosyl) oxy]-kaur-16-en-18-oic acid-(6-O-β-d-xylopyranosyl-β-d-glucopyranosyl) ester (1), 13-[(2-O-β-d-glucopyranosyl-β-d-glucopyranosyl) oxy]-17-hydroxy-kaur-15-en-18-oic acid β-d-glucopyranosyl ester (2), and 13-[(2-O-β-d-glucopyranosyl-β-d-glucopyranosyl) oxy]-17-oxo-kaur-15-en-18-oic acid β-d-glucopyranosyl ester (3) on the basis of extensive NMR and MS spectral studies. Another known diterpenoid glycoside, 13-[(2-O-β-d-glucopyranosyl-β-d-glucopyranosyl) oxy]-kaur-15-en-18-oic acid β-d-glucopyranosyl ester (4) was also isolated and its complete NMR spectral assignments were made on the basis of COSY, HSQC and HMBC spectral data.     

New triterpene oligoglycosides from the Caribbean sponge Erylus formosus

Seven new triterpene glycosides, erylosides R₁ (1), T₁ (3), T₂ (4), T₃ (5), T₄ (6), T₅ (7), and T₆ (8) along with the known formoside (2) were isolated from the sponge Erylus formosus collected along the Caribbean coast of Mexico. Glycoside 1 was determined as a trisaccharide, glycoside 2 as a tetrasaccharide while glycosides 3–8 were hexasaccharide. Their carbohydrate chains were unprecedented and have never been found in oligosaccharides from other biological sources, except Erylus spp. Three carbohydrate chains in the glycosides 3 and 6, 4 and 7, 5 and 8 correspondingly are new. The glycosides 1–5 have penasterol as aglycone while glycosides 6–8 proved to be glycoconjugates of 24-methylene-14-carboxy-lanost-8(9)-en-3β-ol.     

New lanostane-type triterpenoids, inonotsutriols D, and E, from Inonotus obliquus

Two new lanostane-type triterpenoids, inonotsutriols D (1) and E (2), were isolated from the sclerotia of Inonotus obliquus (Pers.: Fr.) Pil. (Japanese name: kabanoanatake; Russian name: chaga). Their structures were determined to be lanost-8-ene-3β,22R,24R-triol (1) and lanost-8-ene-3β,22R,24S-triol (2) on the basis of spectral data, including 2D NMR analysis. In addition, major compounds, inotodiol (3), trametenolic acid (4), 3β-hydroxylanosta-8,24-dien-21-al (5), 21-hydroxylanosterol (6), inonotsuoxide A (7) and inonotsuoxide B (8) were identified, and all compounds, except 2, were evaluated for their cancer cell growth inhibitory activity against P388, HL-60, L1210 and KB cell lines.     

Phytochemical and Bioactivity Studies on Constituents of the Leaves of Vitex Quinata

A phytochemical investigation of the leaves of Vitex quinata (Lour.) F.N. Williams (Verbenaceae), guided by a cytotoxicity assay against the MCF-7 human breast cancer cell line, led to the isolation of a new δ-truxinate derivative (1) and a new phytonoic acid derivative (2), together with 12 known compounds. The structures of the new compounds were determined by spectroscopic methods as dimethyl 3,4,3′,4′-tetrahydroxy-δ-truxinate (1) and methyl 10R-methoxy-12-oxo-9(13),16E-phytodienoate (2), respectively. In a cytotoxicity assay, (S)-5-hydroxy-7,4′-dimethoxyflavanone (3) was found to be the sole active principle, with ED₅₀ values of 1.1–6.7 μM, respectively, when tested against a panel of three human cancer cells. Methyl 3,4,5-O-tricaffeoyl quinate (4) showed activity in an enzyme-based ELISA NF-κB p65 assay, with an ED₅₀ value of 10.3 μM.     

Structures of the novel diterpene glycosides from Stevia rebaudiana

From the commercial extract of the leaves of Stevia rebaudiana, two new diterpenoid glycosides were isolated besides the known steviol glycosides including stevioside, rebaudiosides A–F, rubusoside, and dulcoside A. The structures of the two new compounds were identified as 13-[(2-O-6-deoxy-β-d-glucopyranosyl-β-d-glucopyranosyl)oxy] ent-kaur-16-en-19-oic acid β-d-glucopyranosyl ester (1), and 13-[(2-O-6-deoxy-β-d-glucopyranosyl-3-O-β-d-glucopyranosyl-β-d-glucopyranosyl)oxy] ent-kaur-16-en-19-oic acid β-d-glucopyranosyl ester (2), on the basis of extensive NMR and MS spectral data as well as chemical studies.     

Halimodendrin I, a new acylated triterpene glycoside from Halimodendron halodendron (Fabaceae)

Halimodendrin I, a new acylated triterpene glycoside (1), was isolated and chemically characterized as 3β-O-palmitoyl-28-[3′-palmitoyl-β-d-glucopyranosyl]-olean-12-en-28-oic acid from the aerial part of Halimodendron halodendron (Fabaceae) by IR, 1D and 2D NMR, HR-ESI-MS and LR-ESI-MS experiments. In addition, seven known compounds were isolated and identified as: palmitic acid, glycerol-2-linoleneate, glycerol-1,3-dilinoleneate, ferulic acid, 3-O-methylquercetin, β-sitosterol, and β-sitosterol-3-O-β-d-glucopyranoside. Nine fatty acids were identified and quantified in the saponifiable matter of the hexane extract. These fatty acids are: myristic, n-pentadecanoic, palmitoleic, palmitic, linoleic, oleic, stearic, arachidic, and behenic acids. The volatile oil was isolated by hydrodistillation (0.013%, w/w) with unpleasant smell. Twenty-seven components were identified in the oil by GC/MS.     

A new epoxidic ganoderic acid and other phytoconstituents from Ganoderma lucidum

A new epoxidic ganoderic acid, 8α,9α-epoxy-3,7,11,15,23-pentaoxo-5α-lanosta-26-oic acid (1), together with the known compounds 3β-hydroxy-7,11,15,23-tetraoxo-5α-lanosta-8-en-26-oic acid (2), ergosta-7,22-diene-3β-yl pentadecanoate (3), ergosta-7,22-diene-3β-ol (4), β-sitosterol (5), fatty acids (6–10), fatty acid ester (11) and octadecane (12) were isolated from the fruiting bodies of Ganoderma lucidum from south India. Their structures were determined by ¹H, ¹³C, ¹³C DEPT, ¹H–¹H COSY, HMBC, HSQC, NOESY NMR, FT-IR, UV–vis and FABMS spectral analysis. Compounds (1–3) exhibited good antifungal activity against Candida albicans in disc diffusion assay (100 μg/disc). Steroid ester (3) showed moderate anti-inflammatory activity (59.7% inhibition, 100 mg/kg body weight) in carrageenan-induced paw edema.     

Interconverting flavanone glucosides and other phenolic compounds in Lippia salviaefolia Cham. ethanol extracts

Four interconverting flavanone glycosides [(2R)- and (2S)-3′,4′,5,6-tetrahydroxyflavanone 7-O-β-d-glucopyranoside, and (2R)- and (2S)-3′,4′,5,8-tetrahydroxyflavanone 7-O-β-d-glucopyranoside], in addition to eight known flavonoids [naringenin, asebogenin, sakuranetin, 6-hydroxyluteolin 7-O-β-d-glucoside, (2R)- and (2S)-eriodictyol 7-O-β-d-glucopyranoside, aromadendrin and phloretin], three phenylpropanoid glycosides [forsythoside B, alyssonoside and verbascoside] and the epoxylignan lariciresinol 4′-O-β-d-glucopyranoside were isolated and identified in the EtOH extract of the aerial parts of Lippia salviaefolia Cham. The phytochemical study herein was guided by preliminary antioxidant tests, namely, β-carotene protection and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity. The crude extracts, their active fractions and the isolated compounds were assayed against intracellular reactive oxygen species (ROS) and human embryonic kidney HEK-293 and human melanoma M14 cancer cell growth. Aromadendrin and phloretin were able to counteract elevation of ROS induced by the oxidant t-butylhydroperoxide (t-BOOH) in HEK-293 cells, whereas phloretin strongly protected HEK-293 cells from ROS damage at 1 μM. Additionally, phloretin exhibited a significant growth inhibitory effect at 20–40 μM in both HEK-293 and M14 cells and induced a concentration dependent apoptosis at 20 μM in M14 cells, suggesting a selective action towards malignant cells. Due to their equilibria, the four interconverting flavanone glycosides were studied using 1D and 2D NMR, HPLC–CD–PDA and HRMS analyses.