Assigning stereodiversity of the 27-Me group of furostane-type steroidal saponins via NMR chemical shifts

Applicability of (13)C and (1)H NMR chemical shifts for the assignment of the 25R/25S configuration of the 27-methyl group in the case of furostane-type steroidal saponins has been investigated. A comparative study of (13)C NMR data suggest that chemical shift values for C-20, C-21, C-22, C-23, C-24, C-25, C-26 and C-27 resonances were not much influenced by R/S configuration of the 27-Me group, thus reflecting limited application of (13)C NMR chemical shifts for such stereochemical determinations. In contrast, (1)H NMR chemical shifts (delta(a), delta(b)) for geminal protons of glycosyloxy methylene (H(2)-26) exhibit pronounced dependence and the difference (Delta(ab)=delta(a)-delta(b)) among their chemical shifts [Delta(ab)= or <0.48 for 25R; Delta(ab)= or >0.57 for 25S] seems to be of general applicability for ascertaining 25R/25S orientation of the 27-methyl group of furostane-type steroidal saponins.     

Steroidal saponins from the tuber of Ophiopogon japonicus

Eight novel steroidal saponins, ophiopogonins H-O (1-8), along with seven known steroidal saponins (9-15) were isolated from the tubers of Ophiopogon japonicus. The structures of these new compounds were determined by detailed spectroscopic analysis, including extensive 1D and 2D NMR data, and the analysis of hydrolytic reaction products. For the first time, rare furostanol saponins with disaccharide moiety linked at position C-26 of the aglycone were reported to be isolated from a natural source.     

Preparation of (25R)- and (25S)-26-functionalized steroids as tools for biosynthetic studies of cholic acids

A new synthesis of both epimeric forms of 26-cholestanoic acids and 26-alcohols containing a 3beta-hydroxy-Delta(5)- or a Delta(4)-3-keto-functionality in ring A is described starting from stigmasterol or (20S)-3beta-acetoxy-pregn-5-en-20-carboxylic acid. The obtained compounds are useful as standards for studies of cholic acids. Construction of the side chain was achieved by linkage of steroidal 23-iodides to sulfones prepared from (2R)- and (2S)-3-hydroxy-2-methylpropanoates. Oxidation of intermediate 26-alcohols into the corresponding carboxylic acids ensuring preservation of stereochemistry at C-25 and functional groups in the cyclic part was achieved with sodium chlorite catalyzed by TEMPO and bleach.     

Steroidal saponins from the fresh tubers of Ophiopogon japonicus

Eleven novel furostanol saponins, named ophiofurospisides C–E, G–N (1–3, 5–12), one new spirostanol saponin, named ophiopogonin R (13), were isolated from the fresh tubers of Ophiopogon japonicus. Their structures were determined on the basis of spectroscopic techniques (1D and 2D NMR) and HRESIMS. The isolated furostanol saponins possessed two sugar chains located at C-3 and C-26, respectively. Six furostanol saponins (1, 5–9) with disaccharide moiety linked at position C-26 of the aglycone were rare in the plant kingdom.     

Cytotoxic steroidal saponins from Polygonatum punctatum

Four new steroidal saponins, polypunctosides A-D (1-4, resp.), were isolated from the rhizomes of Polygonatum punctatum, together with five known steroidal saponins. On the basis of chemical and spectral evidence, the structures of the new saponins were established as (3beta,23S,25R)-23-(alpha-L-arabinopyranosyloxy)spirost-5-en-3-yl 4-O-(6-deoxy-alpha-L-mannopyranosyl)-D-glucopyranoside (1), (3beta,23S,25R)-23-[(2-O-acetyl-alpha-L-arabinopyranosyl)oxy]spirost-5-en-3-yl 4-O-(6-deoxy-alpha-L-mannopyranosyl)-D-glucopyranoside (2), (3beta,23S,25R)-23-[(3-O-acetyl-alpha-L-arabinopyranosyl)oxy]spirost-5-en-3-yl 4-O-(6-deoxy-alpha-L-mannopyranosyl)-D-glucopyranoside (3), and (3beta,23S,25R)-23-[(4-O-acetyl-alpha-L-arabinopyranosyl)oxy]spirost-5-en-3-yl 4-O-(6-deoxy-alpha-L-mannopyranosyl)-D-glucopyranoside (4). The cytotoxic activity of the isolated saponins was evaluated towards HeLa cells.     

Steroidal saponins from the rhizomes of Smilax sieboldii.

Six new steroidal saponins were isolated from the rhizomes of Smilax sieboldii. Their structures were determined by spectroscopic analysis and hydrolysis to be 3 beta-hydroxy-(25R)-5 alpha-spirostan-6-one (laxogenin) 3-O-beta-D-glucopyranosyl-(1----4)-O-[alpha-L-arabinopyranosyl-(1- ---6)]-beta-D-glucopyranoside, laxogenin 3-O-alpha-L-arabinopyranosyl-(1----6)-beta-D-glucopyranoside, 3 beta,27-dihydroxy-(25S)-5 alpha-spirostan-6-one 3-O-beta-D-glucopyranosyl-(1----4)-O-[alpha-L-arabinopyranosyl-(1- ---6)]- beta-D-glucopyranoside, 26-O-beta-D-glucopyranosyl-3 beta,22 xi,26-trihydroxy-(25R)-5 alpha-furostan-6-one 3-O-alpha-L-arabinopyranosyl-(1----6)-beta-D-glucopyranoside, 26-O-beta-D-glucopyranosyl-3 beta,22 xi,26-trihydroxy-(25R)-5 alpha-furostan-6- one 3-O-beta-D-glucopyranosyl-(1----4)-O-[alpha-L-arabinopyranosyl-(1- ---6)]- beta-D-glucopyranoside and (25R)-5 alpha-spirostan-3 beta-ol (tigogenin) 3-O-beta-D-glucopyranosyl-(1----4)-O-[alpha-L-arabinopyranosyl- (1----6)]-beta-D-glucopyranoside. The inhibition of cAMP phosphodiesterase by the saponins was evaluated.     

New steroidal glycosides from rhizomes of Clintonia udensis

A total of 10 steroidal glycosides, together with three new spirostanol glycosides (6-8), a new furostanol glycoside (9), and a new cholestane glycoside (10), were isolated from the rhizomes of Clintonia udensis (Liliaceae). The structures of the new compounds were determined on the basis of extensive spectroscopic analyses, including 2-D nuclear magnetic resonance (NMR) data, and of hydrolytic cleavage followed by chromatographic or spectroscopic analyses. The isolated glycosides were evaluated for their cytotoxic activity against HL-60 leukemia cells. Spirostanol glycosides 1 and 2, and furostanol glycoside 4 showed cytotoxic activity with IC(50) values of 3.2+/-0.02, 2.2+/-0.12, and 2.2+/-0.06 microg/ml, respectively. Neither the spirostanol and furostanol saponins with a hydroxy group at C-1 (6 and 9) and C-12 (7 and 8) nor cholestane glycosides (5 and 10) exhibited apparent cytotoxic activity at a sample concentration of 10 microg/ml.     

New steroidal saponins from rhizomes of Costus spiralis

Two new steroidal saponins were isolated from the rhizomes of Costus spiralis Rosc. Their structures were established as (3beta,25R)-26-(beta-D-glucopyranosyloxy)-22-hydroxyfurost-5-en-3-yl O-D-apio-beta-D-furanosyl-(1-->2)-O-[alpha-L-rhamnopyranosyl-(1-->4)]-beta-D-glucopyranoside (1) and (3beta,25R)-26-(beta-D-glucopyranosyloxy)-22-hydroxyfurost-5-en-3-yl O-D-apio-beta-D-furanosyl-(1-->4)-O-[alpha-L-rhamnopyranosyl-(1-->2)]-beta-D-glucopyranoside (2). Their structural identifications were performed using detailed analyses of 1H and 13C NMR spectra including 2D NMR spectroscopic techniques (DEPT, COSY, HETCOR and COLOC) and chemical conversions. The steroidal saponins were evaluated for anti-inflammatory activity.     

Jatropham derivatives and steroidal saponins from the bulbs of Lilium hansonii.

Two new jatropham derivatives and three new steroidal saponins were isolated from the fresh bulbs of Lilium hansonii, along with previously known compounds. The structures of the new compounds were elucidated, on the basis of spectroscopic data and chemical evidence, and by comparing them with those of known compounds, as (-)-5-hydroxy-3-methyl-3-pyrrolin-2-one (jatropham) 5-O-beta-D-glucopyranosyl-(1----3)-beta-D-glucopyranoside, (2S*,4R*)-1-(3-methyl-2-oxo-3-pyrrolinyl)-4-methyl-5-oxo-2-pyrr olidinecarboxyli c acid, 26-O-beta-D-glucopyranosyl-(25R)-5 alpha-furostan-3 beta,22 zeta-diol 3-O-alpha-L-rhamnopyranosyl-(1----2)-O-[beta-D-glucopyranosyl-(1----4)]- beta-D-glucopyranoside, (25R)-5 alpha-spirostan-3 beta,12 alpha-diol 3-O-alpha-L-rhamnopyranosyl-(1----2)-O-[beta-D-glucopyranosyl-(1----4)]- beta-D-glucopyranoside and (25R)-spirost-5-en-3 beta,12 alpha-diol 3-O-alpha-L-rhamnopyranosyl-(1----2)-O-[beta-D-glucopyranosyl-(1----4)]- beta-D-glucopyranoside, respectively. The stereostructure of jatropham dimer, the plain structure of which was presented previously, was confirmed by X-ray crystallographic analysis. The inhibitory activity on cyclic AMP phosphodiesterase of the steroidal saponins was evaluated.     

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.     

Steroidal saponins from Asparagus africanus.

The structures of two new monodesmosidic spirostanosides and a new bisdesmosidic furostanol glycoside isolated from the roots of Asparagus africanus Lam. (Liliaceae) have been elucidated as (25R)-3 beta-hydroxy-5 beta-spirostan-12-one 3-O-{beta-D-glucopyranosyl-(1-->2)-[alpha-1-arabinopyranosyl-(1--> 6)]-beta- D-glucopyranoside} (1), (25R)-5 beta-spirostan-3 beta-ol 3-O-{beta-D-glucopyranosyl-(1-->2)-[alpha-L-arabinopyranosyl-(1--> 6)]-beta- D-glucopyranoside} (2) and 26-O-beta-D-glucopyranosyl]-22 alpha-methoxy-(25R)-furostan-3 beta,26-diol 3-O-{beta-D-glucopyranosyl-(1-->2)-[beta-D-glucopyranoside} (3), respectively, by the combined use of one and two dimensional NMR experiments. The complete 13C and 1H assignments of the peracetyl spirostanosides and the furostanol oligoside were derived. The interconversions between the methoxyl and hydroxyl group at C-22 of the furostanol glycoside was investigated and the genuine furostanol oligoside of A. africanus appears to be the hydroxyl type based on the comparative study of the methanol, pyridine and dioxane extracts.     

Configuration at C-25 in 5 beta-cholestane-3 alpha,7 alpha,12 alpha,25,26-pentol excreted by patients with cerebrotendinous xanthomatosis: circular dichroism and 13C-NMR studies

The configuration at C-25 in 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha,25,26-pentol isolated from the bile and feces of patients with cerebrotendinous xanthomtosis (CTX) was determined from the lanthanide-induced circular dichroism (CD) Cotton effects and 13C-NMR measurements. Under anhydrous conditions, CD spectra of 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha,25,26-pentol in the presence of Eu(fod)3 exhibited a large induced negative Cotton effect at 320 nm. On the basis of the empirical rule (primary-tertiary-alpha-diols) in which R compounds have positive Cotton effects and S compounds have negative Cotton effects at 320 nm, it was concluded that 25,26-pentol has the 1,2,glycol structure with C-25 having the S-configuration. This assignment was based upon comparison with model compounds, 25(R and S),26-dihydroxy cholesterols and 25(R and S),26-dihydroxy cholecalciferols whose single-crystal X-ray structure and 13C-NMR studies have been performed. It is suggested that these data may be helpful to clarify the stereospecificity of the hydroxylation of the terminal methyl group of the cholesterol side chain in CTX.     

Two new sulfated furostanol saponins from Tribulus terrestris

The known furostanol saponins methylprotodioscin and protodioscin and two new sulfated saponins, sodium salt of 26-O-beta-glucopyranosyl-22alpha-methoxy-(25R)-furost-5-ene-3beta,26-diol-3-O-alpha-rhamnopyranosyl-(1-->2)-beta-4-O-sulfo-glucopyranoside (methylprototribestin) and sodium salt of 26-O-beta-glucopyranosyl-22alpha-hydroxy-(25R)-furost-5-ene-3beta,26-diol-3-O-alpha-rhamnopyranosyl-(1-->2)-beta-4-O-sulfo-glucopyranoside (prototribestin) have been isolated from the aerial parts of Tribulus terrestris L. growing in Bulgaria. The structures of the new compounds were elucidated on the basis of 1D and 2D (DQF-COSY, TOCSY, HSQC-TOCSY, HSQC, HMBC, ROESY) NMR data, ESI mass spectra and chemical transformation.     

Steroidal Saponins from the Rhizomes of Aspidistra typica

Eleven new furostanol saponins, typaspidosides B-L (1–11), one new spirostanol saponin, typaspidoside M (12), and five known spirostanol saponins, 25S-atropuroside (13), neoaspidistrin (14), (25S)-pratioside D₁ (15), 25S-aspidistrin (16) and 25S-neosibiricoside (17) were isolated from the rhizomes of Aspidistra typica Baill. The structures of the new compounds were established using 1D and 2D NMR (¹H-¹H COSY, HMQC, HMBC and ROESY) spectroscopy, high resolution mass spectrometry, and chemical methods. The aglycones of 1–3 (unusual furostanol saponins with opened E ring type), 9 and 10 (the methoxyl substituent at C-23 position) were found, identified from natural products for the first time. Moreover, the anti-HIV activities of the isolated steroidal glycosides were assessed, and compounds 13, 14, 16 and 17 exhibited high active against HIV-1.     

Steroidal saponin production in callus cultures of Solanum aculeatissimum Jacq.

 Callus was induced from the epicotyl of S. aculeatissimum, and the relation between culture conditions and the production of steroidal saponins in the callus was studied. The results indicated that the callus produced the steroidal saponins aculeatiside A and B. The highest production of steroidal saponins occurred at the middle of the log phase. Optimal conditions for the production of steroidal saponins were culturing on MS basal medium supplemented with the combination of 0.05 ppm or 0.1 ppm NAA and 10 ppm BA, and fructose as a carbon source, in the dark at 25  °C. Under these optimal conditions, the callus produced 0.8% (per dry weight) steroidal saponins, or 0.32% aculeatiside A and 0.48% aculeatiside B. Received: 24 December 1999 / Revision received: 21 February 2000 / Accepted: 16 May 2000     

Modulation of sodium pumps by steroidal saponins

Costus spicatus, used in Brazilian traditional medicine to expel kidney stones, contains steroidal saponins with different chemical characteristics. In spite of its popular utilization as potent diuretic, no scientific reports correlate this activity with the chemical constituents of the extract. Therefore, two steroidal saponins (3 beta,22 alpha,25R)-26-(beta-D-glucopyranosyloxy)-2-methoxyfurost-5-en-3-yl O-D-apio-beta-D-furanosyl-(1-->2)-O-[6-deoxy-alpha-L-mannopyranosyl-(1-->4)]-beta-D-glucopyranoside (1) and (3 beta,22 alpha,25R)-spirostan-3-yl O-D-apio-beta-D-furanosyl-(1-->2)-O-[6-deoxy-alpha-L-mannopyranosyl-(1-->4)]-beta-D-glucopyranoside (1a), were isolated from the rhizomes of this plant and their effects on the Na+-ATPase and (Na+ + K+)-ATPase activities of the proximal tubule from pig kidney were evaluated. It was observed that 1 and 1a inhibit specifically the Na+-ATPase activity.     

C-25 epimeric 26-haloponasterone A: synthesis, absolute configuration and moulting activity

A convenient synthesis of inokosterone has been accomplished. Inokosterone exists as two C-25 epimers, which could be separated from each other through their diacetonide derivatives. The absolute configuration of these compounds was determined. Two C-25 epimers of 26-chloroponasterone A were synthesized from the respective C-25 epimeric inokosterone. Two epimeric 26-bromo and 26-iodoponasterone A compounds were also synthesized. Moulting activity of these compounds was evaluated using the Musca bioassay, and it was found that the (25S)-26-halo analogues were more active than the corresponding (25R)-26-halo analogues. Among the 25S series, an increase in activity with an increase in size of the halogen atom was observed, indicating that the steric factor was more important than the electronic factor in binding of these ecdysteroid analogues to the receptor. On the other hand, a decrease in activity with an increase in size of the halogen atom was noted in the 25R series, suggesting that the steric factor was less important than the electronic factor. The results indicated that the configuration at C-25 and the substituent at C-26 have significant influences on the interaction of ecdysteroids with their receptor.     

Structural and biosynthetic studies of a principal bile alcohol, 27-nor-5beta-cholestane-3alpha,7alpha,12alpha,24,25-pentol, in human urine

The stereochemistry at C-24 and C-25 of 27-nor-5beta-cholestane-3alpha,7alpha,12alpha,24 ,25-pentol, a principal bile alcohol in human urine, and its biosynthesis are studied. Four stereoisomers of the C(26)-24,25-pentols were synthesized by reduction with LiAlH(4) of the corresponding epoxides prepared from (24S)- or (24R)-27-nor-5beta-cholest-25-ene-3alpha, 7alpha,12alpha,24-tetrol. The stereochemistries at C-25 were deduced by comparison of the C(26)-24,25-pentols with the oxidation products of (24Z)-27-nor-5beta-cholest-24-ene-3alpha,7alpha, 12alpha-triol with osmium tetraoxide. On the basis of this assignment, the principal bile alcohol excreted into human and rat urine was determined to be (24S,25R)-27-nor-5beta-cholestane-3alpha,7alpha, 12alpha,24,25-pentol, accompanied by a lesser amount of (24R, 25R)-isomer. To elucidate the biosynthesis of the C(26)-24,25-pentol, a putative intermediate, 3alpha,7alpha, 12alpha-trihydroxy-27-nor-5beta-cholestan-24-one, derived from 3alpha,7alpha, 12alpha-trihydroxy-24-oxo-5beta-cholestanoic acid by decarboxylation during the side-chain oxidation of 3alpha,7alpha, 12alpha-trihydroxy-5beta-cholestanoic acid, was incubated with rat liver homogenates. The 24-oxo-bile alcohol could be efficiently reduced to yield mainly (24R)-27-nor-5beta-cholestane-3alpha,7alpha, 12alpha,24-tetrol. If a 25R-hydroxylation of the latter steroid occurs, it should lead to formation of (24S,25R)-C(26)-24,25-pentol. Now it has appeared that a major bile alcohol excreted into human urine is (24S,25R)-27-nor-5beta-cholestane-3alpha,7alpha, 12alpha, 24, 25-pentol, which might be derived from 3alpha,7alpha, 12alpha-trihydroxy-27-nor-5beta-cholestan-24-one via (24R)-27-nor-5beta-cholestane-3alpha, 7alpha,12alpha,24-tetrol.     

Lanostanes and friedolanostanes from the bark of Garcinia speciosa

The CHCl(3) extract of the bark of Garcinia speciosa contained four 17,14-friedolanostanes and five lanostanes as well as friedelin and common plant constituents. The friedolanostanes were the previously known methyl ester of (24E)-3 alpha,23 alpha-dihydroxy-17,14-friedolanostan-8,14,24-trien-26-oic acid and the methyl esters of three hitherto unknown acids, 3 alpha-hydroxy-16 alpha,23 alpha-epoxy-17,14-friedolanostan-8,14,24-trien-26-oic acid, 3 alpha,23 alpha-dihydroxy-8 alpha,9 alpha-epoxy-17,14-friedolanostan-15-oxo-24-en-26-oic acid and 3 alpha,23 alpha-dihydroxy-17,14-friedolanostan-15-oxo-8(14),24-dien-26-oic acid. New lanostanes were 3 beta,9 alpha-dihydroxylanost-24-en-26-al and the methyl ester of 3 beta-hydroxy-23-oxo-9,16-lanostadien-26-oic acid. Structures were established by analysis of spectroscopic data. In the case of the lanostanes the previously unassigned C-25 stereochemistry was shown to be 25R by X-ray analysis of 3 beta-hydroxy-23-oxo-9,16-lanostadien-26-oic acid. In the case of the friedolanostanes the configuration at C-23 was established as 23R, identical with the absolute configuration at C-23 of mariesiic acids A and B.