Isolation of the lignan secoisolariciresinol diglucoside from flaxseed (Linum usitatissimum L.) by high-speed counter-current chromatography

High-speed counter-current chromatography was successfully used for the isolation and purification of secoisolariciresinol diglucoside, a bioactive lignan from flaxseed (Linum usitatissimum L.). The solvent system consisted of tert.-butylmethyl ether-n-butanol-acetonitrile-water (1:3:1:5). The purity and identity of the isolated compound was checked by high-performance liquid chromatography analysis in combination with mass spectrometry and NMR measurements.     

DNA-protector and cytotoxic activity of secoisolariciresinol diglucoside derivatives

The relationship between the chemical structure and DNA-protector and cytotoxic activities of phenylpropane lignans was studied. Analogs were synthesized from the lignan secoisolariciresinol diglucoside (SDG) isolated from Linum usitatissimum seeds. It was shown that SDG derivatives secoisolariciresinol and secoisolariciresinol-4′,4″-diacetate, which were not glucosides, exhibited greater cytotoxic activity in vitro than the starting lignan. The cytotoxicity was slightly elevated upon acetylation of the aglycon phenol hydroxyls whereas the DNA-protector activity decreased substantially. The DNA-protector activity of the derivative without the carbohydrate was slightly greater than that of the starting SDG. This was explained by binding of free radicals by the butanediol hydroxyls. It was proposed that the activity of the cytotoxic derivatives was mediated by induction of apoptosis of the tumor cells.     

Purification of secoisolariciresinol diglucoside with column chromatography on a sephadex LH-20

A simplified and efficient method is developed for the large-scale purification of the secoisolariciresinol diglucoside (SDG) from defatted flaxseed after aqueous ethanol extraction. Extractant from defatted flaxseed with aqueous ethanol is hydrolyzed with basic solution, concentrated under vacuum, subjected to Sephadex LH-20 column chromatography, and eluted with aqueous ethanol of different concentrations. Elution is monitored by a UV detector at 280 nm, and fractions containing SDG are pooled, concentrated, and applied to a second column chromatography under the same conditions. Elution with water results in a better resolution of SDG [94.5% by high-performance liquid chromatography (HPLC)] than that with pure ethanol or 50% (v/v) aqueous ethanol. HPLC-photodiode array detection-mass spectrometry and NMR are applied to identify SDG and to determine the purity of the eluted fraction. This simplified purification scheme avoids toxic organic solvent used in the common silica gel separation process and, thus, increases the safety of the process.     

Human intestinal bacteria capable of transforming secoisolariciresinol diglucoside to mammalian lignans, enterodiol and enterolactone

Seven metabolites were isolated after anaerobic incubation of secoisolariciresinol diglucoside (1) with a human fecal suspension. They were identified as (-)-secoisolariciresinol (2), 3-demethyl-(-)-secoisolariciresinol (3), 2-(3-hydroxybenzyl)-3-(4-hydroxy-3-methoxybenzyl)butane-1,4-diol (4), didemethylsecoisolariciresinol (5), 2(3-hydroxybenzyl)-3-(3,4-dihydroxybenzyl)butane-1,4-diol (6), enterodiol (7) and enterolactone (8). Furthermore, two bacterial strains, Peptostreptococcus sp. SDG-1 and Eubacterium sp. SDG-2, responsible for the transformation of 1 to a mammalian lignan 7, were isolated from a human fecal suspension. The former transformed 2 to 3 and 5, as well as 4 to 6, and the latter transformed 5 to 6 and 7.     

High-performance liquid chromatographic analysis of secoisolariciresinol diglucoside and hydroxycinnamic acid glucosides in flaxseed by alkaline extraction

A HPLC method was developed for the analysis of secoisolariciresinol diglucoside (SDG) and hydroxycinnamic acid glucosides in milled defatted flaxseed flour. Direct extraction by 1 M NaOH for 1 h at 20 degrees C resulted in a higher yield than that obtained by hydrolysis of alcoholic extracts. An internal standard, o-coumaric acid, was used and the method was found to be easy, fast, and with good repeatability. On dry matter basis, different samples of flaxseeds varied considerably in their content of (+)-SDG (11.9-25.9 mg/g), (-)-SDG (2.2-5.0 mg/g), p-coumaric acid glucoside (1.2-8.5 mg/g), and ferulic acid glucoside (1.6-5.0 mg/g).     

Validation of a reversed phase high performance thin layer chromatographic-densitometric method for secoisolariciresinol diglucoside determination in flaxseed

The validation of a HPTLC-densitometric method for the determination of secoisolariciresinol diglucoside (SDG) in flaxseed was performed improving the reproducibility of a previously reported HPTLC densitometric procedure by the use of fully wettable reversed phase plates (silica gel 60 RP18W F(254S), 10cmx10cm) with MeOH:HCOOH 0.1% (40:60, v/v) mobile phase. The analysis required only the alkaline hydrolysis in aqueous medium of undefatted samples and densitometry at 282nm of HPTLC runs. The method was validated following the protocol proposed by the Société Francaise des Sciences et Techniques Pharmaceutiques (SFSTP) giving rise to a dependable and high throughput procedure well suited to routine application. SDG was quantified in the range of 321-1071ng with RSD of repeatability and intermediate precision not exceeding 3.61% and accuracy inside the acceptance limits. Flaxseed of five cultivars of different origin was elected as test-bed.     

Separation and determination of secoisolariciresinol diglucoside oligomers and their hydrolysates in the flaxseed extract by high-performance liquid chromatography

Flaxseed contains the largest amount of lignan secoisolariciresinol diglucoside (SDG) oligomers and is the richest dietary source of SDG. SDG oligomers in the flaxseed extract are often hydrolyzed to break the ester linkages for the release of SDG and the glycosidic bonds for the release of secoisolariciresinol (SECO). The hydrolysates of SDG oligomers are complicated because of the production of esters in an alcohol-containing medium. In this study, a new gradient reversed-phase high-performance liquid chromatography (HPLC) method has been developed to be suitable for the separation and determination of: (1) SDG oligomers extracted from the defatted flaxseed powder by a 70% aqueous methanol solution; (2) SDG oligomers and their alkaline hydrolysates, including SDG, p-coumaric acid glucoside and its methyl ester, ferulic acid glucoside and its methyl ester in an alkaline hydrolytic solution; and (3) the succedent acid hydrolysates, including secoisolariciresinol monoglucoside (SMG), SECO, anhydrosecoisolariciresinol (anhydro-SECO), p-coumaric acid and its methyl ester, ferulic acid and its methyl ester, 5-hydroxymethyl-2-furfural (HMF) and its degradation product in an acid hydrolytic solution. The content of SDG oligomers in a defatted flaxseed powder was found to be 38.5 mg/g on a dry matter basis, corresponding to a SDG content of 15.4 mg/g, which was determined after alkaline hydrolysis. Furthermore, this study presented a major reaction pathway for the hydrolysis of SDG oligomers.     

On-line liquid-chromatography-nuclear magnetic resonance spectroscopy-mass spectrometry coupling for the separation and characterization of secoisolariciresinol diglucoside isomers in flaxseed

The effect of endcapping on an octdecyl bonded phase synthesized by the silanization/hydrosilation method is investigated. The endcapping reagent is a 1:1 molar ratio of trimethylchlorosilane (TMCS) and hexamethyldisilizane (HMDS). Two approaches for endcapping are possible for this synthetic method that produces a silica hydride intermediate: bonding of TMCS-HMDS after silanization (on the hydride intermediate) or after hydrosilation (on the C18 product stationary phase). The use of TMCS-HMDS is designed to eliminate the few remaining silanols on the silica hydride intermediate. The endcapping process is characterized spectroscopically by diffuse reflectance infrared Fourier transform (DRIFT), 29Si cross polarization magic angle spinning nuclear magnetic resonance spectroscopy (CP-MAS-NMR) and 13-C-CP-MAS-NMR. The octadecyl bonded phases are characterized chromatographically by measuring the capacity factors of several hydrophobic and basic test solutes as well as the separation factors among various solute pairs. Finally, long-term stability tests are done on both products at high and low pH.     

Chiral separation of the plant lignan matairesinol by capillary electrophoresis

Lignans are dimeric phenylpropanoid compounds in plants that enjoy increasing medicinal interest because of their phytoestrogen activity. Lignans are chiral compounds and for most natural occurring lignans, chirality is not known. Separation of racemic matairesinol by CE in a non-coated silica capillary with carboxymethyl-beta-cyclodextrin as chiral selector in phosphate buffer was successful. Electrolyte and selector concentrations and pH were systematically optimized in order to obtain baseline separation and short analysis times. Matairesinol from safflower fruit was determined as (-)-enantiomer. Quantitation results for matairesinol with the optimized method after calibration with authentic lignan were very similar to those by HPLC. The limit of detection is 2 microg/mL sample by DAD detection.     

New lignan glycosides from Chinese medicinal plant,Sinopodophillum emodi

Two new podophillotoxin glucosides, L-picropodophillotpxin 7'-O-(beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranoside) (2) and L-picropodophillotpxin 7'-O-beta-D-glucopyranoside (3), were isolated from Chinese medicinal plant, Sinopodophillum emodi, together with 4 known compounds, podophillotoxin (1), podorhizol 4'-O-beta-D-glucopyranoside (4), deoxypodophillotoxin (5), and dehydropodophillotoxin (6). The structures of 2 and 3 were finally determined by the extensive decouping and nuclear Overhauser effect (NOE) experiments in NMR spectra and circular dichroism (CD) spectra. Compound 2 is the second example of podophillotoxin diglucoside, and both the first one and 2 were isolated from S. emodi. X-ray crystal structure analysis of 1, 5, and 6 was carried out. Compounds 1 and 5 showed the different conformations from those reported.     

Sylvone, a new furanoid lignan of

The structure of a novel 2,3,4- trisubstituted furanoid lignan, designated sylvone, was established as from detailed spectroscopical and chemical studies.     

Isolation of secoisolariciresinol diglucoside from lignan-containing extract of <Emphasis Type="Italic">Linum usitatissimum</Emphasis> seeds

An effective method for obtaining secoisolariciresinol diglucoside (SDG) purified of lignan from extract of Linum usitatissimum seeds was proposed. The lignan-containing concentrate obtained by aqueous ethanol extraction with microwave irradiation was purified using column chromatography. The structure of the compound was confirmed using IR, mass, and NMR spectra. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 21-23, January–February, 2009.     

Metal chelation aptitudes of bis(o-azaheteroaryl)methanes as tuned by heterocycle charge demands

We describe the synthesis of a number of 1,3-azol-2-yl-, 1,3-benzazol-2-yl-, and azinyl-based bis(o-azaheteroaryl)methanes (LH, L(-) = Het(2)CH(-)) and their coordinating properties toward divalent transition metals (Zn, Cu, Co, Ni, Hg, Pd). This extended investigation includes both symmetrical and unsymmetrical ligands based on several substituted and/or unsubstituted thiazole, benzothiazole, benzoxazole, benzimidazole, pyridine, and quinoline derivatives. Depending on the structure and electron properties of the ligand, a vast set of neutral chelates ML(2) were obtained, where the ligand is present in its carbanionic form L(-). Additionally, we have prepared salt complexes [M(LH)(n)]X(m), where the ligand is present as a neutral system. Neutral chelates were typically obtained by the reaction of the ligand with metal acetates in alcoholic solution; salt complexes were formed by reaction with other metal salts such as chlorides. By exploring the coordinating properties of several bisheteroarylmethane ligands based on heteroaromatics of variable pi-electron structure and substitution pattern, we demonstrate that the formation of neutral chelates is strictly dependent on the electron-withdrawing capacity (charge demand) of the heteroaromatic moiety. The latter primarily dictates the efficiency by which the negative charge of the anionic ligand L(-) is stabilized by delocalization in ML(2) and, therefore, the stability of the chelate itself. On the basis of the large number and the variable nature of the nitrogen ligands used, we confirm the general validity of the charge-demand-dependent formation of chelates. This key factor can therefore be used for the efficient design of new pi-deficient heteroaromatic nitrogen ligands in chelates of great potential in many synthetic, catalytic, and technological fields.     

The total synthesis of sevanol,a novel lignan isolated from the thyme plant (Thymus armeniacus)

Recently, a novel lignan sevanol was isolated from the thyme plant Thymus armeniacus. During structure-functional elucidation it showed significant biological activity on ASIC3 acid sensing channels. Herein we describe the first synthesis of sevanol with a 3% overall yield. The construction of a dihydronaphthalene ring by oxidative dimerization of a protected dihydroxycinnamic acid ester in the presence of ferric chloride (III) is a key step in this first total synthesis of sevanol.     

Alkali metal chelation by diacetamide

Proton NMR spectroscopy indicates that diacetamide exists as an equilibrium mixture of Z,Z and E,Z diastereomers in methanol solution. Addition of Lil, Na1 or K1 (configurational titration) shifts the quilibrium because of bidentate complexation (chelation) by the amide carbonyl oxygens.     

(+)-Africanal,a new lignan of the aryltetrahydronaphthalene class

The absolute configuration (1R,2R,3R,3aS) and structural relationships of africanal, a novel lignan from Olea africana, are defined.     

Officinalioside,a new lignan glucoside from Borago officinalis L.

A new lignan glucoside, officinalioside (1), was isolated from n-BuOH fraction of the aerial parts of Borago officinalis L., together with four known compounds: actinidioionoside (2), roseoside (3), crotalionoside C (4) and kaempferol 3-O-β-D-galactopyranoside (5). The structure of the new compound was established by means of spectroscopic and chemical analyses. Compounds 1 and 2 showed a moderate DPPH radical scavenging activity (IC₅₀: 52.6 ± 1.70 and 41.3 ± 0.25 μM, respectively) comparable with that of the standard trolox (16.6 ± 2.2 μM) without any significant cytotoxicity towards human cell line A549 (IC₅₀ > 100 μM).     

Hydrogen-bond driven assembly of a molecular capsule facilitated by supramolecular chelation

Resorcinarene-based cavitands functionalized with acetamido groups capable of self-complementary hydrogen-bond interactions, were synthesized in order to construct supramolecular capsules. The 1,3-bifunctionalized cavitand produced a polymeric assembly, whereas the tetra-functionalized analogue yielded a discrete capsule held together via N-H···O hydrogen bonds. The ethynyl species attached to the rim of these host molecules deepen each cavitand and expands the volume of the resulting capsule.     

Fluoride ion chelation by a bidentate phosphonium/borane Lewis acid

The phosphonium borane [1-Mes2B-2-MePh2P-(C6H4)]+ ([2]+) has been synthesized as an iodide salt by alkylation of 1-Mes2B-2-Ph2P-(C6H4) with MeI. This novel cationic borane complexes fluoride to afford the corresponding zwitterionic fluoroborate complex 1-FMes2B-2-MePh2P-(C6H4) (2-F) with a binding constant in MeOH exceeding that of 1-Mes2B-4-MePh2P-(C6H4) ([1]+) by at least 4 orders of magnitude. Structural and computational results indicate that the high fluorophilicity of [2]+ arises from both Coulombic and cooperative effects which lead to formation of a B-F-->P interaction with a F-->P distance of 2.666(2) A. These results, which are supported by NBO and AIM analyses, show that the latent phosphorus-centered Lewis acidity of the phosphonium moiety in [2]+ can be exploited to enhance fluoride binding via chelation.