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Natural products and traditional medicine products with known safety profiles are a promising source for the discovery of new drug leads. Natural products as sesame were reported to exhibit potential to protect from COVID-19 disease. In our study, the total methanolic extract of Sesamum indicum L. seeds (sesame) were led to isolation of seven known compounds, five lignan; sesamin 1, sesamolin 2, pinoresinol 3, hydroxymatairesinol 6, spicatolignan 7, together with two simple phenolic compounds; ferulic acid 4 and vanillic acid 5. All isolated compounds were evaluated in silico against three important SARS-CoV-2 protein targets; main protease (Mpro), papain-like protease (PLpro) and RNA-dependent RNA polymerase (RdRp) which possessed crucial role in replication and proliferation of the virus inside the human cell. The results revealed that compound 6 has the high affinity against the three main proteins, specially towards the SARS-CoV-2 Mpro that exceeded the currently used SARS-CoV-2 Mpro inhibitor darunavir as well as, exhibiting a similar binding energy at SARS CoV-2 PLpro when compared with the co-crystallized ligand. This activity continued to include the RdRp as it displayed a comparable docking score with remdesivir. Inferiorly, compounds 1 and 2 showed also similar triple inhibitory effect against the three main proteins while compound 7 exhibited a dual inhibitory effect against SARS CoV-2 PLPro and RdRp. Further molecular dynamic simulation experiments were performed to validate these docking experiments and to calculate their binding free energies (ΔGs). Compounds 1, 2, 3, 6, and 7 showed comparable binding stability inside the active site of each enzyme with ΔG values ranged from −4.9 to −8.8 kcal mol−1. All the compounds were investigated for their ADME and drug likeness properties, which showed acceptable ADME properties and obeying Lipinski's rule of five parameters. It can be concluded that the isolated compounds from sesame lignans could be an alternative source for the development of new natural leads against COVID-19.

A scalable, fixed-bed adsorption system for the removal and selective recovery of polyphenols (lignans and stilbenes) from medium-density fiberboard (MDF) process waters was developed. Before adsorption, fibers and non-colloidal substances were removed from process water by centrifugation, while colloidal fatty and resin acids were removed by filtration through a 30-kDa cut-off membrane. Polyphenols were then isothermally adsorbed on a medium-pressure liquid chromatography (MPLC) column packed with Divergan® RS, a regenerable macroporous, cross-linked pyrrolidone-based [polyvinylpolypyrrolidone (PVPP)] resin. Loading at acidic pH and subsequent gradient elution of polyphenols with methanol were monitored at 280 nm, and elution conditions for selective polyphenol recovery were optimized based on gas chromatography/mass spectrometry (GC/MS) analyses of the obtained fractions. Lignans were eluted in successive fractions containing the individual lignans in different proportions, followed by pinosylvin in a separate fraction. The capacity of the PVPP for hydroxymatairesinol (HMR) as a model lignan was determined to be 37.4 mg g−1 at 1% breakthrough. Highly polar substances such as sugars and sugar alcohols, however, were not retained on the column and remained in the flow-through. The results revealed the benefits of PVPP for the recovery of potentially valuable polyphenols from MDF process waters while reducing carbon load and toxicity for subsequent biological treatment.

openaire: EC/H2020/730872/EU//CALIPSOplus Lignans are bioactive compounds that are especially abundant in the Norway spruce (Picea abies L. Karst.) knotwood. By combining a variety of chromatographic, spectroscopic and imaging techniques, we were able to quantify, qualify and localise the easily extractable lignans in the xylem tissue. The knotwood samples contained 15 different lignans according to the gas chromatography-mass spectrometry analysis. They comprised 16% of the knotwood dry weight and 82% of the acetone extract. The main lignans were found to be hydroxymatairesinols HMR1 and HMR2. Cryosectioned and resin-embedded ultrathin sections of the knotwood were analysed with scanning transmission X-ray microscopy (STXM). Cryosectioning was found to retain only lignan residues inside the cell lumina. In the resin-embedded samples, lignan was interpreted to be unevenly distributed inside the cell lumina, and partially confined in deposits which were either readily present in the lumina or formed when OsO4 used in staining reacted with the lignans.Furthermore, the multi-technique characterisation enabled us to obtain information on the chemical composition of the structural components of knotwood. A simple spectral analysis of the STXM data gave consistent results with the gas chromatographic methods about the relative amounts of cell wall components (lignin and polysaccharides). The STXM analysis also indicated that a torus of a bordered pit contained aromatic compounds, possibly lignin.

Lignans are bioactive compounds that are especially abundant in the Norway spruce (Picea abies L. Karst.) knotwood. By combining a variety of chromatographic, spectroscopic and imaging techniques, we were able to quantify, qualify and localise the easily extractable lignans in the xylem tissue. The knotwood samples contained 15 different lignans according to the gas chromatography-mass spectrometry analysis. They comprised 16% of the knotwood dry weight and 82% of the acetone extract. The main lignans were found to be hydroxymatairesinols HMR1 and HMR2. Cryosectioned and resin-embedded ultrathin sections of the knotwood were analysed with scanning transmission X-ray microscopy (STXM). Cryosectioning was found to retain only lignan residues inside the cell lumina. In the resin-embedded samples, lignan was interpreted to be unevenly distributed inside the cell lumina, and partially confined in deposits which were either readily present in the lumina or formed when OsO4 used in staining reacted with the lignans. Furthermore, the multi-technique characterisation enabled us to obtain information on the chemical composition of the structural components of knotwood. A simple spectral analysis of the STXM data gave consistent results with the gas chromatographic methods about the relative amounts of cell wall components (lignin and polysaccharides). The STXM analysis also indicated that a torus of a bordered pit contained aromatic compounds, possibly lignin.

Epoxidation of the C=C double bond in unsaturated norlignans derived from hydroxymatairesinol was studied. The intermediate epoxides were formed in up to quantitative conversions and were readily further transformed into tetrahydrofuran, aryltetralin, and butyrolactone products&mdash, in diastereomeric mixtures&mdash, through ring-closing reactions and intramolecular couplings. For epoxidation, the classical Prilezhaev reaction, using stoichiometric amounts of meta-chloroperbenzoic acid (mCPBA), was used. As an alternative method, a catalytic system using dimeric molybdenum-complexes [MoO2L]2 with ONO- or ONS-tridentate Schiff base ligands and aqueous tert-butyl hydroperoxide (TBHP) as oxidant was used on the same substrates. Although the epoxidation was quantitative when using the Mo-catalysts, the higher temperatures led to more side-products and lower yields. Kinetic studies were also performed on the Mo-catalyzed reactions.

The biosynthetic potential for six lignans accumulation in two lines of Taxus x media hairy roots was investigated. The cultures of KT and ATMA hairy root lines were supplemented with precursors: coniferyl alcohol (CA 1, 10 or 100 µM) and/or l-phenylalanine (100 µM PHEN) and/or methyl jasmonate (100 µM MeJa). Moreover the two-phase in vitro cultures supported with perfluorodecalin (PFD) as a gas carrier and in situ extrahent were used. The hairy root lines differed in lignan production profiles. In the control untreated cultures KT roots did not accumulate secoisolariciresinol and lariciresinol while ATMA roots did not accumulate matairesinol. In ATMA roots the treatment with CA (1 or 10 µM) resulted in the production of lariciresinol and secoisolariciresinol whereas solely lariciresinol was present after 100 µM CA application. Elicitation with 1 µM CA and MeJa yielded with hydroxymatairesinol aglyca and lariciresinol glucosides with their highest content 37.88 and 3.19 µg/g DW, respectively. The stimulatory effect of simultaneous treatment with 1 µM CA, PHEN and MeJa on lignan production was observed when the cultures were supplemented with PFD-aerated or degassed. In ATMA root cultures these applied conditions were the most favourable for matairesinol content which amounted to 199.86 and 160.25 µg/g DW in PFD-aerated and PFD-degassed supported cultures, respectively. In KT root cultures solely, hydroxymatairesinol and coniferin/CA content was enhanced with their highest yield 59.29 and 134.60 µg/g DW in PFD-aerated and PFD-degassed cultures, respectively.

The preparation of 7R-HMR (allo-hydroxymatairesinol) is reported by: (a) NaBH4 kinetic reduction of 7R/7S diastereomeric mixture, and (b) epimerization of the C7 hydroxyl group by Mitsunobu reaction and subsequent ester hydrolysis. The availability of highly pure target compound (7R-HMR) made it possible to confirm the structure of the target compound and to complete the full spectroscopic characterization.

Lignans are generally known for their beneficial impact on human health. In this study, we found that the water extract of silver fir (Abies alba) wood contains lignans, which constitute approximately 10% of the extract and include isolariciresinol, hydroxymatairesinol, secoisolariciresinol, lariciresinol, pinoresinol, and matairesinol. The antioxidant activity of the extract was measured by several in vitro assays and an assay in a eukaryotic cell model (yeast). The extract had greater in vitro antioxidative activity than ascorbic acid, resveratrol, or butylated hydroxytoluene (BHT) and similar antioxidative activity to epigallocatechin gallate. The intracellular antioxidant effect in the yeast gave indirect evidence that the components of the silver fir wood extract (SFWE) effectively pass through eukaryotic cell membranes and have higher in vivo antioxidative activity than ascorbic acid, resveratrol, tocopheryl succinate, or BHT and similar to epigallocatechin gallate. The in vitro gastrointestinal dig...

Lignans are natural products widely distributed in the plant kingdom. They are composed of two β-β-linked phenylpropane (shikimate-derived biogenetic subunits). Although the backbone of lignans is composed of phenylpropane units, there is enormous diversity in the structure of lignans leading to different classes of lignans, such as γ-butyrolactone derivatives, eg. Hymatairesinol, bicyclooctadiene derivatives, e.g. pinoresinol, tetrahydrofuran derivatives e.g.lariciresinol, di-arylbutandiol derivatives, e.g. secoisolariciresinol. Introduction of a further carbon –carbon linkage leads to a class of lignans collectively known as cyclolignans such as tetrahydro-naphthalene derivatives, for example podophyllotoxin. Lignans have a broad range of biological activities; many of them show significant antitumour, antimitotic, and antiviral effects. They also have cardiovascular effects, antimicrobial and insecticidal activities. The efflux mechanisms of bacteria to some antibiotics and resistance of bacteria to many antibiotics led to search for antibacterial compound of plant origin to overcome these problems. The antibacterial activity of HMR lignan was determined using the disc diffusion method and the MIC of the isolated compound was tested by the broth micro-dilution method. HMR lignan showed activity against Staphylococcus epidermidis(17 mm), Candida albicans (13mm), Proteussp(12mm) and Klebsiella sp (12mm). Key words: Lignans, Hydroxymatiaresinol, Antimicrobial activity

Lignans, neolignans, norlignans and norneolignans constitute a large class of phenolic natural compounds. 9-Norlignans, here defined to contain a &beta, &ndash, &beta, &rsquo, bond between the two phenylpropanoid units and to lack carbon number 9 from the parent lignan structure, are the most rarely occurring compounds within this class of natural compounds. We present here an overview of the structure, occurrence and biological activity of thirty-five 9-norlignans reported in the literature to date. In addition, we report the semisynthetic preparation of sixteen 9-norlignans using the natural lignan hydroxymatairesinol obtained from spruce knots, as starting material. 9-Norlignans are shown to exist in different species and to have various biological activities, and they may therefore serve as lead compounds for example for the development of anticancer agents. Hydroxymatairesinol is shown to be a readily available starting material for the preparation of norlignans of the imperanene, vitrofolal and noralashinol family.

Key message Fungal infection was outlined as a potential reason for the onset of indented annual growth ring formation during the juvenile phase of hazel wood growth. Annual growth ring indentations resulted from the formation of disturbed zones which originated solely in close proximity to leaf traces. Context Hazel wood is an abnormal type of woody tissue that is formed as a result of exogenous stimuli that may trigger long-term responses in the cambium. Cambial responses produce anatomical alterations in the surrounding xylem tissue that can be observed as an indentation of annual growth rings. The chemical profiles of lignan hydroxymatairesinol may provide an indication of its possible role in the protection of a living tree against the spread of a fungal or microbial infection at the onset of indentation. Aims The objectives of this study were to reveal the anatomical differences in the altered woody tissue of Picea abies hazel wood at both the onset and the later stages of annual growth ring indentation and to determine the chemical profiles for hydroxymatairesinol upon elicitation by a fungal infection in the disturbed zones. Methods Light and scanning electron microscopy observations were carried out on radial, tangential, and cross sections of hazel wood zones separated from P. abies stems. Concentrations of hydroxymatairesinol were determined for both the disturbed zones and the non-indented zones using a gradient high-performance liquid chromatography. Results The formation of disturbed zones was accompanied by significant changes in both the direction and width of the tracheids which produced an abnormal formation of intertwined and twisted tracheids. Fungal hyphae, radial cell wall cracks, and unusually large cross-field pitting were all found in the tracheids of the disturbed zones. Conclusion The content of hydroxymatairesinol in the acetone extract determined from the disturbed zones was 3.4 times greater than that present in the non-disturbed tissues. By means of vascular dysfunction in the leaf traces, host trees responded to the fungal infection by plugging the lumens of conductive leaf trace tissue and filling the vascular pathway with polyphenolic compound deposits.

The structures of the naturally occurring lignan hydroxymatairesinol (HMR) and TADDOL-like α -conidendrin-based chiral 1,4-diols (LIGNOLs) have been studied at DFT/B3LYP/TZVP level of theory, for the first time applying the density functional dispersion correction (DFT-D3) [1] and employing the BJ-damping (-D3(BJ)) [2] . This study establishes the necessity of treating the dispersion interactions properly in DFT optimizations. Several of the conformers received were not found in previous studies and the 4Ph4 structure received applying D3 is now published for the first time as a quantum chemically optimized structure.

The heterogeneously catalyzed aerobic selective oxidation of naturally occurring lignan hydroxymatairesinol (HMR) to another lignan oxomatairesinol (oxoMAT) was carried out at 70 °C and atmospheric pressure over gold nanoparticles with different sizes supported on alumina prepared from organo-metallic precursor by the sol–gel method. Precursor of gold nanoparticles (i.e. gold hydroxide) was supported on alumina by deposition–precipitation with urea from HAuCl 4 aqueous solution followed by washing with ammonium hydroxide. The size of the supported gold nanoparticles was changed by either treatment under hydrogen flow at different temperatures or exposure to ultraviolet (UV) irradiation at the wavelength of 254 nm. The catalysts were characterized by inductively coupled plasma atomic emission spectroscopy (ICP-AES), nitrogen adsorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), and UV–visible spectroscopy (UV–vis). Structure sensitivity in HMR oxidation was studied showing that the reaction rate passes through a maximum when the gold cluster size is ca. 4 nm.

Highly efficient methods for synthetic modifications of the natural lignan hydroxymatairesinol into chiral diphosphines similar to DIOP were developed. Catalytic activity and induction of enantioselectivity for the prepared phosphines were evaluated in rhodium catalyzed hydrogenations of different functionalized alkenes. High catalytic activities were observed with low catalyst loading at atmospheric pressure. The phosphines showed moderate to high enantioselectivity depending on the substrate used. Hydrogenation of 1-acetamidostyrene gave 84% ee of the S -enantiomer.

The lignan 7′-hydroxymatairesinol (1), extracted from the knotwoods of fir (Abies alba), spruce (Picea abies), and Douglas fir (Pseudotsuga menziesii), exhibited unexpected reactivity when esterification reactions were attempted on the hydroxy group at position C-7′. To circumvent the rapid intramolecular cyclization procedure, leading quantitatively to the lignan conidendrin (7), a simple strategy for 7′-esterification of 1 under mild conditions (three steps, up to 80% overall yield) was developed. Compared to hydroxymatairesinol (1) (log K′w = 1.49), the derivatives (2–5) had increased lipophilicity with log K′w > 3.1, as determined by a UHPLC method. Compounds 1–5 exhibited potent antioxidant properties in the same range as the standards ascorbic acid and α-tocopherol (IC50 = 20–25 μM) and higher than that of BHT using a DPPH radical-scavenging assay.

Structure sensitivity in heterogeneous catalytic oxidative dehydrogenation of lignan hydroxymatairesinol (HMR) extracted from Norway spruce knots was investigated over a series of alumina-supported gold catalysts. A mathematical model was developed based on the concept of noncompetitive adsorption of reactants. The model, being consistent with kinetic regularities, such as reaction orders in reactants, explains well the dependence of catalytic activity on the gold cluster size.

Methods for synthetic modifications of the natural dibenzylbutyrolactone lignan hydroxymatairesinol into chiral 1,4-diols with different lignan-derived backbones have been developed. A stepwise procedure, involving alkylation and oxidation, was shown to be successful and several highly substituted 1,4-diols were prepared. Some substituted butyrolactones resisted alkylation and led to the formation unusually stable hemiketals (butyrolactols). The formation of stable hemiketals was investigated in detail, showing that different backbone structures influence the formation and reactivity of the hemiketals.

Flaxseed is a major source of lignans, which are important bioactive compounds. The aims of this work were to validate a liquid chromatographic method for the rapid and simultaneous determination of the main lignans in flaxseed using high-performance liquid chromatography coupled with electrochemical detection and to analyze the composition of commercial samples of flaxseed. The performance criteria of the proposed method demonstrate that the method can be used for the analysis of secoisolariciresinol diglucoside (SDG), secoisolariciresinol (SECO), matairesinol (MATA), pinoresinol (PINO), lariciresinol (LARI), hydroxymatairesinol (HYDROXY), and isolariciresinol (ISOLARI) in flaxseeds at suitable levels. Calibration curves were determined for six different concentrations of standard solutions injected in triplicate. The sensitivity of the calibration curve was evaluated considering the confidence intervals of the intercept and slope. The limit of detection and limit of quantification were 7.4 and 10.9 μg/l, respectively, for LARI and 17.7 and 37.5 μg/l, respectively, for MATA. The relative standard deviation of repeatability values were lower than 2.59 %, which are acceptable because the Horwitz ratio values were 0.1 for all of the lignans. The recoveries of lignans were in the range of 74–100 % of SECO, which are consistent with the literature. The precision of the proposed method was determined by analyzing four flaxseed samples of different years and varieties. SDG was the main lignan present in all the samples, followed by ISOLARI and HYDROXY.

Bioactive compounds of acetone-water extracts obtained from the root neck (RN) of Norway spruce (Picea abies [L.] Karst.) have been studied for the first time. RN samples were divided into different zones and cut, and wood and bark were extracted separately with acetone-water. The extracts were analyzed by gas chromatography-mass spectrometry. The extractives have a tissue-specific distribution. Several lignans were identified in the heartwood. High concentrations (10%) of hydroxymatairesinol were found from the heartwood at the lowermost part of the RN. The inner part of the bark contained the highest concentrations of stilbene glucosides (20%), which were present in the outer bark only to a minor extent (0.2%). Pressurized hot water extraction was also applied and was found to be effective in separating lignans from biomass. Norway spruce roots and stumps are usually utilized for gaining bioenergy. The results presented here show that these abundant residual materials of forest economy may be a valuable source of highly bioactive compounds such as the lignan hydroxymatairesinol and stilbenes.

The readily available natural lignan hydroxymatairesinol was transformed into sterically hindered and optically pure diphenyl, di-2-naphthyl, and tetramethyl 1,4-diol derivatives via arylation/alkylation of the aryltetralinbutyrolactone lignan (−)-conidendrin. In addition, the diastereoselective formation of stable hemiketals from the highly substituted butyrolactone was studied in detail. The conformations of the molecules prepared were studied computationally at molecular mechanics (MM), Hartree–Fock (HF)/6-31G ∗ , and (DFT/B3LYP/TZVP) levels including entropy contributions and by NMR-spectroscopy. The conformations adopted showed that these novel chiral 1,4-diols may be suitable as chiral ligands for the development of new chiral transition metal and organo catalysts.

Despite the extensive literature describing the biological effects of phenolic compounds from cereals, little is known about their bioaccessibility in the food matrix. This paper describes a validated LC-MS/MS method for the quantification of free and total content (free + bound) of eight plant lignans (matairesinol, hydroxymatairesinol, secoisolariciresinol, lariciresinol, isolariciresinol, syringaresinol, medioresinol, and pinoresinol) and two enterolignans (enterodiol and enterolactone) in cereal-based diets/bread and feces. The method consisted of alkaline methanolic extraction combined with enzymatic hydrolyses, for the measurement of the total concentration of lignans, and methanolic extraction combined with enzymatic hydrolysis, for the measurement of free lignans, followed by solid phase extraction (SPE). The strength of this LC-MS/MS method is that it can be combined with different types of samples, because the SPE and LC-MS/MS platforms are similar to our previously published method for plasma and urine.

The main goal of this work was optimization of GC-MS method for the analysis of lignans trimethylsilyl (TMSi-) derivatives of two model compounds hydroxymatairesinol(HMR) and enterolactone (ENTL). It included validation of GC-MS metod for TMSiHMR and TMSi-ENTL, comparison of chosen derivatization reagents and verification of time stability for TMSi-HMR. It was shown that TMSi-HMR and TMSi-ENTL provide a nonlinear calibration curve. Second order polynomial curve gave the best fitting and was used for method validation. N-Methyl-N-(trimethylsilyl)trifluoroacetamide activated I and II (Sigma Aldrcih) were selected as the best choice for simultaneous derivatization for HMR and ENTL mixture. Room temperature was confirmed to be appropriat for 3 days storage of TMSi-HMR. Also it was shown that storage at -80 °C preserve the lignan samples for at least 90 days storage.

Dietary lignans show some promising health benefits, but little is known about their fate and activities in the small intestine. The purpose of this study was thus to investigate whether plant lignans are taken up by intestinal cells and modulate the intestinal inflammatory response using the Caco-2 cell model. Six lignan standards [secoisolariciresinol diglucoside (SDG), secoisolariciresinol (SECO), pinoresinol (PINO), lariciresinol, matairesinol (MAT), and hydroxymatairesinol] and their colonic metabolites [enterolactone (ENL) and enterodiol] were studied. First, differentiated cells were exposed to SDG, SECO, PINO, or ENL at increasing concentrations for 4 h, and their cellular contents (before and after deconjugation) were determined by HPLC. Second, in IL-1β-stimulated confluent and/or differentiated cells, lignan effects were tested on different soluble proinflammatory mediators quantified by enzyme immunoassays and on the NF-κB activation pathway by using cells transiently transfected. SECO, PINO, and ENL, but not SDG, were taken up and partly conjugated by cells, which is a saturable conjugation process. PINO was the most efficiently conjugated (75% of total in cells). In inflamed cells, PINO significantly reduced IL-6 by 65% and 30% in confluent and differentiated cells, respectively, and cyclooxygenase (COX)-2-derived prostaglandin E(2) by 62% in confluent cells. In contrast, MAT increased significantly COX-2-derived prostaglandin E(2) in confluent cells. Moreover, PINO dose-dependently decreased IL-6 and macrophage chemoattractant protein-1 secretions and NF-κB activity. Our findings suggest that plant lignans can be absorbed and metabolized in the small intestine and, among the plant lignans tested, PINO exhibited the strongest antiinflammatory properties by acting on the NF-κB signaling pathway, possibly in relation to its furofuran structure and/or its intestinal metabolism.

Acetone-soluble compounds found in different root zones and stumps of Norway spruce (Picea abies [L.] Karst), which were grown on either peatland or a mineral soil site, were studied. Samples from stumps and roots of different sizes and ages were collected a day after the trees were felled. The wood and bark of stumps and three zones of the roots were separated and extracted with acetone in an ultrasonic bath. Extracts were silylated and analysed by gas chromatography–mass spectrometry. The stilbene glucosides astringin and isorhapontin were major compounds in the spruce bark samples. The resveratrol glucoside piceid and the flavonoid catechin were also extracted from spruce bark. We also found the lignan hydroxymatairesinol in some wood extracts. Total concentrations of stilbene glucosides in bark of stumps and different root zones varied between 0.53 and 8.29 % (w/w, dry weight) with isorhapontin being the major compound. Isorhapontin concentrations were highest in the spruce samples grown on mineral soil. The bark of the roots close to the stem is a rich source of stilbenes for commercial utilisation.

Aerobic selective oxidation of the naturally occurring lignan hydroxymatairesinol (HMR) to another lignan oxomatairesinol (oxoMAT) was carried out at 70 °C and atmospheric pressure over different gold and gold–palladium catalysts. Several groups of gold catalysts were prepared: Au ion-exchanged on Y-zeolites promoted by Cu, Ni, Fe; Au and Au–Pd supported via deposition–precipitation with urea – DPU on metal oxides (magnesia, alumina, ceria, zirconia, and lanthanum oxide); and Au on alumina, and alumina–ceria–zirconia mixed oxides prepared by the sol–gel method. The catalysts were characterized by ICP-AES, TEM, XPS and UV–Vis techniques. Acidity of supports was studied by an FTIR method using pyridine as a probe molecule. No catalytic activity was detected in case of gold catalysts based on zeolites. Au and Au–Pd catalysts supported on metal oxides showed different activity and selectivity in the HMR transformation depending on the support acidity/basicity and the active phase. The highest activity was reached over Au supported on alumina with big transport pores displaying 100% selectivity to oxoMAT.

The lignan oxomatairesinol was synthesized from the biomass-derived lignan hydroxymatairesinol via selective aerobic oxidation over a heterogeneous gold catalyst. The catalyst was prepared by direct ion-exchange and characterized by XRD, TEM and ICP-OES methods. The reaction was carried out at 70 °C and atmospheric pressure in a semi-batch reactor. To reveal the origin of catalyst deactivation, spent catalysts were studied by TEM, XRD, nitrogen physisorption, ICP-OES, TPO, and DSC-TGA techniques. Several regeneration procedures were applied—extraction by several solvents and calcinations in the oxidizing atmosphere. The former one was found to be the most effective way for the catalyst regeneration.

Synthesis of the lignan oxomatairesinol via oxidative dehydrogenation of the naturally occurring lignan hydroxymatairesinol was studied over gold catalysts supported on C, TiO2, SiO2, Al2O3, and MgO. In order to investigate the reaction performance over the gold catalyst, synthesis of lignan oxomatairesinol was carried out in different organic solvents/water mixtures under synthetic air and nitrogen atmosphere at 373 K, and using also isolated hydroxymatairesinol isomers as a starting material. The results were compared with those obtained over palladium catalysts. Synthesized supported gold catalysts as well as the corresponding supports were characterized by TEM, XRD, ICP-OES, CO2-TPD, FTIR (using pyridine as a probe molecule), and XPS. Gold catalysts were shown to display superior performance compared with palladium ones: the activity was 4 times higher, with selectivity toward oxomatairesinol being 100%, while 60–85% were obtained over palladium catalysts. In contrast to palladium, the activity of gold catalysts is high in aerobic conditions and water–propan-2-ol mixture. However, activity and selectivity of gold catalysts were shown to be dependent on the electronic state of the metal and, similar to palladium catalysts, on the support acidity.

The structures of TADDOL-like α-conidendrin-based chiral 1,4-diols (LIGNOLs) have been studied at molecular mechanics, Hartree-Fock (HF)/6-31G* and DFT/B3LYP/TZVP level of theory. The molecules included were 1,1-diphenyl, two diastereomers of 1,1,4-triphenyl, 1,1,4,4-tetraphenyl, and 1,1,4,4-tetramethyl 1,4-diol. Several conformers of each molecule were studied thorougly also including the entropy contributions. For the triphenyl 1,4-diols, which can form π − π interactions between phenyl rings, the DFT optimized structures differed significantly from the HF optimized ones. A property for the most stable structures, in addition to the ability to form π − π interactions, seemed to be the possibility to have the aliphatic six-membered ring in a boat conformation. For all of the studied LIGNOLs some conformers were found, where the two OH groups pointed almost to the same direction. By this an intramolecular hydrogen bond can be formed between them. The bridging hydrogen atom falls at the same place as a chelate-bonded metal ion would be situated, as in the case of the analogous molecules, TADDOLs, but only a few of these molecules would be able to work well as ligands for asymmetric catalysis. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011