A Cytotoxic Neolignan from Schisandra propinqua （Wall.） Baill.

In the course of our study of bioactive natural products from Schisandra plants, we isolated a neolignan from an EtOAc extract of the stems of Schisandra propinqua （Wall.） Baill. The structure of the new com- pound was determined to be 4, 4-di （4-hydroxy-3-methoxyphenly）-2, 3-dimethylbutanol （compound 1） on the basis of 1H- and 13C-NMR spectra and 2D NMR methods. Eight known compounds, compounds 2-9, were also isolated and identified, of which compounds 3, 4, 6 and 9 were isolated for the first time from this plant. In addition, compounds 1-4 were evaluated for cytotoxicity by an 3-（4,5-dimethyl-2 thiazoyl）-2,5-diphenyl-2H- tetrazolium bromide （MTT） assay. Compound 1 showed significant potential cytotoxic ability in the bioassay.     

Chemical Diversity of Essential Oils from Asteriscus graveolens (Forssk.) Less.: Identification of cis‐8‐Acetoxychrysanthenyl Acetate as a New Natural Component

Asteriscus graveolens is an endemic medicinal plant mainly distributed in south‐western Algeria and south‐eastern Morocco. The essential oils of leaves, stems, and flowers of A. graveolens had been studied by GC, GC/MS, and ¹³C‐NMR. The spectral data of two nerolidol derivatives, 6‐oxo‐ and 6‐hydroxycyclonerolidol, were reassigned by 1D‐ and 2D‐NMR spectroscopy. These compounds can be considered as chemical markers of this genus. The structure of a monoterpenic diester with a chrysanthenane skeleton, i.e., cis‐8‐acetoxychrysanthenyl acetate, was determined for the first time on the basis of GC/MS, and 1D‐ and 2D‐NMR. The stem and leaf oils were characterized by high content of oxygenated sesquiterpenes with 6‐oxo‐ and 6‐hydroxycyclonerolidol as major components, and the flower essential oils were dominated by the new monoterpenic compound cis‐8‐acetoxychrysanthenyl acetate.     

Solution structure and function of YndB,an AHSA1 protein from Bacillus subtilis

The solution structure of the Bacillus subtilis protein YndB has been solved using NMR to investigate proposed biological functions. The YndB structure exhibits the helix‐grip fold, which consists of a β‐sheet with two small and one long α‐helix, forming a hydrophobic cavity that preferentially binds lipid‐like molecules. Sequence and structure comparisons with proteins from eukaryotes, prokaryotes, and archaea suggest that YndB is very similar to the eukaryote protein Aha1, which binds to the middle domain of Hsp90 and induces ATPase activity. On the basis of these similarities, YndB has been classified as a member of the activator of Hsp90 ATPase homolog 1‐like protein (AHSA1) family with a function that appears to be related to stress response. An in silico screen of a compound library of ～18,500 lipids was used to identify classes of lipids that preferentially bind YndB. The in silico screen identified, in order of affinity, the chalcone/hydroxychalcone, flavanone, and flavone/flavonol classes of lipids, which was further verified by 2D ¹H‐¹⁵N HSQC NMR titration experiments with trans‐chalcone, flavanone, flavone, and flavonol. All of these compounds are typically found in plants as precursors to various flavonoid antibiotics and signaling molecules. The sum of the data suggests an involvement of YndB with the stress response of B. subtilis to chalcone‐like flavonoids released by plants due to a pathogen infection. The observed binding of chalcone‐like molecules by YndB is likely related to thesymbiotic relationship between B. subtilis and plants. Proteins 2010. © 2010 Wiley‐Liss, Inc.     

Crassocolides G–M,Cembranoids from the Formosan Soft Coral Sarcophyton crassocaule

Seven new polyoxygenated cembranoids possessing an α‐methylene‐γ‐lactone group, crassocolides G–M ( 1 – 7 , resp.), have been isolated from the AcOEt extract of the Formosan soft coral Sarcophyton crassocaule. The structures of compounds 1 – 7 were established by detailed spectroscopic analyses, including 2D‐NMR spectroscopy (¹H,¹H‐COSY, HMQC, HMBC, and NOESY), while the absolute configuration of 1 was determined using a modified reaction of Mosher's method. The cytotoxicity of compounds 1 – 7 against a limited panel of cancer cell lines was also determined.     

A Novel Sulfated Holostane Glycoside from Sea Cucumber Holothuria leucospilota

A new sulfated holostane glycoside, leucospilotaside B ( 1 ), together with the two related structurally known compounds holothurin B₂ ( 2 ) and holothurin B ( 3 ), was isolated from sea cucumber Holothuria leucospilota collected from the South China Sea. The structure of 1 was elucidated by spectral analysis (¹H‐, ¹³C‐, and 2D‐NMR, ESI‐MS, and HR‐ESI‐MS) and chemical methods. The compounds 1 – 3 possess the same disaccharide moiety, but were different in the side chains of the triterpene aglycone. Compound 1 showed significant cytotoxicities against four human tumor cell lines, HL‐60, MOLT‐4, A‐549, and BEL‐7402.     

Synthesis, X-ray crystal structure and optical properties of novel 2-aryl-3-ethoxycarbonyl-4-phenylpyrido[1,2-a]benzimidazoles

A series of novel 2‐aryl‐3‐ethoxycarbonyl‐4‐phenylpyrido[1,2‐a]benzimidazole derivatives were synthesized by the tandem reaction of 2‐benzoyl benzimidazole and (Z)‐ethyl 4‐bromo‐3‐arylbut‐2‐enoate in the presence of potassium carbonate. The compounds were characterized using IR, ¹H‐NMR, ¹³C‐NMR, HRMS and the structure of 6f was further determined by X‐ray crystallography. Both absorption and fluorescence spectra characteristics of the compounds were investigated in acetonitrile and dichloromethane. The results showed that the absorption maxima of the compounds varied from 220 to 284 nm, depending on the structure of 2‐aryl group. The fluorescence results revealed that these compounds exhibited blue‐green fluorescence (463–475 nm) in dilute solutions and showed acceptable fluorescence quantum yields (Ф_PL = 0.13–0.73) in dichloromethane. Copyright © 2011 John Wiley & Sons, Ltd.     

13,14‐seco‐Withanolides from Physalis minima with Potential Anti‐inflammatory Activity

Four new 13,14‐seco‐withanolides, minisecolides A – D ( 1  –  4 ), together with three known analogues 5  –  7 , were isolated from the whole plants of Physalis minima. The structures of new compounds were determined on the basis of spectroscopic analysis, including ¹H‐, ¹³C‐NMR, 2D‐NMR (HMBC, HSQC, ROESY), and HR‐ESI‐MS. Evaluation of all isolates for their inhibitory effects on nitric oxide (NO) production was conducted on lipopolysaccaride‐activated RAW264.7 macrophages. Compounds 2 , 3 , 5 , and 6 showed inhibitory activities, especially for compound 5 with IC₅₀ value of 3.87 μm .     

Design,Synthesis and in Vitro Tumor Cytotoxicity Evaluation of 3,5‐Diamino‐N‐substituted Benzamide Derivatives as Novel GSK‐3β Small Molecule Inhibitors

Glycogen synthase kinase‐3 (GSK‐3) plays an important regulatory role in various signaling pathways; such as PI3 K/AKT, which is closely related to the occurrence and development of tumors. At present, the most reported active GSK‐3 inhibitors have the same structure: lactam ring or amide structure. To find out the GSK‐3β small molecule inhibitor with novel, safe, efficient and more uncomplicated synthesis method, we analyzed in‐depth reported crystal‐binding patterns of GSK‐3β small molecule inhibitor with GSK‐3β protein, and designed and synthesized 17 non‐reported 3,5‐diamino‐N‐substituted benzamide compounds. Their structures were confirmed by ¹H‐NMR, ¹³C‐NMR, and HR‐MS. The preliminary screening of tumor cytotoxicity of compounds in vitro was detected by MTT, and their structure–activity relationships were illustrated. The results have shown that 3,5‐diamino‐N‐[3‐(trifluoromethyl)phenyl]benzamide ( 4d ) exhibited significant tumor cytotoxicity against human colon cancer cells (HCT‐116) with IC₅₀ of 8.3 μm and showed commendable selectivity to GSK‐3β. In addition, Compound 4d induced apoptosis to some extent and possessed modest PK properties.     

Synthesis,crystal structure,optical properties and antibacterial evaluation of novel imidazo[1, 5‐a]pyridine derivatives bearing a hydrazone moiety

A series of novel imidazo[1,5‐a]pyridine‐hydrazone derivatives were synthesized and characterized by infrared spectroscopy (IR), ¹H NMR, ¹³C NMR and high resolution mass spectrometer (HRMS). Typically, the spatial structure of compound 3j was determined using X‐ray diffraction analysis. The UV–vis absorption and fluorescence spectral characteristics of the compounds in dichloromethane and acetonitrile were investigated. Absorption peaks could be observed in the wavelength range 290–450 nm. It can also be seen that they display very similar maximum emission. The group attached to hydrazone hardly influenced the maximum emission. Furthermore, all the compounds were evaluated for antibacterial activity and were found to be more effective against Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, Salmonella typhimurium, Pseudomonas aeruginosa and Shigella compared with chloramphenicol. Copyright © 2013 John Wiley & Sons, Ltd.     

Structural and dynamical characterization of tubular HIV‐1 capsid protein assemblies by solid state nuclear magnetic resonance and electron microscopy

The wild‐type HIV‐1 capsid protein (CA) self‐assembles in vitro into tubular structures at high ionic strength. We report solid state nuclear magnetic resonance (NMR) and electron microscopy measurements on these tubular CA assemblies, which are believed to contain a triangular lattice of hexameric CA proteins that is similar or identical to the lattice of capsids in intact HIV‐1. Mass‐per‐length values of CA assemblies determined by dark‐field transmission electron microscopy indicate a variety of structures, ranging from single‐wall tubes to multiwall tubes that approximate solid rods. Two‐dimensional (2D) solid state ¹³C? ¹³C and ¹⁵N? ¹³C NMR spectra of uniformly ¹⁵N,¹³C‐labeled CA assemblies are highly congested, as expected for a 25.6 kDa protein in which nearly the entire amino acid sequence is immobilized. Solid state NMR spectra of partially labeled CA assemblies, expressed in 1,3‐¹³C₂‐glycerol medium, are better resolved, allowing the identification of individual signals with line widths below 1 ppm. Comparison of crosspeak patterns in the experimental 2D spectra with simulated patterns based on solution NMR chemical shifts of the individual N‐terminal (NTD) and C‐terminal (CTD) domains indicates that NTD and CTD retain their individual structures upon self‐assembly of full‐length CA into tubes. 2D ¹H‐¹³C NMR spectra of CA assemblies recorded under solution NMR conditions show relatively few signals, primarily from segments that link the α‐helices of NTD and CTD and from the N‐ and C‐terminal ends. Taken together, the data support the idea that CA assemblies contain a highly ordered 2D protein lattice in which the NTD and CTD structures are retained and largely immobilized.     

Rubrolides as Model for the Development of New Lactones and Their Aza Analogs as Potential Photosynthesis Inhibitors

Natural phytotoxins and their synthetic analogs are a potential source of new bioactive compounds for agriculture. Analogs of rubrolides, a class of γ‐alkylidene‐γ‐lactones isolated from different ascidians, have been shown to interfere with the photosynthetic electron‐transport chain, yet their activity needs to be improved. With this aim, ten 5‐aryl‐6‐benzyl‐4‐bromopyridazin‐3(2H)‐ones were prepared in yields ranging from 44 to 88% by reaction of their correspondent γ‐alkylidene‐γ‐lactones with NH₂NH₂. The structures of these rubrolide analogs were determined by ¹H‐ and ¹³C‐NMR, 2D‐NMR (COSY and HETCOR), NOE difference, and MS techniques. These compounds were evaluated for their abilities of interfering with the light‐driven reduction of ferricyanide by isolated spinach chloroplasts. Lactones with electron‐withdrawing substituents in the para‐position of the benzylidene ring were the most effective inhibitors. Characterization of the activity of 11b / 11b′ suggested a mechanism based on the interaction with the plastoquinone binding site of photosystem II. Addition of several compounds to the culture medium of a cyanobacterial model strain was found to inhibit algal growth. However, the relative effectiveness was not consistent with their activity in vitro, suggesting the occurrence of multiple targets and/or detoxyfication mechanisms. Indeed, the compounds showed differential effects on the heterotrophic growth of some crop species, Cucumis sativus and Sorghum bicolor. Pyridazin‐3(2H)‐ones 12e, 12i , and 12j , which have been found poorly active against the photosynthetic electron transport, were the most effective in inhibiting the growth of some weeds, Ipomoea grandifolia and Brachiaria decumbens, under greenhouse conditions.     

Zwitterionic Phosphorylated Quinines as Chiral Solvating Agents for NMR Spectroscopy

Because of their unique 3D arrangement, naturally occurring Cinchona alkaloids and their synthetic derivatives have found wide‐ranging applications in chiral recognition. Recently, we determined the enantioselective properties of C‐9‐phosphate mixed triesters of quinine as versatile chiral solvating agents in nuclear magnetic resonance (NMR) spectroscopy. In the current study, we introduce new zwitterionic members of this class of molecules containing a negatively charged phosphate moiety (i.e., ethyl, n‐butyl and phenyl hydrogen quininyl phosphate). An efficient approach for synthesizing these compounds is elaborated, and full characterization, including conformational and autoaggregation phenomena studies, was performed. Therefore, their ability to induce NMR anisochrony of selected enantiomeric substrates (i.e., primarily N‐DNB‐protected amino acids and their methyl esters) was analyzed compared to uncharged diphenyl quininyl phosphate and its positively charged quaternary ammonium hydrochloride salt. In addition, ¹H and ¹³C NMR experiments revealed their enantiodiscrimination potential toward novel analytes, such as secondary amines and nonprotected amino acids. Chirality 27:752–760, 2015. © 2015 Wiley Periodicals, Inc.     

Synthesis,conformational study,and spectroscopic characterization of the cyclic Cα,α‐disubstituted glycine 9‐amino‐9‐fluorenecarboxylic acid

A series of terminally blocked peptides (to the pentamer level) from l ‐Ala and the cyclic C^α,α‐disubstituted Gly residue Afc and one Gly/Afc dipeptide have been synthesized by solution method and fully characterized. The molecular structure of the amino acid derivative Boc‐Afc‐OMe and the dipeptide Boc‐Afc‐Gly‐OMe were determined in the crystal state by X‐ray diffraction. In addition, the preferred conformation of all of the model peptides was assessed in deuterochloroform solution by FT‐IR absorption and ¹H‐NMR. The experimental data favour the conclusion that the Afc residue tends to adopt either the fully‐extended (C₅) or a folded/helical structure. In particular, the former conformation is highly populated in solution and is also that found in the crystal state in the two compounds investigated. A comparison with the structural propensities of the strictly related C^α,α‐disubstituted Gly residues Ac₅c and Dϕg is made and the implications for the use of the Afc residue in conformationally constrained analogues of bioactive peptides are briefly examined. A spectroscopic (UV absorption, fluorescence, CD) characterization of this novel aromatic C^α,α‐disubstituted Gly residue is also reported. Copyright © 1999 European Peptide Society and John Wiley & Sons, Ltd.     

A New Benzoylphloroglucinol Derivative with an Adamantyl Skeleton and Other Constituents from Garcinia multiflora: Effects on Neutrophil Pro‐Inflammatory Responses

A novel benzoylphloroglucinol derivative, garcimultiflorone D ( 1 ), with an unusual adamantyl‐caged skeleton was isolated from the fruits of Garcinia multiflora, together with four known compounds. The structure of 1 was determined through extensive 1D/2D‐NMR and mass‐spectrometric analyses. Garcimultiflorone D ( 1 ) exhibited inhibitory activities with IC₅₀ values of 7.21±1.07 and 6.01±0.37 μg/ml against fMLP/CB‐induced superoxide anion generation and elastase release, respectively.     

Immunosuppressive Withanolides from Withania coagulans

Six new withanolides, withacoagulins A–F ( 1 – 6 , resp.), together with ten known withanolides, 7 – 16 , were isolated from the aerial parts of Withania coagulans. Their structures were determined by spectroscopic techniques including 1D‐ and 2D‐NMR (¹H, ¹³C, HMQC, and HMBC) and MS experiments. These compounds, including the crude extracts of this herb, exhibited strong inhibitory activities on the T‐ and B‐cell proliferation.     

Effect of head‐to‐tail cyclization on conformation of histatin‐5

Histatin‐5 (Hst‐5, DSHAKRHHGYKRKFHEKHHSHRGY) is a member of a histidine‐rich peptide family secreted by major salivary glands, exhibiting high fungicidal activity against Candida albicans. In the present work, we demonstrate the 3D structure of the head‐to‐tail cyclic variant of Hst‐5 in TFE solution determined using NMR spectroscopy and molecular dynamics simulations. The cyclic histatin‐5 reveals a helix‐loop‐helix motif with α‐helices at positions Ala⁴‐His⁷ and Lys¹¹‐Ser²⁰. Both helical segments are arranged relative to each other at an angle of ca. 142°. The head‐to‐tail cyclization increases amphipathicity of the peptide, this, however, does not affect its antimicrobial potency. Copyright © 2014 European Peptide Society and John Wiley & Sons, Ltd.     

Structure Elucidation of the Main Tetrahydroxyxanthones of Hypericum Seeds and Investigations into the Testa Structure

Seeds from Hypericum species have recently been identified as an interesting source of xanthone derivatives. Extraction of seeds from H. perforatum with MeOH and subsequent concentration via polyamide adsorption yielded a fraction enriched in tetrahydroxyxanthones (THX), which were further semipurified by silica gel chromatography. Based on tentative structure assignment of the two main THX X1 and X2 by NMR a total synthesis was performed for both compounds (THX 1 and 2 , respectively), starting with an Ullmann ether synthesis. The synthesized 1 and 2 were characterized via 1D‐ and 2D‐NMR methods as well as by LC/HR‐MS analysis and proven to be 1,4,6,7‐THX ( 1 ) and 1,2,6,7‐THX ( 2 ). Final structure assignment of the natural Hypericum THX constituents was accomplished by comparing chromatographic and spectroscopic data (LC/MSⁿ and GC/MS) with those of 1 and 2 which were obtained by synthesis. Beyond, investigations into the seeds of H. perforatum and H. tetrapterum by scanning electron microscopy (SEM) provided insights of the structure of the testa (seed coat), which is established by two cell layers, with the lignified sclerenchyma presumably being the depository of the xanthones.     

Novel Nucleolipids of Pyrimidine β‐D‐Ribonucleosides: Combinatorial Synthesis,Spectroscopic Characterization,and Cytostatic/Cytotoxic Activities

Four series of nucleolipids with either uridine, 5‐methyluridine, 5‐fluorouridine, and 6‐azauridine as β‐D ‐ribonucleoside component have been prepared in a combinatorial (not parallel!) manner (see Formulae). All compounds have been characterized by elemental analyses, ESI mass spectrometry as well as by ¹H‐, and ¹³C‐NMR, and UV spectroscopy. A selection of eight nucleolipids with different lipophilizing moieties, based on earlier findings, as well as of 5‐fluorouridine as control were first tested on their cytotoxic effect towards PMA‐differentiated human THP‐1 macrophages. Those compounds which did not exhibit a significant inhibitory effect on the survival of the macrophages were next tested on their cytostatic/cytotoxic effect towards the human astrocytoma/oligodendroglioma GOS‐3 cells as well as against the rat malignant neuroectodermal BT4Ca cell line. Additionally, induction of apoptosis of the cell lines was evaluated. It turned out that particularly a combined lipophilization of the nucleosides by an 2′,3′‐O‐ethyl levulinate residue plus a farnesyl moiety at N(3) of the pyrimidine moiety of the corresponding nucleolipids leads to an active compound with the highest probability.     

Enantioselective recognition of carboxylic acids by novel fluorescent triazine‐based thiazoles

Hydrogen bonding and π‐π interactions take special part in the enantioselectivity task. In this regard, because of having both hydrogen acceptor and hydrogen donor groups, melamine derivatives become more of an issue for enantioselectivity. In the light of such information, triazine‐based chiral, fluorescence active novel thiazole derivatives L1 and L2 were designed and synthesized from (S)‐(?)‐2‐amino‐1‐butanol and (1S,2R)‐(+)‐2‐amino‐1,2‐diphenylethanol. The structural establishment of these compounds was made by spectroscopic methods such as FTIR, ¹H, and ¹³C NMR. While the solution of these compounds in DMSO did not show any fluorescence emission, it was observed that the emission increased 44‐fold for L1 and 55‐fold for L2 in 95% water, similar to the aggregation‐induced emission (AIE) characterized compounds. In this regard, enantioselective capabilities of these compounds against carboxylic acids were tested, and in experiments carried out at a ratio of 40/60 DMSO/H₂O, it was determined that R‐2ClMA increased the fluorescence emission of L1 chiral receptor by 2.59 times compared to S‐isomer.     

New Cytotoxic Bibenzyl and Other Constituents from Bauhinia ungulata L. (Fabaceae)

A new bibenzyl, 2′‐hydroxy‐3,5‐dimethoxy‐4‐methylbibenzyl ( 1 ) and four known compounds identified as 2′‐hydroxy‐3,5‐dimethoxybibenzyl ( 2 ), liquiritigenin ( 3 ), guibourtinidol ( 4 ) and fisetinidol ( 5 ) were isolated from the roots of Bauhinia ungulata L. Phytochemical investigations of the stems of B. ungulata led to the isolation of the known compounds identified as liquiritigenin ( 3 ), guibourtinidol ( 4 ), fisetinidol ( 5 ), taraxerol ( 6 ), betulinic acid ( 7 ), taraxerone ( 8 ), glutinol ( 9 ), a mixture of sitosterol ( 10 ) and stigmasterol ( 11 ), pacharin ( 12 ), naringenin ( 13 ) and eriodictyol ( 14 ). The structures of these compounds were elucidated on the basis of their spectral data (IR, MS, 1D‐ and 2D‐NMR). The cytotoxicity of the bibenzyl 1 has been evaluated against four human cancer cell lines, showing the IC₅₀ values of 4.3 and 6.5 μg ml^?1 against pro‐myelocytic leukemia (HL‐60) and cervical adenocarcinoma (HEP‐2) cell lines, respectively. This article also registers for the first time the ¹³C‐NMR data of the known bibenzyl 2 .