Comprehensive chemical analysis of extracts and fractions of marine actinomycete strains led to the discovery of a new minor secondary metabolite, salternamide E (1), from a saltern-derived halophilic Streptomyces strain. The planar structure of salternamide E (1) was elucidated by a combinational analysis of spectroscopic data including NMR, MS, UV, and IR. The absolute configuration of salternamide E (1) was determined by circular dichroism spectroscopic analysis. Salternamide E displayed weak cytotoxicity against various human carcinoma cell lines.
Cell Line ; Circular Dichroism ; Humans ; Streptomyces*

Dicarabrols B and C (1 and 2), two new carabrane sesquiterpenoid dimers, along with one new carabrane sesquiterpenoid (3) were isolated from the whole plant of Carpesium abrotanoides L. Their full structures were established by extensive analysis of HR-ESI-MS and NMR spectroscopic data, and time-dependent density functional theory (TDDFT) electronic circular dichroism (ECD) calculations. Dicarabrol B possesses a novel C
Asteraceae ; Circular Dichroism ; Humans ; Molecular Structure ; Sesquiterpenes

Structural elucidation of natural products is always one of the most important tasks for natural product researchers in related fields. Particularly, the absolute configuration (AC), being a great challenge for natural product chemists, has attracted much attention. During the past few decades, many techniques and approaches have been developed to determine the AC of natural products, including direct (or absolute) methods, e.g. X-ray diffraction (XRD), electronic and vibrational circular dichroism (ECD and VCD), and Raman optical activity (ROA), as well as indirect (or relative) methods using a reference or a derivatizing agent with known AC, e.g. CD with empirical rules and nuclear magnetic resonance (NMR) utilizing anisotropic effects of chiral derivatizing agents. However, none of the currently applied techniques is capable of dominating AC determination, since they each have their respective limitations corresponding to the different structural features. This mini review summarizes most of the techniques and methods which are commonly used in AC assignment of natural products, or have potential application prospects, and briefly describes their principles, advantages and limitations.
Biological Products ; chemistry ; Circular Dichroism ; Molecular Structure ; Optical Rotation ; X-Ray Diffraction

In this study, we presented the isolation and characterization of eight novel seco-guaianolide sesquiterpenoids (1-8) and two known guaianolide derivatives (9 and 10), from the aerial part of Achillea alpina L.. Compounds 1-3 were identified as guaianolides bearing an oxygen insertion at the 2, 3 position, while compounds 4-8 belonged to a group of special 3-nor guaianolide sesquiterpenoids. The structural elucidation of 1-8, including their absolute configurations, were accomplished by a combination of spectroscopic data analysis and quantum electronic circular dichroism (ECD) calculations. To evaluate the potential antidiabetic activity of compounds 1-10, we investigated their effects on glucose consumption in palmitic acid (PA)-mediated HepG2-insulin resistance (IR) cells. Among the tested compounds, compound 7 demonstrated the most pronounced ability to reverse IR. Moreover, a mechanistic investigation revealed that compound 7 exerted its antidiabetic effect by reducing the production of the pro-inflammatory cytokine IL-1β, which was achieved through the suppression of the NLRP3 pathway.
Humans ; Hypoglycemic Agents/pharmacology* ; Circular Dichroism ; Cytokines ; Glucose ; Hep G2 Cells ; Insulin Resistance

Six new abietane diterpenoids (1-6) and five undescribed iridoids (7-11) have been isolated from the aerial parts of Caryopteris mongolica. The intricate structural characterization of these compounds was meticulously undertaken using an array of advanced spectroscopic techniques. This process was further enhanced by the application of DP4+ probability analyses and electronic circular dichroism (ECD) calculations. Following isolation and structural elucidation, the cytotoxicity of these compounds was evaluated. Among them, compound 3 stood out, displaying significant cytotoxic activity against HeLa cells with an IC₅₀ value of 7.83 ± 1.28 μmol·L^-1. Additionally, compounds 1, 2, 4, 9, and 10 manifested moderate cytotoxic effects on specific cell lines, with IC₅₀ values ranging from 11.7 to 20.9 μmol·L^-1.
Humans ; Abietanes/chemistry* ; HeLa Cells ; Lamiaceae/chemistry* ; Circular Dichroism ; Diterpenes/chemistry* ; Molecular Structure

The relationship between the conformation of interferon-α (IFN-α) and its anti-viral activity were analyzed by circular dichroism (CD) and flow cytometry (FCM) techniques. The recombinant human IFN-α (rIFN-α2b and rIFN-α2a) were used. CD spectra from 190 nm to 240 nm indicated that two the IFN-α showed stable secondary structure at 65 degrees C, but unstable when the temperature was above 65 degrees C, and the change was irreversible. FCM data of the anti-viral activity of IFN-α indicated that the change of its secondary structures partly weakened its anti-viral activity. The rIFN-α2b and rIFN-α2a showed the same phenomenon. These data indicated that the conformation of IFN-α is one of the factors to influence its anti-viral activity and the combination of CD and FCM is a good method to analyze the relationship between the conformation of protein drugs and their biological activities in single cell level.
Antiviral Agents ; chemistry ; Circular Dichroism ; Flow Cytometry ; Humans ; Interferon-alpha ; chemistry ; Protein Structure, Secondary ; Recombinant Proteins ; chemistry

OBJECTIVETo study the conjugation reaction characteristics of caffeic acid micromolecule cistanoside F and bovine serum albumin.

METHODThe interaction between bovine serum albumin (BSA) and cistanoside F that was separated from Callicarpa plant for the first time and abbreviated CF was detected by fluorescence (FS), UV-vis absorbance and circular dichroism (CD) under simulative physiological conditions.

RESULTCF-BSA's static apparent binding constant (K(a)), number of binding sites (n), efficiency of energy transfer (E), spatial distance (r), thermodynamic parameters deltaG, deltaH and deltaS and changes in alpha-helical structure content in BSA before and after CF's effect were calculated to define the binding site of CF in BSA and analyze the impact of several common metal ions on the interaction of CF and BSA.

CONCLUSIONGround state compounds formed by CF and BSA could cause intrinsic fluorescence quenching. Their binding constant K(a) of cistanoside F with BSA was 4.36 x 10(4) L x mol at 25 degrees C, the number of binding site n was 1, and the spatial distance r was 3.09 nm. The results indicated that the hydrogen bond played a major role in cistanoside F-BSA association. The displacement experiments confirmed that cistanoside F can bind to site I of BSA. In addition, the binding constant of cistanoside F with BSA was enhanced after the addition of some common metal ions Mg2+, Fe3+, Cu2+ and Zn2+. The intrinsic fluorescence of BSA was quenched by cistanoside F via forming cistanoside F-BSA complex and non-radiation energy transfer. CD spectra showed that the binding of cistanoside F with BSA induced conformational changes in BSA.

Animals ; Caffeic Acids ; chemistry ; Catechols ; chemistry ; Cattle ; Circular Dichroism ; Glycosides ; chemistry ; Serum Albumin, Bovine ; chemistry ; Spectrometry, Fluorescence ; Spectrophotometry, Ultraviolet ; Thermodynamics

DNA binding compounds were previously shown to bind to the right-handed DNA forms and hybrid B-Z forms in a highly cooperative manner and indicate that structural specificity plays a key role in a ligand binding to DNA. In this study, the modes of binding and structural specificity of agents to unusual DNA are examined by a variety of fluorescence techniques (intensity, polarization and quenching, etc.) to explore a reliable method to detect the association environment of ligands to deoxyoligonucleotides initially containing a B-Z junction between the left-handed Z-DNA and right-handed B-DNA. The results of fluorescence energy transfer measurement demonstrated that the ligand molecules bind to the allosterically converted DNA structures by intercalation. In the absence of high-resolution structural data, this fluorescence energy transfer measurement allowed reliable measures and infer the binding environment of ligands to the allosteric DNA structures.
Allosteric Regulation ; Circular Dichroism ; DNA/*chemistry/*metabolism ; Energy Transfer ; Ethidium/*metabolism ; Exodeoxyribonucleases/metabolism ; Ligands ; Motion ; Nucleic Acid Conformation ; Oligodeoxyribonucleotides/*metabolism

The stereochemistry of two 6, 9-oxygen bridge dibenzocyclooctadiene lignans from Kadsura coccinea, are difficult to separate and very unstable. The present study was designed to develop a high-performance liquid chromatography using circular dichroism detection for the analysis of the stereochemistry. A new 6, 9-oxygen bridge dibenzocyclooctadiene lignans named Kadsulignan Q was firstly found with an S-biphenyl configuration. The other compound was identified as Kadsulignan L with an R- biphenyl configuration. In order to obtain kinetic data on their reversible interconversion, the stability was measured at different deuterated solvents such as deuterated methanol, deuterated chloroform and deuterated dimethylsulfoxide. The lignans were more unstable and converted more easily in deuterated methanol than in deuterated chloroform and deuterated dimethylsulfoxide.
Chromatography, High Pressure Liquid ; Circular Dichroism ; Cyclooctanes ; chemistry ; Kadsura ; chemistry ; Lignans ; chemistry ; Molecular Structure ; Oxygen ; Plant Extracts ; chemistry ; Stereoisomerism

OBJECTIVETo characterize the relationship between the refolding process of recombinant bovine β-lactoglobulin and its immunoreactivity for clinical purposes. To establish a spectral method which examine the extent of recombinant allergen renaturation.

METHODSThe refolding process of recombinant bovine β-lactoglobulin was investigated by using circular dichroism, fluorescence and synchronous fluorescence spectra. IgE-binding capacity of recombinant protein was analyzed by ELISA. In addition, bioinformatic methods were used to explain the spectral characteristics and analyze the relationship between the conformational changes and the immunoreactivity of the protein during renaturation in vitro.

RESULTSRenaturation of recombinant bovine β-lactoglobulin resulted in a more compact structure resembling the natural counterpart with stronger IgE-binding capacity.

CONCLUSIONThe degree of protein renaturation correlated with the IgE-binding capacity of the protein. Results from this study may be of help for food allergy therapy and development of vaccination in the future.

Allergens ; Animals ; Cattle ; Circular Dichroism ; Enzyme-Linked Immunosorbent Assay ; Immunoglobulin E ; Lactoglobulins ; chemistry ; metabolism ; Models, Molecular ; Protein Binding ; Protein Conformation ; Protein Denaturation ; Protein Folding ; Spectrometry, Fluorescence ; methods