Conformational characterization of the mammalian-expressed SARS-CoV-2 recombinant receptor binding domain, a COVID-19 vaccine

The COVID-19 pandemic has caused a large number of diseases worldwide. There are few vaccines to constrain this disease and the value of them is high. In this sense, the antigens of the vaccine platform Soberana, the receptor binding domain from SARS-CoV-2 Spike protein, both the monomeric (mRBD) and dimeric (dRBD) forms, have been developed. This study encompassed several analyses by different techniques like circular dichroism (CD), fluorescence spectroscopy (FS) and Gel Filtration- High Performance Liquid ChLC of mRBD and dRBD. Monomer and dimer exhibited similar far-UV CD spectral characteristics with 54% of ß-sheet content. Similar conformational features according to near-UV CD and FS studies were observed in both RBD. Stress stability studies by far-UV CD, FS, biological activity and GF-HPLC at 37 °C showed that mRBD is very stable. On the other hand, dRBD fluorescent emission showed a shift towards higher wavelengths as the incubation time increases, suggesting exposition of tryptophan residues, unlike what happens with mRBD. Biological activity outcome confirms these results. GF-HPLC profiles showed that in mRBD, the product of molecular stress are dimers and does not increase over time. However, dRBD showed dimer fragmentation as the main degradation species. This study reveals the usefulness of CD techniques for the analysis of degradation of RBD molecules as well as showed the difference in stability of both RBD molecules. Besides, our work provides useful insights into the production of a key protein used in diagnosis and therapeutics to fight COVID-19 pandemia.

Macromolecular properties and partial amino acid sequence of a Kunitz-type protease inhibitor from okra (Abelmoschus esculentus) seeds

A Kunitz-type protease inhibitor (OPI, okra protease inhibitor) has been purified from okra (Abelmoschus esculentus) seedsby a combination of ammonium sulfate precipitation, anion-exchange chromatography and reverse-phase high-performanceliquid chromatography. The protein shows an apparent mass of 21 kDa on sodium dodecyl sulfate-polyacrylamide gelelectrophoresis under reducing condition. OPI exhibits inhibitory activity against trypsin. Analysis of the far-UV circulardichroism spectrum showed that the protein contains *39% b-sheets but only *5% a-helices. The protein is thermallyquite stable, and exhibits a cooperative thermal unfolding transition at *70C, as determined by circular dichroismspectroscopy and differential scanning fluorimetry. De novo sequencing of OPI by nanoESI-Q-ToF mass spectrometry (MS)allowed the assignment of about 83% of its primary structure, which indicated that the protein shares 43% sequence identitywith a putative 21 kDa trypsin inhibitor from Theobroma bicolor. An intramolecular disulfide linkage between Cys149 andCys156 was also detected. The protein showed *24 and *25% sequence identity with a-amylase/subtilisin inhibitor frombarley and soybean (Kunitz) trypsin inhibitor, respectively. Comparative structure modeling of OPI revealed a structuralfold similar to other Kunitz-type TIs. The presence of Cys149–Cys156 disulfide bond as detected by MS and a seconddisulfide bond connecting Cys44–Cys91, conserved in all Kunitz-type TIs, is also identified in the model.

Glycyrrhetinic acid binds to the conserved P-loop region and interferes with the interaction of RAS-effector proteins

Members of the proto-oncogene superfamily are indispensable molecular switches that play critical roles in cell proliferation, differentiation, and cell survival. Recent studies have attempted to prevent the interaction of RAS/GTP with RAS guanine nucleotide exchange factors (GEFs), impair RAS-effector interactions, and suppress RAS localization to prevent oncogenic signalling. The present study aimed to investigate the effect of the natural triterpenoic acid inhibitor glycyrrhetinic acid, which is isolated from the roots of plant species, on RAS stability. We found that glycyrrhetinic acid may bind to the P-loop of RAS and alter its stability. Based on our biochemical tests and structural analysis results, glycyrrhetinic acid induced a conformational change in RAS. Meanwhile, glycyrrhetinic acid abolishes the function of RAS by interfering with the effector protein RAF kinase activation and RAS/MAPK signalling.

Effects of dihydromyricetin on biological properties of Bloom syndrome helicase / 中国药理学通报

; Aim To explore the anti-tumor mechanism of dihydromyricetin (DMY), a kind of flavonoid compound with anti-inflammatory and anti-tumor effects, via studying the effect of DMY on biological activities of Bloom helicase. Methods The effect of DMY on the biological activities of BLM helicase was studied by ultraviolet spectrum (UV), circular dichroism (CD), fluorescence polarization and free phosphorus detection. Results The results of CD and UV showed that DMY could bind to a site of the BLM helicase. In the concentration of DMY in 0 ~ 25 μmol . L 1 range, DMY showed a positive correlation with the interference ability of BLM helicase secondary structure with the increase of concentration, while in the concentration of DMY in 25 ~ 75 μmol . L 1 range, DMY showed a negative correlation. Fluorescence polarization and free phosphorus detection experiments showed that DMY could bind to BLM helicase, thus inhibiting the helicase activity of BLM helicase. Conclusions DMY can competitively bind to the DNA binding site of BLM helicase and change the spatial structure of BLM helicase, inhibiting the binding of BLM helicase to DNA and the biological activity of BLM helicase accordingly.

Flavonoids from twigs of Morus multicaulis / 中草药

Objective: To investigate the chemical compounds from the twigs of Morus multicaulis. Methods: The chemical constituents were isolated by various chromatographic methods from 90% ethanol aqueous extract of M. multicaulis and the structures were elucidated by a combined analysis of physicochemical properties, as well as spectroscopic methods including UV, IR, MS ECD and NMR. Results: Six flavonoids were isolated and the structures were identified as moritwigsone A (1), carpachromene (2), isobavachalcone (3), isoliquiritigenin (4), apigenin (5), and quercitrin (6). The absolute configuration of compound 1 was determined by electronic circular dichroism (ECD) calculation. Conclusion: Compound 1 is a new compound, named moritwigsone A, and compounds 2-4 are isolated from this plant for the first time.

Novel sesquiterpenoids isolated from Chimonanthus praecox and their antibacterial activities / 中国天然药物

In the present study, four new sesquiterpenoids, chimonols A-D (compounds 1-4), together with four known compounds (5-8) were isolated from the EtOAc extract of Chimonanthus praecox Link. The structures of these new compounds were elucidated on the basis of spectroscopic techniques (UV, IR, MS, and 1D and 2D NMR), and their absolute configurations were established by comparing experimental and calculated electronic circular dichroism (ECD) spectra. Compounds 1-8 were evaluated for antimicrobial activities and the minimum inhibitory concentrations (MICs) were determined by the broth microdilution method in 96-well culture plates. Compounds 1, 2, and 7 exhibited weak antibacterial effects for S. aureus (ATCC 6538), E. coli (ATCC 11775), and P. aeruginosa (ATCC 10145) with MIC values being 158-249 µg·mL. Compounds 3-7 showed activities against C. glabrata (ATCC 2001) and S. aureus (ATCC 43300) with MIC values being 128-197 µg·mL. Compounds 1-4 showed activity against S. aureus (ATCC 25923) with MIC values being 162-254 µg·mL. The present study provided a basis for future evaluation of these compounds as antibacterial agents.

Novel sesquiterpenoids isolated from Chimonanthus praecox and their antibacterial activities / 中国天然药物

In the present study, four new sesquiterpenoids, chimonols A-D (compounds 1-4), together with four known compounds (5-8) were isolated from the EtOAc extract of Chimonanthus praecox Link. The structures of these new compounds were elucidated on the basis of spectroscopic techniques (UV, IR, MS, and 1D and 2D NMR), and their absolute configurations were established by comparing experimental and calculated electronic circular dichroism (ECD) spectra. Compounds 1-8 were evaluated for antimicrobial activities and the minimum inhibitory concentrations (MICs) were determined by the broth microdilution method in 96-well culture plates. Compounds 1, 2, and 7 exhibited weak antibacterial effects for S. aureus (ATCC 6538), E. coli (ATCC 11775), and P. aeruginosa (ATCC 10145) with MIC values being 158-249 µg·mL. Compounds 3-7 showed activities against C. glabrata (ATCC 2001) and S. aureus (ATCC 43300) with MIC values being 128-197 µg·mL. Compounds 1-4 showed activity against S. aureus (ATCC 25923) with MIC values being 162-254 µg·mL. The present study provided a basis for future evaluation of these compounds as antibacterial agents.

Proteolytic activity of recombinant DegP from Chromohalobacter salexigens BKL5

Background: DegP is a serine protease that specifically cleaves and refolds unfolding proteins in the periplasmic space of the cells. To date, there is no information regarding DegP from halophilic bacteria. Chromohalobacter salexigens BKL5 is a moderately halophilic bacterium that has the ability to grow in a media containing more than 15% salt. Therefore, the objectives of this work were to clone and overexpress DegP-encoding gene from C. salexigens BKL5 and characterize its biochemical properties. Results: DegP-encoding gene was overexpressed in Escherichia coli BL21(DE3) CodonPlus in an active form. SDS-PAGE analysis showed that the molecular weight of the recombinant DegP was 45 kDa. Size-exclusion chromatography analysis suggested that recombinant DegP was present in two multimeric states, hexameric and dodecameric, with molecular weights of 297.9 and 579.12 kDa, respectively. Both conformations were enzymatically active when casein was used as substrate for enzymatic assay. Circular dichroism analysis showed that recombinant DegP was composed of 0.21­0.29 helical content, which was comparable to the helical content in the crystal structure of E. coli DegP. The basic/acidic residue ratio of recombinant DegP was 0.56, which was slightly higher than that of DegP from extreme halophiles (average, 0.45) but significantly lower than that of DegP from nonhalophiles (average, 0.94). Conclusions: Recombinant DegP from C. salexigens BKL5 showed proteolytic activity when ß-casein was used as a substrate. In silico analysis indicated that recombinant DegP had characteristics similar to those of halophilic proteins depending on its amino acid composition.

A set of interesting sequoiatones stereoisomers from a wetland soil-derived fungus

Four interesting sequoiatones stereoisomers (-) were isolated from a wetland soil-derived fungusby chiral HPLC. On the basis of comprehensive NMR and mass analyses, their planar structures were elucidated as the same as that of sequoiatone B. Among them,and(orand) were a pair of enantiomers, andand(orand) were a pair of stereoisomers with epimerization at C-12, which indicated that sequoiatione-type metabolites exist as enantiomers rather than as optically pure compounds in some strains. With the quantum chemical ECD calculations, the absolute configurations of C-8 in-were determined, which is the first report to establish the absolute configuration of C-8 in sequoiatones. However, the absolute configurations of C-12 in sequoiatones are still unsolved.

Four new phenolic glycosides from Baoyuan decoction

Four new phenolic glycosides, including two flavonoid glycosides (and) and two lignan glycosides (and), were isolated from the traditional Chinese medicine formula, Baoyuan decoction. Their structures were established by detailed analysis of the NMR and HR-ESI-MS spectroscopic data and their absolute configurations were determined by the experimental electronic circular dichroism data as well as chemical methods. Furthermore, the sources of the four new compounds were determined by the UPLC-Qtrap-MS method, which proved thatandare originated from, andandare from.

Investigation of binding behaviour of procainamide hydrochloride with human serum albumin using synchronous, 3D fluorescence and circular dichroism / 药物分析学报

Interaction of procainamide hydrochloride (PAH) with human serum albumin (HSA) is of great significance in understanding the pharmacokinetic and pharmacodynamic mechanisms of the drug. Multi-spectroscopic techniques were used to investigate the binding mode of PAH to HSA and results revealed the presence of static type of quenching mechanism. The number of binding sites, binding constants and thermodynamic parameters were calculated. The results showed a spontaneous binding of PAH to HSA and hydrophobic interactions played a major role. In addition, the distance between PAH and the Trp–214 was estimated employing the F?rster's theory. Site marker competitive experiments indicated that the binding of PAH to HSA primarily took place in subdomain ⅡA (Sudlow's site I). The influence of interference of some common metal ions on the binding of PAH to HSA was studied. Synchronous fluorescence spectra (SFS), 3D fluorescence spectra and circular dichroism (CD) results indicated the conformational changes in the structure of HSA.

Validação dos sistemas computadorizados empregados na determinação dos enantiômeros do nadolol e dos homólogos da ivermectina e da abamectina / Validation of the computer systems used in the determination of nadolol enantiomers and homologous of ivermectin and abamectin

O nadolol é um agente bloqueador de receptores ß-adrenérgicos empregado principalmente, na "angina pectoris", hipertensão, certas arritmias cardíacas e no tratamento do glaucoma (SING, 2006). A ivermectina e a abamectina são fármacos que apresentam ação antiparasitária (SHOOP, 1995). Na presente pesquisa, a cromatografia em fase líquida de alta eficiência foi uma das técnicas estudadas para a quantificação dos enantiômeros do nadolol e dos homólogos presentes na abamectina e ivermectina. A versatilidade desta técnica reside no grande número de fases estacionárias existentes, as quais possibilitam análises, separações e determinações quantitativas de uma ampla gama de compostos com alta eficiência (Aquino Neto e Nunes, 2003). Para identificação dos enantiômeros do nadolol foi utilizado o dicroísmo circular que permite a determinação da configuração absoluta de enantiômeros (LIMA, 1997). Para os enantiômeros do nadolol e dos homólogos presentes na abamectina e na ivermectina também foram realizados testes para desenvolvimento de uma metodologia de quantificação por meio de uma técnica relativamente recente chamada de eletroforese capilar (EC), a qual tem alcançado desde sua introdução um rápido desenvolvimento e ampla aplicação na análise de fármacos em medicamentos (SANTORO, 2000). Para a comprovação da qualidade e segurança dos sistemas computadorizados dos equipamentos de cromatografia em fase líquida de alta eficiência (CLAE) e de eletroforese capilar (EC) foram efetuadas, neste trabalho, as respectivas validações. Após esta validação, pode-se confirmar o correto funcionamento de um software, e suas interações com o hardware, onde devem ser levados em consideração, dentre outros, os aspectos relacionados à infra-estrutura, segurança e manutenção de dados (AGÊNCIA NACIONAL DE VIGILÂNIA SANITÁRIA, 2010). As metodologias analíticas desenvolvidas a para quantificação do nadolol, abamectina e ivermectina por cromatografia em fase líquida de alta eficiência foram validadas. A validação analítica deve garantir, por meio de estudos experimentais, que o método atenda às exigências das aplicações analíticas, assegurando a confiabilidade dos resultados. Para tanto, o método deve apresentar especificidade, linearidade, intervalo, precisão, sensibilidade, limite de quantificação e detecção, exatidão, adequados à análise (AGÊNCIA NACIONAL DE VIGILÂNCIA SANITÁRIA, 2003). Portanto, o objetivo proposto nesta pesquisa é primeiramente a validação dos sistemas computadorizados dos equipamentos de cromatografia em fase líquida de alta eficiência (CLAE) e de eletroforese capilar (EC). Para isto, serão desenvolvidos e validados os métodos analíticos de separação, identificação e quantificação dos enantiômeros do nadolol e dos homólogos presentes na abamectina e na ivermectina, em medicamentos, empregando as técnicas analíticas selecionadas

Nadolol is a blocking agent with activity in the ß -adrenergic receptors. It is mainly used in angina, hypertension, certain heart arrhythmias and in the treatment of glaucoma (SING, 2006). Ivermectin and abamectin are drugs with antiparasitic activity (SHOOP, 1995). In the present research, high performance liquid chromatography is one of the techniques used in the quantification of the enantiomers of nadolol and homologues present in abamectin and ivermectin. The versatility of this technique and the large number of existing stationary phases, enables the separation and quantitative determination of a wide range of compounds with high efficiency (Aquino Neto e Nunes, 2003). For identification of the nadolol enantiomers, circular dichroism was used which allows the determination of the absolute configuration of the enantiomers (LIMA, 1997). Nadolol enantiomers and the homologues present in abamectin and ivermectin will be also quantified by capillary zone electrophoresis (CE), a separation technique relatively recent, which has achieved, since its introduction, a wide application in the analysis of drugs in pharmaceutical preparations (SANTORO, 2000). In order to assure the quality of the analytical results, the computer systems of the liquid chromatograph and capillary electrophoresis equipments, must be validated prior to the analytical methods validation. Computer systems validation is used to verify and confirm the proper operation of softwares, and their interactions with the hardwares, besides the infrastructure, safety and storage of data (AGÊNCIA NACIONAL DE VIGILÂNIA SANITÁRIA, 2010). The analytical methodologies developed for quantification of nadolol, abamectin, ivermectin by using high efficiency liquid chromatography and capillary electrophoresis were validated. The analytical methods validation should ensure, through experimental studies, that the method meets the requirements for analytical applications, ensuring the reliability of the results. Parameters like, specificity, linearity, range, accuracy, sensitivity, limits of detection and quantification and accuracy, must be determined (AGÊNCIA NACIONAL DE VIGILÂNCIA SANITÁRIA, 2003). The objective of this study is to validate the computer systems of the high performance liquid chromatograph and capillary electrophoresis equipments and then to develop and validate analytical methods for separation, identification and quantification of nadolol enantiomers and the homologues of abamectin and ivermectin

Two new cyclic bisbibenzyl derivatives from Hebertus dicranus / 中国天然药物

In the present study, two new cyclic bisbibenzyls (1, 2) co-occuring with a known compound, isoplagiochins C (3) were isolated from Hebertus dicranus. The structures were determined mainly by extensive 1D and 2D NMR experiments, and the absolute configurations of 1 and 2 were established by the circular dichroism spectrum. Furthermore, all these three rare compounds were tested in vitro for inhibitory activity against the growth of human cancer cell lines (A549, HCT116, MDA-MB-231, and BEL7404) by the MTT assay, and compound 2 exhibited moderately inhibitory activity with IC50 values ranging from 13.89 to 31.62 μmol·L(-1). In conclusion, our results provided a basis for future development and modification of these compounds for cancer therapy.

Interaction between bovine serum albumin and pullulan acetate nanoparticles / 国际生物医学工程杂志

Objective To investigate the interaction of pullulan acetate nanoparticles (PANs) and bovine serum albumin (BSA),and to provide the basis for in vivo pharmacokinetic study of PANs.Methods Mixed solutions of different concentration of PANs and BSA solution was prepared,the interaction was studied by fluorescence quenching method and circular dichroism (CD) measurement.Apparent quenching constant (Kq) between the PANs and BSA was calculated,and the anti-stress effect induced by urea and heating of PANs-BSA solution was observed.Results The fluorescence spectrum of BSA was affected by PANs on density-related manner,and Kq calculated by the modified Stern-Volmer plot increased from 2.64×104 to 3.55 ×l05 with the concentration of PANs increased from 0.015 mg/ml to 0.25 mg/ml.With the denaturation of urea or heating,the CD spectrum of PANs-BSA and free BSA had the similar variation tendency.Conclusions The fluorescence spectrum display results show that interaction between PANs and BSA exists,but the interaction does not protect the BSA from degeneration by urea and heating.

CARACTERIZACIÓN DE LA ESTRUCTURA SECUNDARIA DE SUBTIPOS DE LA HISTONA H1 POR DICROÍSMO CIRCULAR / CHARACTERIZATION OF THE SECONDARY STRUCTURE OF HISTONE H1 SUBTYPES BY CIRCULAR DICHROISM (CD)

Introducción: Las histonas H1 modulan la estructura y la función de la cromatina. Las células somáticas de mamífero contienen los subtipos H1º, H1a, H1b, H1c, H1d y H1e; en células germinales de testículo y en ovocito, se encuentran respectivamente H1t y H1oo. Su estructura está conformada por un dominio central globular flanqueado por los dominios N-Terminal (DNT) y C-Terminal (DCT). Objetivo: Caracterizar la estructura secundaria de subtipos de la histona H1 mediante dicroísmo circular (DC). Materiales y Métodos: La histona H1 total se extrajo de núcleos de cerebro de rata por cromatografía de intercambio catiónico; la H1º se purificó por filtración en gel y las H1a, H1b, H1c y H1e por cromatografía líquida de alta resolución de fase reversa (RF-HPLC). Los espectros de DC se realizaron en tampón fosfato 10 mM; tampón fosfato 10 mM, 20% TFE (trifluoroetanol); tampón fosfato 10 mM, 40% TFE; tampón fosfato 10 mM, 60% TFE; tampón fosfato 10 mM, 150 mM NaCl y tampón fosfato 10 mM, 1 M NaCl. El análisis de los espectros se realizó con el programa Standard Analysis. Resultados: El porcentaje de hélice-alfa se calculó por diferentes métodos matemáticos teniendo en cuenta elipticidad molar a 193 nm y a 222 nm; con programa de deconvolución K2D y con relaciones cualitativas R1 y R2. El TFE induce la estructura en hélice-alfa en cada uno de los subtipos, mientras que NaCl no induce ningún cambio importante. Conclusión: Los subtipos con mayor contenido de hélice-alfa son H1a y H1c. Las diferencias observadas en el porcentaje de hélice-alfa entre los diferentes subtipos puede ser importante para su diferenciación funcional.

H1 histones modulate the structure and function of chromatin. Mammalian somatic cells contain H1º, H1a, H1b, H1c, H1d and H1e subtypes; H1t and H1oo are found in testicular germ cells and oocyte, respectively. Its structure consists of a globular core domain flanked by N-terminal (DNT) and C-terminal (DCT) domains. Objective: To characterize the secondary structure of histone H1 subtypes through circular dichroism (CD). Materials and Methods: Total histone H1 was extracted for rat brain nuclei by cation exchange chromatography; histone H1º was purified by gel filtration and the histones H1a, H1b, H1c and H1e were purified by reversed phase high performance liquid chromatography (RP-HPLC). CD spectra were performed in 10 mM phosphate buffer; 10 mM, 20% TFE phosphate buffer (trifluoroethanol); 10 mM, 40% TFE; phosphate buffer 10 mM, 60% TFE; phosphate buffer 10 mM, 150 mM NaCl and phosphate buffer 10 mm, 1 M NaCl. The analysis of the spectra was performed with JASCO Standard Analysis. Results: The percentage of alpha-helix was calculated using different mathematical methods, taking into account the molar ellipticity at 193 nm, and 222 nm, with K2D deconvolution program and the R1 and R2 qualitative relationships. The results indicate that TFE induced the alpha-helix structure in each of the subtypes, whereas NaCl did not induce any significant change. Conclusion: H1a and H1c are subtypes with highest content of alpha-helix. The observed differences in the percentage of alpha-helix between different subtypes may be important for their functional differentiation.

A high-performance liquid chromatography with circular dichroism detector for determination of stereochemistry of 6, 9-oxygen bridge dibenzocyclooctadiene lignans from kadsura coccinea / 中国天然药物

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.

Several stereogenic problems regarding structural elucidation of marine natural products / 国际药学研究杂志

During the structural elucidation of natural products, one of the key steps is attributed to the solution of configuration including chiral carbons, axial and planar asymmetry. Stereogenic assignment is an essential work involved in natural product chemistry, while identification of stereogenic centers may be helpful to recognize the structure related to target function. Modern spectroscopic technology provided a reliable tool for the configurational assignment. In this paper, we intend to summarize part of our work regarding the application of extensive spectroscopic methods for the determination of the absolute configurations of marine-derived natural products.

Advances of circular dichroism application in determination of absolute configuration of flavonolignans / 国际药学研究杂志

Flavonolignans, as a special class of flavonoid, have attracted people's attention for their remarkable hepatopro-tection and anti-cancer activity. However, separation of flavonolignans and identification of their absolute configuration have met with great challenges due to the complexity and similarity of structures. The circular dichroism (CD) rules and their application in analyzing the absolute configuration of flavonolignans are summarized in the review and hopefully it may be helpful for the structure elucidation of flavonolignans.

Absolute determination of stereochemical configuration of some marine natural products / 国际药学研究杂志

The determination of stereochemical absolute structure is an important issue in structural elucidation of natural products. The absolute configuration of natural compounds with a chiral α, β -unsaturated ketone chromorphore can be determined by the Cotton effect in 320-350 nm (n→π,* transition) and 220-260 nm (π→π,* transition) regions of the circular dichroism (CD) spectrum. This paper reviews the absolute stereochemical asignment of some α, β-unsaturated ketone compounds as well as some of the longer fatty chain derived compounds.

Determination methods for absolute configuration of natural products / 国际药学研究杂志

The physical, chemical, biological and pharmacological properties of natural products (NP)are closely related to their absolute configurations, and the determination of the NP configurations is a great challenge for natural product chemists and has attracted widespread attention of researchers. People have summed up a variety of determination methods, such as single-crystal X-ray diffraction (XRD), Mosher" s method based on the chemical reaction with the chiral reagents and nuclear magnetic resonance NMR, circular dichroism CD and organic synthesis methods, etc. These methods have advantages and disadvantages for the determination of absolute configuration of NP with different structure characteristics. This paper reviewes the principles, advantages and limitations of these common methods.