A new nor-sesquiterpene glycoside from Corydalis edulis / 中国中药杂志

This study is to investigate the chemical constituents from the whole plant Corydalis edulis. The chemical constituents were separated and purified by macroporous resin D101, silica gel, Sephadex LH-20, ODS, and semi-preparative HPLC. Their structures were determined by physicochemical properties and spectroscopic data. Four compounds were isolated from the dichloromethane and water extracts of the whole plant C. edulis, and identified as 6'-β-D-xylosylicariside B2(1),(3S,5R,6S,7E)-5,6-epoxy-3-hydroxy-7-megastigmen-9-one(2), loliolide(3), and 5,5'-dimethoxybiphenyl-2,2'-diol(4), respectively. Compound 1 is a new compound, of which the absolute configuration was established by electronic circular dichroism(ECD) calculations. Compound 4 is obtained from the plants of Papaveraceae family for the first time. Compounds 2 and 3 are firstly isolated from the Corydalis genus.

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.

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.

Electronic circular dichroism calculation method in the assignment of absolute configuration of natural products / 国际药学研究杂志

Assignment of absolute configuration is an important and challenging work in the structure elucidation of natural products. Electronic circular dichroism (ECD) calculation is a method to determine the absolute configurations by comparing experimental ECD data and calculated ECD data derived from quantum chemical calculation. With the development of the quantum chemical calculation, the calculated ECD data have become closer and closer to the experimental ones, which attracts more and more scientists to use ECD calculation to determine the absolute configuration of natural products. In this review, we recommend some general softwares and methods in ECD calculation. In addition, we give some of our works as examples to introduce ECD calculation in assignment of absolute configuration of natural products.

Theoretical calculation of electronic circular dichroism: A promising tool for the determination of absolute configuration of natural products / 国际药学研究杂志

Determination of the absolute configuration is one of the most important and long-standing issues in the structure elucidation of natural products. Some natural products have difficulty forming crystal structures or yield few crystal structures, making it impossible to determine their absolute configuration by X-ray diffraction (XRD) and chemical derivatization such as Mosher reaction. Circular dichroism (CD) can be measured in solution, needs only small amount of sample, requires no standards and can be recycled after measurement, so the absolute configurations of chiral natural products can be determined reliabley by comparison of electronic circular dichroism (ECD) spectra with experimental CD spectra. In this paper, we attempt to use the bioactive natural product found by our group, (-)-alternarlactam, together with its synthetic by-product (+)-alternarlactam, to help us understand the applicability of this approach in determining the absolute configurations of complex chiral natural molecules.

Theoretical methods in configuration determinations for natural chiral products: Research advances / 国际药学研究杂志

Identification of natural products has been a big challenge because of their structural complexity and diversity. Recently, with the development of separation materials, more and more complex compounds have been found with small quantity, which causes difficulty in absolute configuration assignment. Now, the computational methods, such as to compute the 13C NMR data and compare them with experimental results, could be used for relative configuration study other methods, for example, to compute optical rotation (OR), or optical rotatory dispersion (ORD), electronic circular dichroism (ECD or CD) or vibrational circular dichroism VCD, could be efficiently used for absolute configuration determinations for chiral compounds, including the derminant computations for chiral acyclic compounds. Now, two or two more methods are applied for the absolute configuration study and exhibit very powerful reliability.

Electronic circular dichroism behavior of chiral Phthiobuzone

Phthiobuzone is a bis(thiosemicarbazone) derivative with a single chiral center which has been used as a racemate in the clinical treatment of herpes and trachoma diseases. In this study, its two enantiomers were prepared from chiral amino acids and their absolute configurations were investigated by electronic circular dichroism (ECD) combined with modern quantum-chemical calculations using time-dependent density functional theory. It was found that solvation changed both the conformational distribution and the ECD spectrum of each conformer. The theoretical ECD spectra of the two enantiomers were in good agreement with the experimentally determined spectra of the corresponding isomers in dimethyl sulfoxide. The ECD behavior of the bis(thiosemicarbazone) chromophore in a chiral environment is also discussed. Our results indicate that ECD spectroscopy may be a useful tool for the stereochemical evaluation of chiral drugs.