ABSTRACT
To investigate the chemical constituents of Anisodus tanguticus, silica gel column chromatography, Sephadex LH-20 column chromatography, preparative thin layer chromatography, and semi-preparative HPLC were used to separate and purify the chemical constituents from the extract of A. tanguticus. The planar structure of the isolated compound was identified by HRMS, IR, and 2D NMR experiments. The absolute configuration of the isolated compound was determined by a combination of NOESY, coupling constant, circular dichroism (CD), and transition metal chelate reagent dimolybdenum tetraacetate [Mo2(OAc)4]-induced circular dichroism (ICD) data analysis. A new compound of the anisotane-type sesquiterpene (1) was isolated, which was determined to be (1R,2S,3R,4R,6R,7R,9R)-anisotane-11(13)-ene-3,4,9-triol and named anisotanol F. This is the second report of anisotane-type sesquiterpene, which has previously been reported as a novel sesquiterpenoid skeleton by our research group. Furthermore, the cytotoxicity against HUVECs and inhibitory effect on NO release in LPS-induced RAW264.7 cells of compound 1 were investigated. However, the results showed that it was inactive. Compound 1 is a new compound isolated from A. tanguticus. It belongs to the unusual anisotane-type sesquiterpene. This result enriches the chemical composition of A. tanguticus.
ABSTRACT
A new compound was isolated from the 95% ethanolic extract of the rhizomes of Curcuma longa L. using silica gel column chromatography, medium pressure liquid chromatography, and semi-preparative high performance liquid chromatography. The structure and absolute configuration of the compound was elucidated by HR-ESI-MS, NMR, and electronic circular dichroism (ECD) calculations. It is a novel sesquiterpenoid, which is named as isoturmeronol B (1). The carbon skeleton of compound 1 is similar to that of bisabolane-type sesquiterpenoid. The only difference is that the methyl group at C-4 in bisabolene-type sesquiterpenoid is migrated to C-5 in compound 1. Besides, the anti-inflammatory and antioxidant activities of the compound 1 were evaluated. The results showed that 1 has no anti-inflammatory and antioxidant activities.
ABSTRACT
Abstract In this study, sahandone (1) and a new diterpenoid named sahandol II (2) were isolated from the roots of Salvia chloroleuca Rech. f. & Aellen, Lamiaceae. The absolute configurations of compounds 1 and 2 were assigned by comparison of experimental electronic circular dichroism spectra and comparing with published data. Cytotoxic and apoptotic evaluation of the isolated compounds and the methanol crude extract and its subfractions including petroleum ether, dichloromethane, ethyl acetate, n-butanol and aqueous fraction on two human prostate cancer cell lines and a breast cancer cell lines, showed that non-polar and semi-polar subfractions had the potent cytotoxic effect on PC3 cells with the IC50 values of 24.19, 33.59, and 47.15 µg/ml, respectively. Sub-G1 peak in flow cytometry histogram of cells treated with petroleum ether, dichloromethane and ethyl acetate subfractions showed the induction of apoptosis. Change in the Bax/Bcl-2 ratio and cleavage of poly ADP-ribose polymerase were observed.
ABSTRACT
Five alkaloids were isolated from a decoction of Uncaria rhynchophylla by a combination of various chromatographic techniques, including macroporous adsorbent resin, MCI resin, silica gel, Sephadex LH-20, and reversed phase HPLC. Their structures were characterized by comprehensive analyses of spectroscopic data as monoterpene indole alkaloids (+)-(7R)-3-oxo-7-hydroxy-3,7-seco-dihydrorhynchohylline (1), (+)-(7S)-3-oxo-7-hydroxy-3,7-seco-dihydrorhyncho-hylline (2), (+)-(7R)-3-oxo-7-hydroxy-3,7-seco-rhynchohylline (3) and (+)-(7S)-3-oxo-7-hydroxy-3,7-seco-rhynchohylline (4), and a β-carboline alkaloid 1,2,3,4-tetrahydro-1-oxo-β-carboline (5). Among them, 1 and 2 are new compounds, 3 and 4 are new natural products that were semi-synthesized from isorhynchohylline with incorrect specific rotations, and 5 is isolated for the first time from the genus Uncaria.
ABSTRACT
Two cyclopeptides, celogentin L (1) and its epimer lyciumin A (2) were firstly isolated from Celosia argentea L.. The planar structures of the two compounds were fully determined by spectroscopic data, including 1D-, 2D-NMR, and HR-ESI/MS. The absolute configurations of amino acid components were assigned via chiral-phase HPLC analyses after acid hydrolysis. Furthermore, the configuration of C-N linkage at the glycine Cα was elucidated by extensive analyses of 2D-NMR and comparison of the experimental and calculated electronic circular dichroism (ECD) spectra. Cytotoxicity of the two compounds against human alveolar epithelial A549, hepatocellular carcinoma HepG2, and cervical cancer Hela cell lines was assayed. Although both of them were inactive in these cells, the present findings add new facets for the chemistry of Celosia argentea.
Subject(s)
Humans , A549 Cells , Cell Survival , Celosia , Chemistry , Chemistry Techniques, Analytical , HeLa Cells , Hep G2 Cells , Molecular Conformation , Molecular Structure , Peptides, Cyclic , Chemistry , Toxicity , Seeds , Chemistry , StereoisomerismABSTRACT
Two new limonoids, 12-ethoxynimbolinins G and H (compounds 1 and 2), and one known compound, toosendanin (Chuanliansu) (compound 3), were isolated from the bark of Melia toosendan. Their structures were elucidated by spectroscopic analysis and X-ray techniques. The absolute configuration of toosendanin (3) was established by single-crystal X-ray diffraction. Compounds 1-3 were evaluated for their cytotoxicity against five tumor cell lines.
Subject(s)
Humans , Cell Line, Tumor , Cell Proliferation , Limonins , Melia , Chemistry , Molecular Structure , Plant Bark , Chemistry , Plant Extracts , Chemistry , Pharmacology , X-Ray DiffractionABSTRACT
Two cyclopeptides, celogentin L (1) and its epimer lyciumin A (2) were firstly isolated from Celosia argentea L.. The planar structures of the two compounds were fully determined by spectroscopic data, including 1D-, 2D-NMR, and HR-ESI/MS. The absolute configurations of amino acid components were assigned via chiral-phase HPLC analyses after acid hydrolysis. Furthermore, the configuration of C-N linkage at the glycine Cα was elucidated by extensive analyses of 2D-NMR and comparison of the experimental and calculated electronic circular dichroism (ECD) spectra. Cytotoxicity of the two compounds against human alveolar epithelial A549, hepatocellular carcinoma HepG2, and cervical cancer Hela cell lines was assayed. Although both of them were inactive in these cells, the present findings add new facets for the chemistry of Celosia argentea.
Subject(s)
Humans , A549 Cells , Cell Survival , Celosia , Chemistry , Chemistry Techniques, Analytical , HeLa Cells , Hep G2 Cells , Molecular Conformation , Molecular Structure , Peptides, Cyclic , Chemistry , Toxicity , Seeds , Chemistry , StereoisomerismABSTRACT
Two new limonoids, 12-ethoxynimbolinins G and H (compounds 1 and 2), and one known compound, toosendanin (Chuanliansu) (compound 3), were isolated from the bark of Melia toosendan. Their structures were elucidated by spectroscopic analysis and X-ray techniques. The absolute configuration of toosendanin (3) was established by single-crystal X-ray diffraction. Compounds 1-3 were evaluated for their cytotoxicity against five tumor cell lines.
Subject(s)
Humans , Cell Line, Tumor , Cell Proliferation , Limonins , Melia , Chemistry , Molecular Structure , Plant Bark , Chemistry , Plant Extracts , Chemistry , Pharmacology , X-Ray DiffractionABSTRACT
Monosaccharides are one of the most important structural components of biomolecules, such as polysaccharides, nucleic acids, glycolipids and glycoproteins. In structural analysis of polysaccharides and glycoconjugates, the absolute configurations (D or L) of the constituent monosaccharides are usually determined by measurement of the optical rotation, CD spectra or characteristic chromatographic retention behavior. However, each method has its unique advantages and limitations which should be considered while using them. In this review, an overview of the different methods for the determination of absolute configuration of monosaccharides and their underlying principles are summarized to serve as a reference for researchers.
ABSTRACT
Determination of the absolute configuration is considered one of the most complicated works in the natural products study. Mosher's method provides a practical solution for the stereochemistry determination of natural products by means of NMR spectroscopy. This article, which reviews the classic application of Mosher's method, is one of the series of historical stories on natural product chemistry published in this journal.
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Two new steroidal saponins, named timosaponin P (1) and timosaponin Q (2), were isolated from the rhizome parts of Anemarrhena asphodeloides Bunge using various chromatographic methods. Their structures and absolute configurations were elucidated by a combination of spectroscopic and spectrometric data, including 1D, 2D NMR, HR-ESI-MS and ECD calculations, and this is the first time the absolute configuration of C-23 of steroidal saponin was confirmed by ECD calculations.
Subject(s)
Anemarrhena , Chemistry , Drugs, Chinese Herbal , Chemistry , Magnetic Resonance Spectroscopy , Mass Spectrometry , Molecular Structure , Saponins , Chemistry , Steroids , ChemistryABSTRACT
Three pairs of glycosidic 8,4'-oxyneolignane diastereoisomers, named isatioxyneolignosides A-F (-), were isolated from an aqueous extract ofroots. Their structures and absolute configurations were elucidated by comprehensive spectroscopic data analysis and enzyme hydrolysis. The validity of Δvalues to distinguishandaryl glycerol units and Cotton effects at 235±5 nm to determine absolute configurations at C-8 in-and their aglycones (-) are discussed.
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The difficulty in the structure elucidation of natural products is in the elucidation of stereochemistry, especially the determination of absolute configuration, which generally involves the key techniques of structure elucidation of natural products. This paper shows some examples of our work in elucidating the stereochemistry of new chiral natural products by the application of several physicochemical techniques, such as the dimolybdenum tetraacetate [Mo2(OAc)4] induced CD (ICD, Snatzke’s method), empirical rules of classical CD, modified Mosher’s method, theoretical ECD calculation and modified Marfey’s analysis. The fundamental rules of the techniques and our experiences in the application of these techniques are also described for related researcher’s reference in relevant studies.
ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
The presentation of chemical and biological properties of natural products is directly related to its absolute configuration. To have a comprehensive understanding of natural products, it is important to determine the absolute configuration of natural products. The traditional methods for the determination of absolute configuration are limited in some cases. With the development in computational technology and quantum chemistry theory, the spectroscopic properties of natural products, such as optical rotatory dispersion(ORD), circular dichroism(CD) and nuclear magnetic resonance(NMR) , can be calculated with accuracy. The combination of theoretical and experimental spectroscopy provides a new insight for determining the absolute configuration. Recently, computational chemistry has become a powerful tool, and in this review we presents its application in the determination of absolute configuration of natural products, which provides a guideline for readers in choosing an appropriate method when facing a particular case.
ABSTRACT
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.
ABSTRACT
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.
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The determination of the absolute configuration of natural products has drawn great attention for a long time. The circular dichroism (CD) spectroscopy appears to be an efficient method for determining the absolute configuration of chiral compounds in solution. Studies from abroad indicated a straightforward method which employed a transition metal chelate dirhodium reagent Rh2(OCOCF3)4 for the assignment of the absolute configurations of the secondary and tertiary alcohols. The CD spectra of the in situ complexes of chiral alcohols with Rh2(OCOCF3)4 showed up to 6 Cotton effects (A-F) at the range of 600-270 nm. It was demonstrated that the E band, appearing at ca. 350 nm, can be used for correlation of its sign and the stereochemistry of the secondary or tertiary alcohols, by applying the bulkiness rule. In this review, the methodology including theory, procedures and results, as well as the application examples are presented.