ABSTRACT
Five new terpenoids, including two vibsane-type diterpenoids (1, 2) and three iridoid allosides (3-5), together with eight known ones, were isolated from the leaves and twigs of Viburnum odoratissimum var.sessiliflorum. Their planar structures and relative configurations were determined by spectroscopic methods, especially 2D NMR techniques. The sugar moieties of the iridoids were confirmed as β-D-allose by GC analysis after acid hydrolysis and acetylation. The absolute configurations of neovibsanin Q (1) and dehydrovibsanol B (2) were determined by quantum chemical calculation of their theoretical electronic circular dichroism (ECD) spectra and Rh2(OCOCF3)4-induced ECD analysis. The anti-inflammatory activities of compounds 1, 3, 4, and 5 were evaluated using an LPS-induced RAW264.7 cell model. Compounds 3suppressed the release of NO in a dose-dependent manner, with an IC50 value of 55.64 μmol·L-1. The cytotoxicities of compounds 1-5 on HCT-116 cells were assessed and the results showed that compounds 2 and 3 exhibited moderate inhibitory activities with IC50 values of 13.8 and 12.3 μmol·L-1, respectively.
Subject(s)
Terpenes/pharmacology , Viburnum/chemistry , Molecular Structure , Diterpenes/chemistry , Plant Leaves/chemistryABSTRACT
Two new lignan glucosides, tinsinlignans A and B (1 and 2), two new oxyneolignans, tinsinlignans C and D (3 and 4), along with one known analogue (5), were isolated from the stems of Tinospora sinensis. The structures of the new compounds were elucidated based on analysis of spectroscopic data, and the absolute configuration of 1 was determined through electronic circular dichroism (ECD) calculation based on the time-dependent density functional theory (TD-DFT). Compounds 1-4 were evaluated for their inhibitory effects on nitric oxide (NO) production induced by lipopolysaccharide (LPS) in murine RAW264.7 macrophage cells and compounds 1 and 2 exhibited moderate inhibitory activities with IC
Subject(s)
Animals , Mice , Glucosides/pharmacology , Lignans/pharmacology , Lipopolysaccharides , Molecular Structure , Nitric Oxide , Phytochemicals/pharmacology , Tinospora/chemistryABSTRACT
Eight cembrane-type diterpenoids, namely, (+)-(6)-6-hydroxyisosarcophytoxide (), (+)-(6)-6-acetoxyisosarcophytoxide (), (+)-17-hydroxyisosarcophytoxide (), sarcomililatins A-D (-), and sarcomililatol (), were isolated from the soft coral collected from Weizhou Island, Guangxi Autonomous Region, together with 2 known related analogues, (+)-isosarcophytoxide () and (+)-isosarcophine (). The structures of these compounds were elucidated by a combination of detailed spectroscopic analyses, chemical methods, and comparison with reported data. The absolute configuration of compound was established by the modified Mosher׳s method, while the absolute configurations of compounds and were assigned by electronic circular dichroism (ECD) spectroscopy and that of compound was established by time-dependent density functional theory electronic circular dichroism (TD-DFT ECD) calculation. In bioassays, compound displayed significant cytotoxicity against the human cancer cell lines human promyelocytic leukemia cells (HL-60) and human lung adenocarcinoma cells (A-549) with IC values of 0.78±0.21 and 1.26±0.80 μmol/L, respectively. Compounds and also showed moderate inhibitory effects on the TNF-induced Nuclear factor kappa B (NF-B, a therapeutical target in cancer) activation, showing IC values of 35.23±12.42 and 22.52±4.44 μmol/L, respectively.
ABSTRACT
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
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.