Sesquiterpenoids from Vernonia cinerea

A new sesquiterpenoid, vernocinolide A (1), as well as ten known ones (2-11), were isolated from the ethyl acetate soluble fraction of Vernonia cinerea. The structure of vernocinolide A (1) was elucidated by spectroscopic methods. Among the known sesquiterpenoids, nine of them were isolated from this plant for the first time.

Alkaloids from the fungus Lactarius subplinthogalus

A new alkaloid, namely laccarin A (1), along with four known alkaloids, laccarin (2), adenosine (3), indole-3-carboxaldehyde (4) and nicotinamide (5), was isolated from the fungus Lactarius subplinthogalus. The structure of laccarin A (1) was established mainly by spectroscopic methods.

Turrapubesins A and B, First Examples of Halogenated and Maleimide-Bearing Limonoids in Nature fromTurraeapubescens

[structure: see text] Two novel tetranortriterpenoids, turrapubesins A (1) and B (2), representing the first examples of halogenated and maleimide-bearing limonoids, were isolated from the twigs and leaves of Turraea pubescens. The structures of 1 and 2 were elucidated by extensive spectroscopic analysis. Their absolute configurations were determined by X-ray crystallography of 1 and by CD analysis of a dihydrogenated derivative of 2. Turrapubesin A (1) exhibited weak cytotoxicity against the P-388 tumor cell line.

New pregnane steroids from Turraea pubescens

Three new pregnane steroids, 2beta,3beta,5beta-trihydroxy-pregn-20-en-6-one (1), 3beta-hydroxy-5alpha-pregn-7,20-dien-6-one (2), and 3beta-acetoxy-5alpha-pregn-7,20-dien-6-one (3) were isolated from the twigs and leaves of Turraea pubescens, and were structurally elucidated on the basis of spectroscopic data and chemical method.

Lignans from Saussurea conica and their NO production suppressing activity

Three new lignan derivatives, conicaols A and B and conicaoside, together with seven known compounds were identified from Saussurea conica. Their structures were elucidated by spectral methods including 1D and 2D NMR techniques. Six 2,3-dibenzylbutyrolactone-type lignans were biologically evaluated, and two of them, arctigenin and matairesinol, showed potent activity to suppress NO production in vitro in LPS-activated macrophages of SD rat.

New bisbenzylisoquinoline alkaloids from Cocculus laurifolius

Two new bisbenzylisoquinoline alkaloids, alpha, alpha'-dioxo-7'-O-demethylstebisimine (1) and 7'-O-demethylstebisimine (2), along with 14 known alkaloids, were isolated from the roots of Cocculus laurifolius. These alkaloids were characterized mainly by spectroscopic methods.

Flueggenines A and B, Two Novel C,C-Linked Dimeric Indolizidine Alkaloids from Flueggea virosa

[structure: see text] Two unprecedented C,C-linked dimeric indolizidine alkaloids, flueggenines A (1) and B (2), as well as their biosynthetic precursor (-)-norsecurinine, were isolated from the roots of Flueggea virosa. Their structures and absolute configurations were elucidated by spectroscopic methods, especially 2D NMR and CD spectral analyses, and supported by their unique biosynthetic pathway as proposed. Both 1 and 2 were tested against two tumor cell lines, and alkaloid 1 showed weak activity against the P-388 cell line.

Daphniyunnines A-E, alkaloids from Daphniphyllum yunnanense

The first chemical study on the stems and leaves of Daphniphyllum yunnanense led to the isolation of five new alkaloids, daphniyunnines A-E (1-5). Daphniyunnines B-E (2-5) are four unusual C-22 nor-Daphniphyllum alkaloids. The structures of these alkaloids were characterized by spectroscopic methods, especially 2D NMR techniques. A single-crystal X-ray diffraction analysis was used to confirm the structure of 1. Daphniyunnine D (4) showed cytotoxicity against two tumor cell lines, P-388 and A-549, with IC(50) values of 3.0 and 0.6 microM, respectively.

Electrophysiological characterization of 14-benzoyltalatisamine, a selective blocker of the delayed rectifier K+ channel found in virtual screening

14-Benzoyltalatisamine is a potent and selective blocker of the delayed rectifier K+ channel found in a computational virtual screening study. The compound was found to block the K+ channel from the extracellular side. However, it is unclear whether 14-benzoyltalatisamine shares the same block mechanism with tetraethylammonium (TEA). In order to elucidate how the hit compound found by the virtual screening interacts with the outer vestibule of the K+ channel, the effects of 14-benzoyltalatisamine and TEA on the delayed rectifier K+ current of rat dissociated hippocampal neurons were compared using whole-cell voltage-clamp recording. External application of 14-benzoyltalatisamine and TEA reversibly inhibited the current with IC50 values of 10.1+/-2.2 microM and 1.05+/-0.21 mM, respectively. 14-Benzoyltalatisamine exerted voltage-dependent inhibition, markedly accelerated the decay of the current, and caused a significant hyperpolarizing shift of the steady-state activation curve, whereas TEA caused voltage-independent inhibition, without affecting the kinetic parameters of the current. The blockade by 14-benzoyltalatisamine, but not by TEA, was significantly diminished in a high K+ (60 mM) external solution. The potency of 14-benzoyltalatisamine was markedly reduced in the presence of 15 mM TEA. The results suggest that 14-benzoyltalatisamine bind to the external pore entry of the delayed rectifier K+ channel with partial insertion into the selectivity filter, which is in conformity with that predicted by the molecular docking model in the virtual screening.

Alkaloids from Daphniphyllum longeracemosum

Four new Daphniphyllum alkaloids, daphnilongeranins A-D (1-4), along with four known ones, daphniphylline, longistylumphylline A, deoxyisocalyciphylline B, and daphnicyclidin D, were isolated from the leaves and stems of Daphniphyllum longeracemosum. Daphnilongeranin A (1) is the first seco-10,17-longistylumphylline A type Daphniphyllum alkaloid, and daphnilongeranin B (2) is a new C-22 nor-Daphniphyllum alkaloid based on a new C21 skeleton. Their structures and stereochemistry were determined using spectroscopic data and chemical methods.

Terpenoid indole alkaloids from Winchia calophylla

Three new indole alkaloids, N(4)-demethyl-12-methoxyalstogustine (1), 17-carboxyl-N(4)-methylechitamidine chloride (2), and 17-carboxyl-12-methoxy-N(4)-methylechitamidine chloride (3), along with 15 known alkaloids, were isolated from the ethanolic extract of the stem bark of Winchia calophylla. The structures of 1-3 were elucidated on the basis of spectroscopic means and chemical methods. The determination of relative configurations at C-19 and C-20 for 1-3 was aided by 13C NMR spectroscopic data. The absolute configurations of alkaloids 1-3 were determined by direct comparison of their CD spectra with those of known alkaloids. All the alkaloids were tested in cytotoxic assays against P-388 and A-549 tumor cell lines, and only two of them showed weak activity against the A-549 cell line.

Sesquiterpenoids fromVernonia cinerea

A new sesquiterpenoid, namely vernocinolide A, as well as ten known ones, were isolated from the ethyl acetate soluble fraction of the Vernoniacinerea. The structure of vernocinolide A was elucidated by spectroscopic methods. Among the known sesquiterpenoids, nine of them were isolated from this plant for the first time.

Sesquiterpene lactones with potent cytotoxic activities from Vernonia chinensis

Five new sesquiterpene lactones, namely vernchinilides A-E (1-5), along with five known compounds, 8 beta-(2-methylacryloyloxy)hirsutinolide 13-O-acetate (6), 8 alpha-(2-methylacryloyloxy)-1beta,4beta-epoxy-1alpha-methoxy-13-O-acetate-10 betaH-germacra-5 E,7(11)-dien-12,6-olide (7), 8 beta-(2-hydroxymethylacryloyloxy)hirsutinolide 13-O-acetate (8), 8 alpha-tigloyloxyhirsutinolide 13-O-acetate ( 9) and vernolide-B (10) were isolated from Vernonia chinensis. The structures of these new compounds were elucidated on the basis of spectral data, especially 2D-NMR techniques. Compounds 2, 5 and 6 exhibited potent cytotoxic activities against P-388 and A-549 tumor cell lines.

Pseudolaric acid B inhibits angiogenesis and reduces hypoxia-inducible factor 1alpha by promoting proteasome-mediated degradation

PURPOSE

Pseudolaric acid B (PAB), the naturally occurring diterpenoid isolated from the root bark of Pseudolarix kaempferi Gordon tree (Pinaceae), possesses potent antifungal and pregnancy-terminating effects that may be tightly associated with angiogenesis. This study was to examine its angiogenic inhibition, impact on vascular endothelial growth factor (VEGF) secretion from tumor cells and the possible mechanism of action.

EXPERIMENTAL DESIGN

Angiogenesis inhibition was assessed by the human umbilical vascular endothelial cell proliferation, migration, and tube-formation assays, as well as the chorioallantoic membrane assay. ELISA, reverse transcription-PCR, and Western blotting analyses were performed to examine VEGF protein secretion, mRNA expression, and the possible mechanism in hypoxic MDA-MB-468 cells.

RESULTS

PAB displayed potent in vitro antiangiogenic activity shown by inhibiting VEGF-stimulated proliferation and migration and fetal bovine serum-stimulated tube formation of human umbilical vascular endothelial cells in a concentration-dependent manner. Moreover, PAB (10 nmol per egg) significantly suppressed in vivo angiogenesis in the chorioallantoic membrane assay. On the other hand, PAB abrogated hypoxia-induced VEGF secretion from MDA-MB-468 cells via reducing HIF-1alpha protein. Additional analyses using LY294002 and U0126 indicated that the increase in hypoxia-inducible factor 1 (HIF-1)alpha protein level was highly dependent on phosphatidylinositol 3'-kinase and p42/p44 mitogen-activated protein kinase activities in hypoxic MDA-MB-468 cells. However, PAB treatment did not affect the active (phosphorylated) forms of Akt and Erk. Interestingly, the selective proteasome inhibitor MG-132 completely reversed the reduction of HIF-1alpha protein in the PAB-treated MDA-MB-468 cells.

CONCLUSIONS

PAB displays the dual antiangiogenic activities of directly inhibiting endothelial cells and abrogating paracrine stimulation of VEGF from tumor cells due to reducing HIF-1alpha protein by promoting its proteasome-mediated degradation in MDA-MB-468 cells, which has potential clinical relevance.