Influence of Cu adatoms on the molecular assembly of 4,4'-bipyridine on Cu(111).

The formation of highly organized structures based on two ligands with pyridyl functionalities, 4,4'-bipyridine (BPY) and 1,4-di(4,4''-pyridyl) benzene (BPYB), and Cu adatoms on the Cu(111) surface has been studied with low temperature and variable temperature scanning tunneling microscopy (STM) and first-principles calculations. We show that the formation of a highly organized adlayer built from adatom-molecule and molecule-molecule units strongly depends on the number of mobile Cu atoms on the surface. While a high concentration of Cu adatoms (high adatom/BPY ratio, ≥1) leads systematically to the formation of organometallic nanolines, their absence (low adatom/BPY ratio, ≈0) gives a compact self-assembled molecular network, and more specifically hydrogen-bond networks (HBN) with BPY molecules organized in a T-shaped fashion. Alternatively, an intermediate concentration of Cu adatoms (0 < adatom/BPY < 1) allows the formation of a well-organized and compact structure where both organometallic and HBN components coexist. Although STM images cannot clearly reveal the presence of Cu adatoms within the organometallic moiety, the bonding of BPY to a single or two Cu adatoms can be clearly identified by scanning tunneling spectroscopy (STS), and is supported by Density Functional Theory (DFT) results. Additional STM simulations suggest that the relative position of the Cu adatom with respect to the organic ligands just above has a significant impact on its detection by STM. This study exemplifies the prominent role of metallic adatoms on the formation of a complex organometallic network and should open more rational practices to optimize the formation of these supramolecular networks.

Portulaca oleracea reduces triglyceridemia, cholesterolemia, and improves lecithin: cholesterol acyltransferase activity in rats fed enriched-cholesterol diet.

PURPOSE: The effects of Portulaca oleracea (Po) lyophilized aqueous extract were determined on the serum high-density lipoproteins (HDL2 and HDL3) amounts and composition, as well as on lecithin: cholesterol acyltansferase (LCAT) activity. METHODS: Male Wistar rats (n = 12) were fed on 1% cholesterol-enriched diet for 10 days. After this phase, hypercholesterolemic rats (HC) were divided into two groups fed the same diet supplemented or not with Portulaca oleracea (Po-HC) (0.5%) for four weeks. RESULTS: Serum total cholesterol (TC) and triacylglycerols (TG), and liver TG values were respectively 1.6-, 1.8-, and 1.6-fold lower in Po-HC than in HC group. Cholesterol concentrations in LDL-HDL1, HDL2, and HDL3 were respectively 1.8, 1.4-, and 2.4-fold decreased in Po-HC group. HDL2 and HDL3 amounts, which were the sum of apolipoproteins (apos), TG, cholesteryl esters (CE), unesterified cholesterol (UC), and phospholipids (PL) contents, were respectively 4.5-fold higher and 1.2-fold lower with Po treatment. Indeed, enhanced LCAT activity (1.2-fold), its cofactor-activator apo A-I (2-fold) and its reaction product HDL2-CE (2.1-fold) were observed, whereas HDL3-PL (enzyme substrate) and HDL3-UC (acyl group acceptor) were 1.2- and 2.4-fold lower. CONCLUSION: Portulaca oleracea reduces triglyceridemia, cholesterolemia, and improves reverse cholesterol transport in rat fed enriched-cholesterol diet, contributing to anti-atherogenic effects.

Antioxidant effect of Ajuga iva aqueous extract in streptozotocin-induced diabetic rats.

The purpose of this study was to investigate the possible antioxidant effect of an aqueous extract of Ajuga iva (Ai) in streptozotocin (STZ)-induced diabetic rats. Twelve diabetic rats were divided into two groups fed a casein diet supplemented or not with Ai (0.5%), for 4 weeks. In vitro, the Ai extract possessed a very high antioxidant effect (1 mg/ml was similar to those of trolox 300 mmol/l). The results indicated that plasma thiobarbituric acid reactive substances (TBARS) values were reduced by 41% in Ai-treated compared with untreated diabetic rats. TBARS concentrations were lower 1.5-fold in liver, 1.8-fold in heart, 1.9-fold in muscle and 2.1-fold in brain in Ai-treated than untreated group. In erythrocytes, Ai treatment increased significantly the activities of glutathione peroxidase (GSH-Px) (+25%) and glutathione reductase (GSSH-Red) (+22%). Superoxide dismutase activity was increased in muscle (+22%), while GSH-Px activity was significantly higher in liver (+28%), heart (+40%) and kidney (+45%) in Ai-treated compared with untreated group. Liver and muscle GSSH-Red activity was, respectively, 1.6- and 1.5-fold higher in Ai-treated than untreated diabetic group. Catalase activity was significantly increased in heart (+36%) and brain (+32%) in Ai-treated than untreated group. Ai treatment decreased plasma nitric oxide (-33%), carbonyls (-44%) and carotenoids (-68%) concentrations. In conclusion, this study indicates that Ajuga iva aqueous extract improves the antioxidant status by reducing lipid peroxidation and enhancing the antioxidant enzymes activities in plasma, erythrocytes and tissues of diabetic rats.

Dynamics of dengue epidemics in urban contexts.

Dengue, similar to other arboviral diseases, exhibits complex spatiotemporal dynamics. Even at town or village level, individual-based spatially explicit models are required to correctly reproduce epidemic curves. This makes modelling at the regional level (province, country or continent) very difficult and cumbersome. We propose here a first step to build a hierarchized model by constructing a simple analytical expression which reproduces the model output from macroscopic parameters describing each 'village'. It also turns out to be a good approximation of real urban epidermic outbreaks. Subsequently, a regional model could be built by coupling these equations on a lattice.

Changes in antioxidant defense status in hypercholesterolemic rats treated with Ajuga iva.

The aim of the study was to investigate the effect of aqueous extract of Ajuga iva (Ai) on serum and tissues lipid peroxidation as well as antioxidant enzymes activities in red blood cells (RBC) and tissues, in high hypercholesterolemic rats (HC). Male Wistar rats (n=12) were fed on 1% cholesterol-enriched diet for 15d. After this adaptation phase, hypercholesterolemic rats (total cholesterol=6.5+/-0.6mol/l) were divided into two groups fed the same diet and treated or not with Ai for 15d. Thiobarbituric acid reactive substances (TBARS) concentrations in serum, LDL-HDL(1), HDL(2) and HDL(3) were respectively, 5-, 7.8-, 2.3- and 5-fold lower in Ai treated than untreated hypercholesterolemic groups. TBARS concentrations were 1.4-fold lower in heart and 2.8-fold higher in kidney in Ai-HC treated than untreated HC group. Superoxide dismutase activity was respectively, 1.2- and 1.4-fold higher in RBC and muscle in Ai treated than untreated group. In RBC, Ajuga iva treatment enhanced glutathione peroxidase (GSH-Px) (+9%) and glutathione reductase (GSSH-Red) (+12%) in Ai-HC treated than untreated HC group. GSSH-Red activity was 1.4- and 1.5-fold higher in adipose tissue and heart, respectively and 3.7-fold lower in kidney in Ai treated than untreated group. Liver catalase activity was 1.6-fold higher in Ai treated than untreated group. Adipose tissue and muscle total glutathione content represented in Ai treated group 35% and 36% of the value noted in untreated group. Nitric oxide values of liver, adipose tissue and heart were 3.3-, 2.5- and 3.4-fold higher in Ai-HC than HC group. Ajuga iva treatment enhanced alpha-tocopherol contents (+25%) in Ai treated than untreated group. In conclusion, Ajuga iva treatment is more effective to improve the antioxidant capacity of RBC than that of tissues. Indeed, Ai is able to reduce the oxidative stress in hypercholesterolemic rats by increasing the antioxidant enzymes activity.

Effect of aqueous extract of Ajuga iva supplementation on plasma lipid profile and tissue antioxidant status in rats fed a high-cholesterol diet.

The present study was designed to explore the possible antioxidant and hypolipidemic effects of the aqueous extract of Ajuga iva (0.5% in the diet) in rats fed a high-cholesterol (1%) diet (HCD). The results indicated that the HCD-Ai versus HCD treatment led to many changes in biochemical parameters. They showed a decrease of plasma total cholesterol (TC) and VLDL-cholesterol but an increase of HDL(2)-cholesterol. The triacylglycerol contents were reduced in plasma and in VLDL. The lipid peroxidation determined by TBARS was decreased by 75% in plasma. TBARS in liver, heart and kidneys were highly reduced excepted in the adipose tissue. Ajuga iva treatment enhanced superoxide dismutase activity in liver and kidney. Glutathione reductase activity was lowered in adipose tissue but increased in liver and in kidney. A significant increase was noted in glutathione peroxidase activity in liver, heart and kidney but a low value in adipose tissue was observed. In conclusion, the present study demonstrates that in addition to its potent TG and TC-lowering effects, Ajuga iva is effective in improving the antioxidant status by reducing lipid peroxidation in plasma and tissues and enhancing the antioxidant enzymes in rats fed high-cholesterol diet. Furthermore, Ajuga iva may reduce intestinal cholesterol absorption.

Bioactive steroidal saponins from Smilax medica.

Two new spirostanol saponins ( 1 and 2) were isolated from the roots of Smilax medica, together with the known smilagenin 3-O-beta-D-glucopyranoside (3). Their structures were determined by spectroscopic methods including 1D- and 2D-NMR experiments. Compounds 1 and 2 exhibited antifungal activity against the human pathogenic yeasts Candida albicans, C. glabrata and C. tropicalis (MICs between 6.25 and 50 microg/mL) whereas 3 was inactive.

Structure-activity-relationship of saponins to enhance toxic effects of agrostin.

Saponins with an aldehyde function bound at C-4 from different plant origins increase the cytotoxicity of the lectin agrostin by enhancing its penetration through the cell membrane. Experiments with different pure saponins in combination with agrostin showed that also the glycosidic part of acidic bisdesmosidic saponins especially the oligosaccharidic ester chain at C-28 plays an important role in the potentiation of agrostin's cytotoxicity as result of an interaction between saponins and lectins at the cell membrane.

An unusual new sulfated triterpene saponin from Arenaria juncea.

A novel triterpene saponin, 3-Osulfate-gypsogenic acid-23-O-beta-D-4-O-sulfate-glucopyranoside (junceoside D), has been isolated from the roots of Arenaria juncea. The structure was characterized mainly by a combination of 2D-NMR techniques, mass spectrometry and chemical methods.

Antinociceptive and anti-inflammatory activities of Acacia pennata wild (Mimosaceae).

The butanolic fraction of dried leaves of Acacia pennata (Mimosaceae) was tested for analgesic and anti-inflammatory activities in animal models. It showed significant protective effects against chemical stimuli (acetic acid and formalin) in the mouse. It also produced a significant increase of the threshold of sensitivity to pressure-induced pain in the rats. The extract revealed an inhibitory effect in carrageenin-induced rat paw oedema in the late phase. The results suggested that a peripheral mechanism is involved in the analgesic, associated to anti-inflammatory effect (NSAIDs-like). Among the class of compounds characterized in this fraction, flavonoids may be mainly responsible for the pharmacological activities.

Antifungal steroid saponins from Dioscorea cayenensis.

From the rhizomes of Dioscorea cayenensis Lam.-Holl (Dioscoreaceae), the new 26- O- beta- D-glucopyranosyl-22-methoxy-3 beta,26-dihydroxy-25( R)-furost-5-en-3- O- alpha- L-rhamnopyranosyl-(1-->4)- alpha- L-rhamnopyranosyl-(1-->4)-[ alpha- L-rhamnopyranosyl-(1-->2)]- beta- D-glucopyranoside ( 1) was isolated together with the known dioscin ( 2) and diosgenin 3- O- alpha- L-rhamnopyranosyl-(1-->4)- alpha- L-rhamnopyranosyl-(1-->4)-[ alpha- L-rhamnopyranosyl-(1-->2)]- beta- D-glucopyranoside ( 3). Their structures were established on the basis of spectral data. Compound 2 exhibited antifungal activity against the human pathogenic yeasts Candida albicans, C. glabrata and C. tropicalis (MICs of 12.5, 12.5 and 25 micro g/mL, respectively) whereas 3 showed weak activity and 1 was inactive.

New ursolic and betulinic derivatives as potential cytotoxic agents.

Fifteen new ursolic and betulinic triterpenoids, bearing various functionalities at C-3 and C-28 were synthesized as potential cytotoxic agents. All compounds were obtained by a hemisynthetic route via ursolic and betulinic acids. Preliminary screening of these compounds on human HT 29 colon cancer cells revealed inhibitory activity for three of them. Beta-D-Glucopyranosyl-3beta-hydroxyurs-12(13)-en-28-oate 1c, 3beta-3-(3-pyridyl)-prop-2-enoyloxyurs-12(13)-en-28-oic acid 1i and the potassium salt of 3beta-cinnamoyloxylup-20(29)-en-28-oic acid 2d demonstrated cytotoxic activity in the micromolar range: 8.0, 45.0 and 8.0 microM, respectively.

A review of natural and modified betulinic, ursolic and echinocystic acid derivatives as potential antitumor and anti-HIV agents.

The aim of this review is to update current knowledge on the betulinic, ursolic and echinocystic acids and their natural and semisynthetic analogs, focussing on their cytotoxic and anti-HIV activities. Then, the last results of the authors' team on unusual semisynthetic derivatives of these triterpenoids will be presented in order to establish structure/activity relationships.

Two new prosapogenins from Albizia adianthifolia.

Two new triterpenoidal prosapogenins 1 and 2 were obtained from the mild alkaline hydrolysate of the crude saponin fraction of Albizia adianthifolia (Mimosaceae) roots. Their structures were mainly determined by spectral analyses as acacic acid 3-O-beta-D-xylopyranosyl-(1-->2)-beta-D-fucopyranosyl-(1-->6)- 2-acetylamino-2-deoxy-beta-D-glucopyranoside (1) and acacic acid 3-O-(beta-D-xylopyranosyl-(1-->2)-beta-D-fucopyranosyl-(1-->6)- [beta-D-glucopyranosyl-(1-->2)]-beta-D-glucopyranosyl)-21-O-(6(S)-2- hydroxymethyl-6-methyl-6-O-(beta-D-quinovopyranosyl)-2,7-octadienoyl) ester (2). Furthermore, the known julibroside A3 was isolated from the crude saponin mixture. Compounds 1 and 2 did not show any ability to potentiate in vitro cisplatin cytotoxicity in a human colon cancer cell line.

Two triterpene saponins from Achyranthes bidentata.

Bidentatoside II(1) and chikusetsusaponin V methyl ester (2) are two further triterpene saponins isolated from the roots of Achyranthes bidentata. Chemical and homo and heteronuclear two-dimensional (2D) NMR techniques have led to the structural elucidation of 1 which is a new seco-glycoside of oleanolic acid and the full 1H- and 13C-NMR assignments of 2. These compounds did not show any potentiation of the in vitro cytotoxicity of cisplatin in the HT 29 human colon cancer cell line.

Three new acylated triterpene saponins from Acanthophyllum squarrosum.

Three new triterpenoid saponins, 1-3, were isolated from the roots of Acanthophyllum squarrosum. Their structures were established mainly by 2D NMR techniques as 3-O-beta-D-galactopyranosyl-(1-->2)-[beta-D-xylopyranosyl-(1-->3)]-beta-D-glucuronopyranosyl-gypsogenin-28-O-beta-D-xylopyranosyl-(1-->3)-beta-D-xylopyranosyl-(1-->4)-beta-D-xylopyranosyl-(1-->4)-3-O-acetyl-alpha-L-rhamnopyranosyl-(1-->2)-3,4-di-O-acetyl-beta-D-fucopyranoside (1), 3-O-beta-D-galactopyranosyl-(1-->2)-[beta-D-xylopyranosyl-(1-->3)]-beta-D-glucuronopyranosyl-gypsogenin-28-O-beta-D-xylopyranosyl-(1-->4)-alpha-L-rhamnopyranosyl-(1-->2)-[5-O-acetyl-alpha-L-arabinofuranosyl-(1-->3)]-4-O-acetyl-beta-D-fucopyranoside (2), and 3-O-beta-D-glucopyranosyl-quillaic acid-28-O-alpha-L-rhamnopyranosyl-(1-->2)-alpha-L-arabinopyranosyl-(1-->2)-[beta-D-glucopyranosyl-(1-->6)]-beta-D-glucopyranoside (3).

Bidentatoside I, a new triterpene saponin from Achyranthes bidentata.

Bidentatoside I (1) is a new triterpene saponin bearing an unusual dioxopropionic acid unit, isolated from the roots of Achyranthes bidentata. Structural elucidation was performed mainly by chemical and homo- and heteronuclear 2D NMR techniques. This compound did not show any potentiation of the in vitro cytotoxicity of cisplatin in the HT 29 human colon cancer cell line.

Effects of the flavonoids extracted from Spergularia purpurea Pers. on arterial blood pressure and renal function in normal and hypertensive rats.

The antihypertensive and diuretic effects of the flavonoids extracted from Spergularia purpurea Pers. (SP) were studied both in normotensive (NTR) and spontaneously hypertensive conscious rats (SHR). Daily oral administration of the flavonoid mixture (5 mg/kg for 1 week) exhibited a significant decrease in blood pressure with variation coefficient (Delta) of 20 in SHR rats and 11 in NTR rats. The systolic and diastolic blood pressure decreased significantly and respectively with 17 and 24% in SHR, and with 11 and 16% in NTR. The flavonoid mixture enhanced significantly the water excretion in hypertensive (P<0.001) and normal rats (P<0.001). Furthermore, oral administration of flavonoids mixture at a dose of 5 mg/kg produced a significant increase of urinary excretion of sodium (P<0.01), potassium (P<0.05) and chlorides (P<0.05) in SHR. Similarly, the flavonoid administration induced a significant increase of urinary electrolytes elimination in NTR (P<0.01 versus controls). No significant changes were noted on heart rate after flavonoids treatment in SHR as well as in NTR. While, glomerular filtration rate showed a significant increase after administration of flavonoids in all groups (P<0.05). These results suggest that oral administration of flavonoids obtained from Spergularia purpurea exhibited antihypertensive and diuretic actions.

Two new glycosides from Astragalus caprinus.

A new glycoside of flavonol (1) and a new glycoside of a cycloartane-type triterpene (2) were isolated from the leaves and the roots of Astragalus caprinus, respectively. Their structures were elucidated in turn by spectroscopic data interpretation as 3-O-[[beta-D-xylopyranosyl(1-->3)-alpha-L-rhamnopyranosyl(1-->6)][beta-D-apiofuranosyl(1-->2)]]-beta-D-galactopyranosyl kaempferol (1) and 3-O-(beta-D-xylopyranosyl)-24-O-(beta-D-glucopyranosyl)-20,25-epoxycycloartane-3beta,6alpha,16beta,24alpha-tetrol (2).

Chronic diuretic effect of the water extract of Spergularia purpurea in normal rats.

The purpose of this study was to examine the chronic diuretic effect of the water extract of the whole plant of Spergularia purpurea (SP) at different doses (100, 200 and 400 mg/kg) in normal rats. Daily oral administration of the water extract was tested for 4 weeks. Urinary water and electrolytes excretion were determined weekly. Oral administration of the water extract at different doses produced a significant and dose-dependent diuresis and increase in electrolytes excretion. The highest dose (400 mg/kg) of the water extract of SP enhanced urine output from 7.15 +/- 0.42 ml/24 h at the start to 23.01 +/- 0.75 ml/24 h after 4 weeks (p < 0.001). It also produced significant increase in urinary excretion of Na+ (P < 0.01), K+ (P < 0.01) and Cl(-) (P < 0.01). Chronic treatment with SP decreased significantly urine osmolality (P < 0.01 vs. control), while a slight increase in glomerular filtration rate was also observed (P < 0.05) for both doses of water extract (100 and 400 mg/kg). It is concluded that the water extract of whole plant of SP has a significant diuretic effect in rats.