Phenolic Glycosides with antiproteasomal activity from Centaurea urvillei DC. subsp. urvillei

A new flavanone glycoside, naringenin-7-O-β-d-glucuronopyranoside, and a new flavonol glycoside, 6-hydroxykaempferol-7-O-β-d-glucuronopyranoside were isolated together with 12 known compounds, 5 flavone glycoside; hispidulin-7-O-β-d-glucuronopyranoside, apigenin-7-O-β-d-methylglucuronopyranoside, hispidulin-7-O-β-d-methylglucuronopyranoside, hispidulin-7-O-β-d-glucopyranoside, apigenin-7-O-β-d-glucopyranoside, a flavonol; kaempferol, two flavone; apigenin, and luteolin, a flavanone glycoside; eriodictyol-7-O-β-d-glucuronopyranoside, and three phenol glycoside; arbutin, salidroside, and 3,5-dihydroxyphenethyl alcohol-3-O-β-d-glucopyranoside from Centaurea urvillei subsp. urvillei. The structure elucidation of the new compounds was achieved by a combination of one- (¹H and ¹³C) and two-dimensional NMR techniques (G-COSY, G-HMQC, and G-HMBC) and LC-ESI-MS. The isolated compounds were tested for their antiproteasomal activity. The results indicated that kaempferol, a well known and widely distributed flavonoid in the plant kingdom, was the most active antiproteasomal agent, followed by apigenin, eriodictyol-7-O-β-d-glucuronopyranoside, 3,5-dihydroxyphenethyl alcohol-3-O-β-d-glucopyranoside, and salidroside, respectively.     

Steroids from the leaves of Chinese Melia azedarach and their cytotoxic effects on human cancer cell lines

Three new (1-3) and several known (4-6) steroids were isolated from the leaves of Chinese Melia azedarach. The structures of the new compounds were elucidated by means of spectroscopic methods including 2D NMR techniques and mass spectrometry to be (20S)-5,24(28)-ergostadiene-3β,7α,16β,20-tetrol (1), (20S)-5-ergostene-3β,7α,16β,20-tetrol (2), and 2α,3β-dihydro-5-pregnen-16-one (3). The cytotoxicities of the isolated compounds against three human cancer cell lines (A549, H460, U251) were evaluated; only compounds 1, 2, and (20S)-5-stigmastene-3β,7α,20-triol (4) were found to show significant cyctotoxic effects with IC₅₀s from 12.0 to 30.1 μg/mL.     

Phenolic compounds from Bursera simaruba Sarg. bark: Phytochemical investigation and quantitative analysis by tandem mass spectrometry

Phytochemical investigation of the methanolic extract of Bursera simaruba bark led to the isolation of 11 compounds, including lignans yatein, β-peltatin-O-β-d-glucopyranoside, hinokinin and bursehernin, and three natural compounds namely 3,4-dimetoxyphenyl-1-O-β-d-(6-sulpho)-glucopyranoside, 3,4,5-trimetoxyphenyl 1-O-β-d-(6-sulpho)-glucopyranoside and 3,4-diidroxyphenylethanol-1-O-β-d-(6-sulpho)-glucopyranoside. Their structures were established by NMR and ESI/MS experiments. Additionally, an LC-ESI/MS qualitative study on the phenolic compounds and an LC-ESI/MS/MS quantitative study on the lignans found in the methanolic extract of B. simaruba bark were performed to give value to the plant as source of these biological active compounds. Quantitative analyses results confirmed that compounds yatein, β-peltatin-O-β-d-glucopyranoside, hinokinin and bursehernin are major compounds in the bark and, in particular, β-peltatin-O-β-d-glucopyranoside appears to be the most abundant.     

Tagalsins A-H, dolabrane-type diterpenes from the mangrove plant, Ceriops tagal

From the stems and twigs of the mangrove plant, Ceriops tagal, seven dolabrane-type diterpenes, namely tagalsins A-G (1-7), and the norditerpene tagalsin H (8) were isolated. Their structures were established on the basis of extensive spectroscopic analysis.     

Phenolic compounds in Hypericum species from the Trigynobrathys section

Phenolic compounds of thirteen Hypericum species growing in South Brazil were investigated aiming to evaluate the usefulness of their distribution as a taxonomic character. The HPLC analysis of the methanolic fractions displayed similar chemical profile and significant contents variation among the investigated taxa, being chlorogenic acid the main metabolite quantified in most of the species (ranging from traces to 16.65 mg% of extract), followed by hyperoside (between 0.27 and 11.48 mg%), quercitrin (0.09 and 13.34 mg%), guaijaverin (0.14 and 2.91 mg%) and isoquercitrin (0.14 and 6.97 mg%), whereas rutin and the xanthone mangiferin were not detected.     

A comparative study: Assessment of the antioxidant system in the invasive green alga Caulerpa racemosa and some macrophytes from the Mediterranean

Reactive oxygen species (ROS) are of great importance in plant metabolism. However, uncontrolled activation of ROS might have deleterious effects in cells. Eleven Mediterranean countries are still under threat of an introduced taxon of Caulerpa racemosa var. cylindracea. In the present study, it has been aimed to compare the antioxidant status of this highly invasive alga with some Mediterranean macrophytes collected in the same habitat. For this purpose, such antioxidant enzyme activities as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), and lipid peroxidation (LPO) as well, levels have been determined in C. racemosa, Cystoseira barbata C. Agardh, Padina pavonica (Linnaeus) Thivy and Enteromorpha sp. The highest SOD, CAT, GSH-Px enzyme activities and the lowest LPO level have been measured in the invasive C. racemosa. In conclusion, C. racemosa var. cylindracea seems more tolerant in warring with ROS than the Mediterranean species tested do. These results could partly explain the amazing success of C. racemosa var. cylindracea introduced in the Mediterranean.     

Phenolic compounds from the fruit of Garcinia dulcis

Dulcinoside (1), dulcisisoflavone (2), dulcisxanthone A (3) and sphaerobioside acetate (6) together with 22 known compounds were isolated from the green fruit of G. dulcis. Dulcisflavan (4), dulcisxanthone B (5) and isonormangostin (7) together with 22 known compounds were isolated from the ripe fruit. Compounds 6 and 7 were synthetic known compounds. Their structures were determined by spectroscopic methods. The radical scavenging and antibacterial activities of some of the compounds were investigated.     

Pongamone A-E, five flavonoids from the stems of a mangrove plant, Pongamia pinnata

Chemical investigation of stems of the mangrove plant, Pongamia pinnata, resulted in isolation and characterization of five structurally unusual flavonoids pongamones A-E, along with 16 known flavonoid metabolites. Their structures were determined on the basis of spectroscopic analyses and by comparison of their spectroscopic data with those of related compounds reported in the literature. Pongamones A-E were assayed against DHBV RCs DNAP and HIV-1 RT in vitro. A possible biogenetic pathway of the isolated compounds is also proposed.     

Characterization and expression of cry4Cb1 and cry30Ga1 from Bacillus thuringiensis strain HS18-1

We characterized a novel Bacillus thuringiensis isolate native to China (HS18-1) that shows a spherical crystal harboring two major proteins of about 70 and 130 kDa, and contains three novel cry genes (cry4Cb1, cry30Ga1, cry54-type). Furthermore, the cry4Cb1 and cry30Ga1 genes were expressed in Escherichia coli BL21 (DE3): pLysS. Insecticidal activity tests showed that the cry4Cb1 protein exhibited larvicidal activity against Aedes aegypti (Diptera) and the cry30Ga1 protein was toxic to both A. aegypti and P. xylostella (Lepidoptera).     

Termiticidal activity of lectins from Myracrodruon urundeuva against Nasutitermes corniger and its mechanisms

The isolation of lectins from Myracrodruon urundeuva bark (MuBL) and heartwood (MuHL) as well as the termiticidal activity of MuHL against Nasutitermes corniger has already been described. This work reports on the purification of a leaf lectin (MuLL) and the characterization of MuBL, MuHL, and MuLL; also described are the resistance of hemagglutinating activity of the three lectins to trypsin activity from N. corniger gut and the termiticidal activity on N. corniger of MuBL (LC₅₀ of 0.974 mg ml⁻¹ on workers and 0.787 mg ml⁻¹ on soldiers) and MuLL (LC₅₀ of 0.374 mg ml⁻¹ on workers and 0.432 mg ml⁻¹ on soldiers). The antibacterial effect of MuBL, MuHL, and MuLL on bacteria from gut of N. corniger was also investigated and lectins showed similar bacteriostatic activity (MIC of 62.5 ??g ml⁻¹ for workers and 125 ??g ml⁻¹ for soldiers). MuBL and MuHL were more efficient bactericidal agents on bacteria in the workers’ gut (MBC of 125 ??g ml⁻¹) than MuLL (MBC of 250 ??g ml⁻¹) and similar bactericidal activity was detected on bacteria in the gut of soldiers (MBC of 250 ??g ml⁻¹). The termiticidal activity of M. urundeuva lectins can be explained by the chitin-binding property, resistance to termite digestive enzyme, and the antibacterial effect on symbiotic bacteria of N. corniger gut.     

Saponins and a lignan derivative of Terminalia tropophylla from the Madagascar Dry Forest

A study of an EtOH extract obtained from the roots of the Madagascan plant Terminalia tropophylla H. Perrier (Combretaceae) led to isolation of the oleanane-type triterpenoid saponin 1, the lignan derivative 2, and the two known saponins arjunglucoside I (3) and sericoside (4). The structures of compounds 1 (terminaliaside A) and 2 (4′-O-cinnamoyl cleomiscosin A) were elucidated using 1D and 2D NMR experiments and mass spectrometry. Compound 1 showed antiproliferative activity against the A2780 human ovarian cancer cell line with an IC₅₀ value of 1.2 μM.     

Steroidal glycosides from the marine sponge Pandaros acanthifolium

The chemical composition of the Caribbean sponge Pandaros acanthifolium was investigated and led to the isolation of seven new steroidal glycosides namely pandarosides A-D (1, 3, 4 and 6) along with the three methyl esters of pandarosides A, C, and D (2, 5 and 7). Their structures were characterized as 3β-[β-glucopyranosyl-(1→2)-β-glucopyranosyloxyuronic acid]-16-hydroxy-5α,14β-poriferast-16-ene-15,23-dione (1) and its methyl ester (2), 3β-[β-glucopyranosyloxyuronic acid]-16-hydroxy-5α,14β-poriferast-16-ene-15,23-dione (3), 3β-[β-glucopyranosyl-(1→2)-β-glucopyranosyloxyuronic acid]-16-hydroxy-5α,14β-cholest-16-ene-15,23-dione (4) and its methyl ester (5), 3β-(β-glucopyranosyloxyuronic acid)-16-hydroxy-5α,14β-cholest-16-ene-15,23-dione (6) and its methyl ester (7) on the basis of detailed spectroscopic analyses, including 2D NMR and HRESIMS studies. Pandarosides A-D and their methyl esters (1-7) are all characterized by a rare 2-hydroxycyclopentenone D-ring with a 14β configuration. The absolute configuration of the aglycon part of pandaroside A (1) was assigned by comparison between experimental and TDDFT calculated circular dichroism spectra on the more stable conformer.     

Molecular characterization and localization of Plasmodium falciparum choline kinase

Generation of phosphocholine by choline kinase is important for phosphatidylcholine biosynthesis via Kennedy pathway and phosphatidylcholine biosynthesis is essential for intraerythrocytic growth of malaria parasite. A putative gene (Gene ID PF14_0020) in chromosome 14, having highest sequence homology with choline kinase, has been identified by BLAST searches from P. falciparum genome sequence database. This gene has been PCR amplified, cloned, over-expressed and characterized. Choline kinase activity of the recombinant protein (PfCK) was validated as it catalyzed the formation of phosphocholine from choline in presence of ATP. The K_m values for choline and ATP are found to be 145 ± 20 μM and 2.5 ± 0.3 mM, respectively. PfCK can phosphorylate choline efficiently but not ethanolamine. Southern blotting indicates that PfCK is a single copy gene and it is a cytosolic protein as evidenced by Western immunoblotting and confocal microscopy. A model structure of PfCK was constructed based on the crystal structure of choline kinase of C. elegans to search the structural homology. Consistent with the homology modeling predictions, CD analysis indicates that the α and β content of PfCK are 33% and 14%, respectively. Since choline kinase plays a vital role for growth and multiplication of P. falciparum during intraerythrocytic stages, we can suggest that this well characterized PfCK may be exploited in the screening of new choline kinase inhibitors to evaluate their antimalarial activity.     

Bioactive polyhydroxylated sterols from the marine sponge Haliclona crassiloba

Four new polyhydroxylated sterols, named halicrasterols A–D (1–4), together with six known analogs (5–10) were isolated from the marine sponge Haliclona crassiloba. Compounds 1 and 2 represented rare examples of steroids featuring 17(20)E-double bonds. The structures of 1–10 were elucidated by spectroscopic analysis and comparison with reported data. This is the first report of a steroid profile for this species. The antimicrobial activities of 1–10 were evaluated against a panel of bacterial and fungal strains in vitro, and compounds 4 and 9 showed moderate activity against some of the Gram-positive strains with MICs ranging from 4 to 32 μg/mL.     

Developmental regulation of protein kinase A expression and activity in Schistosoma mansoni

cAMP-dependent protein kinases (PKAs) are the main transducers of cAMP signalling in eukaryotic cells. Recently we reported the identification and characterisation of a PKA catalytic subunit (SmPKA-C) in Schistosoma mansoni that is required for adult schistosome viability in vitro. To gain further insights into the role of SmPKA-C in biological processes during the schistosome life cycle, we undertook a quantitative analysis of SmPKA-C mRNA expression in different life cycle stages. Our data shows that SmPKA-C mRNA expression is developmentally regulated, with the highest levels of expression in cercariae and adult female worms. To evaluate the biological role of SmPKA-C in these developmental stages, cercariae and adult worms were treated with various concentrations of PKA inhibitors. Treatment of cercariae with H-89 or PKI 14-22 amide resulted in loss of viability suggesting that, as in adults, PKA is an essential enzyme activity in this infectious larval stage. In adult worms, in vitro exposure to sub-lethal concentrations of H-89 or PKI 14-22 amide resulted in inhibition of egg production in a dose-dependent manner. Furthermore, using a murine model of schistosome infection where S. mansoni fecundity is impaired, we show that reduced rates of egg production in vivo correlate with significant reductions in SmPKA-C mRNA expression and PKA activity. Finally, restoration of parasite egg production in vivo also resulted in normalisation of SmPKA-C mRNA expression and PKA activity. Taken together, our data suggest that PKA signalling is required for cercarial viability and may play a specific role in the reproductive activity of adult worms.