New pyranonaphthazarin and 2-naphthoic acid derivatives from the mangrove endophytic fungus Leptosphaerulina sp. SKS032

Two new compounds, named leptospyranonaphthazarin A (1) and leptosnaphthoic acid A (2), together with four known compounds (3–6) were isolated from an endophytic fungus Leptosphaerulina sp. SKS032. Their structures were assigned using spectroscopic methods, computational methods, and single-crystal X-ray diffraction analysis. In the antibiotic assay, compounds 1, 2, and 6 exhibited antibacterial activities against Staphylococcus aureus with minimal inhibitory concentration (MIC) values of 25.0, 50.0, and 50.0 μg/mL, respectively.     

Isolation and partial characterization of 3 nontoxic d‐galactose–specific isolectins from seeds of Momordica balsamina

Three isolectins denoted hereforth MBaL‐30, MBaL‐60, and MBaL‐80 were isolated from seeds extract of Momordica balsamina by 30%, 60%, and 80% ammonium sulfate saturations, respectively. The native molecular weights of these lectins, as judged by gel filtration, were 108, 56, and 160 kDa, respectively. On SDS‐PAGE, under reduced condition, 27 kDa band was obtained for all isolectins. The lectins hemagglutinating activities were variably inhibited by d ‐galactose (minimum inhibitory concentrations = 12.5mM, 50mM, and 0.391mM, respectively). MBaL‐30 and ‐60 could agglutinate all human blood types with slight preference for the A and O blood groups, whereas MBaL‐80 did not agglutinate B and AB blood types. The 3 isolectins were purified from crude seeds extract, collectively, in a single step on the affinity matrix Lactamyl‐Seralose 4B; this purified lectin fraction, which contains all isolectins, is termed MBaL. The N‐terminal of MBaL till the 25th amino acid was NLSLSELDFSADTYKSFIKNLRKQL, which shares 88% sequence identity with Momordica charantia lectin type‐2 ribosomal inactivating protein from Momordica charantia and 50% with momordin II from Momordica balsamina . MBaL retained 100% activity at up to 50°C for 30 minutes. MBaL‐30 and MBaL‐60 exhibited maximum activities in the pH range between 4 and 8, while MBaL‐80 was showing maximum activity in the pH range between 3 and 5. Treatment of MBaL‐30 and MBaL‐60 with EDTA completely abolished their hemagglutinating activities. Addition of Zn and Fe ions to the ethylenediaminetetraacetic acid–treated MBaL‐30 and MBaL‐60 lectins did not only regained the loss of activity but also resulted in 200% to 300% increase in activity, respectively. MBaL‐30 and ‐60 agglutinated gram positive Listeria monocytogenes and Staphylococcus aureus, whereas MBaL‐30 could merely agglutinate Escherichia coli . None of these lectins could arrest bacterial growth. Addition of MBaL to cancer cell lines (Gastric cancer cell line (AGS) and Gastric cencer cell line (MKN45), Glioblastoma (ECV‐304), and Human urinary bladder cancer cell line (U87‐MG)) at varying concentrations did not cause statistically significant changes on cell growth and viability.     

Dosimetric evaluation of Gafchromic EBT2 film for breast intraoperative electron radiotherapy verification

PurposeQuality assurance (QA) is one of the most important issues that should be addressed for intraoperative electron radiotherapy (IOERT), which is not benefiting from image-based treatment planning system. The aim of this study is to evaluate the dosimetric characteristics of Gafchromic EBT2 film for breast IOERT QA procedure.MethodsDue to the fact that some dedicated accelerators are being used for IOERT, dependence of the film response to energy, field size, dose rate and incidence angle of electron beam from the LIAC IOERT accelerator was studied. Then, film response curve to breast IOERT doses was obtained and its accuracy was evaluated and justified through comparison to the results of ionometric dosimetry.ResultsThe results of this study indicated that there are no significant differences between the film responses at different energies of 6, 8, 10 and 12 MeV (P-value = 0.99). Similarly, no field size dependency was found when evaluating the response of the film to different field sizes ranging from 4 to 10 cm (P-value = 0.94). Film response was found to be independent of the dose rate of intraoperative electron beam (P-value = 0.12). Film response variations with changing the beam incidence angle were not significant (P-value > 0.8). Calibration curve at the dose range of 8–24 Gy had an acceptable accuracy. The difference between the results of film dosimetry and ionometric dosimetry was around 5% which was in agreement with the results of dose uncertainty estimation.ConclusionThe EBT2 film was found to be a potentially appropriate tool for breast IOERT verification.     

Design,synthesis and in vitro pharmacology of GluK1 and GluK3 antagonists. Studies towards the design of subtype-selective antagonists through 2-carboxyethyl-phenylalanines with substituents interacting with non-conserved residues in the GluK binding sites

In order to identify compounds selective for the GluK1 and GluK3 subtypes of kainate receptors we have designed and synthesized a series of (S)-2-amino-3-((2-carboxyethyl)phenyl)propanoic acid analogs with hydrogen bond donating and accepting substituents on the aromatic ring. Based on crystal structures of GluK1 in complex with related ligands, the compounds were designed to explore possible interactions with non-conserved residues outside the glutamate ligand binding site and challenge the water binding network. Apart from obtaining GluK1 selective antagonists one analog with a phenyl-substituted urea (compound 31) showed some preference for GluK3 over GluK1-receptors. Docking studies indicate that this preference may be attributed to contacts between the NH of the urea substituent and non-conserved Ser741 and Ser761 residues.     

Involvement of Azopirillum brasilense plasmid DNA in the productio of indole acetic acid

Indole acetic acid (IAA) production in Azospirillum brasilense strain Sp245 is controlled by a 85 MDa plasmid naturally present in this bacterium. In the presence of L-tryptophan, anthranilic acid production and almost no IAA production occurs in a derivative strain harbouring a Tn5-Mob insertion in the 85 MDa plasmid. Agrobacterium tumefaciens strain GM19023, upon transfer of Tn5-Mob labelled 85 MDa plasmid of A. brasilense Sp245, gains the ability to produce anthranilic acid.     

Photosynthesis of herbaceous plants from nutrient-poor tropical forests

Photosynthetic characteristics, specific leaf mass, chlorophyll and total leaf nitrogen concentrations of four herbaceous plants (Dicranopteris linearis, Hanguana malayana, Pentaphragma ellipticum, Tacca integrifolia) from nutrient-poor tropical forests showed that all these plants were well-adapted to their natural growth environments. No photoinhibition was observed even in the understorey plants. This revised version was published online in June 2006 with corrections to the Cover Date.     

Synthesis,biological evaluation and structure-activity relationships of 5-arylidene tetramic acids with antibacterial activity against methicillin-resistant Staphylococcus aureus

The steady rise of the antimicrobial resistance is a major global threat to human health that requires the urgent need for novel antibiotics. In this work we report the synthesis of a small library of 3-subsituted-5-arylidene tetramic acids in order to investigate the scope of our previously established methodology via an intermediate oxazolone and their antimicrobial activity. From this series of 14 tetramic acids, 11 derivatives are novel and one of them is a Schiff base, which was structurally characterized with single-crystal X-ray analysis and NMR spectroscopy. The compounds incorporating a lipophilic acyl group at carbon-3 of the ring showed moderate to high activity with minimum inhibitory activity of 4–32 μg/mL against methicillin-resistant Staphylococcus aureus (MRSA), accompanied by no human cell toxicity and hemolytic activity within the tested concentration range. The substituent at para position of the aryl ring seemed to have no or little effect on the antimicrobial activity of these compounds.     

Synthesis of (1,3,4-thiadiazol-2-yl)-acrylamide derivatives as potential antitumor agents against acute leukemia cells

A lead compound with the (1,3,4-thiadiazol-2-yl)-acrylamide scaffold was discovered to have significant cytotoxicity on several tumor cell lines in an in-house cell-based screening. A total of 60 derivative compounds were then synthesized and tested in a CCK-8 cell viability assay. Some of them exhibited improved cytotoxic activities. The most potent compounds had IC₅₀ values of 1–5 μM on two acute leukemia tumor cell lines, i.e. RS4;11 and HL-60. Flow cytometry analysis of several active compounds and detection of caspase activation indicated that they induced caspase-dependent apoptosis. It was also encouraging to observe that these compounds did not have obvious cytotoxicity on normal cells, i.e. IC₅₀ > 50 μM on HEK-293T cells. Although the molecular targets of this class of compound are yet to be revealed, our current results suggest that this class of compound represents a new possibility for developing drug candidates against acute leukemia.