Mammalian Alkaloids: O-Methylation of (±)-Norcoclaurine-1-carboxylic Acid and Related Isoquinolines Including (S)- and (R)-Norcoclaurine with 14C-Labeled S-Adenosyl-L-Methionine in Presence of Mammalian Catechol O-Methyltransferase

(±)-Norcoclaurine-1-carboxylic acid ( 5 ) and the derived dihydroisoquinolinone 6 (present as quinonemethide 6 a at pH 7) afforded, on methylation with ¹⁴C-labeled S-adenosyl-L -methionine in the presence of mammalian catechol O-methyltransferase, exclusively the 7-O-methylated congeners 7 and 9 , respectively. High stereoselectivity of the O-methylation was observed with (?)-(S)- and (+)-(R)-norcoclaurine ( 2a and 2b , resp.), affording 80% of 6-O-methylated isoquinoline 12 and 20% of the 7-O-methylated isomer 11 from 2a , and the reversed proportion of 12 and 11 from 2b . Synthesis of the reference amino acid 8 was achieved by Pictet-Spengler condensation of O-benzyl-protected dopamine 17 with benzyl-protected keto acid 20 (→ 21 ) followed by methylation with diazomethane (→ 22 + 23 ) and removal of the protecting groups by acid hydrolysis. It is considered unlikely that amino acids such as 5 constitute important precursors in the biosynthesis of isoquinolines related to reticuline.     

Shrinky-Dink microfluidics: rapid generation of deep and rounded patterns

We present a rapid and non-photolithographic approach to microfluidic pattern generation by leveraging the inherent shrinkage properties of biaxially oriented polystyrene thermoplastic sheets. This novel approach yields channels deep enough for mammalian cell assays, with demonstrated heights up to 80 microm. Moreover, we can consistently and easily achieve rounded channels, multi-height channels, and channels as thin as 65 microm in width. Finally, we demonstrate the utility of this simple microfabrication approach by fabricating a functional gradient generator. The whole process--from device design conception to working device--can be completed within minutes.     

Swarnalin and cis-swarnalin, two new tetrahydrofuran derivatives with free radical scavenging activity, from the aerial parts of Cuscuta reflexa

The reversed-phase HPLC analysis of a methanol extract of the aerial parts of Cuscuta reflexa afforded a non-separable mixture (55 : 45) of two novel tetrahydrofuran derivatives, named swarnalin (1) and cis-swarnalin (2), and a known coumarin, 5,6,7-trimethoxycoumarin (3). The structures of the compounds were elucidated unequivocally by UV, HRFABMS and a series of 1D and 2D NMR analyses. The mixture of 1 and 2 showed significant free radical scavenging activity in the DPPH assay and the RC50 value was found to be 3.80 x 10(-4) mg mL(-1) for the mixture, compared to 2.88 x 10(-5) mg mL(-1) for the positive control, quercetin.     

Effects of arc3, arc5 and arc6 mutations on plastid morphology and stromule formation in green and nongreen tissues of Arabidopsis thaliana

Mutations in the ARC3, ARC5 and ARC6 genes of Arabidopsis thaliana affect chloroplast division. We investigated whether ARC3, ARC5 and ARC6 are also involved in determining plastid morphology in nongreen tissues, where stromules, stroma-filled tubular extensions of the plastid envelope membrane, are more abundant than in mesophyll cells. Using plastid-targeted green fluorescent protein to observe plastids throughout the organs of these mutants, we have discovered a number of new mutant phenotypes. The size of arc3 plastids was heterogeneous in various tissues. arc5 plastids appeared wild-type in the majority of nongreen tissues examined. However, in cells of stamen filaments, the arc5 mutant showed an increase in the frequency of stromules. Increased stromule frequency was observed for a number of organs in the arc6 mutant. Some arc6 cells contained heterogeneous mixtures of plastids; epidermal cells of hypocotyls, stamen filaments and the bases of petals possessed both very large chloroplasts as well as much smaller nongreen plastids. Quantitative analysis in hypocotyl cells revealed that the alteration in stromule length in arc3 and arc6 mutants occurred despite wild-type plastid densities. Thus, in hypocotyls, the effects of the arc3 and arc6 mutations on stromule length and frequency are independent of changes in plastid division. Although electron micrographs of stromules emanating from chloroplasts have rarely been reported, within the arc3 mutant, narrow, 40-50 nm diameter, recoiled stromules could be followed for about 10 microm in electron micrographs of leaf tissue.     

Biological activity and coordination modes of copper(II) complexes of Schiff base-derived coumarin ligands

The coordination modes of copper(II) complexes of Schiff base-derived coumarin ligands, which had previously shown good anti-Candida activity, were investigated by pH-potentiometric and UV-Vis spectroscopic methods. These studies confirmed the coordination mode of the ligands to be through the N of the imine and deprotonated phenol of the coumarin-derived ligand in solution. In addition, the more active complexes and their corresponding ligands were investigated in the presence of copper(II) in liquid and frozen solution by ESR spectroscopic methods. A series of secondary amine derivatives of the Schiff base ligands, were isolated with good solubility characteristics but showed little anti-Candida activity. However, cytotoxicity studies of the secondary amines, together with the copper complexes and their corresponding ligands, against human colon cancer and human breast cancer cells identified the chemotherapeutic potential of these new ligands.     

Reactions of some quinazoline compounds with ethoxymethylenemalonic acid derivatives

The reactions of ethyl (1,4-dihydro-4-oxoquinazolin-2-yl)acetate 4 and 2-aminoquinazolin-4(1H)-one 5 with diethyl ethoxymethylenemalonate (EMME), (ethoxymethylene)malononitrile (EMMN) and ethyl (ethoxymethylene)cyanoacetate (EMCA) are reported, and rather different results are obtained to those previously found with quinoline analogs. Reaction of 4 with EMME gives a pyrido[1,2-a]quinazoline, while with EMMN and EMCA ethyl 2-(pyridin-2-yl)aminobenzoates are formed, presumably by ring-opening of intermediate pyrido[2,1-b]quinazolines. Reaction of 5 with EMME likewise results in ultimate cyclization onto N-1 of the quinazoline, while the EMMN and EMCA reactions give isolable pyrimido[2,1-b]quinazolines. These are readily cleaved under mild conditions.     

Engineered nanoforce gradients for inhibition of settlement (attachment) of swimming algal spores

Current antifouling strategies are focused on the development of environmentally friendly coatings that protect submerged surfaces from the accumulation of colonizing organisms (i.e., biofouling). One ecofriendly approach is the manipulation of the surface topography on nontoxic materials to deter settlement of the dispersal stages of fouling organisms. The identification of effective antifouling topographies typically occurs through trial-and-error rather than predictive models. We present a model and design methodology for the identification of nontoxic, antifouling surface topographies for use in the marine environment by the creation of engineered nanoforce gradients. The design and fabrication of these gradients incorporate discrete micrometer-sized features that are associated with the species-specific surface design technique of engineered topography and the concepts of mechanotransduction. The effectiveness of designed nanoforce gradients for antifouling applications was tested by evaluating the settlement behavior of zoospores of the alga Ulva linza. The surfaces with nanoforce gradients ranging from 125 to 374 nN all significantly reduced spore settlement relative to a smooth substrate, with the highest reduction, 53%, measured on the 374 nN gradient surface. These results confirm that the designed nanoforce gradients may be an effective tool and predictive model for the design of unique nontoxic, nonfouling surfaces for marine applications as well as biomedical surfaces in the physiological environment.     

Bis-phenanthroline copper(II) phthalate complexes are potent in vitro antitumour agents with 'self-activating' metallo-nuclease and DNA binding properties

Three, structurally characterised, bis-phen Cu(II) complexes of the phthalate isomers display rapid, low micromolar in vitro cytotoxicity against a range of epithelial tumour cells. The complexes induce relaxation of supercoiled plasmid DNA in the absence of external reducing agents and display efficient CT-DNA, Poly[d(A-T)](2) and Poly[d(G-C)](2) binding.