Novel catechol-derived phosphorus-based precursors for coating applications

Polymer Bulletin - Depletion of the petroleum resources and poor flame-retardant properties of the epoxy resins drive researchers to develop an epoxy resin with good heat stability from...     

Surface tension and contact angle of herbicide solutions affected by surfactants

Contact angle and surface tension were measured for distilled and hard water solutions of adjuvants, Ortho X-77, Span-20, Sterox-NJ. Surfactant-WK, Triton B-1956, Triton X-114, Tween-20, and Sun Oil 11E. The same parameters were measured for suspensions of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] and ametryne [2-(ethylamino)-4-(isopropylamino)-6-(methylthio)-s-triazine] with and without each adjuvant. All adjuvants reduced surface tension and contact angle of distilled water; Surfactant-WK was most effective and Tween-20 was least effective. Increasing concentration of surfactants from 0 to 0.1% (v/v) gave progressive reduction in surface tension and contact angle while higher concentrations, 0.1 to 2.0% (v/v), had no further effect. Surfactant-WK at 0.1% (v/v) in distilled water reduced the surfact tension from 72.8 dynes/cm to 27 dynes/cm and contact angle from 110° to 41°. An additional increase in Surfactant-WK concentration from 0.1% (v/v) to 2% (v/v) did not further reduce surface tension and contact angle. Sun Oil 11E was identical in behavior except that it was less effective than the surfactants. Water hardness up to 1,000 ppm as Ca ions did not affect surface tension and contact angle in surfactant solutions. An aqueous solution of atrazine had a higher surface tension and contact angle than ametryne in the absence of surfactants. However, these differences were not observed when surfactants were added to either herbicide.     

HPLC identification of allelopathic compounds fromLantana camara

Aqueous extracts ofLantana camara L. leaves inhibited ryegrass (Lolium multiflorum Lam.) germination and seedling growth. Phytotoxic compounds were fractionated from crude aqueous extracts and fractions were evaluated for their phytotoxicity. Inhibition was most pronounced with the alkaline and acid hydrolysates. Plant inhibition by the crude extract reflected a complex interaction of numerous individual components of diverse chemical compositions and potencies. Presumptive identification of the individual components was accomplished with high-performance liquid chromatography (HPLC). Thirteen phenolic compounds were identified, and most of these compounds were phytotoxic to ryegrass seedlings. Radicle elongation was more sensitive to the toxins than shoot elongation.Florida Agricultural Experiment Station Journal Series No. 7906.     

α-Glucosidase inhibitors from Devil tree (Alstonia scholaris)

α-Glucosidase inhibitors are used in the treatment of non-insulin-dependent diabetes mellitus. We attempt to isolate α-glucosidase inhibitors from 24 traditional Thai medicinal plant samples. Potent α-glucosidase inhibitory activity was found in aqueous methanol extract of dried Devil tree (Alstonia scholaris) leaves. Active principles against α-glucosidase, prepared from rat small intestine acetone powder, were isolated and identified. The structures of these isolated compounds were found to be quercetin 3-O-β-d-xylopyranosyl (1? → 2″)-β-d-galactopyranoside and (−)-lyoniresinol 3-O-β-d-glucopyranoside on the basis of chemical and spectral evidence. The latter exhibited an inhibitory activity against both sucrase and maltase with IC₅₀ values of 1.95 and 1.43 mM, respectively, whereas the former inhibited only maltase with IC₅₀ values of 1.96 mM. This preliminary observation will provide the basis for further examination of the suitability of Alstonia scholaris as a medicinal supplement that contributes toward the treatment and prevention of diabetes.     

Activation of Pah by Ozone Derived Oxidants: Results Using Fly Ash as Particulate [1]

The fly ash bound polycyclic aromatic hydrocarbons (PAH), phenanthrene, pyrene, and cyclopenta[cd]pyrene, are converted to arene oxides when exposed to the products of the gas phase reaction of tetramethylethylene and ozone. These same PAH are also converted to the same oxides when treated with dimethyldioxirane vapors while adsorbed on the fly ash. Exposure to ozone alone does not give oxide formation under the same conditions. Several other PAH fail to give oxides when treated with the tetramethylethylene/ozone product stream. The results support the hypothesis that the products of the ozonolysis of alkenes in polluted atmospheres may be responsible for the activation of PAH in these atmospheres.     

α-Glucosidase and α-amylase inhibitory activities of Nepalese medicinal herb Pakhanbhed (Bergenia ciliata, Haw.)

Herbal medicine has been used for many years by different cultures around the world for the treatment of diabetes. The Nepalese herb Pakhanbhed, is one of the traditional remedies used for diabetes since prehistoric times. In this study, we examined the anti-diabetic activity using an in vitro model and isolated the active compounds from Pakhanbhed. Extraction and fractionation of the extract lead to the isolation of two active compounds, (−)-3-O-galloylepicatechin and (−)-3-O-galloylcatechin and these are reported from this plant species for the first time. These isolated compounds demonstrated significant dose dependent enzyme inhibitory activities against rat intestinal α-glucosidase and porcine pancreatic α-amylase. IC₅₀ value for sucrose, maltase and α-amylase were 560, 334 and 739 μM, respectively for [(−)-3-O-galloylepicatechin] and 297, 150 and 401 μM, respectively for [(−)-3-O-galloylcatechin]. Our study, for the first time, revealed the anti-diabetic potential of Pakhanbhed and this study could be helpful to develop medicinal preparations or nutraceutical and functional foods for diabetes and related symptoms.     

Electronic and Steric Control of n→π* Interactions: Stabilization of the α-Helix Conformation without a Hydrogen Bond

The preferred conformations of peptides and proteins are dependent on local interactions that bias the conformational ensemble. The n→π* interaction between consecutive carbonyls promotes compact conformations, including the α-helix and polyproline II helix. In order to further understand the n→π* interaction and to develop methods to promote defined conformational preferences through acyl N-capping motifs, a series of peptides was synthesized in which the electronic and steric properties of the acyl group were modified. Using NMR spectroscopy, van't Hoff analysis of enthalpies, X-ray crystallography, and computational investigations, we observed that more electron-rich donor carbonyls (pivaloyl, iso-butyryl, propionyl) promote stronger n→π* interactions and more compact conformations than acetyl or less electron-rich donor carbonyls (methoxyacetyl, fluoroacetyl, formyl). X-ray crystallography indicates a strong, electronically tunable preference for the α-helix conformation, as observed directly on the φ and ψ torsion angles. Electron-donating acyl groups promote the α-helical conformation, even in the absence of the hydrogen bonding that stabilizes the α-helix. In contrast, electron-withdrawing acyl groups led to more extended conformations. More sterically demanding groups can promote trans amide bonds independent of the electronic effect on n→π* interactions. Chloroacetyl groups additionally promote n→π* interactions through the interaction of the chlorine lone pair with the proximal carbonyl π*. These data provide additional support for an important role of n→π* interactions in the conformational ensemble of disordered or unfolded proteins. Moreover, this work suggests that readily incorporated acyl N-capping motifs that modulate n→π* interactions may be employed rationally to promote conformational biases in peptides, with potential applications in molecular design and medicinal chemistry.     

Phenolic acids affect photosynthesis and protein synthesis by isolated leaf cells of velvet-leaf

The effects ofp-coumaric, ferulic, chlorogenic, and vanillic acids on photosynthesis and protein synthesis by isolated leaf cells of velvetleaf (Abutilon theophrasti Medik) were investigated. Photosynthesis and protein synthesis were measured in cell suspensions by the incorporation of¹⁴CO₂ and [¹⁴C]leucine, respectively. None of the tested phenolic acids except vanillic reduced photosynthesis by more than 50% at the highest concentration and 30 min of incubation. At 100M concentrations and 60-min incubation periods,p-coumaric, ferulic, chlorogenic, and vanillic acids inhibited photosynthesis by 33, 37, 57, and 65%, respectively. Ferulic acid was the most inhibitory to protein synthesis and reduced the incorporation of [¹⁴C]leucine by 50% at about 1.0M after 60 min of incubation. At the highest concentrations tested in this study, vanillic and ferulic acids were inhibitory to photosynthesis and protein synthesis, respectively, whereas chlorogenic andp-coumaric acids did not inhibit either physiological process. The maximum inhibition of protein synthesis by chlorogenic acid was 19% and by vanillic acid was 28% at 100M concentrations. Chlorogenic, vanillic, andp-cou-maric acids at 0.1M caused increased protein synthesis over the untreated control. Overall, photosynthesis was more sensitive than protein synthesis to the four phenolic acids tested.Florida Agricultural Experiment Station Journal Series No. 9228.     

Allelopathic effect of parthenium (Parthenium hysterophorus L.) extract and residue on some agronomic crops and weeds

Allelopathic effects of entire shoot extract, plant part extracts, and shoot residue of parthenium (Parthenium hysterophorus L.) on corn (Zea mays L.), ryegrass (Lolium multiflorum Lam.), wheat (Triticum aestivum L.), velvetleaf (Abutilon theophrasti Medik.), and soybean [Glycine max (L) Merr.] growth were examined. Parthenium shoot contained water-soluble materials that were toxic to root growth of velvetleaf and wheat. At 4% (w/ v) concentration, root growth of velvetleaf and wheat were reduced by 60 and 75%, respectively. The order of increasing sensitivity to parthenium was ryegrass, corn, wheat, and velvetleaf. There was a strong correlation between extract concentration and increased toxicity to test species. The toxicity of plant part extracts was also concentration dependent. At 1 and 2% (w/v), the inflorescence and leaves caused more root inhibition than stem extract. Parthenium shoot incorporated in soil at 1% (w/w) caused significantly more root inhibition of wheat than soybean, corn, and ryegrass. At 4% (w/w), root growth of all the test species was inhibited compared to the control. Toxicity of parthenium residue to wheat diminished with increasing periods of decomposition. Residue decomposed for four weeks was less toxic than the undecomposed residue.Florida Agricultural Experiment Stations Journal Series No. 7506.