1,720,976 research outputs found
Isolation of lignans as seed germination and plant growth inhibitors from Mediterranean plants and chemical synthesis of some analogues
No full textLignans and lignins are among the main metabolic products of phenylpropanoid metabolism in vascular plants. They are compounds representing the building blocks of plant cell walls. Moreover they have a broad range of biological activities such as antitumoral, antimitotic, antiviral and cytotoxic and are thought to be involved in the plant defense against pathogens and pests. In this paper we report a survey of the past and current literature about lignans and neolignans and their germination inhibitory activity on cultivated and wild species from plants of the Mediterranean area. Some examples of synthetic methodologies of these molecules have also been reported
A mild approach to diarylfuranones via functionalized 2-arylfurans
No full text5,5- and 3,5-Diarylfuranones have been obtained in a three-step one-pot manner. The procedure starts
from photooxygenation of easily accessible arylfurans followed by in situ base treatment and finally by
triflic anhydride mediated acylation of activated aromatic substrates. The regioselectivity of the acylation
reaction depends on the reaction conditions and/or activation of both acid and aromatic reagents. The
5,5-diarylfuranone products have the same carbon skeleton as some rearranged tetrahydrofuran lignans
Phytotoxic activity of Cleome arabica L. and its principal discovered active compounds
No full textThe aimof this studywas to assess the phytotoxic potential of Cleome arabica L, as well as to isolate the main bioactive
compounds. Phytotoxicity was evaluated on germination and seedling growth of Lactuca sativa, Raphanus
sativus, Peganum harmala and Silybum marianum, through testing aqueous and organic extracts of different C.
arabica organs (roots, shoots, siliquae and seeds). Results showed that siliquae methanol extract caused the
greatest negative effect on lettuce germination and growth. For the bioactive subfractions (petroleum ether,
ethyl acetate andmethanol–water), the ethyl acetate induced highly significant reduction, showing 100% inhibition
of lettuce growth at 6 g/L. The bioactive ethyl acetate subfraction was chromatographed and subjected to
NMR techniques. Based on bio-guided chromatographic fractionation, five bioactive allelochemical compounds
were isolated from ethyl acetate extract of siliquae of C. arabica. The most inhibitory compound on lettuce seedling
growth was elucidated as 11-α-acetylbrachy-carpone-22(23)-ene
Regiodivergent synthesis of trisubstituted furans through Tf2O-catalyzed Friedel–Crafts acylation: a tool for access to tetrahydrofuran lignan analogues
No full text3- or 4-Aroylfurans have been prepared selectively and in high yields from a common precursor by
simple tuning of reaction conditions in Friedel–Crafts acylation promoted by triflic anhydride. The
formation of products can be explained on the basis of the ring-chain tautomerism occurring in
compounds equipped with two neighbouring carboxylic functions. Since 4-aroylfuran derivatives show
a typical lignan backbone, suitable hydrogenation conditions were found out to gain tetrahydrofuran
lignans
Lignans from Phillyrea angustifolia L.
No full textA new lignan epoxide together with the seven known lignans: pinoresinol, pinoresinol-O-beta-D-glucopyranoside, pinoresinol monomethyl ether-O-beta-D-glucopyranoside, lariciresinol, lariciresinol-4-O-beta-D-glucopyranoside, lariciresinol-4'-O-beta-D-glucopyranoside, and syringaresinol monoglucopyranoside were isolated from the hydroalcoholic and organic extracts of the whole plant of Phillyrea angustifolia L. (Oleaceae). The structure of the new constituent was elucidated by spectroscopic methods (UV, IR, and 1D- and 2D-NMR) and by mass spectrometry (HR-ESI-MS), mainly using 2D-NMR techniques. The effects of these compounds on germination and growth of dicotyledon Lactuca sativa L. (lettuce) were studied in the 10(-4) to 10(-7) M concentration rang
Potential contact and intraocular lenses based on hydrophilic/hydrophobic sulfonated syndiotactic polystyrene membranes
No full textCrystalline films of syndiotactic polystyrene (s-PS), a commercially available thermoplastic polymer, having a highly hydrophilic amorphous phase, were achieved by using a mild solid-state sulfonation procedure. Despite the used mild process conditions, an easy and uniform sulfonation of the phenyl rings of the amorphous phase is obtained. The crystallinity of the polymer was not affect by the sulfonation degree (S), at least at S less than 20%, and the obtained polymer films show the nanoporous crystalline form of s-PS. As widely reported in literature, the nanoporous nature of the polymer crystalline phase gives to these materials the ability to absorb and release organic molecules of appropriate size and polarity. This property, coupled to transparency, makes these materials potentially useful intraocular lens (IOLs) and contact lens applications. Sulfonation procedure and sulfonated film samples characterization by using wide-angle X-ray diffraction (WAXD), Fourier-transform infrared (FTIR) and ultraviolet-visible (UV-vis) spectroscopy techniques and water sorption tests were reported. Furthermore, the biocompatibility study demonstrated no cytotoxicity and appropriate cell interaction properties for the specific applications
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Single-ended Long Period Fiber Grating coated with Polystyrene Thin Film for Butane Gas Sensing
No full textA safe detection of hydrocarbons is a major concern in industrial and public environment, due to their high volatility and flammability. In this work, we report the development and characterization of an in-fiber sensor for the detection of aliphatic hydrocarbon gas operating at room temperature, focusing the attention on the butane (C4H10). A Long Period Grating (LPG) was used as optical transducer, integrated with a nano-scale high refractive index sensitive overlay of atactic Polystyrene (aPS). Both LPG and aPS thin film were carefully designed to work in mode transition, in order to enhance the final device sensitivity. Moreover, a practical single ended probe was developed by integrating a mirror on the fiber tip. The sensor was tested with butane vapor concentrations up to 1.0 vol%, obtaining a maximum sensitivity of -2.2 nm/vol%, and demonstrating the possibility to detect concentrations as low as one tenth of the Lower Explosive Limit (LEL) of 1.8 vol%
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