Natural dibenzoxazepinones from leaves of Carex distachya: Structural elucidation and radical scavenging activity

Two new dibenzoxazepinones have been isolated from the leaves of Carex distachya, an herbaceous plant growing in the Mediterranean area. The structures have been elucidated on the basis of their spectroscopic properties. Bidimensional NMR (DQ-COSY, TOCSY, NOESY, ROESY, HSQC, and HMBC) furnished important data useful for the characterization of the molecules. The compounds have been assayed, for the antioxidant activity, by measuring its capacity to scavenge the DPPH, the superoxide anion, and nitric oxide radicals.     

Natural feruloyl monoglyceride macrocycles as protecting factors against free-radical damage of lipidic membranes

Nine novel natural feruloyl monoglyceride (MGs) macrocycles have been isolated from the leaves of Carex distachya, an herbaceous plant growing in the Mediterranean maquis. All the structures have been elucidated on the basis of their spectroscopic features, especially two-dimensional NMR (DQ-COSY, TOCSY, NOESY, ROESY, HSQC, HMBC, HSQC-TOCSY) and ESI-MS. All the compounds have been assayed as protecting factors against the radical damage of the lipids by using different antioxidant tests.     

Structural characterization of phytotoxic terpenoids from Cestrum parqui

Isolation, chemical characterization and phytotoxicity of nine polyhydroxylated terpenes (five C13nor-isoprenoids, two sesquiterpenes, a spirostane and a pseudosapogenin) from Cestrum parqui L'Herr are reported. In this work we completed the phytochemical investigation of the terpenic fraction of the plant and described the structural elucidation of polar isoprenoids using NMR methods. All the configurations of the compounds have been assigned by NOESY experiments. Four new structures have been identified as (3S,5R,6R,7E,9R)-5,6,9-trihydroxy-3-isopropyloxy-7-megastigmene, 5alpha-spirostan-3beta,12beta,15alpha-triol, and 26-O-(3'-isopentanoyl)-beta-d-glucopyranosyl-5alpha-furost-20(22)-ene-3beta,26-diol, and as an unusual tricyclic sesquiterpene. The compounds have been assayed for their phytotoxicity on lettuce at the concentrations ranging between 10(-4) and 10(-7)M. The activities of some compounds were similar to that of the herbicide pendimethalin.     

Radical-scavenging activities of new hydroxylated ursane triterpenes from cv. Annurca apples

Two new ursolic acid triterpene derivatives, compounds 2 and 3, have been isolated from cv. Annurca apple fruit, a high-quality apple variety widely cultivated in southern Italy, together with the known 2-oxopomolic acid (1). The new compounds were identified by means of different spectroscopic techniques as 3-epi-2-oxopomolic acid (= (3alpha)-3,19-dihydroxy-2-oxours-12-en-28-oic acid; 2) and (1alpha)-1-hydroxy-3-oxours-12-en-28-oic acid (3). Compounds 1-3 were tested for their radical-scavenging activities with the aid of a 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay (Fig. 2). All three constituents showed activities similar to that of the reference antioxidant alpha-tocopherol (vitamin E).     

Structures of bioactive carexanes from the roots of Carex distachya Desf

Four metabolites, named carexanes I-L, have been isolated from the roots of Carex distachya Desf, an herbaceous plant living in the Mediterranean maquis, together with three known compounds, already isolated from the aerial part of the plant. All the compounds have been characterized on the basis of their spectroscopic properties. Carexane I derived from the lose of a proton from the C-18 carbon of an intermediate isopropyl cation. Its stereostructure has been elucidated by Mosher's method, NOESY/ROESY experiments and computational calculations. The bioactivity on seed germination and root/shoot growth of Lactuca sativa L. of all the isolated compounds is also reported.     

Characterization of two chemotypes of <Emphasis Type="Italic">Pinus pinaster</Emphasis> by their terpene and acid patterns in needles

The existence of two chemotypes of Pinus pinaster, on the basis of the chemical composition of the resin acids in their needles, is known. An investigation was performed on 54 samples of needles of Spanish Pinus pinaster to study the differences between these chemotypes on the basis of monoterpene, sesquiterpene, neutral diterpene, fatty acid, and resin acid composition. One-hundred and twelve compounds were identified by GC–FID and GC–MS. Statistical analysis of the results established the existence of two groups or chemotypes, in the ratio of 5:1. In one chemotype, total acid compounds were more abundant than neutral compounds, whereas in the other the concentrations of both neutral and acid compounds were similar. Distinction of the chemotypes was based on the presence/absence of a sesquiterpene (germacrene d-4-ol acetate), neutral diterpenes (8(14),13(15)-abietadiene, anticopalol, an isomer of anticopalol, and pimarol), fatty acids (10-octadecenoic, 14-hydroxy-10-octadecenoic, and 13-hydroxy-9-octadenoic acids and an unidentified fatty acid), and resin acids (levopimaric + palustric, eperuic, and anticopalic acids, and three isomers of anticopalic acid); and on the different relative percentages of other compounds of these types. This study gives a wide view of the composition of the needles of Pinus pinaster, improving the differentiation of chemotypes on the basis of terpene and acid composition.     

Structure and modeling studies of the carboxy-terminus region of human tropoelastin.

Elastin macromolecular assembly is a highly complex mechanism involving many steps including coacervation, cross-linking, and probably other (not known) phenomena. In past studies, it has been proposed that the C-terminal part of tropoelastin is also involved in this process and may play a key role in tropoelastin interactions with other proteins of the final elastic fibres scaffold. Presented here are the results of the biophysical studies (biospectroscopy, bioinformatics) of the C-terminal domain of tropoelastin. We report the detailed structures adopted by the oxidized (native) and reduced forms of the free synthetic peptide with sequence encoded by exon 36 of human tropoelastin (GGACLGKACGRKRK) and propose a dynamical interpretation of which structures may be involved in interactions with other extra-cellular matrix proteins. We also suggest that these structures may be retrieved in other proteins sharing a consensus sequence; however no definitive conclusion can be drawn here on a possible structure-function relationship.