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PubMed1999

Structural analysis of a plant sucrose carrier using monoclonal antibodies and bacteriophage lambda surface display.

Monoclonal antibodies were raised and selected against recombinant Plantago major PmSUC2 sucrose carrier protein. Epitopes of two monoclonal antibodies (PS2-1A2 and PS2-4D4) were mapped using N-terminally truncated PmSUC2 proteins and a lambda library displaying random PmSUC2 peptides. PS2-1A2 recognizes an octapeptide close to the N-terminus of PmSUC2, PS2-4D4 binds to a decapeptide at the very C-terminus. Analyses of antibody binding to yeast protoplasts with functionally active, tagged PmSUC2 protein revealed that both epitopes are located in cytoplasmic domains of PmSUC2. These results support a model for plant sucrose transporters containing 12 transmembrane helices with the N-terminus and the C-terminus on the cytoplasmic side of the plasma membrane.

Amino Acid Sequence↗
PubMed2001

Furanocoumarins from Dorstenia gigas.

A series of linear and angular prenylated furanocoumarins and a benzofuran derivative were isolated from leaves and twigs of Dorstenia gigas (Moraceae), a plant occurring endemically on Socotra Island (Yemen). The structures were elucidated by spectroscopic methods (NMR, MS, UV) and chemical derivatization.

Benzofurans↗
PubMed2003

Insecticidal pyrido[1,2-a]azepine alkaloids and related derivatives from Stemona species.

Eight new alkaloids, the pyrido[1,2-a]azepines stemokerrin, methoxystemokerrin-N-oxide, oxystemokerrin, oxystemokerrin-N-oxide, and pyridostemin, along with the pyrrolo[1,2-a]azepines dehydroprotostemonine, oxyprotostemonine, and stemocochinin were isolated from four Stemona species together with the known compounds protostemonine, stemofoline, 2'-hydroxystemofoline, and parvistemonine. Their structures were elucidated by 1H and 13C NMR including 2D methods and two key compounds additionally by X-ray diffraction. Besides the formation of a six membered piperidine ring, additional oxygen bridges and N-oxides contributed to structural diversity. The co-occurrence of pyrrolo- and pyridoazepines suggested biosynthetic connections starting from more widespread protostemonine type precursors. Bioassays with lipophilic crude extracts against Spodoptera littoralis displayed very strong insecticidal activity for the roots of S. curtisii and S. cochinchinensis, moderate activity for S. kerrii, but only weak effects for the unidentified species HG 915. The insect toxicity was mainly caused by the accumulation of stemofoline, oxystemokerrin, and dehydroprotostemonine displaying two different modes of action. Based on the various insecticidal activities of 13 derivatives structure-activity relationships became apparent.

Alkaloids↗
PubMed2000

Sesquiterpene lactones with potential use as natural herbicide models. 2. guaianolides.

A structure-activity study to evaluate the effect of 17 guaianolide sesquiterpene lactones (in a range of 100-0.001 microM) on the growth and germination of several mono- and dicotyledon target species is accomplished. Results are compared with those obtained in the same bioassay with an internal standard, the commercial herbicide Logran, to validate the results with a known active formulation and to compare the results with a commercial product to test their potential use as natural herbicide models. Specific conditions for the selective mono- or polyhydroxylation of guaianolides using the SeO(2)/tert-butyl hydroperoxide system are presented and discussed. The high regio- and stereoselectivities of the reaction are explained through the specific structural requirements of the bulky first adduct formed during the ene reaction. These compounds appear to have deeper effects on the growth of either monocots or dicots than the previously tested germacranolides. Otherwise, the lactone group seems to be necessary for the activity, though it does not necessarily need to be unsaturated. However, the presence of a second and easily accessible unsaturated carbonyl system greatly enhances the inhibitory activity. Lipophilicity and the stereochemistry of the possible anchoring sites are also crucial factors for the activity. Finally, the levels of growth inhibition obtained with some compounds on dicots or monocots are totally comparable to those of Logran and allow proposing them as lead compounds.

Herbicides↗
PubMed2003

Avenanthramides in oats (Avena sativa L.) and structure-antioxidant activity relationships.

Eight avenanthramides, amides of anthranilic acid (1) and 5-hydroxyanthranilic acid (2), respectively, and the four cinnamic acids p-coumaric (p), caffeic (c), ferulic (f), and sinapic (s) acid, were synthesized for identification in oat extracts and for structure-antioxidant activity studies. Three compounds (2p, 2c, and 2f) were found in oat extracts. As assessed by the reactivity toward 1,1-diphenyl-2-picrylhydrazyl (DPPH), all avenanthramides except 1p showed activity. Initially, the antioxidant activity of the avenanthramides decreased in a similar order as for the corresponding cinnamic acids, that is: sinapic > caffeic > ferulic > p-coumaric acid. The avenanthramides derived from 2 were usually slightly more active than those derived from 1. All avenanthramides inhibited azo-initiated peroxidation of linoleic acid. 1c and 1s were initially the most effective compounds. The relative order of antioxidant activities was slightly different for the DPPH and the linoleic acid assays run in methanol and chlorobenzene, respectively.

Amides↗
PubMed2001

A novel dimeric diterpene from Salvia prionitis.

A novel dimeric abietane diterpene, hongencaotone (1), has been isolated from the roots of Salvia prionitis, and its structure was determined by spectral data interpretation and X-ray analysis. Hongencaotone (1) is the first ether-linked heterodimeric diterpene to have been isolated from the genus Salvia.

Antineoplastic Agents, Phytogenic↗
PubMed2006

Schisandrene, a dibenzocyclooctadiene lignan from Schisandra chinensis: structure-antioxidant activity relationships of dibenzocyclooctadiene lignans.

Phytochemical investigation of the fruits of Schisandra chinensis led to the isolation of 13 lignans including schisandrene (13), a new lignan based on a dibenzocyclooctadiene backbone with an exocyclic double bond. Its structure and absolute configuration were established using NMR, MS, and CD data. Antioxidant activity of the lignans was evaluated using a DCFH-DA cellular-based assay. The structure-activity relationships of the dibenzocyclooctadiene lignans showed that the exocyclic methylene functionality was essential for antioxidant activity, with the benzoyloxy group probably enhancing such effects.

Antioxidants↗
PubMed2006

Alkaloids from the roots of Aconitum pseudo-laeve var. erectum.

One new quinazoline (1) and two new norditerpenoid (2 and 3) alkaloids along with 10 known compounds were isolated from the roots of Aconitum pseudo-laeve var. erectum. The new alkaloids were assigned as 2-(2-methyl-4-oxo-4H-quinazoline-3-yl)benzoic acid methyl ester (1), 18-O-2-(2-methyl-4-oxo-4H-quinazoline-3-yl)benzoyllycoctonine (2), and 14-O-acetyl-8-O-methyl-18-O-2-(2-methyl-4-oxo-4H-quinazoline-3-yl)benzoylcammaconine (3). The structures of the new alkaloids were established by spectroscopic methods. This is the first report of the 2-(2-methyl-4-oxo-4H-quinazoline-3-yl)benzoyl ester group being found as an acyl substituent in norditerpenoid alkaloids (compounds 2 and 3).

Aconitine↗
PubMedDate not supplied

Plant antimutagenic agents, 7. Structure and antimutagenic properties of cymobarbatol and 4-isocymobarbatol, new cymopols from green alga (Cymopolia barbata).

Two new compounds, cymobarbatol and 4-isocymobarbatol, were isolated from the marine alga Cymopolia barbata. The complete structures and absolute stereochemistries of these compounds were elucidated by a variety of spectroscopic techniques and X-ray crystallography. Both compounds were found to be nontoxic over a broad concentration range to Salmonella typhimurium strains T-98 and T-100. Both compounds exhibited strong inhibition of the mutagenicity of 2-aminoanthracene and ethyl methanesulfonate toward, respectively, the T-98 strain plus a metabolic activator and T-100.

Benzopyrans↗
PubMed1994

Patuletin acetylrhamnosides from Kalanchoe brasiliensis as inhibitors of human lymphocyte proliferative activity.

The fractionation of the juice of fresh stems and leaves of Kalanchoe brasiliensis was monitored by an assay measuring lymphocyte proliferative activity and allowed the isolation and identification of seven patuletin rhamnoside derivatives [1-7]. Three of them are novel, namely, patuletin 3-O-(4"-O-acetyl-alpha-L-rhamnopyranosyl)-7-O-(2'"-O-acetyl- alpha-L-rhamnopyranoside) [1], patuletin 3-O-alpha-L-rhamnopyranosyl-7-O-(2'"-O-acetyl-alpha-L- rhamnopyranoside) [3], and patuletin 3-O-(4"-O-acetyl-alpha-L-rhamnopyranosyl)-7-O- rhamnopyranoside [4], and four are known [2, 5-7]. Their structures were determined by the analysis of 1H-1H and 1H-13C COSY nmr, ci, and fab mass spectra.

Chromones↗
PubMed1998

Isolation and Structural Elucidation of Two Plant Ecdysteroids, Gerardiasterone and 22-Epi-20-hydroxyecdysone

Two minor plant ecdysteroids, 22-epi-20-hydroxyecdysone (1) and gerardiasterone (2), were isolated from Serratula tinctoria L. (Compositae). The first compound, a new natural product, was characterized by an unusual stereochemistry at C-22 (i.e., 22S). The second compound was identified as (20R,23S)-20,23-dihydroxyecdysone, a compound previously isolated from the Zooanthid Gerardia savaglia.

Journal Article↗
PubMed2001

The first total synthesis of (+/-)-scopadulin, an antiviral aphidicolane diterpene.

[reaction: see text] The first total synthesis of (+/-)-scopadulin was accomplished by a stereoselective construction of a quaternary carbon at C-4, conversion of the hindered cyano group to a methyl group via our novel reaction for conversion of primary aliphatic amines into alcohols, and a highly chemo- and stereoselective methylation at C-16.

Antiviral Agents↗
PubMed2001

The first total synthesis of (+/-)-linderol A, a tricyclic hexahydrodibenzofuran constituent of Lindera umbellata bark, with potent inhibitory activity on melanin biosynthesis of cultured B-16 melanoma cells.

[reaction in text] The first total synthesis of (+/-)-linderol A, a hexahydrodibenzofuran isolated from Lindera umbellata bark, with potent inhibitory activity on melanin biosynthesis of cultured B-16 melanoma cells was achieved via a 20-step of reaction in 7.64% overall yield starting from 4,6-dimethoxysalicylaldehyde.

Benzofurans↗
PubMed2002

Three classes of proteinase inhibitor gene have distinct but overlapping patterns of expression in Pisum sativum plants.

Genes representative of three gene classes encoding proteinase inhibitor proteins, with distinct spatial expression patterns, were isolated and characterized from Pisum. Under standard plant growth conditions, one class is expressed exclusively in seeds, whereas the other two make minor contributions to seed inhibitor proteins but are also expressed in other organs, predominantly in root endodermal and floral reproductive tissues. Two of the gene classes contain few genes and are genetically linked at the Tri locus, whereas the third class displays complex hybridization patterns to genomic DNA and maps to diverse genetic loci. Expression analysis of this last class suggests that only a small number of these genes are expressed. The quantitative effect of the Tri locus on root and floral inhibitor gene expression was examined in near-isogenic lines of pea. The proteins encoded by the three classes are all members of the same family (Bowman-Birk) of enzyme inhibitors but are distinct in terms of overall sequence, active site sequences and inhibitor function.

Amino Acid Sequence↗
PubMed2003

The plant invertase inhibitor shares structural properties and disulfide bridges arrangement with the pectin methylesterase inhibitor.

Attempts to purify the inhibitor of pectin methylesterase (PMEI) from the soluble extract of ripe apricot (Prunus armeniaca) fruit led to isolation of a protein (Pa-INH) similar to PMEI, but having invertase inhibitory activity against vacuolar invertase from tomato. The molecular charge, the native and SDS-PAGE molecular weights were similar to those of PMEI. Partial amino acid sequence indicated a high level of identity with invertase inhibitors and a significant identity with PMEI. Circular dichroism analysis showed a mainly alpha-helix secondary structure for both the inhibitors and a higher thermostability of Pa-INH. Four Cys residues forming disulfide bridges in PMEI were conserved in Pa-INH. Similarly to PMEI, these residues were linked by disulfide bridges (first to second and third to fourth). The free Cys139 of PMEI is substituted by Ala in Pa-INH. The results reported in this study suggest a common structural arrangement of the two inhibitors.

Amino Acid Sequence↗