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Results for “Plant Structures”

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At least 1,063 records · Page 59Linked to original sources
PubMed2002

A new diterpene from Tanaecium jaroba.

One new diterpene, 2 alpha-hydroxy-12beta-hydroxy-isopimara-8(14), 15-diene, and six known compounds as triterpenes, sterols and fatty acid, were isolated from the stem bark of Tanaecium jaroba (Bignoniaceae), a Bolivian plant used in traditional medicine. Their structures were established mainly by 1D and 2D NMR (COSY, HMQC, HMBC, ROESY) and their antiplasmodial activities were evaluated in vitro against Plasmodium falciparum.

Animals↗
PubMed1995

Inhibition of lens aldose reductase by biflavones from Ouratea spectabilis.

Two biflavonoids were isolated from the EtOH extract from leaves of Ouratea spectabilis. Their structures were established to be the novel 6,6"-bigenkwanin and 7,7"-dimethoxyagathisflavone on the basis of spectroscopic data. The inhibition of bovine lens aldose reductase exerted by these biflavones has been studied.

Aldehyde Reductase↗
PubMed1994

Isolation of bis-indole alkaloids with antileishmanial and antibacterial activities from Peschiera van heurkii (syn. Tabernaemontana van heurkii).

Extracts from leaves and stem bark of Peschiera van heurkii (Muell. Arg.) L. Allorge (syn. Tabernaemontana van heurkii Muell. Arg., Apocynaceae) have been assayed for antileishmanial and antibacterial activities. The activities were concentrated in the alkaloid fractions which yielded 20 indole and bisindole alkaloids. The strongest leishmanicidal and antibacterial activities were observed with the dimeric alkaloids conodurine (1), N-demethylconodurine (= gabunine) (2), and conoduramine (3). Weak toxicity towards macrophage host cells and strong activity against the intracellular amastigote form of Leishmania were observed for compounds 1 and 2. In vivo, 1 was less active than glucantime (= N-methylglucamine antimonate), the drug of reference, while 2 was devoid of activity at 100 mg/kg.

Alkaloids↗
PubMed2006

Novel urease inhibitors from Daphne oleoids.

Phytochemical investigations on the chloroform and ethyl acetate soluble fractions of the roots of the Daphne oleoids led to the isolation of the coumarin glycosides 1-6. Compound 5 with IC50 values 22.05 and 26.30 microM repectively, was found to be the most active of these compounds when screened against Bacillus pasteurii and jack bean urease enzymes in a concentration-dependent fashion.

Daphne↗
PubMed2007

Expressed sequence tags from Cryptomeria japonica sapwood during the drying process.

Secondary metabolites called norlignans are produced in the xylem of Cryptomeria japonica D. Don. Several norlignans have roles in the defense of sapwood against microbial invasion and in the coloration of heartwood. The biosynthetic pathway of norlignans is largely unknown. Norlignans have been reported to accumulate in the sapwood during the drying of C. japonica logs. To search for genes encoding enzymes that catalyze the synthesis of norlignans, we carried out suppression subtractive hybridization using the fresh sapwood of a felled log and the drying sapwood in which a norlignan, agatharesinol, accumulated. A total of 1050 expressed sequence tags were obtained from the subtracted cDNA library, and these were assembled into 146 contigs and 361 singletons. Of these 507 unique sequences, 263 were functionally classified into 12 categories. "Metabolism" was the largest category, with 23% (61) of classified sequences. Twenty-six sequences that encode 16 enzymes were assigned to "secondary metabolism." Expression analysis of 15 genes related to "secondary metabolism" revealed that 12 of these genes had transcripts that were induced during the sapwood drying process. Of the 12 genes, 10 encoded enzymes that use aromatic compounds as substrates. In addition, 58 sequences representing 22 defense-related proteins were found. Our subtraction library should be a useful source for isolating genes encoding proteins involved in secondary metabolism including norlignan biosynthesis and defense in C. japonica xylem.

Color↗
PubMed1995

Cellulose-Lignin Interactions (A Computational Study).

Within a broader program of study of the molecular structure of plant cell walls, molecular dynamics calculations were used to explore the character of the motion of lignin model compounds near a cellulose surface. Model cellulose microfibrils, which have a large number of hydroxyl groups on the surface, appear to have a net attractive interaction with the lignin models examined in this study. The lignin monomer coniferyl alcohol rapidly adsorbed onto the surface from a water layer after it was released 13 A from the surface. The major long-range force responsible for this adsorption is likely electrostatic. The attractive interaction is sufficient to restrict the motion of coniferyl alcohol when it is within 1 A of the surface and to orient the phenyl ring parallel to the surface. The [beta]-O-4-linked trimer also was observed to adsorb onto the surface with two of its phenyl rings parallel to the surface. These results suggest a mechanism by which the polysaccharide component of the plant cell wall could influence the structure of lignin. Furthermore, they provide a rationalization of the experimental observation that polysaccharides can change the course of dehydrogenation polymerization of cinnamyl alcohols.

Journal Article↗
PubMed1979

Cell Surfaces in Plant-Microorganism Interactions: I. A Structural Investigation of Cell Wall Hydroxyproline-rich Glycoproteins Which Accumulate in Fungus-infected Plants.

Infection of muskmelon Cucumis melo seedlings by the fungus Colletotrichum lagenarium causes a 10-fold increase in the amount of cell wall hydroxyproline-rich glycoprotein. Evidence for this increase was provided by studying two specific markers of this glycoprotein, namely hydroxyproline and glycosylated serine. The lability of the O-glycosidic linkage of wall-bound glycosylated serine in the presence of hydrazine, was used to determine the amount of serine which is glycosylated.A large increase in the hydroxyproline content of infected plants is shown, but the ratios of glycosylated serine to hydroxyproline are similar in healthy and infected plants. As far as these markers are concerned, the hydroxyproline-rich glycoproteins secreted into the wall as a result of the disease are similar to those of healthy plants. In addition, the extent of glycosylation of the wall serine, in both healthy and infected plants, decreases as the plant ages.Serine- and hydroxyproline-rich (glyco)peptides were also isolated after trypsinolysis of the wall. These (glyco)peptides include the galactosyl-containing pentapeptide, serine-hydroxyproline(4). This pentapeptide is characteristic of cell wall protein.

Journal Article↗
PubMed1989

Structural studies on the biosides of Digitalis lanata: bisdigitoxosides of digitoxigenin, gitoxigenin and digoxigenin.

The crystal structures and conformations of bisdigitoxosides of digitoxigenin (I), gitoxigenin (II) and digoxigenin (III and IV) have been determined using single-crystal X-ray crystallographic techniques. Crystals of (I), (II) and (IV) were grown from ethyl acetate solutions of the glycosides while (III) was grown from a solution of the digitoxoside in ethanol. As in other cardiac glycosides the ring junctions A-B and C-D are cis. The D ring in these structures shows different conformations while the A, B and C rings remain conformationally similar. Although digitoxigenin bisdigitoxoside and gitoxigenin bisdigitoxoside differ from each other in the absence and presence of a hydroxyl group at C(16) of the D ring, these two biosides crystallize in the space group P2(1)2(1)2 [corrected] and are isomorphous. The presence of the hydroxyl group at C(16) does not affect the orientation of the lactone ring and the conformation of the molecule. Digoxigenin bisdigitoxoside crystallizes in two different crystal systems with four molecules of water in the orthorhombic form and one molecule of ethyl acetate in the triclinic form. In both forms the hydroxyl at C(3') of the first sugar forms a hydrogen bond with the ring oxygen of the second sugar. This has also been observed in the trioside digoxin. The torsion angle C(13)-C(17)-C(20)-C(22) in the two forms differs by 7 degrees.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardenolides↗
PubMed2004

Innate immunity in plants and animals: striking similarities and obvious differences.

Innate immunity constitutes the first line of defense against attempted microbial invasion, and it is a well-described phenomenon in vertebrates and insects. Recent pioneering work has revealed striking similarities between the molecular organization of animal and plant systems for nonself recognition and anti-microbial defense. Like animals, plants have acquired the ability to recognize invariant pathogen-associated molecular patterns (PAMPs) that are characteristic of microbial organisms but which are not found in potential host plants. Such structures, also termed general elicitors of plant defense, are often indispensable for the microbial lifestyle and, upon receptor-mediated perception, inevitably betray the invader to the plant's surveillance system. Remarkable similarities have been uncovered in the molecular mode of PAMP perception in animals and plants, including the discovery of plant receptors resembling mammalian Toll-like receptors or cytoplasmic nucleotide-binding oligomerization domain leucine-rich repeat proteins. Moreover, molecular building blocks of PAMP-induced signaling cascades leading to the transcriptional activation of immune response genes are shared among the two kingdoms. In particular, nitric oxide as well as mitogen-activated protein kinase cascades have been implicated in triggering innate immune responses, part of which is the production of antimicrobial compounds. In addition to PAMP-mediated pathogen defense, disease resistance programs are often initiated upon plant-cultivar-specific recognition of microbial race-specific virulence factors, a recognition specificity that is not known from animals.

Animals↗
PubMed2006

Characterization of a BAHD acyltransferase responsible for producing the green leaf volatile (Z)-3-hexen-1-yl acetate in Arabidopsis thaliana.

Green-leaf volatiles are commonly emitted from mechanically and herbivore-damaged plants. Derived from the lipoxygenase pathway, these compounds may serve as attractants to predators and parasitoids of herbivores, prevent the spread of bacteria and fungi, and induce several important plant defense pathways. In Arabidopsis thaliana, the major volatile released upon mechanical wounding of the leaves is the GLV ester, (Z)-3-hexen-1-yl acetate. We have characterized a member of the BAHD acyltransferase gene family At3g03480 which catalyzes the formation of (Z)-3-hexen-1-yl acetate from acetyl-CoA and (Z)-3-hexen-1-ol. The encoded acetyl CoA:(Z)-3-hexen-1-ol acetyltransferase (CHAT) has the ability to accept several medium-chain-length aliphatic and benzyl-derived alcohols, but has highest catalytic efficiency with (Z)-3-hexen-1-ol. The highest expression of CHAT occurs in the leaves and stems. Upon mechanical damage, the (Z)-3-hexen-1-yl acetate emission peaked after 5 min and declined to pre-damage levels after 90 min. However, CHAT gene transcript levels increased much more slowly with the highest levels detected between 3 and 6 h after wounding. An increase in CHAT enzyme activity in vitro followed the transcript increase, with levels peaking between 10 and 12 h after wounding. Plants expressing either an RNAi cassette for the CHAT gene or plants harboring a T-DNA insertion in the CHAT coding region had greatly reduced (Z)-3-hexen-1-yl acetate emission, showing that the CHAT enzyme is responsible for the in planta production of this ester.

Acetates↗
PubMed2006

Positive interactions between alpine plant species and the nurse cushion plant Laretia acaulis do not increase with elevation in the Andes of central Chile.

In alpine habitats, positive interactions among plants tend to increase with elevation as a result of altitudinal increase in environmental harshness. However, in mountains located in arid zones, lower elevations are also stressful because of scarce availability of water, suggesting that positive interactions may not necessarily increase with elevation. Here we analysed the spatial association of plant species with the nurse cushion plant Laretia acaulis at two contrasting elevations, and monitored the survival of seedlings of two species experimentally planted within and outside cushions in the semiarid Andes of central Chile. Positive spatial associations with cushions were more frequent at lower elevations. Species growing at the two elevations changed the nature of their association with cushions from neutral or negative at higher elevations to positive at lower elevations. Survival of seedlings was higher within cushions, particularly at lower elevations. The increased facilitation by cushions at lower elevations seems to be related to provision of moisture. This result suggests that cushion plants play a critical role in structuring alpine plant communities at lower elevations, and that climatic changes in rainfall could be very relevant for persistence of plant communities.

Altitude↗
PubMed2002

A novel cytotoxic C-methylated biflavone, taiwanhomoflavone-B from the twigs of Cephalotaxus wilsoniana.

A novel C-methylated biflavone, taiwanhomoflavone-B (1), together with known compounds, 7,4',7"-tri-O-methylamentoflavone, 6-C-methylnaringenin and apigenin-7-O-beta-glucoside were isolated from an ethanolic extract of Cephalotaxus wilsoniana. The structure of 1 was elucidated on the basis of spectroscopic analysis. Taiwanhomoflavone-B is cytotoxic with ED(50) values of 3.8 and 3.5 microg/ml, against KB oral epidermoid carcinoma and Hepa-3B hepatoma cells, respectively.

Cell Survival↗