| alternative pathways of xanthone biosynthesis in cell cultures of hypericum androsaemum l. | the biosynthesis of xanthones was studied in cell cultures of hypericum androsaemum l. we have detected a new benzophenone synthase, for which the preferred substrate is benzoyl-coa, itself supplied by 3-hydroxybenzoate:coenzyme a ligase. the stepwise condensation of benzoyl-coa with three molecules of malonyl-coa, catalyzed by benzophenone synthase, yields 2,4,6-trihydroxybenzophenone. this intermediate is subsequently converted by benzophenone 3'-hydroxylase, a cytochrome p450 monooxygenase. t ... | 1997 | 9459298 |
| xanthone 6-hydroxylase from cell cultures of centaurium erythraea rafn and hypericum androsaemium l. | xanthone 6-hydroxylase activity was detected in the microsomal fractions from two plant cell cultures. the enzyme from cultured cells of centaurium erythraea (gentianaceae) exhibited absolute specificity for 1,3,5-trihydroxyxanthone as substrate, whereas xanthone 6-hydroxylase from cell cultures of hypericum androsaemum (hypericacaea) preferred the isomeric 1,3,7-trihydroxyxanthone but used 1,3,5-trihydroxyxanthone also to a small extent. both xanthones were regioselectively hydroxylated in posi ... | 2000 | 10731018 |
| xanthones in cell cultures of hypericum androsaemum. | cell cultures of hypericum androsaemum contain an array of prenylated xanthone aglycones and their glucosides, when grown in modified b5 medium in the dark. derivatives of 1,3,6,7-tetrahydroxyxanthone prevail over compounds with the 1,3,5,6-oxygenation pattern. 1,7-dihydroxyxanthone was also isolated. xanthone accumulation parallels cell growth, is repressed by light and strongly influenced by the culture medium used. | 2000 | 10865463 |
| cinnamic acid is a precursor of benzoic acids in cell cultures of hypericum androsaemum l. but not in cell cultures of centaurium erythraea rafn. | benzoic acids are precursors of xanthone biosynthesis which has been studied in cell cultures of hypericum androsaemum (hypericaceae) and centaurium erythraea (gentianaceae). in both cell cultures, methyl jasmonate induces the intracellular accumulation of a new xanthone. under these inductive conditions, feeding experiments were performed with [u-14c]l-phenylalanine, [7-14c]benzoic acid and [7-14c]3-hydroxybenzoic acid. all three precursors were efficiently incorporated into the elicited xantho ... | 2001 | 11216850 |
| benzoic acid biosynthesis in cell cultures of hypericum androsaemum. | biosynthesis of benzoic acid from cinnamic acid has been studied in cell cultures of hypericum androsaemum l. the mechanism underlying side-chain shortening is coa-dependent and non-beta-oxidative. the enzymes involved are cinnamate:coa ligase, cinnamoyl-coa hydratase/lyase and benzaldehyde dehydrogenase. cinnamate:coa ligase was separated from benzoate:coa ligase and 4-coumarate:coa ligase, which belong to xanthone biosynthesis and general phenylpropanoid metabolism, respectively. cinnamoyl-coa ... | 2002 | 11882941 |
| antioxidant activity of hypericum androsaemum infusion: scavenging activity against superoxide radical, hydroxyl radical and hypochlorous acid. | hypericum androsaemum is a medicinal plant species containing many polyphenolic compounds, namely flavonoids and phenolic acids. since polyphenolic compounds have high antioxidant potential, the ability of h. androsaemum infusion to act as a scavenger of reactive oxygen species (superoxide radical, hydroxyl radical and hypochlorous acid) was investigated. superoxide radical was generated by the xanthine/xanthine oxidase and phenazine methosulphate/nadh systems. the infusion-mediated prevention o ... | 2002 | 12392087 |
| essential oils from plants and in vitro shoots of hypericum androsaemum l. | the essential oil yields obtained by hydrodistillation of the aerial parts of hypericum androsaemum cultivated plants varied from 0.94 to 4.09 mg/g of biomass dry weight, depending of the harvest time. the respective analyses performed by gas chromatography and gas chromatography-mass spectrometry revealed more than 80 compounds, 72 of which were identified. most of the compounds were sesquiterpene hydrocarbons, which, depending of the harvest time, corresponded to 43-78% of the total essential ... | 2003 | 12590488 |
| variability in phenolic composition of hypericum androsaemum. | the methanolic extracts of fifteen hypericum androsaemum samples, growing spontaneously or cultivated in portugal, were analysed by hplc/dad, allowing the identification of 9 phenolic compounds and the detection of 6 phloroglucinols. total amounts of phenolics found ranged from 11 to 39 g/kg, and the influence of some factors which may be responsible for this variation is discussed. the individual compounds were also quantified. four different phenolic profiles were found concerning both qualita ... | 2003 | 12713126 |
| benzophenone synthase and chalcone synthase from hypericum androsaemum cell cultures: cdna cloning, functional expression, and site-directed mutagenesis of two polyketide synthases. | benzophenone derivatives, such as polyprenylated benzoylphloroglucinols and xanthones, are biologically active secondary metabolites. the formation of their c13 skeleton is catalyzed by benzophenone synthase (bps; ec 2.3.1.151) that has been cloned from cell cultures of hypericum androsaemum. bps is a novel member of the superfamily of plant polyketide synthases (pkss), also termed type iii pkss, with 53-63% amino acid sequence identity. heterologously expressed bps was a homodimer with a subuni ... | 2003 | 12795704 |
| protective activity of hypericum androsaemum infusion against tert-butyl hydroperoxide-induced oxidative damage in isolated rat hepatocytes. | hypericum androsaemum l. (guttiferae) is a medicinal plant with antioxidant activity. increasing evidence regarding free radical generating agents suggests that hepatotoxic-related disorders may involve reactive oxygen species (ros). the purpose of this study was to investigate the protective effect of hypericum androsaemum infusion on isolated rat hepatocytes oxidative injury induced by tert-butyl hydroperoxide (t-bhp). the results showed that pretreatment of the cells with this infusion (16, 6 ... | 2004 | 15099852 |
| variation of the essential oil content and composition in leaves from cultivated plants of hypericum androsaemum l. | the amount and composition of the essential oil from leaves of hypericum androsaemum l. cultivated in arouca (portugal) were determined in six samples harvested during 1 year at intervals of 2 months. the seasonally dependent essential oil content ranged from 0.7 mg/g biomass dry weight in september to 3.4 mg/g in february. the oil contained more than 80 compounds, 70 of which (constituting 88-93% of the total oil) were identified by gc and gc-ms. an approximation of the absolute quantification ... | 2004 | 15202597 |
| hypericum androsaemum infusion increases tert-butyl hydroperoxide-induced mice hepatotoxicity in vivo. | increasing evidence regarding free radical generating agents indicates that the sustained production of high levels of reactive oxygen species (ros) can cause hepatotoxicity. being a short chain analog of lipid peroxide, tert-butyl hydroperoxide (t-bhp) is metabolized into free radical intermediates by cytochrome p450 in hepatocytes, which initiate lipid peroxidation, glutathione depletion and cell damage. the aim of the present study was to evaluate the putative protective effect of hypericum a ... | 2004 | 15325741 |
| metabolic engineering of the phenylpropanoid pathway in saccharomyces cerevisiae. | flavonoids are valuable natural products derived from the phenylpropanoid pathway. the objective of this study was to create a host for the biosynthesis of naringenin, the central precursor of many flavonoids. this was accomplished by introducing the phenylpropanoid pathway with the genes for phenylalanine ammonia lyase (pal) from rhodosporidium toruloides, 4-coumarate:coenzyme a (coa) ligase (4cl) from arabidopsis thaliana, and chalcone synthase (chs) from hypericum androsaemum into two sacchar ... | 2005 | 15932991 |
| in vitro protective effect of hypericum androsaemum extract against oxygen and nitrogen reactive species. | hypericum androsaemum l. (gutiferae) is a medicinal plant growing in western europe that has been used in traditional medicine in the prevention or treatment of liver diseases. oxidative stress and nitrosative stress are common pathogenetic mechanisms contributing to initiation and progression of hepatic damage in several liver disorders. in the present study, an ethanol:water (4:6) extract from h. androsaemum branches and leaves were evaluated for its putative in vitro scavenging effects on 1,1 ... | 2009 | 19614890 |
| the role of secreting structures position on the leaf volatile organic compounds of hypericum androsaemum. | hypericum androsaemum l. presents typical translucent, essential oil producing glands, which are distributed on the leaf along both margins (margin glands) and on the lamina (lamina glands). the gland secretion was studied by histochemical and chemical analysis; the gland content was sampled directly from the secretory glands, and the volatile organic compounds (voc) of the margin and lamina glands were separately analyzed. the lipophilic fraction of the lamina glands had as main components: (e) ... | 2010 | 20184033 |
| Does forest fragmentation affect the same way all growth-forms? | Fragmentation of natural habitats is one of the main causes of the loss of biodiversity. However, all plants do not respond to habitat fragmentation in the same way due to differences in species traits. We studied the effect of patch size and isolation on the biodiversity of vegetation in the mixed-oak forests in the north of the Iberian Peninsula. The aim was to evaluate whether all the growth-forms of vegetation are equally affected by forest fragmentation in order to improve the management st ... | 2012 | 21924813 |
| molluscicidal activity of crude water and hexane extracts of hypericum species on radix peregra snails. | in spite of the intense research on both chemical constituency and biological activity of hypericum species, potential applications of their active components on pest control have been less investigated. in the present study, hypericum androsaemum (tutsan), hypericum foliosum (malfurada), and hypericum undulatum (wavy st. john's wort) aqueous and hexane extracts were studied for their molluscicidal and ovicidal activities against radix peregra. the molluscicidal activity of the aqueous extracts ... | 2011 | 22170085 |