Cimiracemates A-D,phenylpropanoid esters from the rhizomes of Cimicifuga racemosa

Four phenylpropanoid esters, cimiracemates A-D (1-4), along with three known compounds, isoferulic acid, ferulic acid and methyl caffeate were isolated from the EtOAc fraction of the rhizome of Cimicifuga racemosa. The structures of the esters were elucidated by means of spectral data, including 2D NMR spectroscopy.     

Phenylpropanoid glycosides from Smilax glabra

Five phenylpropanoid esters of sucrose glycosides, trivially named smiglasides A-E, were isolated from the rhizomes of Smilax glabra. Their structures were elucidated on the basis of spectroscopic studies.     

Antioxidant phenylpropanoid glycosides from Smilax bracteata

From the ethanolic extract of Smilax bracteata, six phenylpropanoid glycosides, smilasides G-L (1-6), along with four known phenylpropanoid compounds, helonioside A, helonioside B, smilaside E, and (1-p-O-coumaroyl-6-O-feruroyl)-beta-d-fructofuranosyl-alpha-d-glucopyranoside, and fourteen known phenolic compounds were isolated. Their structures were elucidated on the basis of spectroscopic analyses. Moreover, 1-6 exhibited moderate scavenging activities against DPPH radicals.     

Profiling of phenylpropanoids in transgenic low-sinapine oilseed rape (Brassica napus)

A dsRNAi approach silencing a key enzyme of sinapate ester biosynthesis (UDP-glucose:sinapate glucosyltransferase, encoded by the UGT84A9 gene) in oilseed rape (Brassica napus) seeds was performed to reduce the anti-nutritive properties of the seeds by lowering the content of the major seed component sinapine (sinapoylcholine) and various minor sinapate esters. The transgenic seeds have been produced so far to the T6 generation and revealed a steady suppression of sinapate ester accumulation. HPLC analysis of the wild-type and transgenic seeds revealed, as in the previous generations, marked alterations of the sinapate ester pattern of the transformed seeds. Besides strong reduction of the amount of the known sinapate esters, HPLC analysis revealed unexpectedly the appearance of several minor hitherto unknown rapeseed constituents. These compounds were isolated and identified by mass spectrometric and NMR spectroscopic analyses. Structures of 11 components were elucidated to be 4-O-glucosides of syringate, caffeyl alcohol and its 7,8-dihydro derivative as well as of sinapate and sinapine, along with sinapoylated kaempferol glycosides, a hexoside of a cyclic spermidine alkaloid and a sinapine derivative with an ether-bridge to a C₆-C₃-unit. These results indicate a strong impact of the transgenic approach on the metabolic network of phenylpropanoids in B. napus seeds. Silencing of UGT84A9 gene expression disrupt the metabolic flow through sinapoylglucose and alters the amounts and nature of the phenylpropanoid endproducts.     

Iridoid and phenolic glycosides from Wulfenia carinthiaca

Two new phenylpropanoid glycosides (2'-O-acetylplantamajoside and 2'-O, 6"-O-diacetylplantamajoside), a new iridoid glycoside (10-O-(cinnamoyl)-6'-O-(desacetylalpinosidyl)-catalpol), the two known iridoid glycosides globularin and isoscrophularioside, and the known phenylpropanoid glycoside platamajoside were isolated from the methanolic extract of the underground parts of Wulfenia carinthiaca. Structure elucidations were based on high-resolution mass spectrometry and extensive 1-D and 2-D NMR spectroscopy.     

Ecdysteroids and a sucrose phenylpropanoid ester from Froelichia floridana

Phytoecdysteroid glycosides (1-5) and a phenylpropanoid ester of sucrose (6) were isolated from the whole plant of Froelichia floridana, along with eight known compounds including three ecdysteroids (7-9), four flavonoids (10-13), and one phenolic compound (14). Structures were determined using a combination of spectroscopic techniques. Compounds 1, 2 and 6-14 were tested in vitro for their activity against human DNA topoisomerase I. Compound 13 (diosmetin) showed marginal inhibition against topoisomerase I with IC₅₀ of 130 μM in conjunction with low intercalation ability.     

4'-deoxy iridoid glycosides from Centranthus longiflorus

The new iridoid glycosides, 4'-deoxykanokoside A and 4'-deoxykanokoside C, were isolated from the methanolic root extract of Centranthus longiflorus ssp. longiflorus. They were accompanied by the three known iridoid glycosides, kanokoside A, kanokoside C and valerosidatum, and two known phenylpropanoid glycosides, coniferin and isoconiferinoside. The structures were elucidated mainly by spectroscopic methods. The presence of 4-deoxy glucose as a part of plant glycosides is rather unusual. Cytotoxic effects of the isolated compounds were also investigated.     

Parameters affecting productivity in the lipase-catalysed synthesis of sucrose palmitate

The industrial application of lipases for the synthesis of sucrose esters is usually limited by its low productivity, as we need a medium where a polar reagent (the sugar) and a non-polar fatty acid donor are soluble and able to react in the presence of the biocatalyst. In this work, we have studied the problems encountered when trying to increase the volumetric productivity of sucrose esters. The synthesis of sucrose palmitate was performed in 2-methyl-2-butanol:dimethylsulfoxide mixtures by transesterification of different palmitic acid donors with sucrose, catalysed by the immobilized lipase from Candida antarctica B (Novozym 435). A protocol for substrate preparation different from that previously reported was found to improve the reaction rate. Several parameters, such as sucrose and acyl donor loadings, the percentage of DMSO in the mixture and the nature of acyl donor, were investigated. Under the best experimental conditions (15% DMSO, 0.1 mol l^?1 sucrose, 0.3 mol l^?1 vinyl palmitate), a maximum of 45 g l^?1 sucrose palmitate was obtained in 120 h. Using methyl or ethyl palmitate, the highest productivity was 7.3 g l^?1 in 120 h using 20% DMSO with 0.2 mol l^?1 sucrose and 0.6 mol l^?1 acyl donor. The formation of free fatty acid, and the effect of the percentage of DMSO on the monoester/diester selectivity were also studied. To our knowledge, this is the first report on enzymatic synthesis of sucrose esters of long fatty acids using alkyl esters as acyl donors.     

Changes in secondary metabolism and deposition of an unusual lignin in the ref8 mutant of Arabidopsis

The end products of the phenylpropanoid pathway play important roles in plant structure and development, as well as in plant defense mechanisms against biotic and abiotic stresses. From a human perspective, phenylpropanoid pathway-derived metabolites influence both human health and the potential utility of plants in agricultural contexts. The last known enzyme of the phenylpropanoid pathway that has not been characterized is p-coumarate 3-hydroxylase (C3H). By screening for plants that fail to accumulate soluble fluorescent phenylpropanoid secondary metabolites, we have identified a number of Arabidopsis mutants that display a reduced epidermal fluorescence (ref) phenotype. We have now shown that the ref8 mutant is defective in the gene encoding C3H. Phenotypic characterization of the ref8 mutant has revealed that the lack of C3H activity in the mutant leads to diverse changes in phenylpropanoid metabolism. The ref8 mutant accumulates p-coumarate esters in place of the sinapoylmalate found in wild-type plants. The mutant also deposits a lignin formed primarily from p-coumaryl alcohol, a monomer that is at best a minor component in the lignin of other plants. Finally, the mutant displays developmental defects and is subject to fungal attack, suggesting that phenylpropanoid pathway products downstream of REF8 may be required for normal plant development and disease resistance.     

Sesquiterpene coumarins from Ferula szowitsiana and in vitro antileishmanial activity of 7-prenyloxycoumarins against promastigotes

Two new sesquiterpene coumarins, named szowitsiacoumarin A (1) and szowitsiacoumarin B (2), and a phenylpropanoid derivative, 2-epihelmanticine (3), together with nine known compounds, auraptene (4), umbelliprenin (5), galbanic acid (6), methyl galbanate (7), farnesiferol B (8), farnesiferol C (9), persicasulfide A (10), beta-sitosterol and stigmasterol were isolated from the roots of Ferula szowitsiana. The structures of these compounds were elucidated by extensive spectroscopic methods including 1D-((1)H and (13)C) and 2D-NMR experiments (DQF-COSY, HSQC, HMBC, and ROESY) as well as HR-MALDI-MS analysis. Since the configuration of 2-epihelmanticine was previously only partly determined, a relative configurational analysis of its four stereocenters was carried out on the basis of the recently reported J-based method. The inhibiting activity of prenylated coumarins, auraptene (4) and umbelliprenin (5), in addition to galbanic acid (6), as major component, and of the Me(2)CO extract of Ferula szowitsiana (Apiaceae) roots has been evaluated against promastigotes of Leishmania major. Umbelliprenin and auraptene showed significant activity with IC(50) values of 4.9microg/ml (13.3microM) and 5.1microg/ml (17.1microM) after 48h incubation, respectively.     

Galloyl, caffeoyl and hexahydroxydiphenoyl esters of dihydrochalcone glucosides from Balanophora tobiracola

Seven galloyl, caffeoyl and (S)-hexahydroxydiphenoyl (HHDP) esters of dihydrochalcone glucosides were isolated from Balanophora tobiracola; based on spectroscopic and chemical evidence, their structures were determined to be 6'-O-galloyl-, 3',4'-di-O-galloyl-, 4',6'-di-O-galloyl-, 4',6'-O-(S)-HHDP-, 3'-O-galloyl-4',6'-O-(S)-HHDP-, 3'-O-caffeoyl-4',6'-O-(S)-HHDP-3-hydroxyphloretin 4'-O-beta-D-glucosides and 3'-O-galloyl-4',6'-O-(S)-HHDP-phloretin 4'-O-beta-D-glucoside, respectively. By contrast, these compounds were not found in the taxonomically related B. japonica. The 3'-galloyl-4',6'-HHDP esters of the dihydrochalcone glucosides showed strong inhibitory activities against alpha-glucosidase. Four known compounds were also isolated namely, (+/-)-eriodictyol 7-O-beta-D-glucoside, 1-O-caffeoyl-3-O-galloyl-beta-D-glucose, phloretin 4'-O-beta-D-glucoside, and 3-hydroxyphloretin 4'-O-beta-D-glucoside.     

Mutations that reduce sinapoylmalate accumulation in Arabidopsis thaliana define loci with diverse roles in phenylpropanoid metabolism.

The products of phenylpropanoid metabolism in Arabidopsis include the three fluorescent sinapate esters sinapoylglucose, sinapoylmalate, and sinapoylcholine. The sinapoylmalate that accumulates in cotyledons and leaves causes these organs to appear blue-green under ultraviolet (UV) illumination. To find novel genes acting in phenylpropanoid metabolism, Arabidopsis seedlings were screened under UV for altered fluorescence phenotypes caused by changes in sinapoylmalate content. This screen identified recessive mutations at four Reduced Epidermal Fluorescence (REF) loci that reduced leaf sinapoylmalate content. Further analyses showed that the ref mutations affected other aspects of phenylpropanoid metabolism and some led to perturbations in normal plant development. A second class of mutations at the Bright Trichomes 1 (BRT1) locus leads to modest reductions in sinapate ester content; however, the most notable phenotype of brt1 mutants is the development of hyperfluorescent trichomes that appear to contain elevated levels of sinapate esters when compared to the wild type. These results indicate that at least five new loci affecting the developmentally regulated accumulation of phenylpropanoid secondary metabolites in Arabidopsis, and the cell specificity of their distribution, have been identified by screening for altered UV fluorescence phenotypes.     

Isoangoroside C, a phenylpropanoid glycoside from Scrophularia scorodonia roots

A new phenylpropanoid glycoside isoangoroside C was isolated from the roots of Scrophularia scorodonia. Its structure was determined on the basis of spectral data as: 3-hydroxy-4-methoxy-beta-phenylethoxy-O-alpha-L-arabinopyranosy l-(1-->6)alpha L-rhamnopyranosyl-(1-->3)-4-O-Z-feruloyl-beta-D-glucopyranoside. Additionally, one known phenylpropanoid, angoroside C, and five known iridoid glycosides, harpagoside, bartsioside, 8-O-acetyl-harpagide, aucuboside and harpagide were isolated and identified.     

The Antinociceptive Effect of a Hydroalcoholic Extract of Polygala altomontana and Its Chemical Profile Using UPLC-ESI-QTOF-HR-MS

The hydroalcoholic extract of Polygala altomontana (30, 100, and 300 mg/kg, i.g.) showed a dose-dependent antinociceptive action during the inflammatory phase of the formalin test. In addition, the preparation (30 and 300 mg/kg, i.g.) showed anti-hyperalgesic action when tested on a mechanical nociception model. UPLC-ESI-QTOF-MS data indicated the active extract contained phenylpropanoid sucrose esters, glycosylated quercetin derivatives, styrylpyrones, and coumarins. Some identified compounds, including styrylpyrones and coumarins, have previously demonstrated antinociceptive action. The results also show that P. altomontana shows potential for developing pain-relieving herbal remedies and drugs.     

Stigmastane derivatives and isovaleryl sucrose esters from Vernonia guineensis (Asteraceae)

Vernoguinoside, 16beta,22R;21,23S-diepoxy-3beta-O-beta-D-glucopyranosyloxy-21S,24-dihydroxy-5alpha-stigmasta-8,14-dien-28-one (1), a new stigmastane derivative, 16beta,22R;21,23S-diepoxy-21S,24-dihydroxy-5alpha-stigmasta-8,14-diene-3,28-dione (2) and two new sucrose esters, 1',3,3',4',6'-pentakis-O-(3-methylbutanoyl)-beta-D-fructofuranosyl alpha-D-glucopyranoside (3) and 1',2,3',6,6'-pentakis-O-(3-methylbutanoyl)-beta-D-fructofuranosyl alpha-D-glucopyranoside (4), have been isolated from the stem bark of Vernonia guineensis. The structures of the new compounds were determined on the basis of spectroscopic evidence.     

Studies of the site and mode of biosynthesis of tobacco trichome exudate components

Detached glandular trichome head preparations and epidermal strips with and without trichome heads were used to identify glandular trichome heads as the site of sucrose ester biosynthesis in tobacco. Carbon dioxide in solution as well as sucrose, glucose, and acetate were shown to serve as precursors to both sucrose esters and duvatrienediol diterpenes in detached trichome heads or epidermal strips, and gaseous CO2 was also efficiently utilized by epidermal strips. Thus, glandular heads can biosynthesize these principal exudate components from a molecule as simple as CO2. While formation of duvatriendiols from all precursors tested and conversion of sucrose and glucose to sucrose esters was light dependent, utilization of acetate to label the 6-O-acetyl group of the glucose moiety of sucrose esters occurred equally well in light and dark. The data suggest that CO2 and/or monosaccharides produced in trichome head cells and perhaps that supplied by other epidermal cells can act as carbon sources for sucrose ester and duvatrienediol biosynthesis which occurs in the glandular trichome head.     

Modified branched-chain amino acid pathways give rise to acyl acids of sucrose esters exuded from tobacco leaf trichomes

A major diversion of carbon from branched-chain amino acid biosynthesis/catabolism to form acyl moieties of sucrose esters (6-O-acetyl-2,3,4-tri-O-acyl-alpha-D-glucopyranosyl-beta-D- fructofuranosides) was observed to be associated with specialized trichome head cells which secrete large amounts of sucrose esters. Surface chemistry and acetyl and acyl substituent groups of tobacco (T.I. 1068) sucrose esters were identified and quantified by gas chromatography/mass spectrometry. Sucrose esters were prominent surface constituents and 3-methylvaleric acid, 2- and 3-methylbutyric acid, and methylpropionic acid accounted for 60%, 25% and 9%, respectively, of total C3--C7 acyl substituents. Radiolabeled Thr, Ile, Val, Leu, pyruvate and Asp, metabolites of branched-chain amino acid pathways, were compared with radioactively labeled acetate and sucrose as donors of carbon to sucrose, acetyl and acyl components of sucrose esters using epidermal peels with undisturbed trichomes. Preparations of biosynthetically competent trichome heads (site of sucrose ester formation) were also examined. Results indicate that 3-methylvaleryl and 2-methylbutyryl groups are derived from the Thr pathway of branched-chain amino acid metabolism, 3-methylbutyryl and methylpropionyl groups are formed via the pyruvate pathway, and that acetyl groups are principally formed directly via acetyl-CoA. Arguments are presented which rule out participation of fatty acid synthase in the formation of prominent acyl acids. Results suggest that the shunting of carbon away from the biosynthesis of Val, Leu and Ile may be due to a low level of amino acid utilization in protein synthesis in specialized glandular head cells of trichomes. This would result in the availability of corresponding oxo acids for CoA activation and esterification to form sucrose esters. Preliminary evidence was found for the involvement of cycling reactions in oxo-acid-chain lengthening and for utilization of pyruvate-derived 2-oxobutyrate to form straight-chain acyl substituents.     

Chemotaxonomy of Veroniceae and its allies in the Plantaginaceae

In a chemosystematic investigation of tribe Veroniceae (Plantaginaceae), representatives of Camptoloma, Sibthorpia, Veronica subg. Pentasepalae and subg. Hebe, Veronicastrum, Wulfenia, and the related Ellisiophyllum and Globularia were examined for non-flavonoid glycosides. From the 14 species studied, 28 different iridoid glucosides and 10 caffeoyl phenylethanoid glucosides (CPGs), as well as salidroside and arbutin were isolated and characterized by NMR; of these, five compounds were previously unknown. It was found that the representatives of Veroniceae, as well as Globularia, were characterized by mannitol, aucubin, catalpol and catalpol esters. Each of the three studied species of Veronica subg. Hebe contained at least one of the 6-O-catalpol esters typical for Veronica s. str. (verminoside), supporting the inclusion of Hebe in Veronica. However, their main constituents were esters of 6-O-rhamnopyranosylcatalpol; a CPG, hebeoside (2'-beta-xylopyranosyl-verbascoside) was isolated from V. (Hebe) salicifolia. The two species of Veronicastrum also contained 6-O-rhamnopyranosylcatalpol esters, including the previously unknown 2',3'- and 3',4'-dicinnamoyl derivatives and, in contrast to the earlier reports, they lacked 6-O-catalpol esters. The main iridoid constituents in the three investigated species of Wulfenia were 10-O-aucubin and 10-O-catalpol esters (isoscrophularioside or globularin) while baldaccioside (10-O-cinnamoyl asystasioside E) was isolated from W. baldaccii. Globularia vulgaris contained 10-O-catalpol esters (e.g., globularin) and, in addition, asperuloside together with its benzoyl analogue named besperuloside. The representatives of Sibthorpia and Ellisiophyllum were almost completely devoid of iridoids; this, however, together with the CPGs present implied a close relationship between the two genera. Camptoloma lyperiiflorum lacked hexitols but contained esters of 6-O-rhamnopyranosylcatalpol different from those found in Veroniceae but known from Buddleja, Scrophularia and Verbascum (Scrophulariaceae s. str.).     

Antioxidant phenylpropanoid glycosides from the leaves of Wasabia japonica

From the MeOH extract of the leaves of W. japonica, seven phenylpropanoid gentiobiosides (1-7) were isolated along with eight known phenylpropanoids (8-15). Structures of 1-7 were determined based on spectroscopic data and chemical evidence. The activity of compounds 1-15 to scavenge superoxide anion radicals was investigated using an electron spin resonance (ESR) method.