Phenolic constituents of Artemesia tridentata spp. Vaseyana

Ten coumarins and four flavonoids have been isolated from a single collection of Artemesia tridentata ssp. vaseyana (Rydb.) Beetle. The coumarins are 7-methylesculin, esculin, umbelliferone, skimmin, cichoriin, isoscopoletin, scopoletin, scoparon, esculetin and a new natural product, artelin (5,6,7,8-tetramethoxy coumarin). The flavonoids are luteolin, luteolin-7-glucoside, axillarin and eupafolin.     

New coumarins from the umbels of Seseli sibiricum

Three new coumarins, seselinal, sesibiricol and sibirinol, and 12 known coumarins have been isolated from the umbels of Seseli sibiricum. The new coumarins have been characterized as 5, 7-dimethoxy-8-(2-methyl-2-formylpropyl)-2H-1-benzopyran-2-one, 5-(3-methylbut-2-enyloxy)-7-methoxy-8-(2-hydroxy-3-methylbut-3-enyl)-2H-1-benzopyran-2-one and 5,7-dimethoxy-8-(2-hydroxy-3-methylbut-3-enyl)-2H-1-benzopyran-2-one,respectively. The known ones were identified as sesibiricin, isosibiricin, osthol, coumurrayin, sesebrin, sesebrinol, sibiricin, imperatorin, bergapten, xanthotoxin, isopimpinellin and mexoticin.     

Castanopsone and castanopsol two new triterpenoids from Castanopsis indica

The isolation of two coumarins and five triterpenoids from Castanopsis indica is described. These have not been reported from this genus previously. The structures of two of the three new triterpenoids have been elucidated by chemical reactions and physical methods.     

The coumarins of Philotheca sensu lato: distribution and systematic significance

Five coumarins and two flavonoid glycosides are reported from Philotheca pinoides of which one, 3-(3-hydroxy-3-methylbut-1-enyl)-7,8-dimethoxycoumarin, appears to be novel. HPLC analysis of extracts of a number of other Philotheca species revealed that 5,7-dioxygenated-6,8-prenylated coumarins were present in P. apiculata, P. coccinea, P. deserti, P. pachyphylla, P. rhomboidea, P. thryptomenoides and P. gardneri, but not in P. nodiflora, P. pinoides, P. sericea, P. spicata, P. tomentella or P. woganensis. An analysis of the distribution of coumarins demonstrate that Geleznowia verrucosa is chemically indistinguishable from many species of Philotheca section Philotheca, whereas Philotheca section Erionema is more variable. Typical avicennol type coumarins have been found in the Boronieae only in Philotheca section Philotheca, in Geleznowia and in one species of Asterolasia. Coumarins that characterise Philotheca section Philotheca are not currently known from Eriostemon s.s., and sympatric genera such as Phebalium and Drummondita.     

Neuartige cumarin-derivative aus Ethulia conyzoides

The aereal parts of Ethulia conyzoides contain two new coumarins which are related to those of Erlangea and Bothriocline. They are, however, condensed with a terpene. The structures have been elucidated by spectroscopic methods.     

New coumarins from Coleonema album

Six coumarins have been isolated from the aerial parts of Coleonema album and identified as ulopterol, 7-(3′, 3′-dimethylallyloxy)-coumarin, (R)-(+)-2′,3′-epoxy-suberosin, and the novel coumarins (R)-(+)-7-(2′, 3′-epoxy-3′-methylbutoxy)-coumarin, (R)-(+)-7-(2′,3′-dihydroxy-3′-dihydroxy-3′-methylbutoxy)-coumarin and (R)-(+)-7-methoxy-8-(2′,3′-epoxy-3′-methylbutoxy)-coumarin.     

New coumarins from Seseli sibiricum

Three new coumarins, sesebrin(7-methoxy-5-[3-methylbut-2-enyloxy]-8-[3-methyl-2,3-epoxybutyl] coumarin), sesebrinol(7-methoxy-5-[3-methylbut-2-enyloxy]-8-[3-methyl-2,3-dihydroxybutyl] coumarin) and sibiricol (7-methoxy-5-hydroxy-8-[3-methylbut-2-enyl] coumarin) have been isolated from the roots of Seseli sibiricum, in addition to sitosterol and 7 known coumarins, isobergapten, bergapten, phellopterin, sibiricin, coumurrayin, osthenol and meranzin hydrate.     

A new coumarin from Ferula loscosii and the correct structure of coladonin

From the roots of Ferula loscosii the coumarins umbelliprenin, coladin and coladonin and the new natural isovaleryl derivative of the latter have been isolated. A study which confirms the structure of coladonin and its difference from farnesiferol A is also given.     

Coumarins from Amyris balsamifera

Two new coumarins have been isolated from the aerial parts of Amyris balsamifera. On the basis of spectral and chemical data, these have been identified as (R)-(+)-6-(2′-hydroxy-3′-methyl-3′-butenyl)-7-methoxycoumarin and balsamiferone, 7-hydroxy-3,6-bis (3′-methyl-2′-butenyl)-coumarin.     

Metabolome Analysis of Arabidopsis thaliana Roots Identifies a Key Metabolic Pathway for Iron Acquisition

Fe deficiency compromises both human health and plant productivity. Thus, it is important to understand plant Fe acquisition strategies for the development of crop plants which are more Fe-efficient under Fe-limited conditions, such as alkaline soils, and have higher Fe density in their edible tissues. Root secretion of phenolic compounds has long been hypothesized to be a component of the reduction strategy of Fe acquisition in non-graminaceous plants. We therefore subjected roots of Arabidopsis thaliana plants grown under Fe-replete and Fe-deplete conditions to comprehensive metabolome analysis by gas chromatography-mass spectrometry and ultra-pressure liquid chromatography electrospray ionization quadrupole time-of-flight mass spectrometry. Scopoletin and other coumarins were found among the metabolites showing the strongest response to two different Fe-limited conditions, the cultivation in Fe-free medium and in medium with an alkaline pH. A coumarin biosynthesis mutant defective in ortho-hydroxylation of cinnamic acids was unable to grow on alkaline soil in the absence of Fe fertilization. Co-cultivation with wild-type plants partially rescued the Fe deficiency phenotype indicating a contribution of extracellular coumarins to Fe solubilization. Indeed, coumarins were detected in root exudates of wild-type plants. Direct infusion mass spectrometry as well as UV/vis spectroscopy indicated that coumarins are acting both as reductants of Fe(III) and as ligands of Fe(II).     

Natural and semisynthetic oxyprenylated aromatic compounds as stimulators or inhibitors of melanogenesis

It has been very recently shown how naturally occurring oxyprenylated coumarins are effective modulators of melanogenesis. In this short communication we wish to generalize the potentialities as skin tanning or whitening agents of a wider panel of natural and semisynthetic aromatic compounds, including coumarins, cinnamic and benzoic acids, cinnamaldehydes, benzaldehyde, and anthraquinone derivatives. A total number of 43 compounds have been tested assaying their capacity to inhibit or stimulate melanin biosynthesis in cultured murine Melan A cells. The wider number of chemicals herein under investigation allowed to depict a detailed structure-activity relationship, as the following: (a) benzoic acid derivatives are slightly pigmenting agent, for which the effect is more pronounced in compounds with longer O-side chains; (b) independently from the type of substitution, cinnamic acids are able to increase melanin biosynthesis, while benzaldehydes are able to decrease it; (c) coumarins with a 3,3-dimethylallyl or shorter skeletons as substituents in position 7 are tanning agents, while coumarins with farnesyloxy groups are whitening ones; (d) double oxyprenylation in position 6 and 7 and 3,3-dimethylallyl or geranyl skeletons have slight depigmenting capacities, while farnesyl skeletons tend to marginally increase the tanning effect; (e) the presence of electron withdrawing groups (acetyl, COOH, and -Cl) and geranyl or farnesyl oxyprenylated chains respectively in positions 3 and 7 of the coumarin nucleus lead to a whitening effect, and finally (f) oxyprenylated anthraquinones have only a weak depigmenting capacity.     

Coumarins from the roots of Prangos uloptera

Three new coumarins, 6-O-[β-d-apiofuranosyl-(1 → 6)-β-d-glucopyranosyl]-prenyletin, 3″-O-[β-d-apiofuranosyl-(1 → 6)-β-d-glucopyranosyl]-oxypeucedanin hydrate and 2″-O-[β-d-apiofuranosyl-(1 → 6)-β-d-glucopyranosyl]-oxypeucedanin hydrate, together with six known coumarins, 3″-O-[β-d-apiofuranosyl-(1 → 6)-β-d-glucopyranosyl]-heraclenol, 3″-O-(β-d-glucopyranosyl)-heraclenol, tortuoside, 3″-O-(β-d-glucopyranosyl)-oxypeucedanin hydrate, heraclenol and oxypeucedanin hydrate, have been isolated from the roots of Prangos uloptera, and the structures of these coumarins were unequivocally determined by spectroscopic means, notably UV, HRESIMS, and 1D and 2D NMR spectroscopy.     

Contribution to the physiology ofTrigonella infected withPeronospora trifoliorum

Some biochemical properties ofTrigonella foenum-groecum infected withPeronospora trifoliorum have been investigated. Qualitative changes were observed in lipids, coumarins, amino acids and indole compounds only. A quantitative study of the phosphate content was also carried out. Neutral lipids did not show any significant changes. In addition to the fourteen phospholipid bands, the infected leaves contained a new band corresponding in R_f to phosphatidic acid or polyglycerophosphate. Seven coumarins were present in both the extracts. In addition 3-hydroxy coumarin, 5-hydroxy-4-methylcoumarin and 7-hydroxy-4-methyl-coumarin were detected in infected leaves. Higher levels of indole acetic acid and three of its derivatives were observed due to infection. Infection altered the free amino acid content. Tryptophan appeared and the total phosphate content increased. Increase in phenols and indoles suggest a higher respiratory rate whereas a higher content of inorganic phosphate suggests uncoupling of phosphorylation from respiration.     

Two phytoalexin glycosides from potato tubers infected with Phoma

Four coumarins and seven isoprenoid compounds have been identified in potato tubers infected with Phoma exigua var. foveata. Among these were the 7-O-β-D-glucopyranoside of 7-hydroxy-6,8-dimethoxycoumarin (isofraxidin) and the sesquiterpene 2-(11,12-dihydroxy-11-methylethyl)-6,10-dimethyl-spiro[4,5]dec-6-en-8-one and its 12-O-β-D-glucopyranoside, which apparently have not been previously identified in potato tubers. At least two diastereoisomers of the latter glucoside were present. Analysis of eight fluorescent compounds in different parts of infected potatoes was performed by an improved HPLC technique.     

Discovery of 2,4-thiazolidinedione-tethered coumarins as novel selective inhibitors for carbonic anhydrase IX and XII isoforms

Different 2,4-thiazolidinedione-tethered coumarins 5a–b, 10a–n and 11a–d were synthesised and evaluated for their inhibitory action against the cancer-associated hCAs IX and XII, as well as the physiologically dominant hCAs I and II to explore their selectivity. Un-substituted phenyl-bearing coumarins 10a, 10 h, and 2-thienyl/furyl-bearing coumarins 11a–c exhibited the best hCA IX (K_Is between 0.48 and 0.93 µM) and hCA XII (K_Is between 0.44 and 1.1 µM) inhibitory actions. Interestingly, none of the coumarins had any inhibitory effect on the off-target hCA I and II isoforms. The sub-micromolar compounds from the biochemical assay, coumarins 10a, 10 h and 11a–c, were assessed in an in vitro antiproliferative assay, and then the most potent antiproliferative agent 11a was tested to explore its impact on the cell cycle phases and apoptosis in MCF-7 breast cancer cells to provide more insights into the anticancer activity of these compounds.     

7-methoxycoumarins from Micromelum minutum

Chemical investigation of an Assamese collection of Micromelum minutum gave four known coumarins (osthol, micromelin, murralongin and murrangatin) and five new coumarins, dihydromicromelin A and B, acetyldihydromicromelin A, the threo diastereomer of murrangatin, the 7,12-ether of 5,7-dihydroxy-3,6,8,4′-tetramethoxyfiavone and murrangatin.     

Distribution of limonoids in the rutaceae

Chemical studies on Choisya arizonica, C. mollis, C. ternata, Esenbeckia hartmanii, Hesperethusa crenulata, Eremocitrus glauca, Triphasia trifolia, Coleonema album and Pamburus missionis are described with special reference to the limonoid bitter principles. The distribution of limonoids in the Rutaceae and especarlly the subfamily Aurantioideae is discussed. Two new coumarins, 7-isopentenyloxy-8-isopentenylcoumiain from Choisya arizonica and C. mollis and 2′,3′-dihydroxydihydrosuberosin from Coleonema album have been isolated and their structures determined.     

Synthesis and evaluation of antibacterial and anti-inflammatory properties of naturally occurring coumarins

Coumarins are a group of heterocyclic compounds naturally present in a large variety of plant families. Nevertheless, oxyprenylated coumarins have been only recently seen as valuable and promising biologically active phytochemicals. In this study, we synthesized three naturally occurring O-prenylcoumarins (1), (2), and (3), and evaluated their antibacterial and anti-inflammatory properties in view of their therapeutic potential against periodontal disease. The three O-prenylcoumarins were synthesized using well-known schemes leading to the chromen-2-one nucleus. The periodontal pathogen Porphyromonas gingivalis was found to be highly susceptible to all three O-prenylcoumarins with minimal inhibitory concentration values in the range of 12.5–25 mg/ml; the non-prenylated forms of the coumarins did not show any activity. The antibacterial activity of (1), (2), and (3) appeared to result from its ability to permeate the cell membrane. Using the U937-3xkB-LUC human monocytic cell line, compounds (2) and (3) dose-dependently inhibited lipopolysaccharide-induced NF-kB activation, while (1) did not. The non-prenylated forms of the coumarins were either inactive or much less potent. In conclusion, O-prenylcoumarins (2) and (3) by exhibiting a dual mode of action including antibacterial and anti-inflammatory activities may represent promising targeted therapeutic agents for localized treatment of periodontal diseases.     

Comparison of seven structurally related coumarins on the inhibition of Quorum sensing of Pseudomonas aeruginosa and Chromobacterium violaceum

Quorum sensing (QS) is a cell-to-cell signaling communication system that controls the virulence behavior of a broad spectrum of bacterial pathogens, participating also in the development of biofilms, responsible of the antibiotic ineffectiveness in many infections. Therefore, QS system is an attractive target for antimicrobial therapy. In this study, we compare the effect of seven structurally related coumarins against bacterial growth, biofilm formation and elastase activity of Pseudomonas aeruginosa. In addition, the anti-pathogenic capacity of the seven coumarins was evaluated on the wild type and the biosensor strain of Chromobacterium violaceum.The comparative study of coumarins showed that molecules with hydroxyl groups on the aromatic ring displayed higher activity on the inhibition of biofilm formation of P. aeruginosa over coumarins with substituents in positions 3 and 4 or without the double 3,4-bond. These 3 or 4-hydroxylated positions caused a decrease in the anti-biofilm activity obtained for coumarin. However, the hydroxyl group in position 3 of the pyrone ring was important for the inhibition of C. violaceum QS and elastolytic activity of P. aeruginosa. The effects observed were active independently of any effect on growth. According to our results, coumarin and its hydroxylated derivatives represent an interesting group of compounds to use as anti-virulence agents against the human pathogen P. aeruginosa.