HPLC comparison of supercritical fluid extraction and solvent extraction of coumarins from the peel of Citrus maxima fruit

The efficiency of carbon dioxide supercritical fluid extraction (SFE) of the biologically active compounds imperatorin, meranzin and meranzin hydrate from the fruit peel of Citrus maxima Merr. has been compared with that of solvent extraction with acetone. Under the best SFE conditions tested for the three coumarins, which involved extraction at 50 degrees C and 27.6 MPa, the extractive efficiencies were 84, 76 and 18% for imperatorin, meranzin and meranzin hydrate, respectively. The presence of modifiers significantly affected the extraction efficiency: the highest extraction efficiency of the three coumarins was obtained with ethanol as modifier.     

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.     

Murragleinin,a coumarin from Murraya gleinei leaves

A new trioxygenated C-8 prenylated coumarin, 5,6,7-trimethoxy-8-(2′,3′-dihydroxyisopentenyl)-coumarin and the laevorotatory form of mexoticin, sibiricin and phebalosin were isolated from the leaves of Murraya gleinei together with the coumarins meranzin hydrate, meranzin, murralongin, murrangatin and scopoletin, the flavone exoticin, the alkaloid skimianine and the sterol stigmasterol.     

Coumarins of Skimmia japonica

The coumarins, isoimperatorin, isomeranzin, meranzin hydrate, oxypeucedanin, oxypeucedanin hydrate, oxypeucedanin methanolate and umbelliferone and the triterpene, friedoolean-14-en-3β-ol (taraxerol) were isolated from leaves of Skimmia japonica.     

Studies on the Constituents of Murraya paniculata (L.) jack Grown in Yunnan

Two flavonoids were isolated from the leaves of Murraya paniculata (L.) Jack. (Rutaceae) grown in Yunnan. On the basis of spectroscopy (UV, IR, NMR and MS) analysis compound A and B were identified as 3,3′,4′,5,5′,7, 8-heptamethoxyflavone (Ⅰ), 3′, 4′ 5, 5′, 7, 8-hexamethoxyflavone (Ⅱ), respectively. The latter, named bannamu- rpanisin, is new natural product. In addition, three known coumarins, meranzin hydrate (Ⅲ), murragatin (Ⅳ) and murpanidin (Ⅴ) were obtained.     

Coumarins from Ferulago capillaris and F. brachyloba

Four new coumarins, (+)-senecioylprangol, (-)-3'-senecioyloxymarmesin, (+)-3'-hydroxyprantschimgin and (+)-2"-senecioyloxymarmesin, besides 12 known coumarins have been isolated from two Ferulago species. Their structures have been established by spectroscopic methods and partial synthesis. New synthetic 3'-oxocoumarins are also described. There is a remarkable difference in the contents of the most abundant coumarins found in the roots of both species: osthol and aurapten are specific to F. capillaris and F. brachyloba, respectively.     

Counlarins,limonoids and an alkaloid from Clausena excavata

In addition to a known alkaloid, some limonoids and coumarins, the new coumarins excavatins A–M have been isolated from Clausena excavata. Their structures have been assigned by NMR and CD investigations.     

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.     

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.     

Sesquiterpene coumarins

Plants have a long history as therapeutic tools in the treatment of human diseases and have been used as a source of medicines for ages. In search of new biologically active natural products, many plants and herbs used in traditional medicine are screened for natural products with pharmacological activity. In this paper, we present a group of natural products, the sesquiterpene coumarins isolated from plants, and describe their wide range of biological activity. Sesquiterpene coumarins are found in some plants of the families Apiaceae (Umbelliferae), Asteraceae (Compositae) and Rutaceae. The coumarin moiety is often umbelliferone (7-hydroxycoumarin) but scopoletin (7-hydroxy-6-methoxycoumarin) and isofraxidin (7-hydroxy-6,8-dimethoxycoumarin) are also found. These coumarins are linked to a C₁₅ terpene moiety through an ether linkage. Another group of sesquiterpene coumarins is the prenylated 4-hydroxycoumarins where the link between the coumarin and the C₁₅ terpene moiety is a C–C-bond at carbon 3 of the coumarin moiety. Finally, the prenyl-furocoumarin-type sesquiterpenoids are a separate group of sesquiterpene coumarins based on the suggested biosynthetic pathway. Our relatively limited knowledge on the biosynthesis of sesquiterpene coumarins is reviewed.     

Cytotoxic coumarins from Calophyllum dispar

Six coumarins have been isolated from the fruits and the stem bark of Calophyllum dispar (Clusiaceae). The structures of these minor components were established by means of spectroscopic analysis, including extensive 2D NMR studies. Some of these coumarins exhibited a significant cytotoxic activity against KB cells.     

Coumarins scaffolds as COX inhibitors

The discovery of COX enzymes has led to a better understanding of inflammation and its related biological pathways. Apart from being related to inflammation and pain, it has also been associated with cancer and neuropsychiatric diseases such as schizophrenia. Proverbially speaking, study of these enzymes has been crucial as they happen to “have fingers in many pies”. Non-steroidal anti-inflammatory drugs (NSAID) that act specifically as COX-2 inhibitors have been known for a while; however these are also associated with severe side effects such as cardiac problems. Several heterocylic molecules have been tested for their anti-inflammatory activity specifically as COX-inhibitors. Coumarins also known as benzopyrans are widely found in nature, and are routinely employed as herbal remedies since early days. Over 1300 coumarins have been identified, principally as secondary metabolites in green plants, fungi and bacteria. Recently the use of natural and synthetic coumarins has garnered a lot of attention for their anti-inflammatory activities. In this review we delve further into the study of natural and synthetic coumarins as COX-inhibitors. Although the study is still in its nascent stage, we believe there is scope for a lot of development.     

A Study of Plant Coumarins. 18. Conjugates of Coumarins with Lupane Triterpenoids and 1,2,3-Triazoles: Synthesis and Anti-Inflammatory Activity

Russian Journal of Bioorganic Chemistry - In the reaction of coumarin peuruthenicin with α,ω-dibromoalkanes, the corresponding 7-(ω-bromoalkyloxy)coumarins have been synthesized. The...     

Coumarin as a structural component of substrates and probes for serine and cysteine proteases

Coumarins represent well-established structures to introduce fluorescence into tool compounds for biochemical investigations. They are valued for their small size, chemical stability and accessibility as well as their tunable photochemical properties. As components of fluorophore/quencher pairs or FRET donor/acceptor pairs, coumarins have frequently been applied in substrate mapping approaches for serine and cysteine proteases. This review also focuses on the incorporation of coumarins into the side chain of amino acids and the exploitation of the resulting fluorescent amino acids for the positional profiling of protease substrates. The protease-inhibiting properties of certain coumarin derivatives and the utilization of coumarin moieties to assemble activity-based probes for serine and cysteine proteases are discussed as well.     

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 reaction of coumarins with horseradish peroxidase

The peroxidase catalyzed oxidation of indole-3-acetate is inhibited by naturally occurring coumarins such as scopoletin. This inhibition is due to the preferential reactivity of the coumarins with the peroxidase compounds I, II, and III. In view of the possible growth regulatory role of coumarins in plants, the mechanism of oxidation of scopoletin by horse-radish peroxidase has been investigated.     

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.     

Antimitotic activity of glaupalol-related coumarins from Glaucidium palmatum

Two new coumarins, glaumacidines A (1) and B (2), and the related coumarins (3-7) have been isolated from the rhizomes of Glaucidium palmatum (Glaucidiaceae). The absolute configurations of 1 and 2 and trans- and cis-glaupadiols (3 and 4, respectively) were elucidated by spectroscopic data, chemical derivatization, and exciton chirality method. Glaupalol (5) enhanced the polymerization of tubulin and affected synergistically with paclitaxel on inhibition of KB cell proliferation.