Coumarins as antioxidants.

Coumarins, a well-known class of naturally occurring compounds, display a remarkable array of biochemical and pharmacological actions, some of which suggest that certain members of this group of compounds may significantly affect the function of various mammalian cellular systems. The development of coumarins as antioxidant agents has attracted much attention in recent years. Coumarins afford an opportunity for the discovery of new antioxidants with truly novel mechanisms of action. This review updates and expands the 2006 review by the same author. The review considers and incorporates the most recently published literature on coumarins as related to their antioxidant properties. A lot of coumarins have been identified from natural sources, especially green plants. These natural compounds have served as valuable leads for further design and synthesis of more active analogues. Beyond doubt, a deep understanding of the mechanisms of existing synthetic and natural coumarins will build the basis for the rational design.

Chemical components of Fraxinus species.

A wide range of chemical components including coumarins, secoiridoids, phenylethanoids, flavonoids, and lignans has been isolated from Fraxinus species. Extracts and metabolites have been found to possess antiinflammatory, immunomodulatory, antimicrobial, antioxidative, skin regenerating, photodynamic damage prevention, liverprotecting, diuretic and antiallergic activities. Some species find application in contemporary medicine. In the present review the literature data on the phytochemical and biological investigations on the genus Fraxinus are summarized up to the middle of 2004.

Antimicrobial and cytotoxic activity of Ruta graveolens.

The methanol, petroleum ether, ethyl acetate and water-methanol extracts of Ruta graveolens were found to possess antimicrobial and cytotoxic activities.

A novel furostanol saponin from Tribulus terrestris of Bulgarian origin.

The phytochemical investigation of the aerial parts of Tribulus terrestris of Bulgarian origin has resulted in the isolation of the novel furostanol saponin 1, named tribol, together with the known spirostanol saponins 2 and 3 and sitosterol glucoside. The structure of tribol was determined as (25R)-furost-5(6)-ene-3beta,16,26-triol-3-O-alpha-rhamnopyranosyl-(1-->2)-[alpha-rhamnopyranosyl-(1-->4)]-beta-glucopyranoside (1) by spectral analysis, including extensive 1D and 2D-NMR experiments.

Escuside, a new coumarin-secoiridoid from Fraxinus ornus bark.

A new coumarin-secoiridoid, named escuside, was isolated from the bark of Fraxinus ornus and its structure determined by spectroscopic methods.

New lanthanide complexes of 4-methyl-7-hydroxycoumarin and their pharmacological activity.

Complexes of cerium(III), lanthanum(III) and neodymium(III) with 4-methyl-7-hydroxycoumarin (Mendiaxon, Hymecromone) were synthesized by the mixing of equimolar amounts of the respective metal nitrates and 4-methyl-7-hydroxycoumarin sodium salt in water. The complexes were characterized and identified by elemental analysis, conductivities, IR, (1)H and (13)C NMR spectroscopies and mass spectral data. DTA and TGA have been applied to study the compositions of the compounds. The newly synthesized compounds were assayed for acute intraperitoneal and per oral toxicity, influence on blood clotting time and the most active complex was investigated for spasmolytic activity. The complexes of cerium(III) and neodymium(III) showed marginal cytotoxic activity against transformed leukemic cell lines (P3HR1 and THP-1) as compared to the inorganic salts.

Lignan and coumarin glycosides from Haplophyllum suaveolens.

Two new lignan glycosides of dibenzylbutyrolactol type (haplomarin) and arylnaphthalene type (haploborin) were isolated from the aerial parts of Haplophyllumn suaveolens together with the known arylnaphthalene lignan glycoside arabelline and hydroxycoumarin glycoside xeroboside. So far arabelline is found only in H. buxbaunii. This is the first report of the isolation of xeroboside from Haplophyllum.

Fraxinus ornus L.

The literature on the chemical constituents and the biological activity of Fraxinus ornus bark, leaves and flowers has been reviewed. Chemical studies show the presence of many compounds belonging mainly to the groups of hydroxycoumarins, secoiridoid glucosides, phenylethanoids and flavonoids. Biological studies reveal significant antimicrobial, antioxidative, photodynamic damage prevention, wound healing, anti-inflammatory, immunomodulatory and antiviral activities, and support the use of the bark in the folk medicine.

Antiviral activity of some hydroxycoumarin derivatives.

Esculetin (6,7-dihydroxycoumarin) and its diacetate exhibited a marked inhibitory effect on Newcastle disease virus replication in cell cultures at concentrations of 36 microM and 62 microM, respectively. These compounds were selected from ten hydroxycoumarin derivatives through an in vitro antiviral screen involving viruses of the picorna-, orthomyxo-, paramyxo-, and herpes virus families.

Effect of a total extract from Fraxinus ornus stem bark and esculin on zymosan- and carrageenan-induced paw oedema in mice.

This study investigates the total ethanol extract (TE) of the stem bark of Fraxinus ornus and its constituent esculin (EN). They inhibited classical pathway (CP) and alternative pathway (AP) of complement activation in mouse serum. After intraperitoneal administration the total extract displayed antiinflammatory activity in both zymosan- and carrageenan-induced paw oedema in mice. The results suggest that the traditional use of Fraxinus ornus stem bark extracts in the treatment of inflammatory disorders is at least partially due to its coumarin constituents.