Coumarins furanocoumarin

Allergenic effects. A number of secondary metabolites influence the immune system of animals, such as coumarins, furanocoumarins, hypericin, and helenalin. Common to these compounds is a strong allergenic effect on those parts of the skin or mucosa that have come into contact with the compounds (4,17,312). Activation or repression of the immune response is certainly a target that was selected during evolution as an antiherbivore strategy. The function of alkaloids in this context is hardly known. 

Keywords phenylpropanoid metabolism hydroxycinnamic acid conjugates lignans coumarins furanocoumarins gallotannins eUagitarmins metabolic channelling... 

Isoquinoline alkaloids Phenylpropanoids Flavonoids, stibenes, catechins Lignin, lignans Coumarins, furanocoumarins Cyanogenic glycosides Glucosinolates Quinones,... 

A special group of 8-lactones formally derived from the hydrox-ycinnamic acids are coumarins with a skeleton of 2//-benzopyran-2-one, which is also called chromen-2-one or 5,6-benzo-2-pyrone (8-99). More than 1000 coumarins are found in nature, but only the basic member of the homologous series of coumarins performs as an aromatic compound this is called coumarin. Plant materials also contain a number of non-volatile coumarins substituted with hydroxyl and methoxyl groups and their glycosides. These and other coumarins, generally taking on the role of phytoalexins, such as iso-coumarins, furanocoumarins and pyranocoumarins, are described in Section 10.3.2.5.2. Some isocoumarins are intensely sweet (such as phyllodulcin) or bitter substances (such as 6-methoxymellein),... 

Phytoalexins are low molecular weight compounds produced in plants as a defense mechanism against microorganisms. They do, however, exhibit toxicity to humans and other animals in addition to microbes (30). Coumarins, glycoalkaloids, isocoumarins, isoflavonoids, linear furanocoumarins, stilbenes, and terpenes aU. fall into the category of phytoalexins (31). Because phytoalexins are natural components of plants, and because their concentration may increase as a response to production and management stimuli, it is useful to recogni2e the possible effects of phytoalexins in the human diet. 

The availability of North American specimens of Glehnia made it possible to compare coumarin and acetylene profiles of this widely disjunct system (Hiraoka et al., 2002). Analysis of plant material collected from four widely separated sites, that is, northern California, central Oregon, northern Washington, and northeastern Queen Charlotte Islands, British Columbia, revealed a profile characterized by low levels of furanocoumarins and a comparatively high level of panaxynol. The results are similar to those that characterize the southern Japanese form. The North American... 

Figure 3.4. Synthesis of coumarin and furanocoumarin from p-coumaric acid.

Other coumarin-related compounds include furans, found in moldy sweet potatoes, and the furan coumarin complexes (furanocoumarins) found in parsnip leaves (psoralens). They are photoreactive compounds (primary photosensitizers) that exacerbate sunburn to psoralen exposed skin. 

Hadacek F, Mueller C, Werner A, Greger H, Proksch P, Analysis, isolation and insecticidal activity of linear furanocoumarins and other coumarin derivatives from Peuxedanum (Apiaceae Apioideae),/ Ecol 20 2035—2054, 1994. 

The furanocoumarins xanthotoxin (77) and isopimpinellim (78) from roots of A. acutiloba displayed significant AChE inhibitory activity with IC50 values of 0.58 xM and 0.32 xM respectively." Prenylated coumarins itom. Angelica spp. had only weak activity, with decursinol (79) giving the highest activity (IC50 value 28 xM)." ... 

Coumarins are lactones of o-hydroxycinnamic acids in which side chains often are isoprenoid (78). Coumarin, esculin, and psoralen (a furanocoumarin) all strongly inhibit seed germination. Such inhibitors are produced by a variety of legumes and cereal grains. 

Fig. 5.16. Structures, 13C chemical shifts (in ppm) and one-bond carbon-hydrogen coupling constants (in IIz, italic types) of coumarin (left side) and the furanocoumarin psoralen (right side).

The main degradation path of 2-formylbenzofuran (21) is explained by loss of two molecules of CO, forming possibly a benzocyclopropene ion,26 (21)->[22] [23], which can lose a hydrogen atom to give a fragment of mass 89, thought to be a dehydrotropylium ion [24], which is also found in the spectra of other benzofuran derivatives,226 coumarin,24 and furanocoumarins.27,28... 

Figure 4.3 Structures of coumarins, linear furanocoumarins and angular furanocoumarins.

Sardari, S., Mori, Y., Horita, K., Micetich, R.G., Nishibe, S. and Daneshtalab, M. (1999) Synthesis and antifungal activity of coumarins and angular furanocoumarins. Bioorg. Med. Chem., 7,1933-40. 

Coumarins and furanocoumarins, which serve as potent defence compounds in the Apiaceae and Rutaceae, occur in a few, mostly unrelated, species. Only in the genus Psoralea do they have a wide distribution. An-thraquinones, which are potent Na+, K+-ATPase inhibitors and strong purgatives, occur widely in the genus Cassia (Senna), but otherwise only occasionally in Andira and Abrus. 

Extensive studies by Brov/n continue to elucidate the pathways to the furanocoumarins in various plants. Marmesin (13) and columbianetin (14) are still the only coumarin precursors of the furanocoumarins to retain a whole iso-prenoid unit. The related chromone derivative visamminol (15) is presumably a precursor of the furanochromone visnagin. Full details have appeared on the specific incorporation of mevalonate into the furan ring of skimmi-anine (16). 

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