Furanocoumarins angular

Metabolic Detoxification of Linear and Angular Furanocoumarins by Caterpillars of the Black Swallowtail Butterfly... 

Most insect herbivores appear to be rather effectively repelled by furanocoumarin-containing plants (21-24). A notable exception to this generalization occurs among some butterflies of the family Paplllonldae, whose caterpillars are adapted to feed successfully and in fact preferentially on plants that contain linear, but not angular, furanocoumarlns (22). These circumstances prompted us to undertake studies with the black swallowtail butterfly (Papilio polyxenes) and radiolabeled furanocoumarlns in attempts to elucidate the nature of the Insect/furanocoumarln Interactions Involved. 

Comparative Fate of Linear and Angular Furanocoumarins In P. polyxenes... 

Because the resistance of polyxenes to the toxic effects of linear furanocoumarins apparently does not extend to the angular furanocoumarins (22), we have undertaken comparative metabolic fate studies with a representative of each of these furanocoumarin classes. Tritlated psoralen or isopsoralen (Figure 1) was administered as before to last stage polyxenes caterpillars, and the distribution, elimination, and biochemical fate of the compounds determined (28). 

The disposition patterns of psoralen and Isopsoralen in polyxenes under the parameters studied were not dramatically different. As Indicated in Table III, there were no appreciable differences in the rate of excretion of radioactivity by caterpillars treated with the two compounds. In body tissues, however, levels of total radioactivity in Isopsoralen-treated caterpillars were consistently about twice those observed in psoralen-treated insects (Table IV). Further, levels of unmetabolized parent compounds retained in body tissues (where toxic effects would be expressed) were on the order of 3 times as high in caterpillars treated with the angular furanocoumarin, isopsoralen (Table V). 

Figure 1. Structures of a linear furanocoumarin (psoralen) and an angular furanocoumarin (isopsoralen).

Our studies indicate that rapid metabolic detoxification of linear furanocoumarins is an effective resistance mechanism for K polyxenes against the toxic effects of these compounds. It has been postulated that the adaptation of some plants to produce angular furanocoumarins was in response to the reduced effectiveness of the linear furanocoumarins as deterrents for herbivores such as polyxenes (22). Such may Indeed be true, but our studies on the comparative detoxification of linear and angular furanocoumarins suggest that, at best, the presence of angular furanocoumarins in plants confers only a tenuous margin of relative "safety" against polyxenes. 

Berenbaum, M. R. and Feeny, P. P. 1981. Toxicify of angular furanocoumarins to swallowtail butterflies escalation in a coevolutionary arms race Science, 212 927-929. 

The angular furanocoumarin dorstegin (41) was also isolated from the n- heptane extract. NOE irradiation of H-4 in 41 caused an enhancement of H-4 suggesting the pyran ring annelation at position 5 and 6. Ten... 

Furanocoumarins.3 The angular furanocoumarin sphondin (3) has been synthesized in four steps from Cr(CO)6 via the carbene 1 in 20% overall yield (Scheme I)-... 

The enzyme that catalyses the conversion of DMAPP and umbelliferone into 6-dimethylallylumbelliferone, the first reaction specifically directed to the biosynthesis of linear furanocoumarins, has been isolated394 from suspension cultures and young leaves of Ruta graveolens. The particulate enzyme could utilize neither herniarin as a substitute for umbelliferone nor GPP in place of DMAPP. 8-Dimethylallylumbelliferone, which is an intermediate in the formation of the angular furanocoumarins, was not formed by these preparations. 

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. 

Stanjek, V. and Boland, W. (1998) Biosynthesis of angular furanocoumarins mechanism and stereochemistry of the oxidative dealkylation of columbianetin to an-gelicin in Heracleum mantegazzianum (Apiaceae). Helv. Chim. Acta, 81,1596-607. 

Furanocoumarins are formed when furor ring is joined with coumarins. The plants of Rutaceae, Leguminosae and Apiaceae are rich sources of furanocoumarins. Depending upon the structure, the furanocoumarins are divided into linear and angular types. Furanocoumarin containing preparations are used externally as well as internally for treatment of leucoderma, psoriasis and skin carcinoma. 

Another possibility of producing explicable signal displacements is the addition of complexing reagents. Bose et al. (41) reported that titanium tetrachloride in deuteriochloroform can be used as a shift reagent in H and l3C NMR spectroscopy, and applied this method to coumarin and some angular furanocoumarins (42). 

Ysyn and para (8) effects of alkyl and O-alkyl substituents in linear furanocoumarins can be used to distinguish between the substituent s position, C-5 or C-8 (77). Moreover, such effects of substituents at C-5 allow a differentiation between linear and angular furanocoumarins (77). 

Table 10. 13C chemical shifts of linear (F) and angular furanocoumarins (H), their 2",3 -dihydro derivatives (G and I) and of coumarins with other... 

Coumarins are lactones with the basic structure of 1,2-benzopyrone. Biosynthetically, they are mainly originated from shikimic acid padiway, with the intermediate of cinnamic acid. By the addition of a furan ring, the furanocoumarins are resulted, which are represented by psoralen (linear) and angelicin (angular) [10]. 

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