Angular Furanocoumarins Research Articles

Degree of Dietary Specialization on Furanocoumarin-Containing Hostplants in a Newly Invasive Web Building Caterpillar.

The genus Depressaria (Lepidoptera: Depressariidae) mostly comprises specialist herbivores with varying capacity for detoxification of defensive phytochemistry. Depressaria depressana, a Eurasian moth recently introduced into North America, is a family-level specialist of the Apiaceae, whose hosts include more than a dozen species in multiple tribes; Depressaria radiella is a super-specialist of Eurasian origin that feeds exclusively on species in the genera Pastinaca and Heracleum throughout its native and introduced range. In eastern North America, it feeds upon Pastinaca sativa, an invasive European species, and Heracleum maximum, a native species. We determined whether differences in furanocoumarin metabolism exist between D. depressana and two isolated populations of D. radiella, feeding exclusively on either P. sativa or H. maximum. We also compared gravimetric estimates of feeding efficiency to assess D. depressana larval performance on different diets. Both populations of D. radiella metabolized furanocoumarins at a greater rate than D. depressana. Although there was no difference in rates of metabolism of linear furanocoumarins in the two populations of D. radiella, individuals collected from H. maximum metabolized angular furanocoumarins more rapidly. The gravimetric assessments of feeding efficiencies revealed that D. depressana exhibited highest efficiencies consuming Daucus carota; moreover, this species survived to pupation consuming fruits of Zizia aurea, an apiaceous species native to North America. Our preliminary phylogenetic analysis, building on an earlier morphological analysis, incorporates mitochondrial cytochrome oxidase subunit 1 data from the BOLD database and revealed that the presence or absence of furanocoumarins is not a strong predictor of species-level evolution in Depressaria.

Evaluation of furanocoumarins from seeds of the wild parsnip (Pastinaca sativa L. s.l.)

Although the wild parsnip (Pastinaca sativa L. s.l.) fruits are known to contain linear and angular furanocoumarins, the individual components of the seeds have not been fully identified and quantitated, and, in the case of immature seeds, reported. In view of this, the main furanocoumarin compounds were extracted using pyridine, and were isolated using semi-preparative high-performance liquid chromatography. The structural elucidation of isolated compounds was done based on detailed spectral analysis conducted by liquid chromatography–electrospray ionization–mass spectrometry (LC–ESI/MS), 1H and 13C NMR and, where possible, by gas chromatography–mass spectrometry (GC–MS). The quantitative analysis of furanocoumarin compounds in the wild parsnip was conducted by analytical ultra–performance liquid chromatography (UPLC–DAD), calculated against the standard curves of isolated compounds. The total yields of furanocoumarin compounds from the seeds after extraction with pyridine were 107.2–222.8 mg g−1 (fresh weight) and 50.2–66.4 mg g−1 (soluble dry matter). Thirteen furanocoumarins were identified. The main compounds (percentage in FW) in immature seeds were bergapten (40.8), pimpinellin (10.5), methoxsalen (5.7), isopimpinellin (4.3), imperatorin (3.2), and phellopterin (7.2). Seven constituents previously not described in P. sativa seeds and its products were identified, namely, byakangelicol (14.4), heraclenin (8.5), isobergapten (2.5), byakangelicin (1.3), heraclenol (0.5), psoralen (0.3), and isobyakangelicin (0.8). The latter is a new compound of the Apiaceae family. Extraction of immature seeds using pyridine gave a much higher yield and a greater variety of furanocoumarins. This indicates that the wild parsnip, along with other Apiaceae family plants, may be an important source of bioactive compounds.

Direct analysis of Peucedanum palustre samples by desorption atmospheric pressure photoionization-mass spectrometry

Desorption atmospheric pressure photoionization (DAPPI) is an ambient mass spectrometry (MS) technique that can be used for the analysis of polar and nonpolar compounds directly from surfaces. Here, the feasibility of DAPPI-MS in the screening of plant metabolites from dried Peucedanum palustre leaves and umbels was studied. DAPPI-MS requires no prior sample preparation or chromatographic separation, and the analysis can therefore be performed directly from the untreated plant material. P. palustre contains several linear and angular furanocoumarins, some of which are specific for the species. The DAPPI mass spectra of both leaf and umbel samples showed distinct ions at m/z 445 and 443 in positive and negative ion modes, respectively. MS2 analyses of these ions confirmed that the ions were the protonated and deprotonated molecules, respectively, of peulustrin and its isomers, which have only been identified from P. palustre. The direct analysis of dried plant material by DAPPI-MS was shown to provide a fast and reliable means to confirm the identity of plant materials, to study the metabolite profiles of plants, and to screen biologically relevant compounds from plant surfaces.

Evaluation of antifungal activities and structure-activity relationships of coumarin derivatives.

Osthol is a natural coumarin and lead compound that has been developed into commercial fungicides in China. Natural coumarins comprise five major subtypes: simple coumarins, linear furanocoumarins, angular furanocoumarins, linear pyranocoumarins and angular pyranocoumarins. Studies pertaining to the antifungal activities of linear pyranocoumarins are few, and no reports exist for the antifungal activities of angular pyranocoumarins. In order to discover more antifungal natural coumarins, we synthesised a series of simple natural coumarins and isolated several plant-based furanocoumarins and pyranocoumarins using previously described methods. The compounds were biologically evaluated against some plant fungal pathogens. Several of the 35 coumarins evaluated here exhibited strong activities against specific fungal species, including compound 25 (Pd-D-V, a linear pyranocoumarin), compound 26 (libanorin, an angular furanocoumarin) and compound 34 (disenecioyl khellactone, an angular pyranocoumarin). Compound 25 exhibited a high activity against Sclerotinia sclerotiorum (EC50 = 13.2 µg mL-1 ); compound 34 displayed a strong antifungal activity against Botrytis cinerea (EC50 = 11.0 µg mL-1 ). This study demonstrates that several natural coumarins (one linear pyranocoumarin and one angular pyranocoumarin in particular) exhibit strong antifungal activities. These results call for further studies, where these coumarins can be examined as potential lead compounds for developing novel antifungal agents. © 2016 Society of Chemical Industry.

Determination of coumarins in the roots of Angelica dahurica by supercritical fluid chromatography

The fact that supercritical fluid chromatography (SFC) offers many desirable features is known for a long time. Yet, the number of applications on natural products is still limited, because robust and user-friendly instrumentation became available just a few years ago. As coumarins hardly have been studied by this technique we developed the first SFC assay for their determination in crude plant material. After method optimization eight standard compounds, including simple coumarins, linear and angular furanocoumarins, could be baseline separated in 6min using an Acquity UPC2 CSH Fluoro-Phenyl 1.7μm column with supercritical CO2, methanol and diethylamine as mobile phase. Method validation confirmed that the assay is linear (R2≥0.9995), precise (intra-day variation≤5.8%; inter-day variation≤4.4%) and accurate (recovery rates from 96.5 to 104.2%). Detection limits determined at 300nm were below 2ng on-column, and the method showed to be well suited for the analysis of coumarins in Angelica dahurica roots. It was observed that qualitative as well as quantitative composition vary significantly. In all samples Imperatorin (0.09–0.28%) was the major coumarin, followed either by Isoimperatorin or Oxypeucedanin; the total coumarin content ranged from 0.16 to 0.77%. The results were in good agreement to published data, so that because of its speed and green nature SFC is definitely an interesting alternative for the analysis of this important class of natural products.

Elicitation of furanocoumarins in poison hemlock (Conium maculatum L.) cell culture

Furanocoumarins, such as psoralen, xanthotoxin and bergapten, serve as protectants against phytopathogens and are used in pharmaceutical applications e.g. as DNA-crosslinking agents against non-melanoma skin cancers. Poison hemlock plants (Conium maculatum L.) are a known source of furanocoumarins and toxic alkaloids, but systematic research on callus and suspension cultures with the aim of eliciting secondary metabolites is lacking. Therefore callus cultures of poison hemlock were induced with 0.186 mg L−1 6-benzylaminopurine and 2 or 4 mg L−1 naphthalene acetic acid on McCown’s Woody plant medium. A broad variety of elicitors (alginic acid, cellulase, chitosan, ethylene, methyl jasmonate, salicylic acid, copper(II) sulphate and silver nitrate) were tested with an established cell suspension culture for their capacity to trigger differential metabolite accumulation. Samples were extracted and analysed by gas chromatography-mass spectrometry. Elicitation with alginic acid, cellulase, chitosan, silver nitrate and copper(II) sulphate induced furanocoumarins. Plant hormones (ethylene, methyl jasmonate and salicylic acid) were not able to induce furanocoumarins. Extracts contained bergapten, columbianetin, isopimpinellin, marmesin, oroselone, psoralen and xanthotoxin but not piperidine alkaloids. The relative amount of furanocoumarins was generally higher in the medium than in the cells. The report describes the angular furanocoumarins oroselone and columbianetin together with the linear furanocoumarin marmesin, elicited for the first time in poison hemlock.

Quantitative Insights into Energy Contribution of Weak Intermolecular Interactions in Angular Furanocoumarin Derivatives

Quantitative Insights into Energy Contribution of Weak Intermolecular Interactions in Angular Furanocoumarin Derivatives

Isolation of furanocoumarins from Pastinaca sativa L. callus culture

Four furanocoumarins: bergapten, xanthotoxin, isopimpinellin (linear furanocoumarins) and sphondin (angular furanocoumarin) were isolated for the first time from callus tissues of <em>Pastinaca sativa</em> L.(<em>Apiaceae</em>) cultured in vitro on solid medium. The compounds were identified using spectral methods. They are well-known secondary metabolites of the intact plant. This is the first report on the isolation of sphondin from in vitro plant cultures.

Cachrys pungens Jan inhibits human melanoma cell proliferation through photo‐induced cytotoxic activity

To date, plants belonging to the genus Cachrys have not been amply studied. In the present study, aerial components of Cachrys pungens Jan from Italy, were examined to assess their free radical-scavenging and antioxidant activity, and their phototoxicity on A375 melanoma cells. In view of potential pharmaceutical applications, a relationship between antioxidant, phototoxic activities and polyphenolic composition has also been investigated. Content of sterols, terpenes, fatty acids and coumarins was assessed by gas chromatography-mass spectrometry and GC. Total phenolic content was also determined. Antioxidant activity of the methanol extract and fractions of C. pungens Jan was assessed using DPPH scavenging assay and β-carotene bleaching test. Plant phototoxicity was also investigated in this human tumour cell line (amelanotic melanoma). Analysis of the chloroform extract was particularly interesting, as it led to identification of many coumarins, of which five were linear and one angular furanocoumarins. Methanol and ethyl acetate fractions exhibited substantial antioxidant activity. Moreover, chloroform extract and isolated coumarin fraction had strong phototoxic activity on UVA-induced A375 cells after irradiation at UVA dose of 1.08 J/cm. Plant-derived natural compounds are an important source for development of cancer-fighting drugs. This study has demonstrated strong phototoxic activity of the coumarin fraction of C. pungens, a plant which, to our knowledge, has never been studied before. This investigation offers a new perspective for developing other formulations potentially useful in photodynamic therapy for treatment of non-melanoma skin cancers as well as melanomas.

Isolation and Functional Characterization of CYP71AJ4 Encoding for the First P450 Monooxygenase of Angular Furanocoumarin Biosynthesis

The biosynthesis of linear and angular furanocoumarins is still poorly understood at the molecular level, with only psoralen synthase (CYP71AJ1) identified from Ammi majus. Using cDNA probes inferred from CYP71AJ1, three orthologs were isolated from Apium graveolens (CYP71AJ2) and Pastinaca sativa (CYP71AJ3 and -4) and functionally expressed in yeast cells. CYP71AJ2 and CYP71AJ3 displayed psoralen synthase activity, whereas CYP71AJ4 only catalyzed the conversion of (+)-columbianetin to angelicin and negligible amounts of a hydroxylated columbianetin by-product. CYP71AJ4 thus constitutes the first fully characterized P450 monooxygenase specific for the angular furanocoumarin pathway. The angelicin synthase exhibited an apparent K(m) of 2.1 +/- 0.4 microm for (+)-columbianetin and a k(cat) of 112 +/- 14 min(-1). Moreover, the use of 3'-deuterated (+)-columbianetin as substrate led to an almost complete "metabolic switch," resulting in the synthesis of anti-3'-hydroxy-3'-deuterated(+)-columbianetin. This confirms that angelicin synthase attacks columbianetin by syn-elimination of hydrogen from C-3'. Sequence comparison between psoralen synthase (CYP71AJ3) and angelicin synthase (CYP71AJ4) showed 70% identity, whereas the identity dropped to 40% in those regions thought to provide the substrate recognition sites. Accordingly, CYP71AJ3 and CYP71AJ4 might be derived from a common ancestor of unknown functionality by gene duplication and subsequent molecular evolution.

Natural and Synthetic Furanocoumarins as Treatment for Vitiligo and Psoriasis

Phototherapy has been used for centuries to treat various skin disorders. Numerous inflammatory skin diseases, such as atopic dermatitis and pigment disorders like vitiligo and psoriasis, benefit from ultraviolet light treatment. Psoralen-containing plants have been used for centuries in popular medicine to treat vitiligo, a skin disease characterized by lack of pigmentation. Further advancement in treatments using different psoralen molecules should strive to decrease the possibility of long-term side effects such as cutaneous malignancies. One of the directions for continued refinement of photochemotherapy in the future, as well as one of the new paradigms associated with photochemotherapy itself, is development of other psoralen molecules that do not form bifunctional adducts, which provide a basis for the DNA crosslinking. One such class of furanocoumarins is the methylangelicins (angular furanocoumarins) which only forms monofunctional adducts. There is clearly a theoretical basis that monofunctional adducts would less likely promote cutaneous malignancies as compared to bifunctional adducts. In this review we wish to present recent pharmacological approaches of furanocoumarins, particularly angular furanocoumarins, and a detailed investigation on the photocytotoxicity exerted by these compounds. Furthermore the edible vegetables and fruits which contain these compounds are showed.

One‐pot synthesis of angular furocoumarins: A simple protocol involving unprecedented intramolecular aldol condensation

Abstractmagnified imageRefluxing of hydroxycoumarinyl ketones with methyl γ‐bromocrotonate in dry acetone in presence of anhydrous K2CO3 afforded substituted angelicins (angular furanocoumarins) in satisfactory yields through intramolecular Aldol condensation followed by β‐elimination.

Molecular Cloning and Functional Characterization of Psoralen Synthase, the First Committed Monooxygenase of Furanocoumarin Biosynthesis

Ammi majus L. accumulates linear furanocoumarins by cytochrome P450 (CYP)-dependent conversion of 6-prenylumbelliferone via (+)-marmesin to psoralen. Relevant activities, i.e. psoralen synthase, are induced rapidly from negligible background levels upon elicitation of A. majus cultures with transient maxima at 9-10 h and were recovered in labile microsomes. Expressed sequence tags were cloned from elicited Ammi cells by a nested DD-RT-PCR strategy with CYP-specific primers, and full-size cDNAs were generated from those fragments correlated in abundance with the induction profile of furanocoumarin-specific activities. One of these cDNAs representing a transcript of maximal abundance at 4 h of elicitation was assigned CYP71AJ1. Functional expression in Escherichia coli or yeast cells initially failed but was accomplished eventually in yeast cells after swapping the N-terminal membrane anchor domain with that of CYP73A1. The recombinant enzyme was identified as psoralen synthase with narrow substrate specificity for (+)-marmesin. Psoralen synthase catalyzes a unique carbon-chain cleavage reaction concomitantly releasing acetone by syn-elimination. Related plants, i.e. Heracleum mantegazzianum, are known to produce both linear and angular furanocoumarins by analogous conversion of 8-prenylumbelliferone via (+)-columbianetin to angelicin, and it was suggested that angelicin synthase has evolved from psoralen synthase. However, (+)-columbianetin failed as substrate but competitively inhibited psoralen synthase activity. Analogy modeling and docked solutions defined the conditions for high affinity substrate binding and predicted the minimal requirements to accommodate (+)-columbianetin in the active site cavity. The studies suggested that several point mutations are necessary to pave the road toward angelicin synthase evolution.

CYP6B1 and CYP6B3 of the Black Swallowtail (Papilio polyxenes): Adaptive Evolution through Subfunctionalization

Gene duplication provides essential material for functional divergence of proteins and hence allows organisms to adapt to changing environments. Following duplication events, redundant paralogs may undergo different evolutionary paths via processes known as nonfunctionalization, neofunctionalization, or subfunctionalization. Studies of adaptive evolution at the molecular level have progressed rapidly by computationally analyzing nucleotide substitution patterns but such studies are limited by the absence of information relating to alterations of function of the encoded enzymes. In this respect, evolution of the Papilio polyxenes cytochrome P450 monooxygenases (P450s) responsible for the adaptation of this insect to furanocoumarin-containing host plants provides an excellent model for elucidating the evolutionary fate of duplicated genes. Evidence from sequence and functional analysis in combination with molecular modeling indicates that the paralogous CYP6B1 and CYP6B3 genes in P. polyxenes have probably evolved via subfunctionalization after the duplication event by which they arose. Both enzymes have been under independent purifying selection as evidenced by the low dN/dS ratio in both the coding region and substrate recognition sites. Both enzymes have maintained their ability to metabolize linear and angular furanocoumarins albeit at different efficiencies. Comparisons of molecular models developed for the CYP6B3 and CYP6B1 proteins highlight differences in their binding modes that account for their different activities toward linear and angular furanocoumarins. That P. polyxenes maintains these 2 furanocoumarin-metabolizing loci with somewhat different activities and expression patterns provides this species with the potential to acquire P450s with novel functions while maintaining those most critical to its exclusive feeding on its current range of host plants.

Inhibition of CYP6B1-Mediated Detoxification of Xanthotoxin by Plant Allelochemicals in the Black Swallowtail (Papilio polyxenes)

The structural and biosynthetic diversity of allelochemicals in plants is thought to arise from selection for additive toxicity as a consequence of toxin mixture or for enhanced toxicity as a result of synergism. In order to understand how insects cope with this type of plant defense, we tested the effects of some allelochemicals in host plants of the black swallowtail Papilio polyxenes on the xanthotoxin-metabolic activity of CYP6B1, the principal enzyme responsible for the detoxification of furanocoumarins in this caterpillar. Additionally, the effects of some synthetic compounds not normally encountered by P. polyxenes on CYP6B1 were tested. These studies demonstrate that the integrity of furanocoumarin structure is important for competitive binding to the active site of CYP6B1, even though the carbonyl group on the pyranone ring apparently does not affect its inhibitory capacity, as in the case of furanochromones. Angular furanocoumarins are generally less phototoxic to many organisms than linear furanocoumarins due to their reduced capacity for cross-linking DNA strands, yet they are more toxic than linear furanocoumarins to black swallowtail larvae. This enhanced toxicity in vivo may be due to the ability of angular furanocoumarins to bind to the active site of CYP6B1 without being rapidly metabolized. This binding reduces the availability of CYP6B1 to metabolize other linear furanocoumarins. The structure-activity relationships for methylenedioxyphenyl compounds, flavonoids, imidazole, and imidazole derivatives are also discussed in light of their capacity to inhibit the xanthotoxin-metabolic activity of CYP6B1.

Lutein Sequestration and Furanocoumarin Metabolism in Parsnip Webworms Under Different Ultraviolet Light Regimes in the Montane West

Both biotic and abiotic selection pressures can contribute to geographic variation in allelochemical production in plants. We examined furanocoumarin production in western North American populations of Heracleum lanatum and Pastinaca sativa that, at different latitudes and altitudes, experience different ultraviolet (UV) light regimes. Total furanocoumarins and linear furanocoumarins of fruits were negatively correlated with UV irradiance, whereas amounts of angular furanocoumarins, which are generally less phototoxic, were not. Another factor potentially influencing furanocoumarin production is the presence of the parsnip webworm Depressaria pastinacella, (Lepidoptera: Oecophoridae), an herbivore that feeds on reproductive structures of both plant species. These insects sequester lutein from their host plants; this carotenoid acts to ameliorate furanocoumarin toxicity. Although the concentration of lutein in fruits did not vary with UV irradiance, lutein sequestration by sixth instars was positively correlated with UV irradiance. Webworm populations are variably infested with the polyembryonic webworm parasitoid Copidosoma sosares Walker (Hymenoptera: Encyrtidae). H. lanatum fruits from populations with webworms parasitized by C. sosares had lower concentrations of furanocoumarins, with the exception of sphondin, than fruits from plants infested with webworms free from parasitism. Lower levels of these furanocoumarins may reduce negative effects on the fitness of this parasitoid. In contrast with the variation in furanocoumarin content, the ability of webworms to metabolize furanocoumarins by cytochrome P450 did not differ significantly among populations from New Mexico to Alberta.

An Efficient Synthesis of Bergapten

An efficient synthesis of the linear furanocoumarin, bergapten, is reported. In order to avoid the formation of the angular furanocoumarin, we have adopted iodine as protecting group at the 8 position of the coumarin ring.

Changes of furanocoumarins content in vegetables during storage

Long term experiments, which simulated storage of celery (Apium graveolens) under industrial (airconditioned store)/household (common cellar) conditions, were carried out. Several celery cultivars from both organic and/or conventional production were monitored for furanocoumarins levels for 16–26 weeks. The increase of furanocoumarin concentrations during the storage of all the tested celery cultivars was observed, nevertheless, the extent of toxicants accumulation differed among tested cultivars. The changes of furanocoumarin levels occurring during processing of vegetables were studied, too. Levels of both linear (psoralen, bergapten, xanthotoxin, trioxsalen, isopimpinellin) and angular (angelicin, sphondin, isobergapten) furanocoumarins in tested vegetable were determined by validated GC/MS (SIM) method. The detection limits (LODs) obtained by this analytical method were around 0.003 mg/kg.

Metabolism of linear and angular furanocoumarins by Papilio polyxenes CYP6B1 co-expressed with NADPH cytochrome P450 reductase

One challenge in the heterologous expression of microsomal cytochrome P450 monooxygenases (P450s) is fulfilling their obligatory requirement for electrons transferred from NADPH P450 reductase. We have established co-expression parameters for Papilio polyxenes CYP6B1 and house fly P450 reductase in baculovirus-infected Sf9 cells that allow for efficient expression of both components and significantly enhance metabolic turnover of this insect P450’s substrates. These expression conditions have allowed us to reexamine the turnover capacities of CYP6B1 toward linear and angular furanocoumarins present in the host plants for the specialist caterpillar P. polyxenes. Coexpression of CYP6B1 and P450 reductase at equivalent viral concentrations [MOI (multiplicity of infection) ratio of 1] results in turnover rates for the linear furanocoumarins xanthotoxin and psoralen, which are increased 32–33 fold over the turnover rates obtained with CYP6B1 expressed alone. The turnover rate for the angular furanocoumarin angelicin is also significantly increased to 4.76 nmol/min/nmol P450 compared to its barely detectable level obtained with CYP6B1 expressed alone. Substrate binding analyses indicate that all three of these compounds elicit typical type I binding spectra but with varying magnitudes and affinities that are indicative of each substrate’s effectiveness at coordinating with the heme iron. The relative proportions of high spin state generated with these substrates are consistent with CYP6B1 metabolizing these furanocoumarins in the rank order xanthotoxin>psoralen>angelicin. These differential activities for CYP6B1 suggest that it may have been an ancient participant in the coevolutionary arms race between papilionid butterflies and their apiaceous host plants. Due to its ability to handle a range of furanocoumarin structures, CYP6B1 may have contributed to P. polyxenes’ early colonization of linear furanocoumarin-containing plants and to its subsequent colonization of angular furanocoumarin-containing plants.

Characterization of furanocoumarin metabolites in parsnip webworm, Depressaria pastinacella.

Although metabolites of furanocoumarins have been characterized in a wide range of organisms, to date they have been identified in only a single insect species, Papilio polyxenes. Depressaria pastinacella, the parsnip webworm, like P. polyxenes a specialist on Apiaceae, routinely consumes plant tissues higher in furanocoumarin content than does P. polyxenes and is capable of faster cytochrome P-450-mediated detoxification of these compounds. In this study, we characterized metabolites of xanthotoxin, a linear furanocoumarin, and sphondin, an angular furanocoumarin, in midguts and frass of parsnip webworms. Two metabolites were isolated and identified from webworms fed artificial diet containing xanthotoxin. LC-ESI-MS analysis resulted in the determination of a MW of 266 for the compound in the frass and one of the compounds in the midgut; 1H NMR confirmed its structure as 6-(7-hydroxy-8-methoxycoumaryl)-hydroxyacetic acid (HCHA). The second compound from the midgut had a MW of 252 and was identified by 1H NMR and 13C NMR analysis as 6-(7-hydroxy-8-methoxycoumaryl)-hydroxyethanol) (HMCH). Whereas HCHA has been found in frass of Papilio polyxenes fed xanthotoxin, HMCH has not been reported previously in insects. Although the first step of metabolism of xanthotoxin in webworms as well as P. polyxenes is likely the formation of an epoxide on the furan ring, angular furanocoumarin metabolism in webworms appears to differ. The principal metabolite of sphondin was identified as demethylated sphondin (6-hydroxy-2H-furo[2,3-h]-1-benzopyran-2-one) by LC-ESI-MS and confirmed by 1H NMR and 13C NMR analyses. That webworms produce metabolites of xanthotoxin in common not only with other Lepidoptera (e.g., HCHA) but with other vertebrates (e.g., HMCH) suggests a remarkable conservatism in the metabolic capabilities of cytochrome P-450s and raises the possibility that insects may share other detoxification reactions with vertebrates with respect to toxins in foodplants.