Transcriptomics and metabolomics reveal the role of CYP1A2 in psoralen/isopsoralen-induced metabolic activation and hepatotoxicity.

Psoralen and isopsoralen are the pharmacologically important but hepatotoxic components in Psoraleae Fructus. The purpose of this study was to reveal the underlying mechanism of psoralen/isopsoralen-induced hepatotoxicity. Initially, we applied integrated analyses of transcriptomic and metabolomic profiles in mice treated with psoralen and isopsoralen, highlighting the xenobiotic metabolism by cytochromes P450 as a potential pathway. Then, with verifications of expression levels by qRT-PCR and western blot, affinities by molecular docking, and metabolic contributions by recombinant human CYP450 and mouse liver microsomes, CYP1A2 was screened out as the key metabolic enzyme. Afterwards, CYP1A2 induction and inhibition models in HepG2 cells and mice were established to verify the role of CYP1A2, demonstrating that induction of CYP1A2 aggravated the hepatotoxicity, and conversely inhibition alleviated the hepatotoxic effects. Additionally, we detected glutathione adducts with reactive intermediates of psoralen and isopsoralen generated by CYP1A2 metabolism in biosystems of recombinant human CYP1A2 and mouse liver microsomes, CYP1A2-overexpressed HepG2 cells, mice livers and the chemical reaction system using UPLC-Q-TOF-MS/MS. Ultimately, the high-content screening presented the cellular oxidative stress and relevant hepatotoxicity due to glutathione depletion by reactive intermediates. In brief, our findings illustrated that CYP1A2-mediated metabolic activation is responsible for the psoralen/isopsoralen-induced hepatotoxicity.

Absence of phototoxicity/photoirritation potential of bergamottin determined In Vitro using OECD TG 432.

The phototoxic potential of a number of furocoumarins is well established. On the other hand, studies have shown that bergamottin, a furocoumarin containing a bulky, hydrophobic side chain, has significantly less or is even absent of phototoxicity potential. The OECD Test Guideline 432 3T3/Neutral Red Uptake (NRU) in vitro phototoxicity test has shown to be a highly predictive test for identifying compounds that exhibit no phototoxicological potential. In this study using OECD 432, the established phototoxic furocoumarin 5-methoxypsoralen (5-MOP), 8-methoxypsoralen (8-MOP) and psoralen were phototoxic, whereas bergamottin showed no phototoxic potential. When compared to 5-MOP, 8-MOP and psoralen, bergamottin was clearly negative at molar-adjusted concentrations that were more than 9 times higher than those that produced phototoxicity in 8-MOP; nearly 16 times than those for psoralen and more than 36 times higher than those for 5-MOP. These data using in vitro 3T3 NRU Phototoxicity Test (OECD 432) are supportive of earlier studies showing bergamottin does not exhibit phototoxicological properties. The detection and quantification of bergamottin should therefore not contribute to the potential marker furocoumarins for risk management interventions intended to reduce the phototoxicity of natural furocoumarin containing preparations.

Isopsoralen induces different subchronic toxicities and metabolomic outcomes between male and female Wistar rats.

Isopsoralen is a major active and quality-control component of Fructus Psoraleae, but lacks a full safety evaluation. We evaluated the oral toxicity of isopsoralen in Wistar rats treated for 3 months at doses of 0, 3.5, 7.0, and 14 mg/kg. Additionally, the plasma metabolomics of isopsoralen in male and female rats treated for 3 months at doses of 0 and 14 mg/kg were investigated by gas chromatography-mass spectrometry. Many abnormalities were observed in the isopsoralen-treated rats, including suppression of body weight gain, and changes in serum biochemical parameters and visceral coefficients. Histopathological changes in liver, pancreatic, and reproductive system tissues were also observed in the isopsoralen-treated rats. The metabolomic analyses showed alterations in many metabolites (19 in female rats; 28 in male rats) after isopsoralen administration. The significant changes in these metabolites revealed metabolomic alterations in the isopsoralen-treated rats, especially in amino acid metabolism regardless of sex, including phenylalanine, tyrosine, and tryptophan biosynthesis and glycine, serine, and threonine metabolism. Furthermore, fatty acid metabolism comprised the main affected pathways in female rats, while lipid metabolism and energy metabolism were the main affected pathways in male rats.

Antiproliferative and cytotoxic activities of furocoumarins of Ducrosia anethifolia.

CONTEXT: Phytochemical and pharmacological data on Ducrosia anethifolia (DC.) Boiss. (Apiaceae), an Iranian medicinal plant, are scarce; however, furocoumarins are characteristic compounds of D. anethifolia. OBJECTIVE: Our experiments identify the secondary metabolites of D. anethifolia and assess their antitumor and anti-multidrug resistance activities. MATERIALS AND METHODS: Pure compounds were isolated from the extract of aerial parts of the plant by chromatographic methods. Bioactivities were tested on multidrug resistant and sensitive mouse T-lymphoma cell lines. The inhibition of the cancer MDR efflux pump ABCB1 was evaluated by flow cytometry (at 2 and 20 µM). A checkerboard microplate method was applied to study the interactions of furocoumarins and doxorubicin. Toxicity was studied using normal murine NIH/3T3 fibroblasts. RESULTS: Thirteen pure compounds were isolated, nine furocoumarins namely, pabulenol (1), (+)-oxypeucedanin hydrate (2), oxypeucedanin (3), oxypeucedanin methanolate (4), (-)-oxypeucedanin hydrate (5), imperatorin (6), isogospherol (7), heraclenin (8), heraclenol (9), along with vanillic aldehyde (10), harmine (11), 3-hydroxy-α-ionone (12) and 2-C-methyl-erythrytol (13). Oxypeucedanin showed the highest in vitro antiproliferative and cytotoxic activity against parent (IC50 = 25.98 ± 1.27, 40.33 ± 0.63 µM) and multidrug resistant cells (IC50 = 28.89 ± 0.73, 66.68 ± 0.00 µM), respectively, and exhibited slight toxicity on normal murine fibroblasts (IC50 = 57.18 ± 3.91 µM). DISCUSSION AND CONCLUSIONS: Compounds 2, 3, 5, 7, 10-13 were identified for the first time from the Ducrosia genus. Here, we report a comprehensive in vitro assessment of the antitumor activities of D. anethifolia furocoumarins. Oxypeucedanin is a promising compound for further investigations for its anticancer effects.

Sister chromatid exchange test in river buffalo lymphocytes treated in vitro with furocoumarin extracts.

Furocoumarin extracts from Psoralea morisiana, the endemic Sardinian legume species, were tested for their mutagenic potential on river buffalo blood cells. The results obtained performing the sister chromatid exchange (SCE) test in blood cultures of five river buffalo calves (exposure to furocoumarins for 72h) and five cows (exposure to furocoumarins for 3h, in the absence and presence of S9 metabolic activator) are reported. Significant differences in mean values of SCEs were observed in cells of calves compared to control cells (unexposed), but no differences in SCE mean values were found between treated and untreated cells of cows in the presence or absence of S9. SCE mean values were much higher in cells of cows (exposed and control) than in cells of calves. Indeed, in calf cells, SCE mean values/cell (±SD) were 6.66±2.45 in the control and 7.63±3.01, 9.03±3.90, 9.53±3.60 and 9.99±3.41 in treated cells at 50, 100, 200 and 400 µg/ml of furocoumarin extracts, respectively. In cow cells, grown in presence of S9, SCE mean values/cell were 11.49±4.78 and 11.65±5.19 in treated cells at 100 and 200 µg/ml of furocoumarins and 11.66±5.45 in the control. In cow cells grown in absence of S9, SCE mean values were 11.81±6.14 in the control and 12.35±7.09 and 12.01±5.43, respectively, in the presence of 100 and 200 µg/ml of furocoumarins. Despite their higher SCE values in the absence of S9, no statistically significant differences were found when these values were compared with those shown in presence of S9, suggesting no mutagenic action of furocoumarins in cows, at the doses used in this study.

[Sosnowsky's hogweed - toxicology and threat to health]. / Barszcz Sosnowskiego ­ toksykologia a zagrozenie dla zdrowia.

Sosnowsky's hogweed (Heracleum sosnowskyi Manden.) is a genus of plants in the family Apiaceae which also includes Giant Hogweed (Heracleum mantegazzianum Sommier and Levier). They are both found in Central Europe, mainly in neglected green areas or riversides. Sosnowsky's hogweed was brought to Poland from the Soviet Union in the 1950s to be used in animal feed production. Intended goals couldn't be achieved and the plant spread throughout grounds distant to the primarily cultivated lands. Sosnowsky's hogweed is especially hazardous in direct contact with human skin. It results from the content of photoallergic substances called furanocoumarins in its essential oil. Clinically it is presented as burns, mainly of 2nd and 3rd degree. They mostly occur on the face, upper and lower limbs. Typical symptoms include pain, redness, swelling and heat in the area of exposure. Their extent depends on burn's depth and area and also on time of exposure to plant's toxins. In this article we present Sosnowsky's hogweed's activity and its influence on human health.

Assessment of 8-methosypsoralen, lomefloxacin, sparfloxacin, and Pirfenidone phototoxicity in Long-Evans rats.

Phototoxicity has a strong impact on drug development. Although several animal models have been developed to quantitatively assess human risks, none have been validated for standardized use. In this study, we validated an in vivo phototoxicity model using Long-Evans (LE) rats treated with 4 well-known phototoxic drugs, namely 8-methoxypsoralen, lomefloxacin, sparfloxacin, and pirfenidone. Daily macroscopic observations of skin and eyes, ophthalmological examinations 4 days after dosing, and blood sampling for toxicokinetics (TKs) were performed after exposure of treated animals to ultraviolet, and dose-dependent eye and/or skin reactions were noted for all compounds. Margins of safety were calculated when possible and correlated well with known relative phototoxicity of the 4 compounds. We conclude that the present in vivo phototoxicity assay using LE rats with TK analysis can be used to quantitatively predict the risk of pharmaceutical phototoxicity in humans.

In vitro activity of isoimperatorin, alone and in combination, against Mycobacterium tuberculosis.

UNLABELLED: Previous studies have shown that isoimperatorin (IO), a furanocoumarin isolated from several medicinal plants, has antimycobacterial activity against Mycobacterium tuberculosis strain H37Rv (ATCC 27294). This study demonstrated that IO has antimycobacterial activity against 2 drug-sensitive and 6 drug-resistant isolates, with minimum inhibitory concentrations (MICs) of 50-100 µg ml(-1) and 100-200 µg ml(-1), respectively. IO exhibited synergistic antimycobacterial effects with rifampin (RMP), isoniazid (INH) and ethambutol (EMB) against 6 drug-resistant strains, with fractional inhibitory concentration index (FICI) values of 0·133-0·472, 0·123-0·475 and 0·124-0·25, respectively. The IO/RMP, IO/INH and IO/EMB combination treatments had synergistic effects or no interaction in the 2 drug-sensitive strains and the standard strain ATCC 27294. The synergism of combined drugs against drug-resistant strains was better than drug-sensitive strains. No antagonism was observed in with the aforementioned combinations against all strains tested. IO exhibited relatively low cytotoxicity to Vero cells. Our results indicate that IO may serve as promising a template for future antimycobacterial drug development. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report on the in vitro synergistic antimycobacterial effects of isoimperatorin (IO) in combination with three first-line drugs: rifampin (RMP), isoniazid (INH) and ethambutol (EMB). The results indicated that the antimycobacterial activity of IO was modest; however, IO was a useful and effective agent against Myco. tuberculosis when it was combined with first-line antimycobacterial drugs and is worthy of further development as a lead compound for the development of novel antimycobacterial therapeutic agents.

Biotransformations of 6',7'-dihydroxybergamottin and 6',7'-epoxybergamottin by the citrus-pathogenic fungi diminish cytochrome P450 3A4 inhibitory activity.

Penicillium digitatum, as well as five other citrus pathogenic species, (Penicillium ulaiense Link, Geotrichum citri Link, Botrytis cinerea P. Micheli ex Pers., Lasiodiplodia theobromae (Pat.) Griffon & Maubl., and Phomopsis citri (teleomorph Diaporthe citri)) were observed to convert 6',7'-epoxybergamottin (1) into 6',7'-dihydroxybergamottin (2), bergaptol (3), and an opened lactone ring metabolite 6,7-furano-5-(6',7'-dihydroxy geranyloxy)-2-hydroxy-hydrocoumaric acid (4). Metabolism of 2 by these fungi also proceeded to 4. The structure of 4 was established by high resolution mass spectrometry and (1)H and (13)C NMR techniques. The inhibitory activity of 4 towards human intestinal cytochrome P450 3A4 (CYP3A4) was greatly decreased (IC(50) >172.0 µM) compared to 2 (IC(50)=0.81 µM).

Evaluation of photocytotoxicity liposomal form of furanocoumarins Sosnowsky's hogweed.

Sosnovsky's hogweed, Heracleum sosnowskyi has a high photosensitizing ability. Although Sosnovsky's hogweed is known as a poisonous plant, its chemical composition and phototoxicity are poorly studied. We analyzed the chemical composition of the Sosnovsky's hogweed juice that grew in natural conditions. It was found that the content of 8-methoxypsoralen in the juice is 1332.7 mg/L, and that of 5-methoxypsoralen is 34.2 mg/L. We have developed and analyzed liposomes containing furanocoumarins of Sosnovsky's hogweed juice and studied their photocytotoxicity in L929 mouse fibroblast cell culture. It was found that liposomes containing furanocoumarins of Sosnovsky's hogweed juice are more toxic for L929 cells in comparison with liposomal forms of pure substances 8-methoxypsoralen and 5-methoxypsoralen. It was found that when exposed to UV radiation at 365 nm at a dose of 22.2 J/cm2, the liposomal form of furanocoumarins Sosnovsky's hogweed is 3 times more toxic to L929 cells than in the dark. It was found that the photocytotoxic effect of liposomal furanocoumarins Sosnovsky's hogweed is a strongly stimulation of apoptosis.The data obtained suggest that the raw material of Sosnovsky's hogweed claims to be a source of furanocoumarins, and the liposomal form, given the hydrophobic properties of furanocoumarins, is very suitable for creating a phototherapeutic drug.

Psoralen and isopsoralen from Psoraleae Fructus aroused hepatotoxicity via induction of aryl hydrocarbon receptor-mediated CYP1A2 expression.

ETHNOPHARMACOLOGICAL RELEVANCE: Psoraleae Fructus (PF), a traditional Chinese medicine, has long been used to treat diseases such as cancer, osteoporosis and leukoderma. Psoralen and isopsoralen are main bioactive ingredients of PF with anti-tumor, anti-inflammatory, estrogen-like neuroprotection, etc., meanwhile they are also representative hepatotoxic components of PF. Hepatic CYP1A2 has been reported to be the important metabolic enzymes involved in psoralen and isopsoralen-induced hepatotoxicity. However, the relationship between the hepatotoxicity and CYP1A2 expression, and the underlying mechanism of regulating CYP1A2 expression remain unclear. AIM OF STUDY: The aim of this study was to explore the associated mechanism between psoralen or isopsoralen induced hepatotoxicity and activated aryl hydrocarbon receptor (AhR)-mediated transcriptional induction of CYP1A2 in vitro and in vivo. MATERIALS AND METHODS: Psoralen and isopsoralen at different doses were treated on HepG2 cells (10, 25, 50, 100, 200 µM for 2, 12, 24, 36, 48 h) and mice (20, 80, 160 mg/kg for 3, 7, 14 days) for different time, to assess the correlation of induced hepatotoxicity and CYP1A2 mRNA and protein expression in vivo and in vitro, as well as the effect on CYP1A2 enzyme activity evaluated by phenacetin metabolism. In addition, the potential mechanism of the regulation of CYP1A2 expression mediated by AhR was explored through nucleocytoplasmic shuttling, immunofluorescence, cellular thermal shift assay and molecular docking, etc. RESULTS: Psoralen and isopsoralen induced cytotoxicity in HepG2 cells, and hepatomegaly, biochemicals disorder and tissue pathological impairment in mice, respectively in dose- and time-dependent manners. Simultaneously accompanied with elevated levels of CYP1A2 mRNA and protein in the same trend, and the CYP1A2 activity was remarkably inhibited in vitro but significantly elevated overall in vivo. Besides, psoralen and isopsoralen bound to AhR and activated translocation of AhR from the cytoplasm to the nucleus, leading to the transcriptional induction of target gene CYP1A2. CONCLUSIONS: Hepatotoxicities in HepG2 cells and mice aroused by psoralen and isopsoralen were related to the induction of CYP1A2 expression and activity, whose underlying mechanism might be psoralen or isopsoralen activated AhR translocation and induced increase of CYP1A2 transcriptional expression. Hopefully, these finding are conductive to propose an alert about the combined usage of psoralen or isopsoralen and AhR ligands or CYP1A2 substrates in clinical practice.

Psoralen-Induced Phytophotodermatitis.

Phytophotodermatitis is a cutaneous reaction that occurs after exposure to plant-derived furocoumarins and ultraviolet A light. Psoralen is the most common phototoxic furocoumarin and is present in varying levels within many different plant species. This article focuses on the diagnosis and management of psoralen-induced phytophotodermatitis along with other clinical applications.

Synthesis and Photoactivated Toxicity of 2-Thiophenylfuranocoumarin Induce Midgut Damage and Apoptosis in Aedes aegypti Larvae.

Furanocoumarins are photoactive compounds derived from secondary plant metabolites. They possess many bioactivities, including antioxidative, anticancer, insecticidal, and bactericidal activities. Here, we designed a new scheme for synthesizing 2-arylfuranocoumarin derivatives by condensation, esterification, bromination, and Wittig reaction. We found that 2-thiophenylfuranocoumarin (Iy) had excellent photosensitive activity. Three Iy concentrations (LC25, LC50, and LC75) were used to treat the fourth instar larvae of Aedes aegypti (A. aegypti). The photoactivated toxicity, sublethal dose, mitochondrial dysfunction, oxidative stress level, intestinal barrier dysfunction, and apoptosis were studied. The results showed that Iy induced reactive oxygen species (ROS) production in midgut cells under ultraviolet light. Ultrastructural analysis demonstrated that mitochondria were damaged, and the activities of related enzymes were inhibited. Ultimately, Iy exposure led to excessive ROS production followed by the inhibition of antioxidant enzymes, including SOD, CAT, GPx, and GR, which diminished ROS elimination and escalated oxidative stress in midgut cells, aggravating the degree of oxidative damage in these cells. Histopathological changes were observed in the midgut, which led to intestinal barrier dysfunction. When the elimination of ROS was blocked and it accumulated in cells, apoptosis-related genes, including AeDronc, AeCaspase7, and AeCaspase8, were induced and activated. In addition, Iy affected the growth and development of A. aegypti at sublethal concentrations, and there was an obvious post-lethal effect. Thus, we found that Iy caused midgut damage and apoptosis in A. aegypti larvae under ultraviolet light, which preliminarily revealed the mode of action of Iy in A. aegypti.

Pyridazinopsoralens of wide chemotherapeutic interest.

The synthesis of new 6,10-dimethylpyridazino[4,5-h]psoralens, carrying no (4), one (5), or two (6-9) dialkylaminoalkylcarboxamide side chains on the pyridazine ring is reported. All compounds exert a significant photoantiproliferative activity. Moreover, the derivatives characterised by the protonable side chains show a notable cytotoxicity in the dark. The investigation on the mechanism of action demonstrated the capacity to intercalate into DNA base pairs and to inhibit the relaxation activity of topoisomerase II.

Imperatorin: A review of its pharmacology, toxicity and pharmacokinetics.

As a naturally occurring furanocoumarin, the medicinal value of imperatorin has been studied more and more. We hope to provide useful information for the further development of imperatorin by analyzing the literature of imperatorin in recent years. By collating the literature on the pharmacology of imperatorin, we found that the pharmacological activity of imperatorin is wide and imperatorin can be used for anti-cancer, neuroprotection, anti-inflammatory, anti-hypertension and antibacterial. In addition, we found that some researchers confirmed the toxicity of imperatorin. Pharmacokinetic studies demonstrated that oxidation metabolism is the main metabolic pathways of imperatorin. At present, the shortcomings of research on imperatorin mainly include: most pharmacological studies are concentrated in vitro, lacking enough in vivo experimental data; more and more studies showed that imperatorin has synergistic effect with other drugs in anticancer and other aspects, but lacking the detailed explanation of the mechanism of the synergistic effect; imperatorin has side effect, but it lacks enough experimental conclusions. Based on the above defects, we believe that more in vivo experiments of imperatorin should be carried out in the future; future research need to explore synergistic mechanisms of imperatorin with other drugs, especially in anticancer; the dose affects both the pharmacological activity and the side effect of imperatorin. The relationship between the dose and the two aspects need to be further studied in order to reduce the side effect. In addition, through structural modification of imperatorin, it is possible to improve the treatment effect and reduce side effect.

Relative photomutagenicity of furocoumarins and limettin in the hypoxanthine phosphoribosyl transferase assay in V79 cells.

Furocoumarins are phototoxic and photomutagenic natural plant constituents found in many medicinal plants and food items. Because plants contain mixtures of several furocoumarins, there is a need for a comparative risk assessment of a large number of furocoumarins. Little is known about the photomutagenicity of the structurally related family of coumarins, which are also abundant in many plant species. In this study, we analyzed the photomutagenic potency of the linear furocoumarins 5-methoxypsoralen (5-MOP) and 8-methoxypsoralen (8-MOP), the angular furocoumarin angelicin, and the coumarin limettin. Above certain concentrations, all test compounds were more or less phototoxic in the presence of UVA doses between 50 and 200 mJ/cm(2), 5-MOP being the most phototoxic compound. At nonphototoxic concentrations, linear correlations were found between concentration and mutagenicity at a UVA dose of 125 mJ/cm(2) for all test compounds including limettin. For 5-MOP, strictly linear correlations were also found for the relationships of mutagenicity vs concentration at various UVA doses or vs UVA dose at given concentrations, respectively. These data indicate that the photomutagenicity of 5-MOP is proportional to the UVA dose x concentration product for noncytotoxic combinations of both factors. They also suggest that the slope of the concentration-photomutagenicity correlation at a given UVA dose may provide a basis for comparison between individual compounds. Applying this concept, in vitro photomutagenicity equivalency factors at 125 mJ/cm(2) were as follows: 1.0 (5-MOP, reference compound), 0.25 (8-MOP), and 0.02 (angelicin and limettin, respectively). These findings provide a new concept for the description of the relative photomutagenic potency of coumarins and furocoumarins and indicate that, in V79 cells, 8-MOP is less photomutagenic and limettin and angelicin are much less photomutagenic than 5-MOP.

Assessment of safety in neonates for transfusion of platelets and plasma prepared with amotosalen photochemical pathogen inactivation treatment by a 1-month intravenous toxicity study in neonatal rats.

BACKGROUND: It is estimated that approximately 300,000 neonates undergo transfusions annually. The neonatal immune system is immature, making such patients more susceptible to the effects associated with transfusion-transmitted bacteria, viruses, protozoa, and white blood cells (WBCs). The INTERCEPT Blood System is a photochemical process (PCT) utilizing amotosalen and long-wavelength ultraviolet to inactivate pathogens and WBCs in both platelet (PLT) and plasma components for transfusion. A series of clinical studies has shown PCT PLTs and PCT plasma to be safe and effective for transfusion in adults and pediatric patients. Because clinical studies in neonates are technically difficult and ethically challenging, preclinical toxicologic studies were conducted in neonatal rats to evaluate the safety of PCT blood components for neonates. STUDY DESIGN AND METHODS: This study examined daily intravenous administration to neonatal rats of amotosalen in 35 percent:65 percent plasma:InterSol from 1 microg per kg per day (representing 1-unit transfusion) to 457 microg per kg per day (representing multiple transfusions) from Postnatal Day 4 (PND4) to PND31. Rats were observed for viability, clinical signs, and body weights until PND31 and then subjected to pathology evaluation. Hematology, clinical chemistry, and urinalysis data were also collected on PND31. Toxicokinetic parameters were evaluated on PND4 and PND31. RESULTS: There were no amotosalen-related effects on clinical signs, body weight, hematology, clinical chemistry, urinalysis, gross pathology, or histopathology, despite the exposure of neonatal rats to amotosalen concentrations as high as approximately 48 times the standard exposure in adult patients. CONCLUSION: This study demonstrates the safety of PCT for transfusion in neonatal rats and augments data from other studies and clinical use supporting the use of PCT in neonatal patients.

Wild parsnip (Pastinaca sativa)-induced photosensitization.

Wild parsnip (Pastinaca sativa) has been associated with livestock and human photosensitization. An investigation of a natural occurrence of photosensitization of grazing horses identified wild parsnip as a possible cause. HPLC-MS and MS/MS analysis of this plant identified five furanocoumarins i.e., xanthotoxin, bergapten, isopimpinellin, imperatorin and a putative methoxyimperatorin. Goats fed this wild parsnip were largely unaffected. Xanthotoxin was not detected in the serum of parsnip-fed goats or in the serum of goats dosed orally or intravenous with purified xanthotoxin. Cutaneous application produced severe photodermatitis in goats and a horse consistent with topical exposure as the likely route to produce wild parsnip-induced photosensitivity. Wild parsnip-induced superficial necrotizing dermatitis was consistent with photodermatitis with no evidence of other allergic or inflammatory components.