Chemical comparison and discrimination of two plant sources of Angelicae dahuricae Radix, Angelica dahurica and Angelica dahurica var. formosana, by HPLC-Q/TOF-MS and quantitative analysis of multiple components by a single marker

INTRODUCTION

Angelica dahurica(BZ) and Angelica dahurica var. formosana(HBZ) are two plant sources of Angelicae dahuricae Radix. Although BZ and HBZ are commonly used herbal medicines with great medicinal and dietary values, study on their phytochemicals and bioactive compositions is limited.

OBJECTIVE

To compare the chemical compositions of BZ and HBZ and find the chemical makers for discrimination and quality evaluation of the two botanical origins of Angelicae dahuricae Radix.

METHODOLOGY

A high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry method was established for chemical profiling of BZ and HBZ. Then, a quantitative analysis of multiple components by a single marker method was developed for simultaneous determination of nine bioactive coumarins (xanthotoxol, oxypeucedanin hydrate, byakangelicin, xanthotoxin, bergapten, oxypeucedanin, phellopterin, imperatorin and isoimperatorin). Moreover, chemometrics were performed to compare and discriminate BZ and HBZ samples.

RESULTS

A total of 30 coumarins compounds were identified, and the chemical compositions in BZ and HBZ were quite similar. The quantitative analysis showed that there were significant differences in the contents of bioactive coumarins, and the chemometric analysis indicated five coumarins (xanthotoxol, xanthotoxin, bergapten, phellopterin and isoimperatorin) were responsible for the significant differences between BZ and HBZ, which could be used as chemical markers to distinguish the two original plant sources of Angelicae dahuricae Radix.

CONCLUSION

The present work provided useful information for understanding the chemical differences between BZ and HBZ and also provided feasible methods for quality evaluation and discrimination of herbal medicines originating from multiple botanical sources.

Investigations on the constituents of SagaPro tablets, a food supplement manufactured from Angelica archangelica leaf

Saga Pro is a food supplement product manufactured in Iceland and marketed internationally. It is claimed to have anti-nocturia effect and the flavonoid isoquercitrin has been suggested to play a role in this assumed activity. The purpose of this study was to identify and quantify the main flavonoids and furanocoumarins in the SagaPro tablets and to evaluate the importance of their presence. Isoquercitrin was identified as a constituent in an amount of 158 μg/tablet. This is a p.o. dosage highly unlikely to have an effect on nocturia or any other pharmacologically significant effect in humans. The main furanocoumarins, xanthotoxin and imperatorin, were also identified and quantified to 280 and 2 μg/tablet, respectively.

[Effects of Browning Inhibitors on Suspension Cells Growth and Secondary Metabolites Production in Changium smyrnioides]

OBJECTIVE

To study the effects of browning inhibitors on Changium smyrnioides suspension cells growth and secondary metabolites production.

METHODS

Different concentrations of V(C), AC, AHC, Na2S2O3 and PVP were added to the light brown suspension cells, and the contents of phenols, total coumarins, bergaptol and bergapten were determined by UV-Vis and HPLC.

RESULTS

PVP with low concentration and V(C) improved the growth of the suspension cells in different degrees. It was showed that the content of phenols in the suspension cells was related to the kinds of browning inhibitors. The addition of V(C) in the medium increased the content of total coumarins significantly. After using 2 mg/mL of V(C), the gross increase rate of total coumarins was 51.53%, which was 4.8 times than that of the control group. The browning phenomenon caused by salicylic acid were inhibited by adding 2 mg/mL of V(C) into suspension culture system (with salicylic acid as the inducer). At the same time, the content of bergaptol and bergapten was increased 25.96% and 33.33%, respectively.

CONCLUSION

V(C) is the best anti-browning agent in this study. It can inhibit browning, and promote cell growth and accumulation of secondary metabolites in Changium smyrnioides suspension cells.

The effect of pre-treatment and modified atmosphere packaging on contents of phenolic compounds and sensory and microbiological quality of shredded celeriac

BACKGROUND

The aim of this study was to determine the effect of washing (4 °C, 120 s) or soaking (4 °C, 600 s) of shredded celeriac in tap water on changes in contents of phenolic compounds, including furanocoumarins, and sensory and microbiological quality during 12 days of storage. The product was packaged in air or modified atmosphere containing 2/10/88 kPa O2/CO2/N2.

RESULTS

The applied pre-treatment consisting of washing or soaking of shredded celeriac in water resulted in decreases in 8-methoxypsoralen content by approximately 50 and 70% respectively and phenolic content by 30% compared with samples that were not subjected to pre-treatment. During storage of shredded celeriac, a further significant (P ≤ 0.05) reduction in phenolic compounds and an approximately 2.5-fold increase in the total content of furanocoumarins were found. The application of modified atmosphere packaging had a significant effect on the maintenance of good sensory and microbiological quality of the tested product.

CONCLUSION

Modified atmosphere packaging of shredded celeriac not subjected to pre-treatment made it possible to obtain a product with good sensory and microbiological quality and the highest content of phenolic compounds. The level of furanocoumarins recorded in the tested product does not constitute a health hazard.

[High-performance liquid chromatography for determination of psoralene, bergapten and apigenin in Ficus hirta Vahl]

OBJECTIVE

To establish a high-performance liquid chromatography (HPLC)-based method for determining the contents of psoralene, bergapten and apigenin in Ficus hirta Vahl.

METHODS

A Hypersil C18 column (250 mm × 4.6 mm, 5 µm) was used with the mobile phase of methanol-water (60:40), flow rate of 1.0 ml/min, detection wavelength of 268.7 nm and column temperature of 30 degrees celsius.

RESULTS

The calibration curve was linear within the range of 10.0-30.0 µg/ml for psoralene (r=0.9998), 15.0-45.0 µg/ml for bergapten (r=0.9998) and 5.0-15.0 µg/ml for apigenin (r=0.9992). The average recovery of psoralene was 99.7% (RSD=1.99%), that of bergapten was 99.9% (RSD=1.71%) and that of apigenin was 100.3% (RSD=1.78%).

CONCLUSION

The method is simple, economic and accurate with good reproducibility for the contents of psoralene, bergapten and apigenin.

In vitro photo-induced cytotoxic activity of Citrus bergamia and C. medica L. cv. Diamante peel essential oils and identified active coumarins

CONTEXT

The search for innovative therapeutic approaches is gaining more interest in clinical oncology.

OBJECTIVE

In the present investigation we reported the chemical profile and the photo-induced cytotoxic activity of two endemic Calabrian Citrus species (Rutaceae): Citrus bergamia Risso & Poit. and Citrus medica L. cv. Diamante.

MATERIALS AND METHODS

Essential oils were obtained by hydrodistillation and analyzed by GC and GC/MS. In order to evaluate the cytotoxic activity two melanoma models, such as amelanotic melanoma C32 and malignant melanoma A375, were used.

RESULTS

The essential oil of C. bergamia was characterized by limonene, linalyl acetate, gamma-terpinene, linalool and beta-pinene as major components. The most abundant compounds of C. medica cv. Diamante oil were limonene, gamma-terpinene, citral, geranial, beta-pinene and alpha-pinene. Two coumarins, bergapten and citropten, were also identified in C. bergamia and C. medica cv. Diamante, respectively and tested for biological activity. Both C. bergamia and C. medica cv. Diamante oils exhibited a selective interesting activity against the A375 cell line with IC(50) values of 79.3 and 89.1 microg/mL, respectively, after 100 min exposure to UV irradiation. The strong antiproliferative activity demonstrated with bergapten (IC(50) value of 71.3 microg/mL after 20 min of irradiation) was not found with citropten.

DISCUSSION AND CONCLUSION

Our study suggested that UV irradiation is effective in activating essential oils and in particular bergapten. This phototoxicity may be considered as a treatment option in some cases of lentigo maligna or lentigo maligna melanoma.

Isolation and identification of insecticidal components from Citrus aurantium fruit peel extract

Three active components were identified by bioassay-guided fractionation of bitter orange ( Citrus aurantium L.) fruit peel petroleum ether extract. Silica gel fractionation of the extract yielded a fraction that inflicted up to 96% mortality to adults of the olive fruit fly Bactrocera oleae (Gmelin) three days post-treatment. Subsequent HPLC purification of the active fraction resulted in the isolation of three components, eluted in fractions F 222, F 224, and F 226, that induced adult mortality. Considering the data obtained from UV, FTIR, MS, and (1)H NMR spectra, they were identified as 7-methoxy-8-(3'-methyl-2'-butenyl)-2 H-1-benzopyran-2-one (osthol), 4-methoxy-7 H-furo[3,2- g]benzopyran-7-one (bergapten), and 4-(( E)-3'-methyl-5'-(3'',3''-dimethyloxiran-2''-yl)pent-2'-enyloxy)-7 H-furo[3,2- g][1]benzopyran-7-one (6',7'-epoxybergamottin). Our results are in concordance with those reported in the literature and were further verified by direct comparison to authentic components. 6',7'-Epoxybergamottin was toxic when tested individually, while bergapten and osthol were found to act synergistically to 6',7'-epoxybergamottin.

[Simultaneous determination of 5 active components in Fructus Cnidii by HPLC]

OBJECTIVE

To develop an RP-HPLC method for simultaneous determination of 5 constituents in Fructus Cnidii.

METHOD

Analysis was performed on an Alltech C18 (4.6 mm x 250 mm, 5 microm) column. The mobile phases were acetonitrile water and acetic acid with gradient elution. The flow rate was 1 mL x min(-1). The monitoring wavelength was 325 nm and 245 nm. The column temperature was 40 degrees C.

RESULT

The linear response ranges were 1-20 microg x mL(-1) (r = 0.999 9) for xanthotoxin, 1-20 microg x mL(-1) (r = 0.999 9) for isopimpinellin, 11-20 microg x mL(-1) (r = 0.999 8) for bergapten, 100-1 200 microg x mL(-1) (r = 0.999 7) for imperatorin, 100-2 000 microg x mL(-1) (r = 0.999 9) for osthole. The average recoveries were all above 95%.

CONCLUSION

The method is simple, sensitive and accurate with good reproducibility.

Can dietary furanocoumarin ingestion enhance the erythemal response during high-dose UVA1 therapy?

As phototoxic skin reactions caused by psoralen are induced by wavelengths within the UVA1 spectrum, we assessed the potential of the small amount of psoralen in a normal diet to provoke phototoxicity in volunteers with skin types I and II. Threshold erythema was unaffected by ingestion of a 200-g portion of parsnip.

Variations in content of active ingredients causing drug interactions in grapefruit juice products sold in California

The content of the active ingredients of grapefruit juice, naringin, naringenin and bergapten, was determined in 20 different commercial products of grapefruit juice sold in California. These included Minute Maid, Dole, Tropicana, Ocean Spray, Ralps, Albertson, Stater Bros, Vons, Langers, etc. The concentrations of naringin, naringenin and bergapten in grapefruit juice were assayed by specific HPLC methods. Naringin was found to be the most abundant flavonoid in grapefruit juice products, followed by naringenin and bergapten. The content of naringin varied among the products, ranging from 104 mg/l (Tropicana ruby red) to 628 mg/l (Ralphs white frozen concentrate). The mean contents of naringin in ruby red (158 +/- 66 [SD] mg/l) and pink (279 +/- 123 mg/l) grapefruit juice products were significantly lower than white (481 +/- 94 mg/l) (p <0.005) grapefruit juice products. Content of naringenin also varied from brand to brand and ranged from 3.9 mg/l (Vons white frozen concentrate) to 31.2 mg/l (Tree Sweet pink). Bergapten content was very low in grapefruit juice products ranging from 0 (not detectable) to 5.5 mg/l. There were no significant differences in naringenin and bergapten contents among the three types of grapefruit juice products. The information gained from this study would be useful in predicting the likelihood of grapefruit juice-drug interactions.

A method for quantitative determination of furanocoumarins in capsules and tablets of phytochemical preparations

A method for sample preparation and analysis by high-performance liquid chromatography with UV detection (HPLC-UV) was developed for analysis of psoralen, bergapten and 5-[3-(4,5-dihydro-5,5-dimethyl-4-oxo-2-furanyl)-butoxy]-7H-furo[3-2-g][1]benzopyran-7-one in capsules and tablets employed in Brazil for certain illnesses. The linearity, accuracy, the inter- and intra-day precision of the procedure were evaluated. Analytical curves for furanocoumarins were linear in the range of 1.0-50.0 microg/ml. The recoveries of the furanocoumarins in the products analyzed were 97.3-99.5%, and the percent coefficient of variation for the quantitative analysis of the furanocoumarins in the analyses was under 5%. For inter-equipment study gas chromatography (GC) was employed.

Cytochrome P450-mediated metabolism of xanthotoxin by Papilio multicaudatus

Within the genus Papilio, the P. glaucus group contains the most polyphagous Papilio species within the Papilionidae. The majority of Papilio species are associated with hostplants in the families Rutaceae and Apiaceae, and characterizing most are secondary metabolites called furanocoumarins. Recent phylogenetic studies suggest that furanocoumarin metabolism is an ancestral trait, with the glaucus group derived from ancestors associated with furanocoumarin-containing Rutaceae. In this study, we examined this relationship by conducting a gravimetric analysis of growth that used various concentrations of the furanocoumarin xanthotoxin. Papilio multicaudatus, the putative ancestor of the glaucus group, includes at least one furanocoumarin-containing rutaceous species among its hostplants; this species can consume leaf tissue containing up to 0.3% xanthotoxin with no detectable effect on relative growth rate, relative consumption rate, or efficiency of conversion of ingested food. As is the case for other Papilio species, xanthotoxin metabolism is mediated by cytochrome P450 monooxygenases (P450s). Ingestion of xanthotoxin by ultimate instar P. multicaudatus increases activity up to 30-fold in a dose-dependent fashion. Midguts of induced larvae can also effectively metabolize six other furanocoumarins, including both linear (bergapten, isopimpinellin, imperatorin) and angular (angelicin, sphondin) forms. A metabolite of xanthotoxin in the frass from xanthotoxin-treated larvae, identified as 6-(7-hydroxy-8-methoxycoumaryl)-acetic acid by MS-MS and NMR analyses, is identical to one from the frass of P. polyxenes. The occurrence of this metabolite in two swallowtails and the presence of a second metabolite of xanthotoxin, 6-(7-hydroxy-8-methoxycoumaryl)-hydroxyethanol in the frass of both P. polyxenes and Depressaria pastinacella are consistent with the suggestion that lepidopterans share as the first step of xanthotoxin metabolism the P450-mediated epoxidation of the furan ring 2'-3' double bond.

2D NMR spectroscopic analyses of archangelicin from the seeds of Angelica archangelica

A total of six coumarins, bergapten (1), xanthotoxin (2), imperatorin (3), isoimperatorin (4), phellopterin (5) and archangelicin (6), have been isolated from an n-hexane extract of the seeds of Angelica archangelica. The results of comprehensive 2D NMR analyses of archangelicin are discussed.

A method for fast determination of psoralens in oral solutions of phytomedicines using liquid chromatography

A method for sample preparation and analysis by high performance liquid chromatography with UV detection (HPLC-UV) has been developed for routine analysis of psoralen and bergapten, photosensitizing compounds, in oral solutions of phytomedicines employed in Brazil for some illnesses. The linearity, accuracy, the inter- and intra-day precision of the procedure were evaluated. Calibration curves for psoralen and bergapten were linear in the range of 1.0-600.0 microg ml(-1) and 1.0-400.0 microg ml(-1) respectively. The recoveries of the psoralens in the oral solutions analysed were 94.43-99.97%. The percentage coefficient of variation (CV) of the quantitative analysis of the psoralens in the products analysis was within 5%. In inter-equipment study was employed gas chromatography-flame ionization (CG-FID) detection.

Genetic Variation in Primary Metabolites of Pastinaca sativa; Can Herbivores Act as Selective Agents?

Although insect herbivory has been shown to act as a selective agent on plant secondary metabolism, whether primary metabolites contribute to resistance and can respond to selection by herbivores remains untested. In the wild parsnip (Pastinaca sativa), its principal herbivore, Depressaria pastinacella, acts as a selective agent on furanocoumarin resistance factors. In this study, we determined whether webworms can, by causing differential reductions in fitness, act as selective agents on parsnip primary metabolites. Estimates of narrow-sense heritabilities were significantly different from zero for C18 fatty acids in buds and developing fruits, fructose and sorbitol in buds, fructose, myo-inositol, bergapten, and psoralen in fruits. Wild parsnips protected from webworms by insecticide produced 2.5 times as much seed biomass as unsprayed plants; that webworms accounted for this difference in plant fitness was indicated by a significant negative relationship between reproductive effort and an index of webworm damage. Only a handful of metabolites influenced resistance to webworms; these included osthol, sorbitol, and protein in developing fruits as well as previously documented furanocoumarins. Osthol, a coumarinic compound, enhanced resistance, as did protein content, while sorbitol lowered resistance. Other primary metabolites may affect resistance to webworms, but their effect was context-dependent, that is, their effect depended on concentrations of other metabolites (epistasis). Susceptible plant phenotypes were found to have average chemical compositions. Although there was genetic variation in some of the primary metabolites in parsnips, the epistatic nature of their involvement in resistance and the lack of genetic variation in some suggest that selection on them from webworms will be either inconsistent or ineffective.

Chromatographic determination of the association constant between 8-methoxypsoralen and modified β-cyclodextrin: protective effect of hydroxypropyl-β-cyclodextrin on 8-methoxypsoralen toxicity in human keratinocytes

The retention of 8-methoxypsoralen (8-MOP) on an immobilised hydroxypropyl-beta-cyclodextrin (HP-beta-CD) column was analysed in HPLC by the determination of its Langmuir distribution isotherm. A such method was used to confirm the potential drug complexing role of this cyclodextrin. The 8-MOP/HP-beta-CD association constant (K) was equal to 29.5 and 18.7 M-1, respectively, at a temperature equal to 5 and 25 degrees C, respectively. These association constant values were used to determine the cytotoxicity profile of human keratinocyte cell line (HaCaT) in relation to the complex concentration. It was showed through these data that HP-beta-CD had a cytoprotective since a reverse effect of HP-beta-CD on 8-MOP cytotoxicity was observed.

LC determination of impurities in methoxsalen drug substance: isolation and identification of isopimpinellin as a major impurity by atmospheric pressure chemical ionization LC/MS and NMR

A gradient elution LC method was developed to separate methoxsalen from three of its known impurities: isopimpinellin, bergapten, and ammidin. The method employs a methanol-6%THF (aq) mobile phase, phenyl column, and detection at 254 nm. The gradient LC procedure was applied to seven lots of methoxsalen from five different manufacturers. Six of the seven lots tested contained isopimpinellin as the major impurity at a concentration range of 0.2-2.5%. Identification of the impurity as isopimpinellin was accomplished by a combination of analytical and preparative LC, atmospheric pressure chemical ionization liquid chromatography/mass spectrometry, and NMR.

The furanocoumarins in the roots of Heracleum sibiricum L

From roots of Heracleum sibiricum L (cow parsnip) collected natural state, a raw crystalline furanocoumarin precipitate was obtained containing four compounds: bergapten, isopimpinellin, pimpinellin, sphondin. The isolated compounds were identified with H1NMR.

Effects of storage conditions on furocoumarin levels in intact, chopped, or homogenized parsnips

Furocoumarins represent a family of natural food constituents with phototoxic and photomutagenic properties. They are found mainly in plants belonging to the Rutaceae and Umbilliferae such as celery, carrots, and parsnips. Parsnips (Pastinaca sativa L.) have become more and more popular as a vegetable, e.g., as a constituent of or ingredient in baby food. Previous work has shown that microbial infection of parsnip roots can result in a dramatic increase in furocoumarin levels. In this study, freshly harvested parsnips were stored as whole roots, pieces (cubes), or homogenate at +4 degrees C or -18 degrees C over various time periods under standard conditions. It was found that furocoumarin concentrations (sum of five furocoumarins: angelicin, isopimpinellin, 5-methoxypsoralen, 8-methoxypsoralen, and psoralen) in freshly harvested parsnips, analyzed by HPLC after extraction with diethyl ether and sequential solid phase (reversed-phase and silica) extraction, was generally lower than 2.5 mg/kg, and storage of parsnips in any form investigated at -18 degrees C over up to 50 days did not lead to a marked increase in furocoumarin levels. In contrast, storage of whole parsnips, but not of cubes or homogenate, at +4 degrees C resulted in a marked biphasic increase of furocoumarin concentrations after 7 and 38 days of storage up to levels of about 40 mg/kg. A dramatic increase in furocoumarin concentrations up to 566 mg/kg was observed when whole parsnips obtained from the market were kept at room temperature over 53 days, resulting in a visible microbial (mold) infection. Baby food products from the German market containing parsnips as an ingredient or constituent showed furocoumarin levels < or =0.41 mg/kg, suggesting that properly stored roots/preparations have been used. It is recommended that, after harvesting, parsnips be kept at -18 degrees C or under other conditions that prevent microbial infections.

Simultaneous determination of furanocoumarins in infusions and decoctions from "Carapiá" (dorstenia species) by high-performance liquid chromatography

The use of furanocoumarins, which are photosensitizing compounds, combined with exposure to UV-A radiation is a common treatment for vitiligo, psoriasis, and a number of other skin diseases. Although furanocoumarins plus UV-A treatment is highly effective, several studies have shown that exposure to high doses increases the risk to development of cutaneus carcinoma. Several Dorstenia species are used in folk medicine, mainly against skin diseases, because of the presence of biologically active compounds. We present here analysis of the chemical composition of furanocoumarins from infusion and decoction of "Carapiá" (Dorstenia species), which is used in Brazil against several diseases. We have employed high-performance liquid chromatography (HPLC) procedures for the quantitative determination of psoralen, bergapten, and isopimpinellin. The contents of furanocoumarins revealed an insignificant difference between infusion and decoction. Dorstenia tubicina and D. asaroides contained psoralen and bergapten only in the rhizomes, whereas D. vitifolia shows solely isopimpinellin in both rhizomes and aerial parts.

Simple and rapid determination of psoralens in topic solutions using liquid chromatography

A method for sample preparation and high-performance liquid chromatography detection and quantification has been developed for the routine analysis of psoralen and bergapten, photosensitizing compounds, in topic solutions employed in Brazil for treatment of vitiligo and psoriasis. The linearity, accuracy, the inter- and intra-day precision of the procedure were evaluated. The calibration curve for psoralen and bergapten were linear in the range 1.0-20.0 microg ml(-1). The best recoveries of the psoralens in the topic solutions analysed were 96.3-98.2%. The percentage coefficient of variation of the quantitative analysis of the psoralens in the product analyses was within 5%.

Furanocoumarins in celery and parsnips: method and multiyear Canadian survey

The natural occurrence of biologically active furanocoumarins in common vegetables is an area of increasing interest with respect to human health. In this study, an efficient, rugged, and sensitive liquid chromatographic method with ultraviolet photodiode array detection was developed for the estimation of 5 biologically active furanocoumarins (psoralen, bergapten, xanthotoxin, trioxsalen, and angelicin) in celery and parsnips. When authentic samples were spiked with a mixture of furanocoumarins at individual levels of 2 to 10 microg/g, the method produced overall recoveries of 77 and 75% of all furanocoumarins from celery and parsnips, respectively. The method was applied in 2 laboratories to a multiyear survey of more than 200 samples. Of 110 parsnips samples, 109 (99%) contained quantitatable levels of furanocoumarins. The mean level of total furanocoumarins in the positive parsnip samples was 15.1 microg/g; the maximum level detected was 145 microg/g. Of 114 celery samples, 88 (77%) contained quantitatable levels of furanocoumarins. The mean level of total furanocoumarins in the positive celery samples was 1.9 microg/g; the maximum level detected was 15.2 microg/g. Xanthotoxin and bergapten were the most commonly detected furanocoumarins in both celery (68 and 63%) and parsnips (97 and 96%). Xanthotoxin had the highest mean level of positives in both celery (1.3 microg/g) and parsnips (8.5 microg/g). Little year-to-year variation in either total furanocoumarin levels or incidence was noted.

Seville orange juice-felodipine interaction: comparison with dilute grapefruit juice and involvement of furocoumarins

OBJECTIVE

Our objective was to determine whether Seville orange juice produces a grapefruit juice-like interaction with felodipine and whether bergamottin, 6',7'-dihydroxybergamottin, or other furocoumarins are involved.

METHODS

In a randomized three-way crossover design, 10 volunteers received a felodipine 10-mg extended-release tablet with 240 mL of Seville orange juice, dilute grapefruit juice (that contained equivalent total molar concentrations of bergamottin plus 6',7'-dihydroxybergamottin), or common orange juice (negative control). The pharmacokinetics of felodipine and its dehydrofelodipine metabolite were determined. Juice concentrations of furocoumarins were measured. CYP3A4 inhibitory activity of newly identified furocoumarins was assessed.

RESULTS

The felodipine area under the plasma concentration-time curve was increased by 76% and 93% after Seville orange juice and grapefruit juice ingestion, respectively, compared with common orange juice. The effects of Seville orange juice and grapefruit juice were similar in that the felodipine maximum concentration was augmented while the terminal elimination half-life was unchanged and the dehydrofelodipine area under the plasma concentration time-curve was increased, but the dehydrofelodipine-felodipine area under the plasma concentration-time curve ratio was reduced. Bergamottin and 6',7'-dihydroxybergamottin concentrations were 5 and 36 micromol/L, respectively, in Seville orange juice and were 16 and 23 micromol/L, respectively, in dilute grapefruit juice. A newly identified furocoumarin, bergapten, was detected only in Seville orange juice (31 micromol/L), and it was found to be a mechanism-based inhibitor of recombinant CYP3A4. Relative to the control, 6',7'-dihydroxybergamottin (10 micromol/L) inhibited CYP3A4 activity in cultured intestinal epithelial cells by 93%, whereas bergapten (10 micromol/L) inhibited the activity by only 34%.

CONCLUSIONS

Seville orange juice and grapefruit juice interact with felodipine by a common mechanism, which is probably inactivation of intestinal CYP3A4. Bergamottin and 6',7'-dihydroxybergamottin may be "marker substances" in foods for this interaction. The lack of interaction between Seville orange juice and cyclosporine (INN, ciclosporin) suggests that grapefruit juice may also inhibit intestinal P-glycoprotein, whereas Seville orange juice may selectively "knock out" intestinal CYP3A4.

Content of CYP3A4 inhibitors, naringin, naringenin and bergapten in grapefruit and grapefruit juice products

The flavonoids, naringin and naringenin and the furanocoumarin, bergapten (5-methoxypsoralen), were detected in some fresh grapefruit and commercial grapefruit juices but were not detected in other fruit juices tested (orange; orange with apple base; dark grape; orange and mango with apple base; orange, peach, passion fruit juice). The contents of these three grapefruit constituents in commercial juice and fresh grapefruit varied from brand to brand and also from lot to lot. Juice was prepared from the fresh fruit via different methods (by hand, squeezer or blender). The naringin content, after hand-squeeze, ranged from 115 to 384 mg/l. With hand-squeeze juice production, bergapten was not detected (less than 0.5 mg/l) in two varieties of grapefruit, and naringenin was usually not in detectable levels (less than 2 mg/l) in three varieties. All three constituents were present in New Zealand grapefruit preparations (including juice by hand-squeeze) and different lots showed variation in content (1.5-, 2.3- and 4.7-fold for naringin, naringenin and bergapten, respectively). Differences in the concentrations of these three constituents, which have potential for drug interaction, may contribute to the variability in pharmacokinetics of CYP3A4 drugs and some contradictory results of drug interaction studies with grapefruit juice.

Bath PUVA--an investigation of the distribution of trioxsalen (TMP) and 8-methoxypsoralen (8-MOP) in bathwater

Trioxsalen (TMP) bath PUVA avoids the side effects of nausea and headache associated with oral 8-methoxypsoralen (8-MOP) treatment and allows shorter irradiation times that can be advantageous in some patients. However we noted that a number of patients developed unusual patterns of phototoxic burning. We thought that this was related to an uneven distribution of the TMP in the bathwater and for this reason, a study of bath water TMP concentrations achieved using different TMP preparations was undertaken. The distribution of 8-MOP in an 8-MOP bath was also measured for comparison. Our results confirm that an uneven distribution of TMP is achieved using TMP capsules or suspension and would explain our observed patterns of burning. With an ethanolic solution of TMP, or the commercial equivalent Tripsor, or with Puvasoralen-8 (an 8-MOP preparation), a homogeneous psoralen distribution is achieved, and they are therefore preferable for use in bath PUVA.

Lipophilicity determination of psoralens used in therapy through solubility and partitioning: comparison of theoretical and experimental approaches

The aim of this study was to determine and to compare experimental and theoretical solubilities (S) as well as partition coefficients (PC) in an octanol/water system of psoralen (P), 8-methoxypsoralen (8-MOP), 5-methoxypsoralen (5-MOP) and 4,5',8-trimethylpsoralen (TMP). For each psoralen, experimental results were performed in triplicate with a spectrofluorimetric technique. The measurements were achieved 10 times for each solution. The obtained order of the solubilities in pure octanol was 5-MOP approximately TMP > P > 8-MOP, while in water-saturated octanol it was expressed as follows: TMP approximately 5-MOP > P > 8-MOP. However, the following order was found for hydrophobicity: TMP > 5-MOP > 8-MOP > P. The solubility ratios (SR) in pure octanol and water were assessed (mean +/- SD): 3.13 +/- 0.01 (P), 2.60 +/- 0.01 (8-MOP), 3.75 +/- 0.01 (5-MOP), and 5.11 +/- 0.01 (TMP). In saturated phases, they were 3.27 +/- 0.01, 2.63 +/- 0.01, 3.85 +/- 0.01, and 5.32 +/- 0.01, respectively. The PCs were determined with low concentrations according to the Dearden and Bresnen32 method and they were 1.67 +/- 0.01, 1.93 +/- 0.01, 2.00 +/- 0.01, and 3.14 +/- 0.01, respectively. Solubility parameters (delta), in Hildebrand unit (H) or in (cal/cm3)1/2, were evaluated. They confirmed the polarity of psoralens, previously expressed through the PC, although the positional isomers (5-MOP and 8-MOP) revealed no difference. Hildebrand's approach to the solubility of regular solutions and Yalkowsky's concept of the solubility of nonelectrolytes and weak electrolytes in an octanol/water system permitted a comparison of the theoretical and experimental results. The perspective of this work is to use the physicochemical properties of the psoralens in practice for insuring convenient experimental assays and the prediction, in vitro, of the percutaneous absorption of these compounds.

Rapid identification of some coumarin derivatives in deterpenated citrus peel oil by gas chromatography

Generally on the gas chromatogram of a volatile essential oil, terpenes, oxygenated compounds and sesquiterpenes appear. With temperature programming, it was shown that some non-volatiles are present with the volatiles. They are simple coumarin (2H-1-benzopyran-2-one) derivatives such as citropten (5,7-dimethoxycoumarin) and furocoumarins (psoralen, 7H-furo[3,2-g][1]benzopyran-7-one) such as bergapten (5-methoxypsoralen), some of which are phototoxic. Terpeneless oils are used in perfumes and cosmetics, so it is important to be able to establish rapidly if they contain phototoxic compounds.

Skin pigmentation as a predictor of minimal phototoxic dose after oral methoxsalen

BACKGROUND AND DESIGN

Twenty-eight subjects were phototested to determine their erythemal responses to oral methoxsalen with UV-A and UV-B irradiation. Skin pigmentation was measured by skin reflectance at 550 and 660 nm before irradiation. The smallest UV radiation dose to produce erythema (minimal phototoxic dose and minimal erythema dose, respectively) was determined. The serum concentration of methoxsalen was measured at the time of UV-A irradiation.

RESULTS

There was a positive correlation between skin pigmentation and both 72-hour minimal phototoxic dose and 24-hour minimal erythema dose. No correlation was demonstrated between methoxsalen serum concentration and minimal phototoxic dose. The combination of skin pigmentation and methoxsalen level did not give a better prediction of minimal phototoxic dose than skin pigmentation alone.

CONCLUSIONS

Skin pigmentation measurements can be used to predict the minimal phototoxic and erythema doses. Skin pigmentation measurements are easy to perform and should be included in both phototherapy and photochemotherapy to improve the efficiency and reliability of the treatment.

Characterization and evaluation by 32P-postlabelling of psoralen-type DNA adducts in HeLa cells

Samples of DNA irradiated at 405 and/or 365 nm in the presence of 8-methoxypsoralen (8-MOP) were analysed via a modified postlabelling assay using three hydrolysis enzymes other than those employed previously. These enzymes (deoxyribonucleaseI, venom phosphodiesterase and alkaline phosphatase) liberated 3'-adducted dinucleotide monophosphate instead of the 5'-modified dinucleotide monophosphate normally obtained. The first separation chromatography (D1) of samples irradiated in the presence of 8-MOP showed a single spot above the origin, and the next separation (D2) resolved this spot into two components (spots I and II). Double irradiation experiments in which samples of DNA were first irradiated at 405 nm before being irradiated at 365 nm showed that spot II could be transformed into spot I. The use of 6,4,4'-trimethylangelicin, which induced only photomonoadducts under UVA irradiation, gave only spot II. These two results indicated that spots I and II were respectively due to interstrand cross-links and monoadducts. Dose-effect experiments showed that spots I and II were dose dependent, and low-dose irradiations permitted us to measure one interstrand cross-link and two monoadducts per 10(8) base pairs.

Control of smooth muscle cell proliferation by psoralen photochemotherapy

PURPOSE

Restenosis after balloon angioplasty or the intimal hyperplasia occurring at distal anastomoses of bypass grafts severely limits the long-term therapy for peripheral vascular disease. The aim of this study was to evaluate the application of psoralen photochemotherapy with ultraviolet A (UVA)-activated 8-methoxypsoralen (8-MOP) to suppress smooth muscle cell (SMC) proliferation in vitro by the formation of 8-MOP-DNA monoadducts and interstrand cross-links to inhibit DNA synthesis.

METHODS

Bovine aorta SMC (2 x 10(4)/cm2) were treated with 8-MOP (0 to 1000 ng/ml) for 30 minutes, followed by UVA (2 joule/cm2) to determine the dose of 8-MOP and UVA that inhibits SMC proliferation.

RESULTS

The results show that 8-MOP in the range 30 to 1000 ng/ml in combination with 2 joule/cm2 UVA inhibited SMC proliferation by 40% to 60% 3 days after treatment. In time course studies the growth of SMC treated with 100 ng/ml 8-MOP and 2 joule/cm2 UVA were monitored over 5 days, and this regimen was found to be cytostatic. SMC viability was confirmed by trypan blue exclusion.

CONCLUSIONS

Our studies suggest that 8-MOP/UVA photochemotherapy may represent a novel approach to the control of localized SMC proliferation.

The excitation of 8-methoxypsoralen with visible light: reversed phase HPLC quantitation of monoadducts and cross-links

The formation of 8-methoxypsoralen-DNA monoadducts and cross-links is presumed to be responsible for the efficacy of photochemotherapies that employ 8-methoxypsoralen activated with long-wavelength ultraviolet radiation (UVA, 320-400 nm). In this report it is shown that 8-methoxypsoralen can also be activated with visible light (419 nm). Bovine aorta smooth muscle cells were treated with 8-methoxypsoralen (1,000 ng/mL) and 419 nm light (up to 12 J/cm2). Cellular DNA was isolated, hydrolyzed using nucleolytic enzymes and then analyzed by reversed-phase high-performance liquid chromatography. The primary effect of using visible light instead of long-wavelength ultraviolet radiation is a more than 10-fold reduction in the extent of cross-link formation. Because the extent of monoadduct and cross-link formation has not been routinely measured in experiments in which cellular assays have been performed, it is difficult to correlate cell response to the presence of a particular type of 8-methoxypsoralen photoadduct (monoadduct or cross-link). Thus, the use of visible light allows the study of cells containing nearly 100% monoadducts. In addition, the reduction in cross-link formation when visible light is used to activate the compound may also reduce the mutagenicity of 8-methoxypsoralen and hence enhance its therapeutic efficacy.

Improved high-performance liquid chromatographic analysis of 8-methoxypsoralen monoadducts and cross-links in polynucleotide, DNA, and cellular systems: analysis of split-dose protocols

The distribution of 8-methoxypsoralen-thymidine photoadducts from polynucleotides, calf thymus DNA and mammalian cells treated with [3H]8-methoxypsoralen under a variety of irradiation conditions was determined using high-performance liquid chromatography and scintillation analysis. The split-dose protocol, with samples treated with 8-methoxypsoralen and low doses of long-wavelength UV radiation to generate monoadducts, washed to remove unreacted 8-methoxypsoralen, then irradiated further to convert the monoadducts to cross-links, was examined. The photoadduct distribution in the first step is dependent upon the UVA dose and the wavelength of the radiation, but it is relatively independent of 8-methoxypsoralen concentration. Low fluence and longer wavelengths generate mainly 4',5'-monoadducts, whereas higher fluences and shorter wavelengths yield more cross-links. The second irradiation step converts the 4',5'-monoadducts to cross-links as well as to 3,4-monoadducts. The overall yield of cross-links after the second irradiation step is not dependent upon the wavelength used in the first step. Cellular studies demonstrated that the split-dose protocol is applicable to mammalian systems. These results may affect the interpretation of mutagenesis studies based on the split-dose protocol, because the second step can convert 4',5'-monoadducts to both 3,4-monoadducts, the expected cross-links. Therefore, interpretations that link increases in mutagenicity after the second step in a split-dose study solely to cross-link formation may need re-examination.

High-performance liquid chromatographic determination of methoxsalen in plasma after liquid-solid extraction

An improved method suitable for the determination of 8-methoxypsoralen in the range 50-1500 ng/ml in the plasma of psoriatic patients undergoing PUVA (psoralens and long-wave ultraviolet light) therapy is proposed. A 5-ml aliquot of plasma containing sodium citrate as anticoagulant was centrifuged, griseofulvin was added as internal standard and the sample was denatured with acetonitrile. The supernatant was applied to C18 cartridges and 8-methoxypsoralen was eluted with methanol. The evaporated eluate was reconstituted in the mobile phase for high-performance liquid chromatography (HPLC) and applied to the HPLC column: mobile phase, acetonitrile-0.01 M phosphoric acid (34:66); flow-rate, 1 ml/min; temperature, 40 degrees C; column, Spherisorb 5 ODS, 100 mm x 4.6 mm I.D., 5 microns particle size; UV detection at 248 nm; detection limit, 15 ng/ml of plasma.

Evaluation of phototoxic and photogenotoxic risk associated with the use of photosensitizers in suntan preparations: application to tanning preparations containing bergamot oil

Bases for the elaboration of a standardized protocol are proposed for studying phototoxic effects of skin tanning preparations containing photosensitizing agents. The experimental procedure includes in vivo phototoxicity tests, evaluation of the photogenotoxic risk and determination of the photosensitizer concentration in plasma after topical application. This procedure was carried out with tanning preparations containing a well-known photosensitizer, 5-methoxypsoralen, as a component of bergamot oil. The whole study has been performed using topical application of the commercial suntan product, i.e. containing the sunscreens and all other components. Whereas the exposure to solar simulated radiation never triggered any phototoxic response, a photosensitizing effect was observed for skin type I volunteers exposed to high doses of ultraviolet A. The transepidermal penetration resulted in a 5-methoxypsoralen concentration of 1-4 ng/ml in the suction blister fluid. The photogenotoxicity of this suction blister fluid containing 5-methoxypsoralen and also other ingredients of the tanning preparation was assayed on yeast cells and was found to be rather low. 5-Methoxypsoralen was also detected in plasma after repeated applications but at low concentrations (about 1 ng/ml) which do not present a potential risk for systemic ocular effects.

Extracorporeal photochemotherapy for the treatment of systemic lupus erythematosus. A pilot study

OBJECTIVE

To investigate the effectiveness and feasibility of extracorporeal photochemotherapy (ECP) in the treatment of an autoimmune disease with known cutaneous photosensitivity.

METHODS

Ten patients with systemic lupus erythematosus (SLE) were treated with ECP in an open clinical trial. The efficacy of treatment was analyzed by means of established disease activity scores.

RESULTS

Eight patients completed the trial. In 7 of the 8, there was a significant response to the treatment, with no or minor side effects. The clinical activity score in the group of 8 patients decreased from a median of 7 (range 4-9) to a median of 1 (range 0-5) (P less than 0.05). Laboratory abnormalities did not change significantly, but were mild at the outset.

CONCLUSION

ECP led to clinical improvement of SLE without side effects. The effectiveness of this method should be investigated further in controlled clinical trials.

Quantitation of plasma levels of 8-methoxypsoralen by competitive enzyme-linked immunosorbent assay

An immunologic method for the quantitation of 8-methoxypsoralen (8-MOP) levels in human plasma has been developed. A monoclonal antibody recognizing 8-MOP was prepared by immunizing mice with an 8-MOP derivative conjugated to bovine serum albumin with 1-ethyl-3-(3-dimethylamino-propyl)-carbodiimide-HCl. The antibody was characterized by competitive enzyme-linked immunosorbent assay (ELISA) and recognizes 8-MOP (50% inhibition at 2 pmol) as well as structurally related psoralen derivatives including 4'-aminomethyl-4,5',8-trimethylpsoralen (50% inhibition at 50 pmol), 5-methoxypsoralen (50% inhibition at 150 pmole), and 6,4,4'-trimethylangelicin (50% inhibition at 360 pmol). The assay has a limit of sensitivity of 1 ng/ml plasma. For analysis of 8-MOP levels in plasma, samples were first extracted using SepPak C18 cartridges. The extracts were analyzed for 8-MOP levels both by ELISA and high-pressure liquid chromatography. There was a good correlation between the values determined by both methods (r = 0.92, p less than 0.0005). The development of immunologic methods should greatly facilitate the quantitation of 8-MOP levels in patient plasma.

Variation in 8-methoxypsoralen profiles during long-term psoralen plus ultraviolet A therapy and correlations between serum 8-methoxypsoralen levels and chromametric parameters

Three serum 8-methoxypsoralen (8-MOP) kinetics tests were performed on 15 patients undergoing PUVA therapy. The first test was carried out before beginning PUVA treatment, the 2nd one at the 10th session and the 3rd test at the 20th PUVA session. Blood samples were taken every 30 min after the drug was taken and a standard meal ingestion during 3 h to determine the serum 8-MOP peak level and corresponding time. For 14 patients, UVA-induced erythema was measured with a Minolta CR 200 chromameter, 3 (before beginning PUVA treatment, just before 10th session and 48 h later) or 5 times (before beginning PUVA treatment, just before 10th session and 48 h later, just before 20th session and 48 h later). There was a wider distribution of serum 8-MOP peak levels in the 3rd test than in 2nd one and in the 2nd one than in the first one. These facts suggest a heterogeneity in 8-MOP metabolism in the 15 patients: 11 patients showed an earlier serum 8-MOP peak and an earlier appearance of the drug in blood in the 3rd and 2nd test than in the first one. For 9 of these 11 patients, serum 8-MOP peak levels were higher and higher from the first profile to the 3rd one, suggesting an inhibition of 8-MOP metabolism in time. In the remaining 4 patients, the 8-MOP peak time and the appearance of the drug in blood were delayed in the 3rd test compared with the first profile.(ABSTRACT TRUNCATED AT 250 WORDS)

Study of the skin concentrations after administration of the various phototoxic drugs

The skin concentrations of 8-methoxypsoralen (8-MOP), 5-methoxypsoralen (5-MOP), and 4, 5', 8-trimethylpsoralen (TMP) were studied in the guinea pig following oral administration and bathing. The skin concentration of phototoxic drugs after oral administration peaked at 1.5 hours, and the concentration of 8-MOP was 3.5 times greater than that of 5-MOP. The skin concentration of TMP was not detected in our study (limit of sensitivity 5ng/ml). The skin concentrations of phototoxic drug after bathing decreased in the order of 5-MOP, TMP, and 8-MOP.

8-Methoxypsoralen serum levels in poor responders to photochemotherapy. Importance of drug formulation and individual factors

8-Methoxypsoralen (8-MOP) serum levels of psoriatic patients poorly responsive to photochemotherapy (PUVA) treatment (problem cases) were determined by the HPLC method with 11 single blood probes over 8 hours. Abnormally low or deviated serum levels were found in 7 of 11 PUVA problem patients. There was a great interindividually different first-pass effect for 8-MOP in dependence on the galenic formulation of the 8-MOP brand; therefore, the change to another 8-MOP brand with a modern galenic formulation led only to a slight increase of serum levels, and consequently an increase in the 8-MOP dosage was necessary. It is important to be cautious at this point because patients may show an unproportional increase of 8-MOP serum levels due to the individually limited capacity of biotransformation. The studies of the authors reaffirm the necessity of the determination of 8-MOP serum levels in problem cases of PUVA therapy.

The relationship between plasma psoralen concentration and psoralen-UVA erythema

The plasma 8-methoxypsoralen (8-MOP) concentration was measured in 60 patients commencing psoralen photochemotherapy (PUVA). At the time of blood sampling each patient was phototested using a series of 10 exposures to UVA. The resulting erythema was measured objectively 72 h after irradiation and dose-response curves for psoralen-UVA erythema were constructed. Although the dose of 8-MOP was calculated according to body weight, patients receiving 30 mg of 8-MOP had a significantly lower mean plasma concentration than those receiving higher doses. There was no significant correlation between plasma 8-MOP concentration and minimal phototoxic dose, either estimated visually or calculated from the dose-response curves. However the slope of the dose-response curve showed significant correlation with plasma 8-MOP concentration. The variation between patients in the rate of increase of the erythemal response, but not the variation in threshold sensitivity, can be explained by difference in plasma psoralen concentration.

Simple equilibrium dialysis-high-performance liquid chromatographic method for the in vitro assessment of 5-methoxypsoralen bound to human albumin

Increasingly used in therapeutics, 5-methoxypsoralen (5-MOP), a linear furocoumarin, associated with UVA irradiation (PUVA), is now an established treatment for skin diseases such as vitiligo, mycosis funcoides and particularly psoriasis. Successful PUVA therapy depends on a sufficiently high peak 5-MOP plasma concentration coinciding with the UVA irradiation. However, as with most drugs, only the free plasma fraction is able to enter the target cells and has a pharmacological effect. In this work, the binding of 5-MOP to human albumin was studied in vitro, using a dialysis chamber. Bound and free 5-MOP fractions were quantified by a modification of Stolk's high-performance liquid chromatographic method. Dialysis was performed at 37 degrees C and pH 7.4 for 2 h, against a 4% albumin solution in phosphate buffer. The 5-MOP concentrations used were from 5 x 10(-5) to 5 x 10(-2) g/l in 1 x 10(-1) g/l steps. The 5-MOP bound strongly to human albumin in an unsaturable way. The mean 5-MOP binding to albumin was 95.3%. These results are in accordance with those published by Artuc et al. and not with those of Veronese et al., who found a lower saturable fixation (91%). These two research groups used tritiated 5-MOP. The technique used in this work is simple and inexpensive. It can be employed easily in vivo, e.g., for the assessment of 5-MOP free fractions in different therapeutic conditions.

High-performance liquid chromatographic determination of citropten and bergapten in suction blister fluid after solar product application in humans

Citropten (5,7-dimethoxycoumarin) and bergapten (5-methoxypsoralen) are present in bergamot oil which is used as a tanning cosmetic product. The aim of this study was to quantify, using high-performance liquid chromatography, the amount of citropten and bergapten in the skin after suntan products application (an emulsion and an oil formulation). A suction blister technique performed of the anterior aspect of the forearm permitted the collection of these two accumulated molecules. Fluorometric and ultraviolet detections were used for citropten and bergapten determinations, respectively.

Phototoxicity due to Cachrys libanotis

After classification and identification of the plant, the alcoholic extract of Cachrys libanotis L. was analysed in order to identify the phototoxic agents. The substances responsible for photodermatitis were found to be 4 furocoumarins, of which 3 have been clearly identified, namely 5-methoxy-, 8-methoxy- and 5,8-dimethoxypsoralen. The structure of a 4th compound was not completely defined.

Citropten and bergapten suction blister fluid concentrations after solar product application in man

Citropten (5,7-dimethoxycoumarin) and bergapten (5-methoxypsoralen) are present in bergamot oil which is used as a cosmetic tanning product. The aim of this study was to quantify, using HPLC, the amount of citropten and bergapten in the skin after the application of suntan products (emulsion and oil formulations). A suction blister technique, performed on the volar aspect of the forearm, permitted the collection of these two molecules. The blister fluid concentrations were 37 and 51 ng/ml (emulsion) and 26 and 23 ng/ml (oil), respectively, for citropten and bergapten. Our results show that the suction blister technique could be used for comparing transepidermal penetration of several compounds in vivo in man.

Heracleum mantegazzianum growth phases and furocoumarin content

The observation of photocontact dermatitis from Heracleum mantegazzianum Sommier et Levier in 2 gardeners at work prompted the analysis of furocoumarin content of stem, leaves and fruits of the plant during a period of 1 year. Their concentration was found to be maximal in fruit, intermediate in leaf, and minimal in stem. Psoralen was the most prevalent substance in the leaf and bergapten in the fruit. In the stem, in contrast, individual furocoumarins were found in lower but variable concentrations. 3 furocoumarin seasonal peaks were observed in the leaf: the maximal peak occurred in June, the intermediate in August, the minimal in November. This trend corresponds to 3 biological phases of the weed.

Flow cytometric analysis of 8-methoxypsoralen-DNA photoadducts in human keratinocytes

Flow cytometric methods have been developed for the analysis of 8-methoxypsoralen-DNA adducts in SV40-transformed human keratinocytes (svk-14). Monoclonal antibodies which specifically recognize these adducts were used in conjunction with fluorescein isothiocyanate-labeled second antibodies and propidium iodide staining to simultaneously determine 8-methoxypsoralen-DNA adduct levels and DNA content, respectively. The sensitivity of the method was determined by quantitation of adduct levels in DNA isolated from treated cells by enzyme-linked immunosorbent assay. Adduct formation during various stages of the cell cycle was also investigated. Two separate cell populations with a DNA content indicative of cells in G1 but with different levels of fluorescein isothiocyanate labeling were observed. Pretreatment of cells with aphidicolin decreased the number of cells in S phase, and only one fluorescein isothiocyanate-staining G1 population was observed. There is an indication of greater adduct formation in S-phase cells when immunofluorescence is corrected for DNA content. These results suggest that adduct formation is not simply linear with respect to DNA content.