Furocoumarin glucosides of Angelica archangelica subspecies Litoralis

From the roots of Angelica archangelica subsp. litoralis three new furocoumarin glycosides, tert. O-β-d-glucopyranosyl-(R)-byakangelicin, sec.-O-β-d-glucopyranosyl-(R)-byakangelicin and tert.-O-β-d-glucopyranosyl-(R)-isobyakangelicin were isolated and their structures established mainly by spectroscopic methods. Additionally, tert.-O-β-d-glucopyranosyl-(R)-heraclenol was obtained and characterized.     

Psoralen-sensitized photohemolysis: Dependence on pH

The effect of pH on psoralen-sensitized photohemolysis (irradiation at 366 nm, 23 W/m²) was investigated. The dose (D) dependence of the rate of photohemolysis (V) fitted V = V₀ + kD^x (where V₀ is the rate of dark hemolysis and k is a coefficient). Variation of pH did not influence the exponent x, which was about 2; however, pH had a strong influence on the k value. The lowest V was observed in the pH interval from 8.0 to 8.4. It nearly doubled as the pH was changed from 8.4 to 9.0 as well as from 8.0 to 7.4. At pH below 7.4 the hemolysis rate increased sharply (by another factor of ～4). Since psoralen does not contain acid/base groups, the effect of pH could hardly be a result of changing the photophysical properties of the sensitizer. The increase in V in the alkaline region could be attributed to more pronounced photooxidation of reduced glutathione as a substrate, while the jump at pH ～7.3 would be ascribed to titration of a psoralen photooxidation product. The latter idea was supported by the HPLC data. Psoralen was preirradiated in ethanol and mixed in the dark with phosphate buffer at different pH, after which HPLC analysis revealed several pH-dependent photoproducts; for one of them the pH titration curve closely resembled the pH profile of psoralen-sensitized hemolysis.     

Microwave-facilitated extraction of furanocoumarins onto paper substrates: an imaging technique to analyse spatial distribution and abundance in leaves

An impediment to studying the implications of fine-scale variation in the distribution of secondary compounds within plants has been an inability to map their distribution. Conventional approaches require fine-scale dissections, followed by extraction and analysis, a strategy which is often limited by the large number of extractions required and by the difficulty in quantifying compounds in very small samples. A method has been developed which allows the microwave-facilitated transfer of furanocoumarins from fresh leaves to two-dimensional substrates (phase separation paper). The fluorescence of these compounds under UV light is enhanced by treatment with base, which probably opens the lactone ring of the compounds. The developed prints are then photographed under UV light and the images analysed with commonly available software programs. Images so obtained for furanocoumarins in wild parsnip foliage revealed that the total fluorescence from extracted furanocoumarins is correlated with the amount of furanocoumarins remaining in the leaf. Thus, the images provide information not only on spatial distribution but also quantitative data.     

Coumarins and psoralens in grapefruit peel oil

Four coumarins, four psoralens and two methoxyflavones were isolated and identified from the peel oil of grapefruit. Five of these compounds are reported as constituents of grapefruit oil for the first time, one of which, 5[(3,7-dimethyl-6-epoxy-2-octenyl) oxy]psoralen is a new natural product.     

Effect of psoralens on Fenton-like reaction generating reactive oxygen species

Psoralens (psoralen, 5-methoxypsoralen, 8-methoxypsoralen, khellin, and visnagin) in 1 mM doses were shown to enhance the generation of reactive oxygen species, such as the hydroxyl radical (HO*), the superoxide anion radical (O2(-)), and singlet oxygen ((1)O(2)), from the system generating chemiluminescence (CL), as well as free radicals in the absence of light. The system that generated CL was made up of CoCl(2) and H(2)O(2). Incubation of psoralens in 0.2 mM doses with the generating system showed that only 8-methoxypsoralen and khellin have antioxidative effects. Antioxidative effects were also observed in the case of visnagin but in low concentration (0.05 mM). High doses of psoralens (1 mM) showed prooxidative effects. Measurements were done using a deoxyribose assay, the CL method, and spin-trapping with 5,5-dimethyl-1-pyrroline-N-oxide and 2,2,6,6-tetramethylpiperidine combined with electron spin resonance spectroscopy and spectrophotometry methods.     

Delivery of photoreactive psoralen derivatives to specific biological targets

Psoralens are bifunctional molecules which photoreact with the pyrimidine bases of nucleic acids to form monoadducts and diadducts, or interstrand cross-links. We have prepared psoralen derivatives with additional functional groups which can be specifically directed to chosen biological targets. A sulfhydryl-containing psoralen which can form site-specific cross-links in plasmid DNA has been used to study psoralen repair and mutagenesis. Cloned DNA containing psoralen monoadducts has been cross-linked to specific regions of viral RNA and used to probe virus assembly. A biotinylated psoralen derivative which binds specifically to avidin has been used to detect small amounts of DNA. Finally, a psoralen derivative of insulin has been used to deliver psoralen specifically to activated lymphocytes.