Histological localization of psoralens in fruits of Psoralea bituminosa

Linear furanocoumarins were found on the surface of Psoralea bituminosa (Leguminosae) fruits in concentrations up to 1% of the total furanocoumarins. Most of the remainder was on the surface of the embryos and very young seedlings, with ca. 4% of the total furanocoumarins within the embryos, and very little in the seed coat and fruit. Psoralen was present in the highest concentration, over twice that of xanthotoxin. There was very little bergapten, whose distribution differed from that of the xanthotoxin and psoralen, ca. 20% being on the surface and the rest in dead tissues, i.e., fruit and seed covers. Evidence was obtained, through autofluorescence, that these coumarins are localized in discrete cells of the embryo, on the embryo surface, and on the fruit surface.