Effects of psoralen from Psoralea corylifolia on quinone reductase, ornithine decarboxylase, and JB6 cells transformation promotion.

The cancer chemopreventive effect of psoralen isolated from the seeds of Psoralea corylifolia was investigated in the induction of quinone reductase (QR) activity, intracellular detoxification enzyme, inhibition of 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced ornithine decarboxylase (ODC) activity, a key regulatory enzyme for polyamine metabolism, and tumor promotion in mouse epidermal JB6 cells, sensitive to tumor promoters (clone 415a P+ cells), which are related to suppress multistage carcinogenesis including initiation and promotion. Psoralen was isolated and identified from the ethyl acetate-soluble fraction of the methanolic extract from the seeds. Psoralen was active in induction of QR activity, the concentration of psoralen required to induce 1.5 fold QR activity was 14.8 μg/mL. Also, this pure compound inhibited TPA-induced ODC activity by 50% (designated IC(50)) at the concentration 15.6 μg/mL and exhibited inhibition of TPA-induced tumor promotion in mouse epidermal JB6 cells with an IC(50) value of 17.1 μg/mL. Therefore, it is extrapolated that psoralen has the potential capable of inhibiting the initiation and/or promotion stage of carcinogenesis by induction of QR activity, inhibition of TPA-induced ODC activity and mouse epidermal JB6 cells tumor promotion.