Psoralens are natural products (linear furocoumarins) present in several plant families that are extremely toxic to a wide variety of prokaryotic and eukaryotic organisms. They may react directly with pyrimidine nucleotides forming mono- and di-adducts in DNA or even DNA interstrand cross-links [1,2]. Another cause of their toxicity derives from the ability of UV-A-photoactivated furocoumarins to react with ground state oxygen generating toxic oxyradicals capable of inactivating proteins within cells [3]. This type of reactivity has suggested their use as pharmaceuticals for a broad range of therapeutic applications requiring cell division inhibitors, such as vitiligo, psoriasis, and several types of cancer [4]. In this context, one of the main drug targets is the cytochrome P450 superfamily (CYPs), a large and diverse group of enzymes that catalyze the oxidation of organic substances, such as lipids, steroidal hormones, as well as xenobiotic substances. The inactivation mechanism of P450 by psoralens is not completely understood but is thought to occur in three different ways: a) binding of the inhibitor to the apoprotein, b) binding of the inhibitor to the heme, and c) reaction of the inhibitor with the heme inducing fragmentation.