Biological and structural studies of phosphonium ‘masked thiolate’ compounds

Membrane Permeability of Modified Butyltriphenylphosphonium Cations

The alkyltriphenylphosphonium (TPP) group is the most widely used vector targeted to mitochondria. Previously, the length of the alkyl linker was varied as well as structural modifications in the TPP phenyl rings to obtain the optimal therapeutic effect of a pharmacophore conjugated with a lipophilic cation. In the present work, we synthesized butyltriphenylphosphonium cations halogenated and methylated in phenyl rings (C₄TPP-X) and measured electrical current through a planar lipid bilayer in the presence of C₄TPP-X. The permeability of C₄TPP-X varied in the range of 6 orders of magnitude and correlates well with the previously measured translocation rate constant for dodecyltriphenylphosphonium analogues. The partition coefficient of the butyltriphenylphosphonium analogues obtained by calculating the difference in the free energy of cation solvation in water and octane using quantum chemical methods correlates well with the permeability values. Using an ion-selective electrode, a lower degree of accumulation of analogues with halogenated phenyl groups was found on isolated mitochondria of rat liver, which is in agreement with their permeability decrease. Our results indicate the translocation of the butyltriphenylphosphonium cations across the hydrophobic membrane core as rate-limiting stage in the permeability process rather than their binding/release to/from the membrane.

Development of a novel highly anti-proliferative family of gold complexes: Au(i)-phosphonium-phosphines

A family of gold(i)-phosphonium-phosphine complexes was synthesized thanks to an efficient 5-step strategy, which involves a phospha-Fries rearrangement. It enables the facile variation of the phosphonium moiety. All the complexes along with a synthetic intermediate were fully characterized (a crystal structure was obtained for two of them). The antiproliferative properties of the six novel complexes were evaluated on three human cancer cell lines (A549, MDA-MB-231, and SW480) and compared to those of three benchmark anticancer drugs used in clinics (oxaliplatin, 5-fluorouracil, and paclitaxel) and to a phosphonium-free gold(i) complex [Au(PPh₃)Br]. All the gold(i) complexes, containing a phosphonium, displayed strong anti-proliferative properties. They were more efficient than oxaliplatin and 5-fluorouracil, and one of the complexes was even more efficient than paclitaxel.

Effect of methyl and halogen substituents on the transmembrane movement of lipophilic ions

The introduction of a halogen or a methyl substituent changes the speed of the flip-flop of the penetrating cations and anions in the opposite way.