Visible light-assisted sterilization activity of water-soluble antimonyporphyrin toward Saccharomyces cerevisiae

Sterilization activities of seven kinds of water-soluble dialkyloxo(tetraphenylporphyrinato)antimony(V) bromides (1) were examined against a yeast, Saccharomyces cerevisiae, under visible light irradiation. Sterilization activities were analyzed by the first-order kinetics involving the generation of singlet oxygen (1O2) in the complex between 1 and the cells. The formation of the complexes was confirmed by the measurements of the saturated adsorption concentrations of 1 inside yeast by absorption spectrophotometry using a confocal laser scanning microscope. The quantum yields of 1 for the generation of 1O2 were determined to be 0.48–0.65. In order to ensure efficient sterilization, the requisite was that 1 were both water-soluble and oil-soluble. Presumably the oil-soluble feature of 1 was advantageous in passing through the cell wall of the yeast which consisted of hydrophobic peptideglucan and the water-soluble feature was advantageous in the adsorption occurring at hydrophilic sites inside the cell, causing fatal damage to the yeast.