Photodynamic Inactivation Property of Saffron (Crocus sativus) as a Natural Photosensitizer in Combination with Blue Light in Microbial Strains

 Photodynamic inactivation (PDI) is a new strategy for eliminating pathogenic microorganisms, especially in infectious wounds. PDI occurs using light in combination with a photosensitizer. A new approach in PDI applies natural compounds as a photosensitizer. This study aimed to introduce brewed saffron (Crocus sativus) as a new natural photosensitizer in combination with blue light to induce a phototoxic reaction in Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) strains.

 Isolated and standard S. aureus and E. coli strains and a Candida albicans standard strain were used for PDI. Various final concentrations (2.5-10 mg/mL) of brewed saffron as a photosensitizer was employed with 15 minutes of incubation. A blue LED with 5 minutes of illumination was applied as a light source. Control and treatments were compared using the colony count method.

Using the saffron extract in combination with blue LED could induce a phototoxic reaction in Gram-negative bacteria similar to Gram-positive bacteria. After PDI, there was no significant difference between Gram-positive and Gram-negative strains in terms of cellular death. The highest phototoxic reaction in all bacteria was observed at 10 mg/mL of the final saffron concentration combined with blue light by 0.65-0.75log10 (CFU/mL) cellular death. At the concentration of 2.5 mg/mL of the extract (the lowest concentration), the highest phototoxic reaction was found in the S. aureus isolated strain by a 0.65log10 (CFU/mL) reduction.

 The brewed saffron combined with blue light induces a sub-lethal phototoxic reaction in bacteria. Accordingly, it can be suggested as a natural source for new photosensitizers.