Anti-infective and therapeutic effects of photodynamic therapy with Ligularia fischeri extract against skin pathogens in vitro and in Caenorhabditis elegans

Abstract

aPDT (antimicrobial photodynamic treatment) is the use of photosensitizer and light to generate reactive oxygen species, inducing cell death of pathogens. Due to the low resistance rate, aPDT using natural products is a promising alternative for antibiotics to treat microbial infections. Ligularia fischeri, which is a wild vegetable plant of Korea, possesses many potential cosmeceutical bioactivities like anti-oxidation and anti-inflammation. In this study, the anti-infective effects against various skin pathogens were evaluated in vitro, and C. elegans was exploited to test photopharmaceutical actions of L. fischeri extract and fractions and light. Three compounds were characterized using spectrophotometric analysis, and confirmed as active photosensitizers in vitro. aPDT with L. fischeri extract (20 ？g/mL) and LED red light (120 ± 20 W/m2) reduced 4.3 to 4.9 log(CFU/mL) of Staphylococcus aureus, MRSA, Cutibacterium acnes, Streptococcus mutans; and 2.4 log(CFU/mL) of C. albicans. The effects remained under milder conditions (20 ± 20 W/m2 for 30 min or 10 min). In C. elegans, aPDT decreased the bacterial numbers on worms, recovered the growth retardation and increased the survival rate under S. aureus infection without toxicity. Moreover, the surface eradication of C. acnes after aPDT was demonstrated in micropig skin. Those results support the value of L. fischeri as a natural resource for the photo-treatment of skin diseases in the pharmaceutics and cosmetics industry.