Comparative Photodynamic Evaluation of New Phenothiazinium Derivatives against Propionibacterium acnes^†

Abstract

The screening of recently patented derivatives of the standard phenothiazinium agents methylene blue and toluidine blue was carried out against Propionibacterium acnes, the main bacterium associated with acne vulgaris. Comparative tests were made using the topical agent benzoyl peroxide (BPO) and standard tetracyclines. Each of the photosensitizers employed, including the lead compounds, was photobactericidal at lower concentrations than BPO, and produced a much more rapid kill than the tetracyclines. In addition, the tetracyclic and pentacyclic phenothiazinium derivatives exhibited high light:dark kill ratios, suggesting that these examples might be particularly useful in practice.

In vitro susceptibilities of Neoscytalidium spp. sequence types to antifungal agents and antimicrobial photodynamic treatment with phenothiazinium photosensitizers

“…Both MB and TBO display log Poil/water < 0 which indicate a low lipophilicity. While NMBN and S137 exhibit a higher lipophilic profile (log Poil/water > 0) [68][69][70]. The more lipophilic nature of these PS molecules determines their capacity to bind to cell membranes and is critical to define the extent of photoinduced membrane damage and consequently the efficiency of cell killing [70,44].…”

Photodynamic treatment with phenothiazinium photosensitizers kills both ungerminated and germinated microconidia of the pathogenic fungi Fusarium oxysporum, Fusarium moniliforme and Fusarium solani

“…MB has been used to treat methemoglobinemia and to oral disinfection [59,60]. Other PS, such as hypericin, furanocoumarins and thiophenes are produced by plants of various genera and have been used in vitro to kill plant-pathogenic fungi, such as Colletotrichum sp.…”

In Vitro Photodynamic Inactivation of Plant-Pathogenic Fungi Colletotrichum acutatum and Colletotrichum gloeosporioides with Novel Phenothiazinium Photosensitizers

“…Phenothiazinium photosensitizers are among the most studied PSs, and novel derivatives with improved photochemical and photophysical characteristics have been synthesized (26,(31)(32)(33). APDT with novel MB derivatives such as NMBN and S137 has been shown to be highly effective against human-pathogenic fungi of the genera Candida and Trichophyton (15,16,29).…”

“…This would require the use of environmentally safe PSs. The phenothiazinium derivative methylene blue, the lead compound in this work, has a suitable human toxicity profile, being used routinely for malignancy tracing and the treatment of methemoglobinemia, in both cases at concentrations hundreds of times higher than those required to kill microorganisms (31). Other PSs, such as the above-mentioned furanocoumarins and thiophenes, are produced naturally by plants of several genera and may act as protection against infections caused by plant-pathogenic fungi or bacteria (23,24,41).…”