Evaluation of photodegradation, phototoxicity and photogenotoxicity of ofloxacin in ointments with sunscreens and in solutions

The Microbial Assay for Risk Assessment (MARA) in the Assessment of the Antimicrobial Activity of Ofloxacin and Its Photoproducts

Ofloxacin is one of the most commonly used antibacterial substances in the world. Like most medicines, it ends up in the environment through municipal sewage and undergoes various transformations, e.g., photodegradation. The aim of this study was an extensive analysis of ofloxacin photodegradation in both pure antibiotic and a commercial eye drop forms. In this study, a sunlight simulator, chromatographic methods of quantitative and qualitative determination, and biological methods for the evaluation of toxicity (Microbial Assay for Risk Assessment (MARA), Microtox® and Spirotox) were used. The results showed that ofloxacin decomposed almost completely over 2 h of irradiation. Based on the high resolution mass spectrometry, 22 photoproducts were identified. The most sensitive strain of bacteria in the MARA test (Delftia acidovorans) responded at a concentration of 7.6 µg L-1 of ofloxacin. The antibacterial activity of the irradiated samples was higher than that predicted based on the ofloxacin concentration. This suggests that the resulting photoproducts may have a bacteriostatic effect. The results of additional acute toxicity tests indicate the formation of toxic photoproducts, so it is reasonable to use other organisms that are not focused on a specific target. Such actions may allow for the capture of other, unexpected effects of formed photoproducts.

Study on the impurity profile and influencing factors of photodegradation in non-aqueous ofloxacin ear drops using liquid chromatography combined with ion trap/time-of-flight mass spectrometry

Ofloxacin ear drops contain a large proportion of organic solvents, which have a great effect on the photodegradation of ofloxacin. The photodegradation impurities of ofloxacin in aqueous solution has been studied, however, the photodegradation of ofloxacin in non-aqueous solution with a high proportion of organic solvents has not been reported. In this article, the impurity profile in non-aqueous ofloxacin ear drops was studied for further improvement of official monograph in pharmacopoeia and quality control of drug. The liquid chromatography combined with ion trap/time-of-flight mass spectrometry was applied to separate and characterize the structures of the impurities in non-aqueous ofloxacin ear drops. Mass fragmentation pattern of ofloxacin and its impurities were studied. The structures of seventeen impurities in ofloxacin ear drops were elucidated based on the high-resolution MSⁿ data in positive ion modes, and ten of them were unknown impurities. The results showed that the impurity profile of non-aqueous ofloxacin solution was significantly different from that of aqueous ofloxacin solution. The effects of packaging materials and excipients on the photodegradation of ofloxacin ear drops were also investigated. The results of correlation analysis showed that the packaging materials with low light transmittance could reduce the light degradation, and ethanol of excipients could significantly decrease the light stability of ofloxacin ear drops. This study revealed the impurity profile and key factors affecting the photodegradation of non-aqueous ofloxacin ear drops, and guided enterprises to improve drug prescription and packaging materials to ensure the safety of drug use by the public.

Exploring Mycosporine-Like Amino Acids (MAAs) as Safe and Natural Protective Agents against UV-Induced Skin Damage

Prolonged exposure to harmful ultraviolet radiation (UVR) can induce many chronic or acute skin disorders in humans. To protect themselves, many people have started to apply cosmetic products containing UV-screening chemicals alone or together with physical sunblocks, mainly based on titanium–dioxide (TiO₂) or zinc-oxide (ZnO₂). However, it has now been shown that the use of chemical and physical sunblocks is not safe for long-term application, so searches for the novel, natural UV-screening compounds derived from plants or bacteria are gaining attention. Certain photosynthetic organisms such as algae and cyanobacteria have evolved to cope with exposure to UVR by producing mycosporine-like amino acids (MAAs). These are promising substitutes for chemical sunscreens containing commercially available sunblock filters. The use of biopolymers such as chitosan for joining MAAs together or with MAA-Np (nanoparticles) conjugates will provide stability to MAAs similar to the mixing of chemical and physical sunscreens. This review critically describes UV-induced skin damage, problems associated with the use of chemical and physical sunscreens, cyanobacteria as a source of MAAs, the abundance of MAAs and their biotechnological applications. We also narrate the effectiveness and application of MAAs and MAA conjugates on skin cell lines.

Insights and controversies on sunscreen safety

Although sunlight provides several benefits, ultraviolet (UV) radiation plays an important role in the development of various skin damages such as erythema, photoaging, and photocarcinogenesis. Despite cells having endogenous defense systems, damaged DNA may not be efficiently repaired at chronic exposure. In this sense, it is necessary to use artificial defense strategies such as sunscreen formulations. UV filters should scatter, reflect, or absorb solar UV radiation in order to prevent direct or indirect DNA lesions. However, the safety of UV filters is a matter of concern due to several controversies reported in literature, such as endocrine alterations, allergies, increased oxidative stress, phototoxic events, among others. Despite these controversies, the way in which sunscreens are tested is essential to ensure safety. Sunscreen regulation includes mandatory test for phototoxicity, but photogenotoxicity testing is not recommended as a part of the standard photosafety testing program. Although available photobiological tests are still the first approach to assess photosafety, they are limited. Some existing tests do not always provide reliable results, mainly due to limitations regarding the nature of the assessed phototoxic effect, cell UV sensitivity, and the irradiation protocols. These aspects bring queries regarding the safety of sunscreen wide use and suggest the demand for the development of robust and efficient in vitro screening tests to overcome the existing limitations. In this way, Saccharomyces cerevisiae has stood out as a promising model to fill the gaps in photobiology and to complete the mandatory tests enabling a more extensive and robust photosafety assessment.

Photophysical Properties Controlled by Substituents with Lone-Pair Electrons at the Ortho- or Para-Positions of Fluoroquinolone Antibiotics

The ortho- or para-substituents of NH₂ or N-alkyl-containing lone-pair electrons were found to change the energy levels and transition configurations of the highest occupied molecular orbital for some fluoroquinolone-based antibiotics (FQs) and can significantly influence the electronic structure, intermolecular hydrogen bonding, internal conversion, and fluorescence and intersystem crossing efficiencies of FQs in acetonitrile or aqueous solution after photoexcitation. These findings provide new insights that can help in the molecular design strategies to regulate the photophysical properties of photosensitive medicines, photodynamic therapy reagents, and energy conversion materials that contain similar aromatic carbonyl structures.