Vitamin B2-sensitized degradation of the multifunctional drug Evernyl, in the presence of visible light – microbiological implications

Abstract

Taking into consideration the importance of the photooxidative effects in complex bioenvironments, this paper reports on the visible-light-promoted interactions between Evernyl (methyl 2, 4-dihydroxy-3,6-dimethylbenzoate, Ev) and vitamin B2 (riboflavin, Rf). Ev is a phenolic derivative, transparent to visible light, that possesses important antimicrobial activity. This compound is the first known natural, complete and specific human androgen receptor antagonist. Ev is profusely employed in personal-care products and synthesized as a secondary metabolite by several lichen and plant species. In both sceneries, acting Ev as a cosmetic component for topic applications or as a lichen constituent, may Rf behave as a native visible-light absorber pigment. In this context, kinetic and mechanistic aspects of the Rf-sensitized photooxidation of Ev, has been studied in aqueous solution, irradiating with blue LED light (463-471 nm) and employing stationary and time resolved methods. Results indicate that Ev reacts with the photogenerated reactive oxygen species (ROS) singlet molecular oxygen with a rate constant of k r = 1.1 ± 0.2 × 10 6 M −1 s −1 . In parallel Ev also quenches the electronically excited singlet and triplet excited states of Rf with rate constants close to the difussion limit. As a result the ROS superoxide radical anion and hydrogen peroxide are generated and the latter subsequently reacts with Ev. Possible implications of these photoreactions on the antimicrobial activity of Ev have been investigated employing a Candida albicans (CA) strain, isolated from human skin infection. The simultaneous presence of Rf, Ev in a sub-MIC, and blue-light irradiation produced a significant antimycotic effect, attributed to ROS photogeneration.

Riboflavin sensitized photodegradation of Furaneol in a β-cyclodextrin complex

“…According to previous works, [14,28] this kind of system can be treated was found for FUR. Using the obtained 1  0 value of 5.73 ns, which is in concordance with the published fluorescence lifetime in methanol, [28,45] 1 k q = (2.7 ± 0.1) x 10 9 M -1 s -1 was calculated for FUR (Table 1).…”

“…[11,12] Although FUR is transparent to visible light, it could be degraded by ultraviolet light, or by photosensitized processes induced by visible light irradiation of photosensitizers present in commercial formulations. Among these photosensitizers is Riboflavin (Rf), a visible-light absorbing vitamin with well-known photosensitizing properties, [13][14][15] abundant in meat, beer, wine, dairy products, and topical commercial products. [16][17][18] For example, different studies have reported the Rf-photosensitization of antioxidants, flavorings, or J o u r n a l P r e -p r o o f 5 food-related substances.…”

Photodegradation of prednisolone under UVB solar irradiation. Role of photogenerated ROS in the degradation mechanism

“…The increase in the rate of Predn photo-consumption induced by the presence of the enzyme, supports the idea of the involvement of the O 2 •species. It is well known [37,38]…”

Photo‐Fenton and Riboflavin‐photosensitized Processes of the Isoxaflutole Herbicide

“…It is well known that Rf generates the oxidative species: singlet oxygen (O 2 ( 1 Δ g )) and superoxide anion (O 2 •− ) upon visible light irradiation with quantum yields of 0.47 and 0.009 respectively, and the degradation of the contaminants may be due to the reaction between the pollutant and the excited electronic states of the Rf or with the reactive oxygen species (ROS) generated by these . The usual photochemical mechanism of Rf sensitization is rather complex, as shown by Scheme 1, in the presence of an eventual reactive molecule (Q) .…”

“…•À ) upon visible light irradiation with quantum yields of 0.47 and 0.009 respectively, and the degradation of the contaminants may be due to the reaction between the pollutant and the excited electronic states of the Rf or with the reactive oxygen species (ROS) generated by these (13,(16)(17)(18)(19). The usual photochemical mechanism of Rf sensitization is rather complex, as shown by Scheme 1, in the presence of an eventual reactive molecule (Q) (20,21). Upon absorption of a photon, Rf gives rise to its excited singlet state ( 1 Rf*, process [1]) and, through intersystem crossing, to the excited triplet state ( 3 Rf*, process [2]), 3 Rf* can transfer energy or an electron to ground state oxygen, O 2 ( 3 Σ g À ), in the solution, generating O ÁÀ 2 (process [3]) and O 2 ( 1 D g ) (process [11]).…”