Ki-Min Bark

Physicochemical properties of quinolone antibiotics in various environments

The progress and photosensitivity of quinolone antibiotics are briefly described. By the photolysis of nalidixic acid, the loss of -COOH group is observed. The photoreaction of fluoroquinolones involves heterolytic C-F bond fragmentation. The protonation and divalent cation complexation equilibria are also examined. The spectroscopic properties of these drugs are intensively investigated in biological mimetic systems such as AOT reverse micelle, and H(2)O-CH(3)OH and H(2)O-CH(3)CN mixed solvents. For ofloxacin and norfloxacin, the excited-state intramolecular charge transfer (ICT) is observed. So, fluorescence spectra exhibit reverse solvatochromism in mixed solvents. The change of radiative and non-radiative rate constant can also be explained using this ICT. The influence of dielectric effects of solvent is more significant compared with the specific hydrogen bonding interaction. Theoretical treatments support all of these results.

Spectroscopic Properties of Fluoroquinolone Antibiotics in Water–methanol and Water–acetonitrile Mixed Solvents¶

Abstract The fluorescence properties of ofloxacin (OFL), norfloxacin (NOR) and flumequine (FLU) were studied in H2O–CH3OH and H2O–CH3CN mixed solvents because these solvents were thought to behave as a biological mimetic system. The emission spectra of OFL and NOR were very sensitive to the composition of the solvents. In the Lippert–Mataga analysis of the steady-state fluorescence data of OFL and NOR, clear reverse solvatochromism was exhibited in both mixed solvents. This observation can be explained by the twisted excited-state intramolecular charge transfer, which is accelerated by water. Theoretical treatments further support these results. The radiative and nonradiative rate constants were analyzed as a function of solvent dipolarity–polarizability (π*) and hydrogen-bond donor acidity (α). These results were well consistent with the suggested mechanism of the excited-state chemical process of OFL and NOR, which depended upon the solvent–solute interactions such as bulk dielectric effects and specific hydrogen-bonding interactions. However, the influence of dielectric effects was more significant. The solvent structures of H2O–CH3CN and the preferential solvation by water were also examined. The emission spectra of FLU do not exhibit any characteristic responses to the properties of the environment.

Evaluation of the phototoxic potential of plants used in oriental medicine

AIM OF THE STUDY Phototoxicity can be either harmful or beneficial. Yet the phototoxicity of oriental medicinal plants is an understudied area. The purpose of this study is to fill in this gap. MATERIALS AND METHODS The phototoxic potential of oriental medicinal plants was examined in vitro using photohemolysis and the Candida albicans test. Seventeen medicinal plants [Acorus gramineus (ACG), Panax ginseng C.A. (PAG), Platycodon grandiflorum (PLG), Aractylodes japonica (ATJ), Xanthium strumarium (XAS), Dioscorea batatas (DIB), Anemarrhena asphodeloides (ANA), Polygonatum sibiricum Red (PSR), Cocculus trilobus (COT), Ficus carica (FIC), Chelidonium majus var. asiaticum (CMA), Pulsatilla koreana (PUK), Agrimonia pilosa (AGP), Zanthoxylum schinifolium (ZAS), Angelica gigas (ANG), Ledebouriella seseloides (LES), and Cnidium officinale (CNO)] were selected because they showed strong fluorescence in one of our previous studies of 62 plants. We further evaluated in vivo phototoxicity in mice. 0.75 mL/kg of seed oil for Xanthium strumarium (XAS, ), or 1.25 mL/kg of extracted solutions of Atractylodes japonica (ATJ, ), Chelidonium majus var. asiaticum (CMA, ), Zanthoxylum schinifolium (ZAS, ), and Ledebouriella seseloides (LES, ) were given once, and evaluated for sunburn edema, formation of sunburn cell, decrease of epidermal Langerhans cells and local suppression of contact hypersensitivity by UVA irradiation. RESULTS Sixteen out of the 17 plants tested except COT showed significant photohemolysis, and 5 of those exhibited phototoxic killing of Candida albicans. The phototoxicity of oriental medicines using those 5 plants was then studied in mice. The 5 plants increased sunburn edema and formation of sunburn cell, and suppressed immune responses locally by decreasing epidermal Langerhans cells and contact hypersensitivity by UVA irradiation. CONCLUSIONS More than a quarter of oriental medicinal plants can be phototoxic, and strong fluorescence measured by absorption and fluorescence spectra can be an easier way to screen for phototoxicity. On the other hand, the phototoxicity of the plants may also be used therapeutically. Further studies regarding the phototoxicity of active components extracted from both live and dried oriental medicinal plants are necessary.

Spectroscopic Properties of Quercetin Derivatives, Quercetin‐3‐O‐rhamnoside and Quercetin‐3‐O‐rutinoside, in Hydro‐organic Mixed Solvents

The characteristic fluorescence properties of quercetin‐3‐O‐rhamnoside (QCRM) and quercetin‐3‐O‐rutinoside (QCRT) were studied in CH3OH–H2O and CH3CN–H2O mixed solvents. Although QCRM and QCRT are known as nonfluorescent molecules, significant fluorescence emissions were discovered at 360 nm in CH3OH and CH3CN when they were promoted to the second excited state. The emission band is broad and structureless and the intensity decreases quickly as the H2O composition in the solvent increases. When the amount of H2O exceeds 60% in both mixed solvents, this emission disappears due to the formation of the distorted excited state. This state will be formed due to the strong intermolecular hydrogen bonding between the polar groups of solute and H2O. As the composition of CH3OH or CH3CN in solvent becomes large, the number of molecules having several intramolecular hydrogen bonding increases. Some of these molecules will be changed to a fluorescent species during the decay process, after excitation. The theoretical calculation further supports these results. The change of the lifetimes, quantum yields, and radiative and nonradiative rate constants of molecules was also examined as a function of solvatochromic parameters for CH3OH–H2O and CH3CN–H2O.

Increased phototoxicity of hydrochlorothiazide by photodegradation

The photodegradation products of hydrochlorothiazide produced by ultraviolet (UV) radiation were investigated for their phototoxicity utilizing the photohemolysis and Candida albicans tests. Hydrochlorothiazide was irradiated for 30, 60, 90 and 120 min with a 250 W xenon arc lamp using a WG295 cut‐off filter. Irradiation of hydrochlorothiazide resulted in the gradual decrease of all three absorption bands (225, 270 and 320 nm), the blue shift of the 225 nm band, and the appearance of a new band around 290 nm. Since previous results demonstrated that photosubstitution of chloride could occur, the main product of this photolysis most likely is ethoxyhydrochlorothiazide. The photohemolysis test revealed a significant increase in photohemolysis observed in the photodegradation products produced after 60, 90 and 120 min of UV irradiation. This increase in hemolysis value directly correlated with the UV‐irradiation time. However, there was no significant phototoxic killing of yeast in the Candida albicans test. This suggests photodegradation products of hydrochlorothiazide may play an important role in phototoxicity by acting on the cell membrane, but not on DNA. Considering the high in vitro phototoxicity observed in bendroflumethiazide and the data presented here, substitution of chloride seems to be responsible for the increased phototoxicity of hydrochlorothiazide.

Spectroscopic Properties of Various Quinolone Antibiotics in Aqueous–organic Solvent Mixtures¶

Abstract The spectroscopic properties of enoxacin (ENO), oxolinic acid (OXO) and nalidixic acid (NAL) were studied in various H2O–CH3OH and H2O–CH3CN mixed solvents because these solvents were thought to behave as a biological mimetic system. ENO has piperazinyl group, but OXO and NAL do not have this substituent. The fluorescence emission spectra of ENO were very sensitive to the composition of the solvents. In the Lippert–Mataga analysis of the steady-state fluorescence data, clear reverse solvatochromism was exhibited for ENO in both mixed solvents. This observation can be explained using the excited state twisted intramolecular charge transfer (TICT) from the nitrogen of the piperazinyl group to the keto oxygen. Theoretical calculations further support this observation. The nonradiative and radiative rate constants of these molecules were analyzed as a function of dipolarity–polarizability (π*) and hydrogen bond donor acidity (α) of the mixed solvents. These results for ENO were consistent with the suggested mechanism of the TICT very well. The influence of bulk dielectric effect was more significant relative to the specific hydrogen bonding interactions. The emission spectra of OXO and NAL do not exhibit any characteristic responses to the properties of the solvent.

Determination of Polyphenol Components of Korean Prostrate Spurge (Euphorbia supina) by Using Liquid Chromatography—Tandem Mass Spectrometry: Overall Contribution to Antioxidant Activity

The Korean prostrate spurge Euphorbia supina is a weed that has been used in folk medicine in Korea against a variety of diseases. Nine polyphenols were characterized for this plant by using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) and the results were compared with the literature data. The individual components were validated using the calibration curves of structurally related external standards and quantified for the first time by using the validated method. Correlation coefficients (r 2) were >0.9907. The limit of detection and limit of quantification of the method were >0.028 mg/L and 0.094 mg/L, respectively. Recoveries measured at 50 mg/L and 100 mg/L were 76.1–102.8% and 85.2–98.6%, respectively. The total amount of the identified polyphenols was 3352.9 ± 2.8 mg/kg fresh plant. Quercetin and kaempferol derivatives formed 84.8% of the total polyphenols. The antioxidant activities of the flavonoids were evaluated in terms of 1,1-diphenyl-2-picrylhydrazyl and 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation-scavenging activity, and the reducing power showed a dose-dependent increase. Cell viability was effectively suppressed at polyphenol mixture concentrations >250 mg/L.

Pefloxacin and ciprofloxacin increase UVA-induced edema and immune suppression.

Background: Quinolone antibiotics are popularly prescribed antibiotics because of their wide antibacterial spectrum and lowered bacterial resistance. Quinolone antibiotics are one of the well‐known photosensitizers that induce phototoxicity. Their role in photocarcinogenesis has been suggested in some studies.

New tetradentate Schiff-base polymers: preparation of poly[2,5-(didodecyloxy)phenylene-1,4-diyl-alt-N,N′-(o-phenylene)-bis(salicylideneiminato-4,4′-diyl)] and poly[2,5-(didodecyloxy)phenylene-1,4-diyl-alt-N,N′-(alkylidene)-bis(salicylideneiminato-4,4′-diyl)]s

Abstract New tetradentate Schiff-base polymers, in which phenylene units alternate with salicylideneiminato units, have been prepared by condensation of 2,5-(didodecyloxy)-1,4-bis(3-formyl-4-hydroxyphenyl)benzene (DFHB) with appropriate diamines in a mixed solution of CHCl3/toluene/acetic acid with 31–79% yields. DFHB as the key building block was prepared by the Suzuki reaction of 2,5-(didodecyloxy)benzene-1,4-diboronic acid with 5-bromosalicylaldehyde in a two-phase solution of tetrahydrofuran/water in the presence of NaHCO3/Pd(PPh3)4 in 45% yield. The molecular structures of the prepared compounds were identified by spectroscopy. Their absorption spectroscopic profiles have been analyzed.

Spectroscopic Properties of Morin in Various CH3OH–H2O and CH3CN–H2O Mixed Solvents

The specific fluorescence properties of morin (3,2′,4′,5,7‐pentahydroxyflavone) were studied in various CH3OH–H2O and CH3CN–H2O mixed solvents. Although the dihedral angle is large in the S0 state, morin has an almost planar molecular structure in the S1 state owing to the very low rotational energy barrier around the interring bond between B and the A, C ring. The excited state intramolecular proton transfer (ESIPT) at the S1 state cannot occur immediately after excitation, S1 → S0 fluorescence can be observed. Two conformers, Morin A and B have been known. At the CH3OH–H2O, Morin B will be the principal species but at the CH3CN–H2O, Morin A is the principal species. At the CH3OH–H2O, owing to the large Franck–Condon (FC) factor for S2 → S1 internal convernal (IC) and flexible molecular structure, only S1 → S0 fluorescence was exhibited. At the CH3CN–H2O, as the FC factor for S2 → S1 IC is small and molecular structure is rigid, S2 → S0 and S1 → S0 dual fluorescence was observed. This abnormal fluorescence property was further supported by the small pK1 value, effective delocalization of the lone pair electrons of C(2′)–OH to the A, C ring, and a theoretical calculation.