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Future Medicinal Chemistry Oct 2017Photostability tests applied on commercial specialties for topical use have demonstrated a greater vulnerability of several drugs, due to greater exposure to light than... (Review)
Review
Photostability tests applied on commercial specialties for topical use have demonstrated a greater vulnerability of several drugs, due to greater exposure to light than other pharmaceutical forms. Photodegradation of a drug can considerably modify its pharmacokinetic behavior by varying the therapeutic index. The evaluation of the degradation profile of a drug, according to the ICH rules, is of primary importance in developing an appropriate topical formulation. Advanced strategies have been proposed to increase the protection from the light of the photolabile drugs. Supramolecular systems have been investigated to improve both pharmacokinetic profile and photostability. In this review, the more recent stability-monitoring methods for the analysis of drugs in topical formulations are collected and the main approaches for the drug photostabilization are discussed.
Topics: Administration, Topical; Drug Carriers; Drug Compounding; Drug Stability; Humans; Light; Nanoparticles; Pharmaceutical Preparations; Photolysis
PubMed: 28925725
DOI: 10.4155/fmc-2017-0105 -
The Science of the Total Environment Mar 2022A continuous wintertime observation of ambient OH and HO radicals was first carried out in Shanghai, in 2019. This effort coincided with the second China International...
A continuous wintertime observation of ambient OH and HO radicals was first carried out in Shanghai, in 2019. This effort coincided with the second China International Import Expo (CIIE), during which strict emission controls were implemented in Shanghai, resulting in an average PM concentration of less than 35 μg/m. The self-developed instrument based on the laser-induced fluorescence (LIF) technique reported that the average OH radical concentration at noontime (11:00-13:00) was 2.7 × 10 cm, while the HO concentration was 0.8 × 10 cm. A chemical box model utilizing the Regional Atmospheric Chemical Mechanism 2 (RACM2), which is used to simulate pollutant reactions and other processes in the troposphere and which incorporates the Leuven isoprene mechanism (LIM1), reproduced the OH concentrations on most days. The HO concentration was underestimated, and the observed-to-modelled ratio demonstrated poor performance by the model, especially during the elevated photochemistry period. Missing primary peroxy radical sources or unknown behaviors of RO for high-NOx regimes are possible reasons for the discrepancy. The daytime ROx production was controlled by various sources. HONO photolysis accounted for more than one half (0.83 ppb/h), and the contribution from formaldehyde, OVOCs and ozone photolysis was relatively similar. Active oxidation paths accelerated the rapid ozone increase in winter. The average ozone production rate was 15.1 ppb/h, which is comparable to that of a Beijing suburb (10 ppb/h for the 'BEST-ONE') but much lower than that of Beijing's center (39 ppb/h in 'PKU' and 71 ppb/h in 'APHH') in wintertime. Cumulative local ozone based on observed peroxy radicals was five times higher than the value simulated by the current model due to the underprediction of HO and RO under the high-NOx regime. This analysis provides crucial information for subsequent pollution control policies in Shanghai.
Topics: China; Formaldehyde; Oxidation-Reduction; Ozone; Photolysis
PubMed: 34902401
DOI: 10.1016/j.scitotenv.2021.152275 -
Journal of Hazardous Materials Jan 2022Organic chloramines of little disinfection efficacy commonly exist in disinfection process (chlor(am)ination) due to the wide presence of organic amines in water, of...
Organic chloramines of little disinfection efficacy commonly exist in disinfection process (chlor(am)ination) due to the wide presence of organic amines in water, of which N-chlorodimethylamine (CDMA) is a typical one. For the first time, UV photolysis for the activation of CDMA was investigated. UV photolysis caused the cleavage of N-Cl bond in CDMA to form Cl and subsequently HO, both of which are dominant contributors to the destruction of model contaminant bisphenol A (BPA). Typical spectra of HO were detected by electron paramagnetic resonance (EPR) experiments, while spectra of reactive nitrogen species (RNS) were not detected during UV photolysis of CDMA. The increase of pH (6.0-8.0), HCO/CO, Cl and nature organic matter inhibited the degradation of BPA. We proposed pathways of CDMA and BPA degradation based on the identified transformation products. UV photolysis of CDMA and BPA reduced the formation of N-nitrosodimethylamine (NDMA) at pH 8.0, but increased the formation of trichloronitromethane (TCNM) at pH 7.0 and 8.0. The increasing toxicity and the formation of TCNM and NDMA gave us a hint that formation of organic chloramines should be concerned.
Topics: Chloramines; Disinfection; Photolysis; Ultraviolet Rays; Water Purification
PubMed: 34365233
DOI: 10.1016/j.jhazmat.2021.126459 -
Environmental Science & Technology Apr 2020Secondary organic aerosol (SOA) accounts for a large fraction of the tropospheric particulate matter. Although SOA production rates and mechanisms have been extensively...
Secondary organic aerosol (SOA) accounts for a large fraction of the tropospheric particulate matter. Although SOA production rates and mechanisms have been extensively investigated, loss pathways remain uncertain. Most large-scale chemistry and transport models account for mechanical deposition of SOA but not chemical losses such as photolysis. There is also a paucity of laboratory measurements of SOA photolysis, which limits how well photolytic losses can be modeled. Here, we show, through a combined experimental and modeling approach, that photolytic loss of SOA mass significantly alters SOA budget predictions. Using environmental chamber experiments at variable relative humidity between 0 and 60%, we find that SOA produced from several biogenic volatile organic compounds undergoes photolysis-induced mass loss at rates between 0 and 2.2 ± 0.4% of nitrogen dioxide (NO) photolysis, equivalent to average atmospheric lifetimes as short as 10 h. We incorporate our photolysis rates into a regional chemical transport model to test the sensitivity of predicted SOA mass concentrations to photolytic losses. The addition of photolysis causes a ∼50% reduction in biogenic SOA loadings over the Amazon, indicating that photolysis exerts a substantial control over the atmospheric SOA lifetime, with a likely dependence upon the SOA molecular composition and thus production mechanisms.
Topics: Aerosols; Air Pollutants; Models, Chemical; Particulate Matter; Photolysis; Volatile Organic Compounds
PubMed: 32154714
DOI: 10.1021/acs.est.9b07051 -
Water Research Jul 2022Co-metabolism and photodegradation are two approaches for remediating trace organic compounds (TOrCs), however, interactions between the two with regards to TOrCs...
Co-metabolism and photodegradation are two approaches for remediating trace organic compounds (TOrCs), however, interactions between the two with regards to TOrCs degradation have not been elucidated. In this study, sulfadiazine (SDZ) was chosen as a representative TOrC and Methylocystis bryophila as a typical strain. Under light conditions, about 80.6% of SDZ was removed by M. bryophila, but only 7.6% or 28.9% of SDZ was eliminated by either individual photodegradation or by co-metabolism. The SDZ stimulated more extracellular organic matter (EOM) production by M. bryophila. The enhanced SDZ degradation was attributed to indirect photolysis caused by the excited triplet state of EOM (EOM*) and co-metabolism. The UPLC-QTOF-MS analysis showed that due to co-metabolism, the pyrimidine ring was broken and could further be oxidized into smaller molecules under light conditions, such as formic and acetic acids. The SDZ mineralization ratio increased from 9.9% under the co-metabolic condition alone to 36.5% under co-metabolism coupled with photodegradation. The Ames tests confirmed that the SDZ degradation products by co-metabolism were mutagenic, however, their toxicity was ameliorated by light during co-metabolism. In conclusion, light plays a crucial role in co-metabolic processes of TOrCs.
Topics: Oxidation-Reduction; Photolysis; Sulfadiazine; Water Pollutants, Chemical
PubMed: 35665677
DOI: 10.1016/j.watres.2022.118623 -
Chemosphere Aug 2020The photolysis dynamics of m-fluorophenol (m-FPhOH) and o-fluorophenol (o-FPhOH) have been investigated with time-resolved velocity map imaging (TR-VMI) and...
The photolysis dynamics of m-fluorophenol (m-FPhOH) and o-fluorophenol (o-FPhOH) have been investigated with time-resolved velocity map imaging (TR-VMI) and time-resolved ion-yield (TR-IY) techniques. Following excitation to the origin of S (ππ∗) state of m- and o-FPhOH, H atoms elimination mediated by tunneling through the potential barrier under the S (ππ∗)/S (πσ∗) conical intersection (CI) has been observed as a Gaussian feature signal centered at a total kinetic energy release (TKER) of ∼6000 cm for both molecules. The quantum tunneling mechanism has been identified as the main decay pathway of S state for m-FPhOH, and the tunneling lifetime of 2.1 ns has been obtained from the TR-VMI measurements of H fragments. This tunneling mechanism is further confirmed by the studies on the selective O-H deuterated species, m-FPhOD, and consolidated by our theoretical calculations. However, the photolysis dynamics is quite different for the photoexcited o-FPhOH. The much lower yield of the H atoms originating from tunneling hinders the extraction of a reliable tunneling lifetime for o-FPhOH. Our theoretical calculations exhibit a broader and higher potential barrier exists beneath the S/S CI of o-FPhOH, which increase the difficulty for tunneling. Furthermore, the special existence of intramolecular hydrogen bond in o-FPhOH is probably also the key factor that affects the tunneling rate, which would restrict the O-H stretch motion.
Topics: Hydrogen Bonding; Models, Chemical; Phenols; Photolysis
PubMed: 32464759
DOI: 10.1016/j.chemosphere.2020.126747 -
The Journal of Organic Chemistry Mar 2022A photolabile protecting group (PPG) 2-(2-nitrophenyl)-propyloxycarbonyl (NPPOC) was explored in glycosylation and applied in the consecutive synthesis of...
A photolabile protecting group (PPG) 2-(2-nitrophenyl)-propyloxycarbonyl (NPPOC) was explored in glycosylation and applied in the consecutive synthesis of oligosaccharides. NPPOC displays a strong neighboring group participation (NGP) effect to facilitate the construction of 1,2- glycosides in excellent yield. Notably, NPPOC could be efficiently removed by photolysis, and the deprotection conditions are friendly to typical protecting groups. A branched and asymmetric oligomannose Man6 was rapidly prepared, and the consecutive assembly of oligosaccharides without intermediate purification was further investigated owing to the compatibility conditions between NPPPOC's photolysis and glycosylation.
Topics: Glycosides; Glycosylation; Oligosaccharides; Photolysis
PubMed: 35171610
DOI: 10.1021/acs.joc.1c03006 -
Chemosphere Nov 2021In this study, we systematically investigated the indirect photolysis of five SAs, i.e., sulfamethazine (SMZ), sulfamethoxazole (SMX), sulfathiazole (STZ), sulfapyridine...
In this study, we systematically investigated the indirect photolysis of five SAs, i.e., sulfamethazine (SMZ), sulfamethoxazole (SMX), sulfathiazole (STZ), sulfapyridine (SPD), and sulfamethizole (SMT), under UV-A irradiation (365 nm) and mediated by nitrite (NO) at environmentally relevant concentrations (0.005-0.1 mM). The SAs that are resistant to direct photolysis can be effectively removed in UV/NO system. SAs with a six-membered heterocyclic ring (i.e., SMZ and SPD) were degraded more quickly than those with a five-membered heterocyclic ring (i.e., SMX, STZ and SMT). The pseudo-first-order rate constants (k) at nitrite concentration of 0.1 mM followed the order of k (0.0265 min) > k (0.0245 min) > k (0.0184 min) > k (0.0176 min) > k (0.0154 min). A kinetic model was developed and the contributions of direct UV photolysis, OH, and RNS to SAs degradation in UV/NO system were calculated. At NO concentration of 0.1 mM, the contributions of OH and RNS for SAs removal were 29.17-46.53% and 52.33-63.28%, respectively. Main transformation pathways including hydroxylation and nitration were proposed, based on liquid chromatography mass spectrometry analysis of the degradation products and density functional theory calculation. However, Smile-type rearrangement which generated a SO-extrusion product was only observed in the degradation of SAs with a six-membered ring, which explains their higher degradation rate than those with a five-membered ring. The presence of natural organic matter (NOM) decreased the formation of nitrated products. Overall, these results will be helpful to understand the fate and the potential ecological risks of SAs in sunlit aquatic environments.
Topics: Kinetics; Nitrates; Nitrites; Photolysis; Sulfonamides; Water Pollutants, Chemical
PubMed: 34111634
DOI: 10.1016/j.chemosphere.2021.130968 -
Environmental Science & Technology Apr 2020Heterogeneous oxidation of SO is an effective production pathway of sulfate in the atmosphere. We recently reported a novel pathway for the heterogeneous oxidation of SO...
Heterogeneous oxidation of SO is an effective production pathway of sulfate in the atmosphere. We recently reported a novel pathway for the heterogeneous oxidation of SO by in-particle oxidants (OH, NO, and NO/HNO) produced from particulate nitrate photolysis ( , , 8757-8766). Particulate nitrate is often found to coexist with chloride and other halide ions, especially in aged sea-salt aerosols and combustion aerosols. Reactive uptake experiments of SO with UV-irradiated nitrate particles showed that sulfate production rates were enhanced by a factor of 1.4, 1.3, and 2.0 in the presence of Cl, Br, and I, respectively, compared to those in the absence of halide ions. The larger sulfate production was attributed to enhanced nitrate photolysis promoted by the increased incomplete solvation of nitrate at the air-particle interface due to the presence of surface-active halide ions. Modeling results based on the experimental data showed that the nitrate photolysis rate constants increased by a factor of 2.0, 1.7, and 3.7 in the presence of Cl, Br, and I, respectively. A linear relation was found between the nitrate photolysis rate constant, , and the initial molar ratio of Cl to NO, [Cl]/[NO], as = 9.7 × 10[Cl]/[NO] + 1.9 × 10 at [Cl]/[NO] below 0.2. The present study demonstrates that the presence of halide ions enhances sulfate production produced during particulate nitrate photolysis and provides insights into the enhanced formation of in-particle oxidants that may increase atmospheric oxidative capacity.
Topics: Atmosphere; Nitrates; Nitrogen Oxides; Photolysis; Sulfates
PubMed: 32126769
DOI: 10.1021/acs.est.9b06445 -
Environmental Geochemistry and Health Dec 2023The impacts and mechanisms of natural water constituents, such as humic acid (HA), nitrates, iron and chloride ions, to the photodegradation of bisphenol A (BPA) were...
The impacts and mechanisms of natural water constituents, such as humic acid (HA), nitrates, iron and chloride ions, to the photodegradation of bisphenol A (BPA) were investigated in aqueous media under UV light irradiation. Due to the contributions of ·OH, O, O and BPA* to BPA photodegradation in pure water in 13.4, 7.7, 22.9 and 47.9%, respectively, BPA was attenuated through the reaction pathway of direct photodegradation more than self-sensitized photodegradation. About indirect photodegradation, BPA photolysis through inhibitory effect from HA was mainly by light screening effect and quenching effect was insignificant. NO- 3 and NO- 2 both showed inhibitory effect but due to different reactive oxidization species (ROS). The photodegradation of BPA was significantly enhanced by the addition of iron from the formation of ·OH and HO, due to iron-assisted indirect photolysis for the degradation process. A dual effect of chloride depending on the different concentration levels involved quenching and promotion effect on reactive photo-induced species (RPS). A simple linear model revealed that BPA photodegradation was significantly impacted by the interaction of the above factors. In natural water, the decreased photolytic rate of BPA was mainly attributed to triple-excited dissolved organic matter (DOM*), indicating that indirect photolysis was the primary transformation pathway of BPA. The detected photolysis products, such as nitrate and chlorinated products, suggest that there might be potential ecological risk of BPA photodegradation.
Topics: Photolysis; Chlorides; Hydrogen Peroxide; Iron; Water
PubMed: 38147143
DOI: 10.1007/s10653-023-01780-9