Photodegradation Mechanism of Nonsteroidal Anti-Inflammatory Drugs Containing Thiophene Moieties: Suprofen and Tiaprofenic Acid

Synthesis of new multitarget-directed ligands containing thienopyrimidine nucleus for inhibition of 15-lipoxygenase, cyclooxygenases, and pro-inflammatory cytokines

A new series of thieno[2,3-d]pyrimidine derivatives 4, 5, 6a-o, and 11 was designed and synthesized starting from cyclohexanone under Gewald condition with the aim to develop multitarget-directed ligands (MTDLs) having anti-inflammatory properties against both 15-LOX and COX-2 enzymes. Moreover, the potential of the compounds against the proinflammatory mediators NO, ROS, TNF-α, and IL-6 were tested in LPS-activated RAW 264.7 macrophages. Compound 6o showed the greatest 15-LOX inhibitory effect (IC50 = 1.17 μM) which was superior to that of the reference nordihydroguaiaretic acid (NDGA, IC50 = 1.28 μM); meanwhile, compounds 6h, 6g, 11, and 4 exhibited potent activities (IC50 = 1.29-1.77 μM). The ester 4 (SI = 137.37) and the phenyl-substituted acetohydrazide 11 (SI = 132.26) showed the highest COX-2 selectivity, which was about 28 times more selective than the reference drug diclofenac (SI = 4.73), however, it was lower than that of celecoxib (SI = 219.25). Interestingly, compound 6o, which showed the highest 15-LOX inhibitory activity and 5 times higher COX-2 selectivity than diclofenac, showed a greater poteny in reducing NO (IC50 = 7.77 μM) than both celecoxib (IC50 = 22.89 μM) and diclofenac (IC50 = 25.34), but comparable activity in inhibiting TNF-α (IC50 = 11.27) to diclofenac (IC50 = 10.45 μM). Similarly, compounds 11 and 6h were more potent in reducing TNF-α and IL6 levels than diclofenac, meanwhile, compound 4 reduced ROS, NO, IL6, and TNF-α levels with comparable potency to the reference drugs celecoxib and diclofenac. Furthermore, docking studies for our compounds within 15-LOX and COX-2 active sites revealed good agreement with the biological evaluations. The proposed compounds could be promising multi-targeted anti-inflammatory candidates to treat resistant inflammatory conditions.

Computational Studies of the Photodegradation Mechanism of the Highly Phototoxic Agent Benoxaprofen

Computational quantum chemistry within the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) framework is used to investigate the photodegradation mechanism as well as the photochemical and photophysical properties of benoxaprofen (BP), a non steroid anti-inflammatory molecule (2-[2-(4-chlorophenyl)-1,3-benzoxazol-5-yl] propanoic acid). BP is a highly phototoxic agent that causes cutaneous phototoxicity shortly after its administration. On the grounds of concern about serious side effects, especially hepatotoxicity, it was withdrawn from the world market after only 2 years of its release. Our study shows that the drug has the capability to absorb radiation in the UV region, mainly between 300 and 340 nm, and undergoes spontaneous photoinduced decarboxylation from the triplet state. It shows very similar photochemical properties to the highly photolabile non-steroidal anti-inflammatory drugs (NSAIDs) ketoprofen, suprofen, and tiaprofenic acid. Like ketoprofen, BP can also decarboxylate from excited singlet states by overcoming low energy barriers. The differences in molecular orbital (highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO)) distributions between the neutral and deprotonated BP, their absorption spectra, and the energetics and fate of various photoproducts produced throughout the photodegradation are discussed. Initiation and termination of decarboxylated BP radical species and initiation of propagating lipid peroxidation reactions due to the addition of molecular oxygen giving rise to the corresponding peroxyl radical are also explored in detail.

Ruxolitinib photodegradation mechanisms by theoretical and experimental chemistry

Ruxolitinib is a Janus Kinase inhibitor currently approved for the treatment of myelofibrosis. It is also a promising drug for the treatment of skin and infectious diseases. In terms of pharmaceutical stability, although ruxolitinib has been established as being sensitive to light, no data on photodegradation processes are available to date, while these may be useful for quality risk management and any potential development of other pharmaceutical forms for other routes of administration. One way to partially fill this gap was to carry out a study that combines a consistent determination of the most sensitive sites of the molecule to photolysis through theoretical calculations based on functional density, with the identification of the main photodegradation products obtained after forced degradation. This integrated approach has shown converging results describing the mechanisms based on photo-oxidation that can lead to the opening of the pyrrole ring. Having access to the structure of the degradation products and intermediates then made it possible to carry out an in silico evaluation of their potential mutagenicity and it appears that some of them feature alert structures.

Intrinsic stability of the antiviral drug umifenovir by stress testing and DFT studies

Umifenovir is an antiviral drug approved in China and Russia for the treatment of influenza. The available dosage form consists of capsules marketed under the brand name Arbidol®. Due to its broad spectrum, umifenovir may also be used in other viral contexts, alone or combined with other antiviral drugs. Although knowledge of umifenovir intrinsic stability may be useful for any potential development of other pharmaceutical forms for other routes of administration and for quality risk management, no data regarding this matter is available to date. In this study, the exploration of the molecule's behaviour under hydrolytic, oxidative and photolytic conditions was carried out experimentally and supported by density functional theory (DFT) studies. It comes out that umifenovir is sensitive to these stress conditions giving rise to 6 structurally characterized degradation products. The one-electron oxidation process produced on the sulphur atom is probably the main cause of umifenovir degradation with reference to the structures of the degradation products formed and the DFT data.

Biological activity evaluation and action mechanism of chalcone derivatives containing thiophene sulfonate

A series of novel chalcone derivatives containing a thiophene sulfonate group were designed and synthesized. The structures of all title compounds were determined by ¹H-NMR, ¹³C-NMR and HRMS. Antibacterial bioassays indicated that, compound 2l demonstrated excellent antibacterial activities against Xanthomonas axonopodis pv. citri (Xac), with an EC₅₀ value of 11.4 μg mL⁻¹, which is significantly superior to those of bismerthiazol (BT) (51.6 μg mL⁻¹) and thiodiazole-copper (TC) (94.7 μg mL⁻¹). Meanwhile, the mechanism of action of compound 2l was confirmed by using scanning electron microscopy (SEM). In addition, compound 2e showed remarkable inactivation activity against Tobacco mosaic virus (TMV), with an EC₅₀ value of 44.3 μg mL⁻¹, which was superior to that of ningnanmycin (120.6 μg mL⁻¹). Microscale thermophoresis (MST) also showed that the binding of compounds 2e and 2h to Tobacco mosaic virus coat protein (TMV-CP) yielded K_d values of 0.270 and 0.301 μmol L⁻¹, which are better than that of ningnanmycin (0.596 μmol L⁻¹). At the same time, molecular docking studies for 2e and 2h with TMV-CP (PDB code: 1EI7) showed that the compound was embedded well in the pocket between the two subunits of TMV-CP in each case. These results suggested that chalcone derivatives containing a thiophene sulfonate group may be considered as activators in the design of antibacterial and antiviral agents.

Synthesis, antibacterial, antiviral activities and action mechanism of chalcone derivatives containing thiophene sulfonate.

Pd-Catalyzed thiophene directed regioselective functionalization of arenes: a direct approach to multiply-substituted benzyl amines

A thiophene directed ortho-C–H functionalization via a palladium catalyst in the synthesis of multiply-substituted benzyl amines has been developed.

Formation of cyclobutane thymine dimers by tiaprofenic acid and its photoproducts: approach to the photosensitizer triplet state energy limit value

Tiaprofenic acid family photosensitizes cyclobutane thymine dimer formation allowing to approach the lower limit threshold of a photosensitizer triplet state energy to excite the triplet state of thymine in DNA.

Time-resolved spectroscopic characterization of a novel photodecarboxylation reaction mediated by homolysis of a carbon α-bond in flurbiprofen

Flurbiprofen (Fp), a nonsteroidal anti-inflammatory drug (NSAID) currently in use for arthritis pain relief and in clinical trials for metastatic prostate cancer, can induce photosensitization and phototoxicity upon exposure to sunlight. The mechanisms responsible for Fp phototoxicity are poorly understood and deserve investigation. In this study, the photodecarboxylation reaction of Fp, which has been assumed to underpin its photoinduced side effects, was explored by femtosecond transient absorption (fs-TA), nanosecond transient absorption (ns-TA), and nanosecond time-resolved resonance Raman (ns-TR(3)) spectroscopic techniques in pure acetonitrile (MeCN) solvent. Density functional theory (DFT) calculations were also performed to facilitate the assignments of transient species. The resonance Raman and DFT calculation results reveal that the neutral form of Fp was the predominant species present in MeCN. Analysis of the ultraviolet/visible absorption spectrum and results from TD-DFT calculations indicate that the second excited singlet (S2) can be excited by 266 nm light. Due to its intrinsic instability, S2 rapidly underwent internal conversion (IC) to decay to the lowest lying excited singlet (S1), which was observed in the fs-TA spectra at very early delay times. Intriguingly, three distinct pathways for S1 decay seem to coexist. Specifically, other than fluorescence emission back to the ground state and transformation to the lowest triplet state T1 through intersystem crossing (ISC), the homolysis of the carbon α-bond decarboxylation reaction proceeded simultaneously to give rise to two radical species, one being carboxyl and another being the residual, denoted as FpR. The coexistence of the triplet Fp (T1) and FpR species was verified by means of TR(3) spectra along with ns-TA spectra. As a consequence of its apparent high reactivity, the FpR intermediate was observed to undergo oxidation under oxygen-saturated conditions to yield another radical species, denoted as FOR, which subsequently underwent intramolecular hydrogen transfer (IHT) and dehydroxylation (DHO) to form a final product, which could react with the carboxyl from the decarboxylation reaction to generate a minor final product. TD-DFT and transient state (TS) calculations for predicting the absorption bands and activation energies of the transient species produced in the photodecarboxylation reaction have provided valuable mechanistic insights for the assignment of the intermediate species observed in the time-resolved spectroscopy experiments reported here. The results of the time-resolved spectroscopy experiments and DFT calculations were used to elucidate the reaction mechanisms and intermediates involved in the photochemistry of Fp.