p-Benzoquinone as a Privileged Scaffold of Pharmacological Significance: A Review

Discovery of New Tricyclic Oxime Sampangine Derivatives as Potent Antifungal Agents for the Treatment of Cryptococcosis and Candidiasis

Cryptococcus neoformans (C. neoformans) and Candida albicans (C. albicans) are classified as the critical priority groups among the pathogenic fungi, highlighting the urgent need for developing more effective antifungal therapies. On the basis of antifungal natural product sampangine, herein, a series of tricyclic oxime and oxime ether derivatives were designed. Among them, compound WZ-2 showed excellent inhibitory activity against C. neoformans (MIC80 = 0.016 μg/mL) and synergized with fluconazole to treat resistant C. albicans (FICI = 0.078). Interestingly, compound WZ-2 effectively inhibited virulence factors (e.g., capsule, biofilm, and yeast-to-hypha morphological transition), suggesting the potential to overcome drug resistance. In a mouse model of cryptococcal meningitis, compound WZ-2 (5 mg/kg) effectively reduced the brain C. neoformans H99 burden. Furthermore, compound WZ-2 alone and its combination with fluconazole also significantly reduced the kidney burden of the drug-resistant strain (0304103) and sensitive strain (SC5314) of C. albicans.

Selective electrocatalytic transformation of highly toxic phenols in wastewater to para-benzoquinone at ambient conditions

The selective transformation of organics from wastewater to value-added chemicals is considered an upcycling process beneficial for carbon neutrality. Herein, we present an innovative electrocatalytic oxidation (ECO) system aimed at achieving the selective conversion of phenols in wastewater to para-benzoquinone (p-BQ), a valuable chemical widely utilized in the manufacturing and chemical industries. Notably, 96.4% of phenol abatement and 78.9% of p-BQ yield are synchronously obtained over a preferred carbon cloth-supported ruthenium nanoparticles (Ru/C) anode. Such unprecedented results stem from the weak Ru-O bond between the Ru active sites and generated p-BQ, which facilitates the desorption of p-BQ from the anode surface. This property not only prevents the excessive oxidation of the generated p-BQ but also reinstates the Ru active sites essential for the rapid ECO of phenol. Furthermore, this ECO system operates at ambient conditions and obviates the need for potent chemical oxidants, establishing a sustainable avenue for p-BQ production. Importantly, the system efficacy can be adaptable in actual phenol-containing coking wastewater, highlighting its potential practical application prospect. As a proof of concept, we construct an electrified Ru/C membrane for ECO of phenol, attaining phenol removal of 95.8% coupled with p-BQ selectivity of 73.1%, which demonstrates the feasibility of the ECO system in a scalable flow-through operation mode. This work provides a promising ECO strategy for realizing both phenols removal and valuable organics recovery from phenolic wastewater.

Investigation on the photoinduced chemical reaction between p-benzoquinone and tryptophan in homogeneous solution

Photoinduced electron transfer (PET) and energy transfer between amino acids and bioquinones have become research hotspots, due to the important roles they play in a physiological environment. However, as classic benzoquinones and amino acids, the reaction mechanism of p-benzoquinone (PBQ) and tryptophan (Trp) is still unclear. In this work, the photoinduced chemical reaction of PBQ and Trp was investigated in homogeneous solution using time-resolved electron paramagnetic resonance and laser flash photolysis techniques. Under photoexcitation at 355 nm, the ³PBQ* produced via intersystem crossing (ISC) in ethylene glycol aqueous (EG-H₂O) solution followed by the H-atom transfer (HAT) from EG to ³PBQ* was a significant process in competition with the non-radiative transition of ³PBQ*, which was clearly observed in the transient absorption spectra and chemically induced dynamic electron polarization spectra. When Trp was added into the PBQ/EG-H₂O solution, a new decay channel of ³PBQ* was produced that reacted with Trp to form a p-benzoquinone anion radical (PBQ˙^-) and a tryptophan cationic radical (Trp˙⁺), indicating that the photoinduced chemical reaction mechanism was the electron transfer. By fitting the decay dynamic curves, the quenching rate constant of ³PBQ* to Trp in homogeneous solution was determined as 6.8 × 10⁸ M^-1 s^-1, which was close to the diffusion-controlled rate.

Naphthoquinone as a New Chemical Scaffold for Leishmanicidal Inhibitors of Leishmania GSK-3

More than 1 billion people live in areas endemic for leishmaniasis, which is a relevant threat for public health worldwide. Due to the inadequate treatments, there is an urgent need to develop novel alternative drugs and to validate new targets to fight this disease. One appealing approach is the selective inhibition of protein kinases (PKs), enzymes involved in a wide range of processes along the life cycle of Leishmania. Several PKs, including glycogen synthase kinase 3 (GSK-3), have been validated as essential for this parasite by genetic or pharmacological methods. Recently, novel chemical scaffolds have been uncovered as Leishmania GSK-3 inhibitors with antiparasitic activity. In order to find new inhibitors of this enzyme, a virtual screening of our in-house chemical library was carried out on the structure of the Leishmania GSK-3. The virtual hits identified were experimentally assayed both for leishmanicidal activity and for in vitro inhibition of the enzyme. The best hits have a quinone scaffold. Their optimization through a medicinal chemistry approach led to a set of new compounds, provided a frame to establish biochemical and antiparasitic structure–activity relationships, and delivered molecules with an improved selectivity index. Altogether, this study paves the way for a systemic search of this class of inhibitors for further development as potential leishmanicidal drugs.

Palladium-catalyzed carbonylative synthesis of aryl esters from p-benzoquinones and aryl triflates

A palladium-catalyzed dicarbonylation of p-benzoquinones with aryl triflates has been developed. Using Cr(CO)₆ as the CO source, the reaction proceeds smoothly and efficiently to give a series of aryl esters in moderate to good yields (up to 90%).

Systematic In Silico Design, Synthesis, and Biological Studies of Some Novel 1,4-Benzoquinone Derivatives for the Prospective Management of Cognitive Decline

Cholinesterases are significant biological targets for the regulation of cholinergic neurotransmission, and their inhibitors are being exploited for the management of cognitive decline in various neurological conditions. The 1,4-benzoquinone scaffold possesses antioxidant potential along with AChE inhibition activity in various neurological disorders. To design novel and potent selective 1,4-benzoquinone analogues as cholinesterase inhibitors, a ligand-based drug design strategy was followed to develop a 3D quantitative structure-selectivity relationship (QSSR) model. On the basis of the best fit model, eight novel 1,4-benzoquinone derivatives were designed and synthesized implementing appropriate synthetic procedures and were characterized by various spectral and elemental techniques. All the synthesized compounds were evaluated for their selective in vitro acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory potential at different concentrations using mice brain homogenate as the source of the enzyme. Out of these compounds, the three most selective compounds were further evaluated for behavioral variations using step down passive avoidance and escape learning procedure at a dose of 0.5 mg/kg taking donepezil as the reference drug. Biochemical estimation of the markers of oxidative stress (lipid peroxidation, superoxide dismutase, glutathione, and catalase) has also been carried out to determine the role of the synthesized molecules on the scopolamine induced oxidative damage. Compound 2a displayed appreciable selectivity index values as predicted through the 3D-QSSR model. Further, docked complexes of compound 2a with AChE and BChE were subjected to molecular dynamic simulations for a period of 30 ns to study the orientations and stable conformations of the most active molecules in the catalytic domain of these enzymes. The results obtained from the 3D-QSSR analysis, docking, and molecular dynamic studies were found to be appreciable and provided a deep insight into the structural features required for the selectivity of AChE inhibitors over BChE. The outcome of this study may be used as a novel tool to design new highly selective and more potent molecules.

Effects of Benzoquinones on Radicles of Orobanche and Phelipanche Species

The holoparasitic broomrape weeds (Orobanche and Phelipanche species) cause severe yield losses throughout North Africa, the Middle East, and Southern and Eastern Europe. These parasitic weeds form an haustorium at the tip of their radicles to infect the crop upon detection of the host-derived haustorium-inducing factors. Until now, the haustorial induction in the broomrapes remains less studied than in other parasitic plant species. Known haustorium-inducing factors active in hemiparasites, such as Striga and Triphysaria species, were reported to be inefficient for the induction of haustoria in broomrape radicles. In this work, the haustorium-inducing activity of p-benzoquinone and 2,6-dimethoxy-p-benzoquinone (BQ and DMBQ) on radicles of three different broomrapes, namely Orobanche cumana, Orobanche minor and Phelipanche ramosa, is reported. Additional allelopathic effects of benzoquinones on radicle growth and radicle necrosis were studied. The results of this work suggest that benzoquinones play a role in the induction of haustorium in broomrapes. Although dependent on the broomrape species assayed and the concentration of quinones used in the test, the activity of BQ appeared to be stronger than that of DMBQ. The redox property represented by p-benzoquinone, which operates in several physiological processes of plants, insects and animals, is invoked to explain this different activity. This work confirms the usefulness of benzoquinones as haustorium-inducing factors for holoparasitic plant research. The findings of this work could facilitate future studies in the infection process, such as host-plant recognition and haustorial formation.