Search Results (605)

Arsenic (As) contamination in groundwater represents a critical global environmental health issue. The reductive dissolution of arsenic-bearing iron oxides by dissimilatory metal-reducing bacteria (DMRB) is a key biogeochemical process driving arsenic mobilization and release in groundwater. However, the mechanism of exogenous electron shuttles in this process remains poorly understood. This study investigated the impact of the quinone-based electron shuttle anthraquinone-2,6-disulfonate (AQDS) on the reductive dissolution of arsenic-loaded goethite by the model DMRB Shewanella putrefaciens CN32 (S.P CN32). The mobilization and transformation behaviors of arsenic and iron were compared under different pH conditions and using different arsenic-loading methods (coprecipitation vs. adsorption). Results demonstrated that AQDS acted as an electron transfer mediator. It significantly enhanced the reductive dissolution of Fe(III). It also significantly enhanced the reduction of As(V). These actions collectively accelerated arsenic release and mobilization. The study also revealed a competitive preferential order in microbial reduction, where the thermodynamically more favorable Fe(III) reduction preceded As(V) reduction. Environmental pH co-regulated this process. Its influence worked through microbial activity and mineral surface properties. A neutral pH was most conducive to the AQDS-mediated bioreduction of arsenic and iron. This study elucidates the critical role of electron shuttles in the biogeochemical cycling of arsenic in contaminated sites, providing a scientific basis for a deeper understanding of the formation mechanisms and risk assessment of high-arsenic groundwater. Full article

The increasing prevalence of antimicrobial resistance, together with recurring infectious disease outbreaks, has intensified the need for alternative strategies to control microbial infections beyond conventional antibiotic therapies. Antimicrobial photodynamic therapy has emerged as a promising non-antibiotic approach in which light-activated photosensitising compounds generate reactive oxygen species that induce oxidative damage to microbial cells. Plant-derived photosensitisers have attracted increasing attention due to their structural diversity, biocompatibility, natural abundance, and potential for sustainability. Natural compounds such as curcumin, hypericin, chlorophyll derivatives, flavonoids, anthraquinones, and riboflavin exhibit favourable photochemical properties that enable efficient production of reactive oxygen species upon irradiation with visible light. Through radical- and singlet-oxygen-mediated photochemical pathways, these molecules exhibit broad-spectrum antimicrobial activity against bacteria, fungi, viruses, and biofilm-associated microorganisms. This review examines the photophysical properties and mechanisms of reactive oxygen species generation associated with plant-derived photosensitisers, together with key factors influencing their antimicrobial performance. Recent advances in nanocarrier-based delivery systems, dual-wavelength activation strategies, and synergistic combination therapies are also discussed for their potential to improve photostability, enhance reactive oxygen species generation, and increase microbial inactivation efficiency. Finally, current progress, challenges, and future research directions for advancing plant-derived photosensitisers in antimicrobial photodynamic therapy are discussed. Full article

Direct electrochemical reduction of oxygen to hydrogen peroxide has garnered increasing research attention because of its mild and easy operation relative to the traditional anthra-quinone cycling route. However, currently used carbon supported noble metal electrocatalysts such as Pd and Pt in the form of single atoms or ultrafine nanoparticles greatly suffer from low reactivity and/or selectivity to hydrogen peroxide. We herein report that ultrafine ca. 1 nm Pd nanoparticles that are stabilized on a N and S co-functionalized car-bon support (Pd/NSC) display excellent reactivity and H₂O₂ selectivity toward electro-oxygen reduction reactions. Our support engineering strategy is expected to open up new opportunities to simultaneously attain high reactivity and H₂O₂ selectivity in electro-reductions of oxygen. Full article

Background: Organic cation transporter 2 (OCT2) mediates the renal uptake of cisplatin and is a principal contributor to its dose-limiting nephrotoxicity. Despite reports of OCT2 inhibition by various phytochemicals, the structure–activity relationships (SARs) governing inhibition and their functional implications remain poorly understood. Methods: We systematically evaluated OCT2 inhibitory activity across a structurally diverse library of 146 phytochemicals, including anthraquinones, flavanols, stilbenes, and isoflavones, using Madin–Darby canine kidney (MDCK) cells stably overexpressing OCT2. Structure–activity relationships were analyzed using non-parametric statistics and multivariate logistic regression, and functional relevance was assessed via cisplatin-induced cytotoxicity assays. Results: Inhibitory activity varied widely across the library, with potent inhibitors identified across multiple chemical scaffolds. Non-parametric statistical analyses revealed no significant differences in overall activity distributions among scaffold classes. Notably, chemical substituent patterns, rather than core scaffold identity, were the primary drivers of OCT2 inhibitory potency. Methoxylation was consistently associated with enhanced OCT2 inhibition, particularly within isoflavones, although its impact varied across structural scaffolds. The selected OCT2 inhibitors markedly reduced cisplatin-mediated cell death in OCT2-expressing cells but not in mock-transfected controls, confirming an OCT2-dependent mechanism of protection. Conclusions: This study establishes a structure-guided framework linking phytochemical OCT2 inhibition to nephroprotective potential and identifies methoxylation as a major determinant of OCT2-targeted intervention strategies. Full article

Hydrogen peroxide (H₂O₂) plays a vital role as an eco-friendly oxidizer, extensively used in environmental cleanup, energy transformation, and organic production. Nonetheless, the conventional method of creating anthraquinones is intricate, resulting in significant energy and ecological costs, which calls for the development of more eco-friendly and efficient substitute technologies. The article methodically examines the reaction processes and methods for improving efficiency in photocatalytic H₂O₂ generation in the past few years. This review summarizes the design principles and key structural features of various novel catalytic materials, focusing on light absorption, charge separation and migration, surface redox reactions, and enhanced mass transfer. Approaches such as expanding the range of bandgap absorption, building conjugated structures, and incorporating metal nanoclusters can significantly enhance the efficiency of light absorption. In the charge separation process, constructing built-in electric fields at the interfaces of heterojunctions, homojunctions, and Schottky junctions is crucial for improving reaction efficiency. Additionally, defect engineering may encourage targeted carrier movement and minimize recombination. The review highlights the latest advancements in enhancing selectivity and reducing H₂O₂ breakdown in surface redox reactions, achieved by regulating active sites, introducing new functional groups, and developing dual-channel reaction pathways. Furthermore, constructing three-phase interfaces, regulating asymmetric wettability, and designing cyclic/flow reactors provide innovative engineering solutions to address the challenges of insufficient oxygen supply and large-scale continuous production. Ultimately, the potential for producing H₂O₂ in photocatalytic systems is detailed. Full article

Aloe-emodin is an anthraquinone with a wide range of medicinal applications, including anti-angiogenic, anticancer, antimicrobial, antiviral, anti-inflammatory, and antioxidant activities. In this review, the functionalization of aloe-emodin using various synthetic methods, including alkylation, condensation, esterification, the Finkelstein reaction, and the Kabachnik–Fields reaction was reported. The biological activity of the synthesized aloe-emodin derivatives is discussed, with a focus on their potential future applications as anticancer agents, enzyme inhibitors, anti-inflammatory agents, and antimicrobial agents. This review also discusses the structure–activity relationship (SAR) and the mechanism of action (e.g., molecular docking studies, cell membrane-disrupting capacity, and apoptosis studies). This review highlights the many contributions made towards the design and development of novel, biologically active aloe-emodin derivatives. Full article

Photocatalytic H₂O₂ synthesis emerges as a promising green substitute for the energy-intensive anthraquinone process, yet its efficiency is limited by rapid charge recombination and limited surface active sites in bulk polymeric semiconductors. Herein, we report a topology-directed strategy to tailor the interlayer interactions of graphitic carbon nitride (g-C₃N₄), yielding ultrathin nanosheets with optimized electronic structures. The resulting catalyst exhibits an exceptional H₂O₂ production rate of 1.34 mmol g⁻¹ h⁻¹ under visible light, surpassing bulk g-C₃N₄ by a factor of 2.48. Water contact angle measurements confirm the superior hydrophilicity of the engineered nanosheets, facilitating interfacial mass transfer, while in situ FTIR and EPR spectroscopies unravel that the abundant exposed active sites optimize the adsorption configuration of the key *OOH intermediate and promote the generation of •O₂⁻ and •OH radicals. Regarding charge transfer dynamics, in situ EPR trapping experiments and Kelvin probe force microscopy (KPFM) reveal that the attenuated interlayer coupling induces a robust internal electric field, effectively suppressing carrier recombination and prolonging the exciton lifetime by a factor of 1.249. This work establishes a quantitative structure–activity relationship between interlayer engineering and exciton dynamics, offering a reliable protocol for the rational design of high-performance molecular photocatalysts. Full article

In this study, sodium persulfate was used to oxidize Reactive Black 5 (RB5), an azo dye commonly used in the textile industry, and Reactive Blue 4 (RB4), an anthraquinone dye. Persulfate was activated using Fe(II) and natural solar irradiation to generate sulfate radicals (SO₄^•−), which possess a high redox potential and effectively oxidize organic pollutants in wastewater. Batch experiments demonstrated that the combined use of Fe(II) and solar-activated persulfate achieves up to 99% dye removal. The influence of natural solar irradiation was evaluated under outdoor conditions for both dye solutions, confirming the effectiveness of solar-activated persulfate oxidation. Mineralization was monitored via total organic carbon (TOC) analysis, with up to 97% dissolved organic carbon removal observed at the highest persulfate dosage for RB5. Two activation pathways were examined, and the results indicate that solar activation is a sustainable approach to minimizing energy and chemical consumption. This study also demonstrates the solar activation potential of the Lefke region in Northern Cyprus for advanced oxidation processes. Full article

Climate change and progressive aridification represent a substantial threat to the sustainability of wild medicinal plant resources in Central Asia. Rheum tataricum L.f. (R. tataricum), a mesoxerophytic species with high pharmacological potential and a restricted distribution range, was selected as a model for investigating adaptive responses to combined climatic and edaphic stress. Relationships among climatic parameters, soil agrochemical characteristics, anatomical and morphological traits, and the metabolomic profile of roots and rhizomes were analysed across six ecopopulations distributed along latitudinal and altitudinal gradients in southern and western Kazakhstan. To quantify population-level vulnerability to climatic stress, a Climate Sensitivity Index (CSI) was calculated. All investigated ecopopulations exhibited high climate sensitivity (CSI = 0.30–0.40), indicating persistent climatic stress. Significant altitudinal dependence was detected for such anatomical traits, as primary cortex thickness, as well as for the accumulation of tannins, anthraquinones, and flavonoids. The metabolomic profile was strongly associated with seasonal precipitation, temperature, relative air humidity, soil agrochemical properties, and root elemental composition. These findings demonstrate pronounced anatomical and metabolomic plasticity in R. tataricum, which appears to function as a key adaptive mechanism in arid ecosystems. The results provide a scientific basis for sustainable bioprospecting, conservation of natural populations, and targeted cultivation aimed at obtaining specific metabolomic profiles. Full article

Natural anthraquinones possess a wide range of biological activities, including antibacterial, antiviral, antitumor, and antioxidant effects. However, studies on their ability to inhibit amyloid protein aggregation remain relatively limited. In this study, we used insulin as a model protein to investigate the anti-amyloidogenic potential of several natural anthraquinones. Specifically, the inhibitory mechanisms of five anthraquinones (emodin, anthraflavin, aloe-emodin, alizarin, and purpurin) on insulin amyloid fibrillation were explored in both dilute and crowded environments (PEG 2000 and PEG 4000). Multidisciplinary analytical results demonstrated that all five anthraquinones could effectively inhibit insulin amyloid fibrillation in both dilute and crowded environments. Simultaneously, crowded agents themselves also exhibited inhibitory effects on insulin amyloid aggregation. However, the inhibitory efficacy of anthraquinones was weaker in crowded environments than in dilute solutions, indicating that although crowded agents themselves suppressed insulin aggregation, they may interfere with the regulatory roles of anthraquinones on insulin aggregation behavior. Interestingly, purpurin showed stronger inhibitory activity in crowded environments compared to dilute solutions. Furthermore, fluorescence spectral analysis suggested that the quenching mechanism of insulin by all these anthraquinones was identified as static quenching mode. Molecular simulation studies revealed that anthraquinones could bind to the aggregation-prone regions of insulin via hydrogen bonding and hydrophobic interactions, thereby inhibiting insulin amyloid aggregation. Notably, the inhibitory capacity of these compounds was correlated with their structural features and the binding affinities to insulin. Collectively, this study explored the anti-amyloid activity of anthraquinones, which held significant research value for the development of potential therapeutic agents for amyloid-associated proteinopathies. Full article

Background/Objectives: Cholestasis is a clinically intractable liver disorder. Da-Huang-Xiao-Shi Decoction (DHXSD), a classic traditional Chinese medicine formula, demonstrates notable efficacy, yet the mechanistic basis for its multi-herb synergy remains unclear. The purpose of this study was to decipher the pharmacokinetic interaction underlying the synergy of DHXSD. Methods: A cholestatic rat model was established in male Sprague Dawley rats. Hepatoprotective efficacy was evaluated, and the pharmacokinetics of anthraquinones were profiled. Key interaction mechanisms were investigated using the everted intestinal sac model, the breast cancer resistance protein (BCRP)-overexpressing MDCKII cells, and molecular docking simulations. Results: DHXSD provided significantly stronger hepatoprotection than its principal herb Rheum palmatum L. (DaHuang, DH) alone. This enhanced efficacy correlated with an approximate 2-fold increase in the systemic exposure of rhein compared to DH monotherapy. We identified berberine from Phellodendron amurense Rupr. (Huang Bo, HB) as the key synergist, which potently inhibited the BCRP efflux transporter, thereby enhancing rhein absorption. In contrast, geniposide from Gardenia jasminoides Ellis (Zhi Zi, ZZ) showed minimal effects. Conclusions: This work elucidates a concrete, transporter-mediated pharmacokinetic interaction as the core mechanism underlying herbal synergy in DHXSD. Our findings offer a rational strategy—targeted efflux transporter modulation—for improving the oral bioavailability of challenging drug molecules. Full article

An anthraquinone chromophore displaying a vivid violet color in solution was synthesized and it was thoroughly characterized both spectroscopically and electrochemically, along with its X-ray crystallography. Single crystal X-ray analysis of the chromophore revealed a nearly planar π-conjugated framework with short intermolecular contacts. Cyclic voltammetry revealed two consecutive one-electron reductions, corresponding to the formation of its radical anion and dianion. The spectroelectrochemistry of the chromophore confirmed two distinct and reversible color changes with the stepwise electrochemical reduction. These were quantified via the CIE L a* b* color space. Large optical differences (98%) between the bleached and colored states were observed along with a coloration efficiency of 698 cm²/C. These parameters confirm the anthraquinone is an ideal electrochrome: capable of reversibly switching its colors with applied potential. The three color changes and color bleaching associated with the neutral, radical anion, dianion, and cation, respectively, are also of interest for extending the palette of colors of molecular electrochromes toward panchromatic color tuning with molecular structure for use in smart windows and displays. Full article

Dental caries, one of the most prevalent diseases worldwide, poses a significant threat to oral health. Streptococcus mutans is one of the key pathogenic bacteria associated with dental caries. Numerous Chinese botanical products (CBPs) have been shown to possess antibacterial effects against S. mutans. However, given the wide variety of CBPs that have been investigated, a systematic summary of their effects is needed. To address this need, in the present review, CBPs are categorized into five groups based on their major bioactive components: organic acid-based CBPs, alkaloid-based CBPs, phenol-based CBPs, anthraquinone-based CBPs, and other types. In addition to their chemical composition, the conventional use, pharmacological effects, and toxicity of these CBPs are also discussed, followed by an exploration of their anti-S. mutans mechanisms, including the synthesis of biofilm scaffolds and water-insoluble glucans, energy metabolism and soluble glucan production, acid generation and tolerance, bacterial cell integrity, remineralization processes, and intercellular communication via quorum sensing (QS). In summary, it is suggested that CBPs have considerable benefits in caries prevention and could be promisingly applied in clinical treatments. Full article

Emodin, a trihydroxy-methyl anthraquinone abundant in rhubarb, Polygonum species, and other medicinal plants, exemplifies the therapeutic potential and translational complexity of the broader anthraquinone scaffold. Anthraquinone derivatives have demonstrated antiproliferative, anti-inflammatory, metabolic, cardiovascular, antifibrotic, and immunomodulatory effects, consistently reported across diverse preclinical models, targeting pathways such as NF-κB, PI3K/AKT, MAPKs, AMPK, PPARs, NLRP3, and ferroptosis-related axes. Despite strong preclinical efficacy, clinical development has been limited by unfavorable absorption, distribution, metabolism, and excretion (ADME) characteristics, including poor aqueous solubility, extensive first-pass glucuronidation, and active efflux via intestinal and hepatic transporters. These features result in low and variable systemic exposure, while high local concentrations, particularly in the gastrointestinal tract, contribute to context-dependent toxicity signals that complicate risk assessment. The present review integrates pharmacological, toxicological, and formulation-focused evidence to provide a unified assessment of emodin and the anthraquinone scaffold. Particular emphasis is placed on bidirectional, dose- and context-dependent effects on the liver and kidney; the modulation of cytochrome P450 enzymes, UGTs, and transporters; and emerging preclinical formulation strategies that aim to decouple intrinsic bioactivity from pharmacokinetic limitations. Full article

Safety concerns surrounding skin-lightening agents have intensified following chemical leukoderma linked to rhododendrol. Here, we performed an in vitro safety and hazard profiling comparison of raspberry ketone (RK) and a total anthraquinone fraction from Fallopia multiflora var. cillinerve (Polygonum cillinerve) using an immortalized keratinocyte–melanocyte co-culture model (human HaCaT keratinocytes and murine B10.BR melanocytes, 3:1). Rhododendrol and arbutin were included as contextual references. Following viability-guided range finding, cells were exposed for 48 h and evaluated for melanocyte stress and injury, including ROS generation, UPR/ER-stress activation (PERK/eIF2α–ATF4-associated readouts: ATF4, Hmox1, GADD45a; and IRE1 phosphorylation), IL-8-related chemokine output (CXCL1/KC, a murine functional homolog of IL-8), cell-cycle perturbation, and Caspase-3-associated apoptosis. In parallel, targeted LC–MS metabolomics was performed to resolve pathway-level perturbations. High-dose RK elicited a rhododendrol-like in vitro stress/toxicity signature, characterized by elevated ROS, robust UPR engagement, inflammatory chemokine induction, cell-cycle dysregulation, and pro-apoptotic responses; under viability-adjusted conditions, these effects remained more evident than with arbutin. Metabolomics revealed convergent disturbances between RK and rhododendrol, highlighting purine metabolism as a prominent perturbed pathway and suggesting purine-related metabolites as candidate indicators associated with leukoderma-relevant cellular stress in vitro. In contrast, the anthraquinone fraction did not trigger oxidative or ER stress within the tested range and exhibited a more favorable in vitro safety profile, including reduced ROS. Full article