Signaling of chloramine: a fluorescent probe for trichloroisocyanuric acid based on deoximation of a coumarin oxime

A novel hypochlorous acid-activated NIR fluorescent probe with a large Stokes shift for bioimaging and early diagnosis of arthritis

In this work, we synthesized a novel hypochlorous acid-activated near-infrared (NIR) fluorescent probe (RhSBZ) by a strategy of enhancing π-conjugation through modification the 3,6-substituents of xanthene. Specifically designed for HClO bioimaging and arthritis diagnosis, RhSBZ displayed exceptional performance. RhSBZ exhibited a Stokes shift of 148 nm, high sensitivity, excellent selectivity, and a detection limit as low as 4.95 nM for HClO. Especially, upon reaction with HClO, the fluorescence intensity of RhSBZ enhanced dramatically by 61-fold. Notably, RhSBZ not only can detect exogenous and endogenous HClO in MCF-7 cells, but also has impressive imaging depth of up to 140 μm in rat liver tissues. More encouragingly, RhSBZ can be successfully used for the early diagnosis of abdominal inflammation and arthritis in mice. In summary, RhSBZ displayed excellent bioimaging capabilities and will have the potential application in the early diagnosis of inflammation diseases.

Design, synthesis and antifungal evaluation of low bee-toxicity coumarin oxime derivatives

BACKGROUND

Structural modification of natural products is one of the most effective approaches for discovering new agrochemical compounds. Coumarin, a natural product, is widely found in higher plants from the Brassicaceae, Umbelliferae, Leguminosae, and Orchidaceae families. Coumarin and its derivatives exhibit a wide range of biological activities. Based on our previous research, a series of novel coumarin oxime derivatives were designed and synthesized. The preliminary mechanism of action and bee toxicity of the highly active compound were also investigated.

RESULTS

Most of the target compounds exhibited good antifungal activities. Compound 5k demonstrated moderate to strong broad-spectrum antifungal activities against all seven tested pathogenic fungi. Notably, it showed satisfactory antifungal activity against Rhizoctonia solani (median effective concentration = 3.29 μg/mL), surpassing the performance of the commercial coumarin fungicide osthole. In addition, the protective and curative effects of compound 5k against rice sheath blight at 200 μg/mL were 82.1% and 91.4% on detached rice leaves, and 82.5% and 72.5% on potted rice plants, respectively, outperforming osthole. Preliminary mechanistic studies suggested that compound 5k could alter mycelial morphology and increase catalase activity, promoting antioxidant and free radical scavenging functions to activate the plant's defense system. Furthermore, the median lethal dose of compound 5k was found to exceed 200 μg/bee based on an acute contact toxicity test conducted on honeybees.

CONCLUSION

This study demonstrates that coumarin oxime derivatives, with their novel structures, simple synthesis, excellent activity, and low bee toxicity, have the potential to become practical fungicides for plant protection, offering broad application prospects. © 2025 Society of Chemical Industry.

A BODIPY-Based Far-Red-Absorbing Fluorescent Probe for Hypochlorous Acid Imaging

Hypochlorous acid (HClO) is produced by white blood cells to defend against injury and bacteria. However, as one of the reactive oxygen species, high intracellular HClO concentration could lead to chronic diseases that affect the cardiovascular and nervous systems. To monitor HClO concentrations in bio-samples, the fluorescent probe is preferred to have: a) absorbability in the far-red window with reduced light-toxicity and improved tissue penetration depth, b) ratiometric feature for accurate analysis. In this study, we reported a far-red ratiometric HClO fluorescence probe based on BODIPY chromophore and aldoxime sensing group. Not only the color change of the probe solution can be detected by naked eyes, but also the emission ratios (I₆₄₅/I₆₇₀) showed a significant increase upon the introduction of HClO. More importantly, the feasibility of HClO monitoring in bio-samples was demonstrated in vitro using a confocal microscope.

Oxime as a general photocage for the design of visible light photo-activatable fluorophores

Photoactivatable fluorophores have been widely used for tracking molecular and cellular dynamics with subdiffraction resolution. In this work, we have prepared a series of photoactivatable probes using the oxime moiety as a new class of photolabile caging group in which the photoactivation process is mediated by a highly efficient photodeoximation reaction. Incorporation of the oxime caging group into fluorophores results in loss of fluorescence. Upon light irradiation in the presence of air, the oxime-caged fluorophores are oxidized to their carbonyl derivatives, restoring strong fluorophore fluorescence. To demonstrate the utility of these oxime-caged fluorophores, we have created probes that target different organelles for live-cell confocal imaging. We also carried out photoactivated localization microscopy (PALM) imaging under physiological conditions using low-power light activation in the absence of cytotoxic additives. Our studies show that oximes represent a new class of visible-light photocages that can be widely used for cellular imaging, sensing, and photo-controlled molecular release.

Ultrasound-assisted one-pot three-component synthesis of new isoxazolines bearing sulfonamides and their evaluation against hematological malignancies

In the present study, following a one-pot two-step protocol, we have synthesized novel sulfonamides-isoxazolines hybrids (3a-r) via a highly regioselective 1,3-dipolar cycloaddition. The present methodology capitalized on trichloroisocyanuric acid (TCCA) as a safe and ecological oxidant and chlorinating agent for the in-situ conversion of aldehydes to nitrile oxides in the presence of hydroxylamine hydrochloride, under ultrasound activation. These nitrile oxides could be engaged in 1,3-dipolar cycloaddition reactions with various alkene to afford the targeted sulfonamides-isoxazolines hybrids (3a-r). The latter were assessed for their antineoplastic activity against model leukemia cell lines (Chronic Myeloid Leukemia, K562 and Promyelocytic Leukemia, HL-60).

Multicomponent Synthesis of Iminocoumarins via Rhodium-Catalyzed C-H Bond Activation

We herein establish a multicomponent annulation method for the synthesis of valuable iminocoumarins using aryl thiocarbamates, internal alkynes, and sulfonamides as starting materials, which are safe and readily available. The key step is a Rh-catalyzed and sulfur-directed C-H bond activation. Preliminary mechanistic investigations suggested that the nucleophilic attack of the sulfonamide on an active iminium cation finally completes the imine segment.

A "reactive" turn-on fluorescence probe for hypochlorous acid and its bioimaging application

An aza-BODIPY-CNOH probe attached aldoxime group demonstrated the specific detection for hypochlorous acid by the turn-on red emission signal. NMR and HRMS experiments confirmed that the fluorescence originated from the oxidation degradation of the non-fluorescence, aldoxime-based aza-BODIPY-CNOH probe into the red-fluorescence, nitrile oxide-based aza-BODIPY compound aza-BODIPY-CNO. The aza-BODIPY-CNOH probe showed good biocompatibility and was low toxic to living cells as shown from MTT experiments. Living RAW264.7 cells imaging indicated the aza-BODIPY-CNOH probe had good permeability and either exogenous or endogenous HClO caused the intracellular bright-red fluorescence, showing its potential hypochlorous acid-specific sensing ability in biological systems.

7-Dialkylaminocoumarin Oximates: Small Molecule Fluorescent "Turn-On" Chemosensors for Low-Level Water Content in Aprotic Organic Solvents

The water sensing properties of two efficient two-component fluorescent “turn-on” chemo-sensors based on the 7-dialkylaminocoumarin oxime acid-base equilibrium were investigated. Interestingly, although simple frontier orbital analysis predicts an intramolecular photoinduced electron transfer quenching pathway in conjugated oximates, TD-DFT (Time-dependent density functional theory) quantum chemical calculations support non-radiative dark S₁ excited state deactivation as a fluorescence quenching mechanism. Due to the acid-base sensing mechanism and sensitive “turn-on” fluorescent response, both studied coumarin aldoxime chemosensors exhibit rapid response to low-level water content in polar aprotic solvents, with detection limits comparable to chemodosimeters or chemosensors based on interpolymer π-stacking aggregation.

A novel pyridyl triphenylamine-BODIPY aldoxime: Naked-eye visible and fluorometric chemodosimeter for hypochlorite

An aldoxime containing fluorescent probe based on vinylpydine-appended triphenylamine-BODIPY has been designed and used for hypochlorite detection. OX-PPA-BODIPY was developed by introducing an aldoxime group into the 2-position of BODIPY, which can be used for the detection of hypochlorite with a sharp color change from pink to green. The attachment of 4-vinylpyridine moiety to triphenylamine-BODIPY constructs a fluorogen with desirable conjugated system. The probe, which displays extremely weak fluorescence owing to the CN isomerization mechanism at 2-position of BODIPY, responds to HClO/ClO^- through a dramatic enhancement of its fluorescence intensity. This new probe, a naked-eye visible and fluorometric chemodosimeter, exhibits high selectivity and sensitivity toward hypochlorite over other reactive oxygen species (ROS) and anions. The detection is accompanied by a 20-fold increase in fluorescent intensity (Φ_F from 0.02 to 0.43). The detection limit of the probe for hypochlorite is 7.37×10^-7M. Moreover, OX-PPA-BODIPY can be used to detect hypochlorite in real water samples.

Micelle-assisted signaling of peracetic acid by the oxidation of pyreneboronic acid via monomer-excimer switching

A simple fluorescent probe for the industrial oxidant peracetic acid (PAA) was investigated. PAA-assisted oxidative conversion of pyrene-1-boronic acid into 1-hydroxypyrene was used as the signaling tool. Pyreneboronic acid was found to display selective signaling behavior, being more responsive to PAA than to other commonly used practical oxidants such as H2O2 and HOCl. The changes in pyrene monomer fluorescence to excimer were used in the quantitative analysis of PAA. When using the surfactant hexadecyltrimethylammonium bromide as a micellar additive, the signaling of PAA was markedly enhanced. Selective fluorescence signaling of PAA by pyrene-1-boronic acid with a detection limit of 1.5×10(-6)M in aqueous environment was successfully achieved.