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BACKGROUND: Theabrownins (TBs) are one of most important quality components in dark tea, but have not been produced industrially. In this study, the aqueous extract was obtained from Pu‐erh ripe tea, one kind of dark tea. Caffeine, theaflavin, catechin and saponin were removed by trichloromethane, ethyl acetate and n‐butanol in turn to obtain a TB isolate. The TB isolate was subjected to column chromatography using a macroporous resin HPD‐750 and eluted with a gradient of 0–700 g kg−1 ethanol aqueous solution. Four fractions were obtained, and named as TBs‐FC1, TBs‐FC2, TBs‐FC3 and TBs‐FC4. RESULTS: These four fractions contained polysaccharides and no small molecules such as catechins, caffeine and theaflavins as well as average molecular weights of 123.000 kDa, 23.380 kDa, 89.870 kDa and 106.600 kDa. It was revealed that they were complexes of TBs and tea polysaccharide conjugates (TPCs). Ultraviolet‐visible (UV‐visible) and infrared (IR) spectra showed the properties of TBs and TPCs. Their zeta potentials ranged from −13.40 mV to −38.80 mV in aqueous solutions at pH 3.0–9.0. CONCLUSION: This study reveals that TBs do not exist in free state but in combined state in dark tea, which provide the theoretical basis for the industrialization of TBs. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Bamboo leaf polysaccharides have a variety of biological activities, such as antioxidation and immunomodulation, but their emulsifying properties have rarely been involved. In this study, polysaccharide conjugates were extracted from bamboo leaf residue under alkaline conditions, referred to as BLPC- A. BLPC-A aqueous solution and medium-chain triglycerides (MCT) were used as the raw materials to prepare oil-in-water (O/W) high internal phase emulsions (HIPEs). As a single emulsifier, BLPC-A could stabilize 80% (w/w) MCT. With the increase in the BLPC-A concentration (1.00–2.50%, w/w), the average particle size (APS) (d 3,2) of the HIPEs gradually decreased, while the viscoelasticity of the HIPEs gradually increased. Furthermore, all HIPEs had good stability during a 30-day storage period at 25 ℃. Among them, after the BLPC-A HIPEs (2.00%, w/w) underwent heat treatment at 40–90 °C, the APS (d 3,2) increased from 10.51 µm to 13.01 µm, the tightly packed structure was well maintained, and the HIPEs had good storage stability and enhanced viscoelasticity. When the BLPC-A HIPEs (2.00%, w/w) were exposed to different concentrations of Na+ (0.50–1.00 M) and Ca2+ (0.01–0.05 M), the APS (d 3,2) decreased from 8.55 µm to 7.53 µm, and increased from 10.62 µm to 36.54 µm, respectively, while the viscoelasticity was enhanced for each, though HIPEs exposed to Na+ had superior storage stability. These results show that BLPC-A can be used as a natural emulsifier with a good emulsifying effect, while further providing support for the effective utilization of bamboo leaf resources. [Display omitted] ● HIPEs were prepared at the concentrations of 1.0–2.5 wt% BLPC-A with the inner phase ratio up to 80 wt%. ● HIPEs stabilized with BLPC-A showed excellent rheological and storage (30 days) stability. ● BLPC-A HIPEs have the ability to resist high temperature (40–90 ℃) and salt ions (0.5–1.0 M Na+). [ABSTRACT FROM AUTHOR]

[Display omitted] • Stability of TPC-W and TPC-A aqueous solution treated at 300 and 500 MPa was enhanced. • CD results revealed that UHP led to the steric structure of TPC-W and TPC-A to unfold. • One component of TPC-A treated at 300 and 500 MPa was dissociate into two. • The zeta potential absolute values of UHP treated TPC-W and TPC-W were increased. Previous studies have shown that ultra-high pressure (UHP) processing technology to extract, prepare, and sterilize tea beverages (tea infusion) significantly increases the extraction rate of tea polyphenols (catechins), free amino acids, caffeine, and other small molecules in green tea, besides sterilizing and inactivating residual oxidases, such as polyphenol oxidase and peroxidase. UHP avoids the deterioration of color and aroma, as high-quality green tea infusions were obtained with nutritional value and flavor quality close to the original tea. However, the effect of UHP on polysaccharides in green tea infusions is unclear. The water-extracted tea polysaccharide conjugates (TPC-W) and alkali-extracted tea polysaccharide conjugates (TPC-A) from low-grade green tea were subjected to a UHP treatment of 100, 300, and 500 MPa for 5, 12, and 25 min. The circular dichroism (CD) spectra results showed that UHP transformed the secondary structure of the TPC-W and TPC-A from compact and ordered α-helices and β-sheets to disordered β-turns and random coils; one component of TPC-A was dissociated into two components. The absolute values of the zeta potential of TPC-W treated with 100, 300, and 500 MPa increased by 2.4–5.6, 5.3–8.0, and 5.5–9.1 mV, while those of TPC-A increased by 0.5–2.8, 3.5–5.5, and 4.8–6.9 mV, respectively. The stability of TPC-W and TPC-A aqueous solutions treated with 300 and 500 MPa was enhanced during storage at 5°C. These findings will contribute to applying UHP for tea beverage processing and in-depth investigations on the physiochemical properties of TPC, particularly the protein moiety. [ABSTRACT FROM AUTHOR]

Abstract: An iminofluorescein-Cu2+ ensemble probe was prepared for the detection of thiols in aqueous solution. In HEPES buffer, among various amino acids, only cysteine (Cys) induced fluorescence enhancement of Cu2+ ensemble. The mechanism was proposed that addition of Cys induced decomplexation of Cu2+ from weak-fluorescent ensemble, followed by hydrolytic cleavage of the resulted Schiff base to give a strongly fluorescent fluoresceinaldehyde. By fluorescence titration using 2μM iminofluorescein-Cu2+ ensemble probe, the detection limit for Cys was evaluated to be 9μM with a signal-to-noise ratio of 3. Furthermore, the confocal microscopy experiments demonstrated that this sensor was potential for the imaging of thiols in living cells. [Copyright &y& Elsevier]

Abstract In this work, we reported a di-nuclear Cu(II) complex bearing double guanidinium arms for sensing pyrophosphate (PPi) with high selectivity and sensitivity. Using pyrocatechol violet (PV) and esculetine as colorimetric and fluorescent indicators respectively, the copper complex-indicator ensemble exhibited remarkable colorimetric and fluorescent changes upon addition of PPi in the aqueous solution. Comparing to the di-nuclear Cu(II) complex without guanidinium arms, the introduction of positively-charged guanidinium groups lead to 2.6 × 104-fold enhancement on the binding affinity toward pyrophosphate (PPi). The ensemble containing copper complex and PV was further used to monitor the hydrolysis of PPi catalyzed by pyrophosphatase (PPase). Graphical abstract Comparing to the di-nuclear Cu(II) complex without guanidinium arms, the introduction of positively-charged guanidinium groups lead to 2.6 × 104-fold enhancement on the binding affinity toward pyrophosphate (PPi). Image 1 Highlights • A new Di-nuclear Cu(II) complex-based chemosensor which bearing guanidinium arms for pyrophosphate (PPi) was synthesized. • The introduction of guanidinium groups led to 2.6 × 104-fold enhancement on the binding affinity toward PPi. • The chemosensor was applied to monitor the hydrolysis reaction of PPi. [ABSTRACT FROM AUTHOR]

Esterases are common (biological catalyst) that play an essential role in regulating the physiological processes of organisms, in addition to contributing to disease prevention. Herein, we report the design and synthesis of an esterase-activated chemiluminescent probe (CL-EA) for the selective detection of esterases. Using the 1,2-dioxetane scaffold as the chemiluminescent platform and acetoxymethyl ether as the recognition group, the present probe was successfully lighted in the presence of esterases. As a result, a strong chemiluminescent signal was generated in an aqueous solution, thereby allowing the highly sensitive and specific detection of esterases. Furthermore, the probe is used to screen the activity of three plastic-degrading enzymes and image esterases in live cells and in a mouse model. [Display omitted] • A chemiluminescent probe for detection of esterases activity is developed. • The probe is used to screen the activity of three plastic-degrading enzymes. • The probe is applied to imaging of esterases in living cells and in vivo. [ABSTRACT FROM AUTHOR]

In this paper, highly sensitive and selective fluorescent probe 1 for GSH is designed and synthesized based on modulation of the excited-state intramolecular proton transfer (ESIPT) process of 2-(2′-hydroxy-3′-ethoxyphenyl)benzothiazole. Upon introducing GSH in neutral solution containing CTAB micelles, dinitrophenyl, the protecting group of the probe, is removed via the nucleophilic substitution, thereby retrieving the ESIPT process of 2-(2′-hydroxy-3′-ethoxyphenyl)benzothiazole, which results in a fluorescence enhancement at 485 nm. Additionally, the fluorescence intensity of the probe is linearly proportional to GSH concentration ranging from 0 to 100 μM and the obtained detection limit is as low as 0.81 μM. The enhanced selectivity toward GSH over Cys and Hcy is also attributed to one more carboxyl group in GSH. Importantly, the probe is successfully utilized for monitoring GSH in living HeLa cells. [ABSTRACT FROM AUTHOR]

Polydiacetylenes (PDAs), as smart materials with very unique properties, are widely used for sensing various analytes. Derived from the monomers 1-(1,4,7,10,13-pentaoxa-16-aza-cyclooctadec-16-yl)-pentacosa-10,12-diynamide (PCDA-L) and 10,12-pentacosadiynoic acid (PCDA), we report a conjugated polymer (poly-PDA-L) for lead ions detection. The PDA sensing system showed rapid fluorescent and colorimetric response and high sensitivity to Pb 2+ in 100% aqueous solution, as well as the color change was obvious to the naked eye. Excellent fluorescence response change and a good linear relationship between fluorescent PDA intensity and Pb 2+ amount were observed based on fluorescence microscope images, with a detection limit of 1 μM. The fluorescent and colorimetric responses were attributed to the binding between the moiety 1-aza-18-crown-6-ether of poly-PDA-L and Pb 2+ . This interaction further disturbs the backbone of the PDA polymer, allowing the release of the strain energy imposed on the alkyl side chains generated during polymerization, leading to the observed change in optical properties. [ABSTRACT FROM AUTHOR]

A new fluorescein-based probe is found to be sensitive and selective for the detection of hypochlorite anion in aqueous buffer solution. The probe displays high water solubility, pH-independent fluorescence, and biocompatibility. A possible detection mechanism is that HOCl oxidizes the C N bond into aldehyde, resulting in bright emission. Results show that the probe has a 7.3 nM detection limit to hypochlorite anion. In addition, the probe is successfully utilized for monitoring endogenously produced hypochlorite in living macrophage cells upon stimulation. [ABSTRACT FROM AUTHOR]

A new fluorescein-based fluorescent probe for the detection of Au 3+ has been developed. This probe was derived from 4′,5′-fluoresceindicarboxaldehyde and exhibited highly selective and sensitive response toward gold(III) ions in aqueous solution. There is a good linear relationship between the fluorescence intensity at 523 nm and the concentrations of Au 3+ ranging from 0 μM to 60 μM, which makes it effective for the detection of Au 3+ . The limit of detection (LOD) was evaluated to be 0.07 μM based on S/N = 3. The fluorescence enhancement was attributed to the irreversible C N bond hydrolysis that occurred to this probe in the presence of Au 3+ , generating the fluorescent 4′,5′-fluoresceindicarboxaldehyde. Furthermore, the imaging experiments indicated that this probe is cell-permeable and can be used to detect Au 3+ within living cell. [ABSTRACT FROM AUTHOR]

Abstract: A quinoline-based fluorescent chemosensor was reported for the simultaneous detection of Zn2+ and Cd2+ in aqueous solution. In HEPES buffer, among various metal ions, only Zn2+ and Cd2+ exhibited fluorescence enhancement at 497nm accompanied by the red-shift emission wavelength. The mechanism was proposed that internal charge transfer effect induced by binding with Zn2+ or Cd2+ produced the fluorescence changes. With the addition of cysteine, the fluorescent solution containing sensor and Cd2+ show the decreased fluorescence at 497nm and the increased fluorescence at 420nm, which was attributed to the dissociation of the complex formed by sensor and Cd2+. In contrast, the fluorescence of solution containing sensor and Zn2+ is unchanged with the addition of Cys. Furthermore, the confocal microscopy experiments indicated that this sensor can provide real-time detection for intracellular Zn2+ and Cd2+. [Copyright &y& Elsevier]

Carbon monoxide (CO) is a colorless and odorless gas often used as a fuel and as an important raw material for the synthesis of basic organic compounds in the chemical industry. CO affects respiration and organ coordination in organisms, and is fatal at high concentration. Due to the wide range of industrial applications and biological effects of CO, its research has received considerable attention from researchers. In this study, we designed and synthesized a chemiluminescent sensor CL-CO, which can recognize CO in the presence of palladium chloride (PdCl 2), based on the Schaap's adamantylidene-dioxetane system and allyl ether as the recognition site. In both liquid and solid states, CL-CO can recognize CO gas with high sensitivity and selectivity. This work provides a convenient tool for studying CO gas, and a new application for exploring the adamantylidene-dioxetane system. [Display omitted] • A new chemiluminescence probe for detecting CO was designed. • The probe has very high sensitivity and selectivity for CO released from CORM-3 solution and CO gas. • Whether probe is liquid or solid, it can recognize CO gas. • The detection of gas by chemiluminescence probe is realized in a new way. [ABSTRACT FROM AUTHOR]

• A dioxetane-based chemiluminescent probe for the efficient detection of fluoride ions in vitro and in vivo has been developed. • The dioxetane-based chemiluminescent probe holds superior efficiency for sensing fluoride ions in aqueous environment. • The probe was successfully applied in quantifying fluoride ions in toothpaste and in vivo imaging in living mice. Fluoride plays an important role in our daily life as it associates with a variety of biological and pathological processes. Hence, an analytic method that can detect fluoride ions under physiological conditions with high sensitivity and specificity, and fast response, is needed. Herein, we introduced a dioxetane-based chemiluminescent probe, CL-F, specifically designed for the detection of fluoride ions in physiological environment. The probe CL-F emitted strong green chemiluminescent light within 1 min when incubating with fluoride ions specifically. The linear range for sensing fluoride ions and limit of detection were determined to be 0–30 μM and 0.91 μM, respectively. The probe CL-F was then successfully applied in quantifying fluoride ions in toothpaste and in vivo imaging in living mice, demonstrating CL-F as a promising tool for sensing fluoride ion in vitro and in vivo. [ABSTRACT FROM AUTHOR]