Efficient cleavage of CαCß bonds in lignin using tetrabutylammonium tetrafluoroborate as both the catalyst and auxiliary electrolyte.

Lignin is a promising alternative to fossil resources due to its abundance of benzene ring monomers. However, the stability of the CαCß bond in lignin has hindered its efficient depolymerization. Electrochemical methods for breaking this bond are not well-studied. This paper presents a novel approach for catalytic depolymerization of lignin to produce acetals under mild conditions, without the need for additional catalysts. Under room temperature and in an air atmosphere, the combination of tetrabutylammonium tetrafluoroborate (TBABF4) as an auxiliary electrolyte and methanol (MeOH) as a solvent has shown high selectivity in catalyzing the cleavage of CαCß bonds in lignin. Over 90.0 % of the resulting products are acetals, with the optimal conditions being a substrate concentration of 0.02 M, TBABF4 concentration of 0.008 M, a constant current of 30 mA, and a reaction time of 3 h. This led to a substrate conversion rate of 95.8 % and a product yield of 98.0 % for benzaldehyde dimethyl acetal (Bda). The mechanism study reveals that the tributyl ammonium radical cation decomposed by TBABF4 is adsorbed on the electrode surface. Subsequently, the adsorbed O2 is activated to form superoxide anion radical active species through single electron transfer, which plays a crucial catalytic role. TBABF4 acts as both an auxiliary electrolyte and a catalyst in this process. This research introduces a novel approach for electrocatalytic depolymerization of inert CαCß bonds in lignin, leading to the selective conversion into acetal chemicals.

Study on the efficient electrocatalytic depolymerization of α-O-4 bond in lignin assisted by simple electrolyte.

Lignin is anticipated to serve as a replacement for dwindling fossil fuel resources owing to its abundant sources and renewable nature. The electrochemical oxidation technique for depolymerizing lignin has garnered significant interest for its environmentally friendly and mild operating conditions. Nevertheless, the current utilization of auxiliary electrolytes, predominantly organic bases, ionic liquids, and other specialized substances, poses a constraint on the widespread adoption of this approach. Furthermore, there is a scarcity of instances where electrochemical technology has been employed to depolymerize the α-O-4 bond in lignin for the production of highly selective acetals. In this study, a sodium chloride/methanol (NaCl/MeOH) system was utilized for the direct depolymerization of the α-O-4 bond in a lignin model molecule, specifically benzyl phenyl ether (BPE). The optimal conditions resulted in a 95.2 % conversion rate of the BPE substrate and a high yield of 94.5 % for the main product, benzaldehyde dimethyl acetal(Bda). This research offers a promising approach for the electrocatalytic depolymerization of α-O-4 bonds in lignin, leading to the selective production of acetal chemicals using a common auxiliary electrolyte at room temperature in just 2 h.

High-performance electrochemical sensing platform based on sodium alginate-derived 3D hierarchically porous carbon for simultaneous determination of dihydroxybenzene isomers.

Three-dimensional hierarchically porous carbon (denoted as SA-900) with a microporous, mesoporous and macroporous structure was facilely fabricated via direct carbonization of sodium alginate. SA-900 was fully characterized by N2 adsorption-desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction and Raman spectroscopy to confirm its structure. SA-900 was coated onto a glassy carbon electrode surface to construct an ultrasensitive electrochemical sensing platform (SA-900/GCE). Electrochemical behaviors of hydroquinone (HQ), catechol (CC) and resorcinol (RC) on the SA-900/GCE surface were investigated, and it was found that SA-900 possesses excellent electrocatalytic activity towards them. Experimental conditions including carbonization temperature, pH value, SA-900 concentration, accumulation potential and accumulation time were optimized for quantitative assay. Under optimized conditions, linear ranges for simultaneous determination of HQ, CC and RC are 0.05-1.50 µM, 0.05-1.50 µM and 0.50-15.00 µM, respectively. Detection limits for HQ, CC and RC are calculated to be 0.0183 µM, 0.0303 µM and 0.3193 µM (S/N = 3). The SA-900/GCE based electrochemical sensing platform is applied for determining HQ, CC and RC in lake water samples with satisfactory results.

Glucose-conjugated platinum(IV) complexes as tumor-targeting agents: design, synthesis and biological evaluation.

A new series of glucose-conjugated Pt(IV) complexes that target tumor-specific glucose transporters (GLUTs) was designed, synthesized, and evaluated for their anticancer activities. All six compounds, namely, A1-A6, exhibited increased cytotoxicity that were almost six fold higher than that of oxaliplatin to MCF-7 cells. These Pt(IV) complexes can be reduced to release Pt(II) complexes and cause the death of tumor cells. Simultaneously, the glycosylated Pt(IV) complexes (30.21-91.33 µM) showed lower cytotoxicity that normal LO2 cells compared with cisplatin (5.25 µM) and oxaliplatin (8.34 µM). The intervention of phlorizin as a GLUTs inhibitor increased the IC50 value of the glycosylated Pt(IV) complexes, thereby indicating the potential GLUT transportability. The introduction of glucose moiety to Pt(IV) complexes can effectively enhance the Pt cellular uptake and DNA platination. Results suggested glucose-conjugated Pt(IV) complexes had potential for further study as new anticancer agents.

Synthesis, growth mechanism and photocatalytic H2 evolution of CdS/CuS composite via hydrothermal method.

In recent years, visible light-driven photocatalysts used for confronting energy shortages and environmental pollution have drawn much attention. CdS is regarded as an excellent photoelectric semiconductor for photocatalysis, but photocorrosion and low photocatalytic activity limit its practical application. In order to improve the photocatalytic performance of CdS, we synthesized a II-type CdS/CuS composite via a hydrothermal method in one step. CdS, CuS and the CdS/CuS composite have flower-like structures according to FESEM results. XRD and EDS results confirm that the composite is composed of CdS and CuS, indicating that we have successfully synthesized the CdS/CuS composite. UV-Vis and PL results show that the formation of heterojunction structures with CuS can be used to control the optical properties of CdS. H2 evolution results show that the CdS/CuS composite generates H2 at a rate of 295 µmol g-1 h-1, which is higher than that of CdS.

Glycosylated Platinum(IV) Complexes as Substrates for Glucose Transporters (GLUTs) and Organic Cation Transporters (OCTs) Exhibited Cancer Targeting and Human Serum Albumin Binding Properties for Drug Delivery.

Glycosylated platinum(IV) complexes were synthesized as substrates for GLUTs and OCTs for the first time, and the cytotoxicity and detailed mechanism were determined in vitro and in vivo. Galactoside Pt(IV), glucoside Pt(IV), and mannoside Pt(IV) were highly cytotoxic and showed specific cancer-targeting properties in vitro and in vivo. Glycosylated platinum(IV) complexes 5, 6, 7, and 8 (IC50 0.24-3.97 µM) had better antitumor activity of nearly 166-fold higher than the positive controls cisplatin (1a), oxaliplatin (3a), and satraplatin (5a). The presence of a hexadecanoic chain allowed binding with human serum albumin (HSA) for drug delivery, which not only enhanced the stability of the inert platinum(IV) prodrugs but also decreased their reduction by reductants present in human whole blood. Their preferential accumulation in cancer cells compared to noncancerous cells (293T and 3T3 cells) suggested that they were potentially safe for clinical therapeutic use.

Mono-functionalized glycosylated platinum(IV) complexes possessed both pH and redox dual-responsive properties: Exhibited enhanced safety and preferentially accumulated in cancer cells in vitro and in vivo.

A serious of carbohydrate-conjugated platinum(IV) complexes in the form Pt(L2)(A2)(OH)R based on the clinical drug cisplatin and oxaliplatin were designed, synthesized and evaluated as antitumor agents in vitro and in vivo. The conjugates possessing both pH and redox dual-responsive properties exhibited more potent cytotoxicity in seven different human cancer cell lines and lower toxicity to the normal 3T3 cells than cisplatin, oxaliplatin and even the reported bis-functionalized glycosylated platinum(IV) complexes indicating the enhanced safety of the sugar conjugates. Cellular drug uptake and DNA platination were also superior to cisplatin, oxaliplatin and the reported bis-functionalized ones. Peak current of B7 and B8 with the scan rate of 200mv/s at the concentration of 0.08 mM was 5-fold higher at pH 6.4 than the pH 7.4, indicating that carbohydrate-conjugated mono-functionalized platinum(IV) complexes possessed both pH and redox dual-responsive properties in the cancer cells. The in vivo assays demonstrated that the Pt(IV) compounds could inhibit the growth of MCF-7 tumour and exert more safety than oxaliplatin.

Glycosylated platinum(iv) prodrugs demonstrated significant therapeutic efficacy in cancer cells and minimized side-effects.

Conjugates (A1-A5) of the Pt(iv) derivative (A6) with amino groups from peracetyl glucose, rhamnose and mannose with a propyl amino or ethyl amino linker at the reducing end were synthesized and exhibited significant therapeutic efficacy in tumour cells, especially for prostate cancer (PCa). The antitumor activities are greatly affected by glycosyl groups. Cytotoxic experiments in vitro indicated that the antitumor activities were increased by 5-fold when its Pt(iv) derivative was conjugated to S18 (IC50 = 4.82 ± 0.45 µM) and by 12-fold when conjugated to S21 (IC50 = 1.9 ± 0.67 µM). The mannose substituted Pt(iv) complexes A4 and A5 were also over an order of magnitude more potent towards HeLa, A549, MCF-7 and PC3 than cisplatin and oxaliplatin. Importantly, the glycosylated Pt(iv) derivatives A4 and A5 displayed potential safety for clinical therapeutic exposure with IC50 of 84 µM and 169 µM compared with cisplatin (IC50 = 8 µM) to 3T3. Cellular uptake and DNA platination are higher than cisplatin and oxaliplatin. ESI-MS analysis of A5 binding to 5'-dGMP revealed that bifunctional DNA lesions were formed. The antitumor activities in vivo showed that the MTD and LD50 for A4 and A5 are nearly 4-fold higher than that of oxaliplatin indicating the potential safety for the glycosylated Pt(iv) complexes.

Synthesis and biological evaluations of a series of thaxtomin analogues.

Thaxtomins are a unique family of phytotoxins with unique 4-nitroindole and diketopiperazine fragments possessing potential herbicidal activities. This work presents the total synthesis of natural product thaxtomin C and its analogues. The extensive structure-activity relationship study screens four effective compounds, including thaxtomin A and thaxtomin C. It is indicated that 4-nitro indole fragment is essential for phytotoxicity, while benzyl and m-hydroxybenzyl substituents on the diketopiperazine ring are favorable for the efficacy. The N-methylations on indole and diketopiperazine show weak influence on the herbicidal activities. The four selected compounds show effective herbicidal activities against Brassica campestris, Amaranthus retroflexus, and Abutilon theophrasti, which are comparable or better than dichlobenil, even at a dosage of 187.5 g ha(-1). Moreover, these four compounds show good crop-selective properties to different crops and exhibit moderate protoporphyrinogen oxidase (PPO) enzyme inhibition. The antifungal results indicate that thaxtomin C displays inhibition to a wide range of fungi.