A novel dibenzo[a,c]phenazine-based fluorescent probe for fast and selective detection of thiophenols in environmental water.

We herein report a novel dibenzo[a,c]phenazine-based fluorescent probe with fast response to thiophenols over a wide pH range from 5 to 13. The probe possesses a large Stokes shift (120 nm). More importantly, it displays a high selectivity and sensitivity for thiophenols in the presence of other analytes such as biothiols and common metal ions. A good linear relationship between the fluorescence intensity at 570 nm and the thiophenol concentration in the range of 0-20 µM was observed with a low detection limit at 40 nM. In addition, it has been successfully applied to detect thiophenols in environmental water (such as seawater, tap water and spring water) with high recovery, which confirmed its potential value in environmental monitoring.

DFT and Raman study of all-trans astaxanthin optical isomers.

Astaxanthin (AST) is a xanthophyll carotenoid widely distributed in aquatic animals, which has many physiological functions such as antioxidant, anti-inflammatory, anti-hypertensive and anti-diabetic activities. AST has three optical isomers, including a pair of enantiomers (3S,3'S and 3R,3'R) and a meso form (3R,3'S). Different optical isomers have differences in a variety of physiological functions. Traditionally, High Performance Liquid Chromatography (HPLC) has been used to distinguish these isomers. In this work, it was found that Raman spectroscopy can be employed to distinguish the three optical isomers. The intensities of two Raman bands at 1190 and 1215 cm-1 of three isomers are different. Density Functional Theory (DFT) calculations are performed to analyze the spectral differences. The mainly occupied conformers of these three optical isomers are speculated and identified.

Adonis amurensis Is a Promising Alternative to Haematococcus as a Resource for Natural Esterified (3S,3'S)-Astaxanthin Production.

Astaxanthin (AST) characteristics and pigment productivity of Adonis amurensis, one of the few AST-producing higher plants, have not yet been studied extensively. In this study, the geometrical and optical isomers of AST in different parts of the A. amurensis flower were determined in detail, followed by a separation of the all-trans AST using HPLC chromatography. AST extracted from the flower accounted for 1.31% of the dry weight (dw) and mainly existed in the di-esterified form (>86.5%). The highest concentration was found in the upper red part of the petal (3.31% dw). One optical isomer (3S, 3'S) of AST, with five geometrical isomers (all-trans, 9-cis, 13-cis, 15-cis, and di-cis) were observed in all parts of the flower. All-trans AST was the predominant geometrical isomer accounting for 72.5% of the total content of geometric isomers in total flower, followed by the 13-cis, and 9-cis isomers. The all-trans AST isomer was also isolated, and then purified by HPLC from the crude oily flower extract, with a 21.5% recovery yield. The cis-AST extracted from the combined androecium and gynoecium gives a very strong absorption in the UVA region due to a high level of cis, especially di-cis, isomers, suggesting a prospective use in the preparation of anti-ultraviolet agents. The production cost of AST from Adonis flowers can be as low as €388-393/kg. These observations together with other factors such as the low technology requirement for plant culturing and harvesting suggest Adonis has great potential as a resource for natural esterified (3S,3'S)-AST production when compared with Haematococcus culturing.

Discovery of 5-(3-bromo-2-(2,3-dibromo-4,5-dimethoxybenzyl)-4,5-dimethoxybenzylidene)thiazolidine-2,4-dione as a novel potent protein tyrosine phosphatase 1B inhibitor with antidiabetic properties.

Protein tyrosine phosphatase 1B (PTP1B) is a well-validated target in therapeutic interventions for type 2 diabetes mellitus (T2DM), however, PTP1B inhibitors containing negatively charged nonhydrolyzable pTyr mimetics are difficult to convert to the corresponding in vivo efficacy owing to poor cell permeability and oral bioavailability. In this work, molecules bearing less acidic heterocycle 2,4-thiazolidinedione and hydantoin were designed, synthesized and evaluated for PTP1B inhibitory potency, selectivity and in vivo antidiabetic efficacy. Among them, compound 5a was identified as a potent PTP1B inhibitor (IC50 = 0.86 µM) with 5-fold selectivity over the highly homologous TCPTP. Long-term oral administration of 5a at a dose of 50 mg/kg not only significantly reduced blood glucose levels, triglycerides (TG) and low-density lipoprotein cholesterol (LDL-C) levels but also ameliorated insulin sensitivity in diabetic BKS db mice. Moreover, 5a enhanced the insulin-stimulated phosphorylation of IRß, IRS-1 and Akt in C2C12 myotubes. A histopathological evaluation of liver and pancreas demonstrated that 5a increased liver glycogen storage and improved islet architecture with more ß-cells and fewer α-cells in diabetic mice. Thus, our work demonstrated that compound 5a could serve as a lead compound for the discovery of new antidiabetic drugs.

16S rRNA Sequencing and Metagenomics Study of Gut Microbiota: Implications of BDB on Type 2 Diabetes Mellitus.

Gut microbiota has a critical role in metabolic diseases, including type 2 diabetes mellitus (T2DM). 3-bromo-4,5-bis(2,3-dibromo-4,5-dihydroxybenzyl)-1,2-benzenediol (BDB) is a natural bromophenol isolated from marine red alga Rhodomela confervoides. Our latest research showed that BDB could alleviate T2DM in diabetic BKS db mice. To find out whether BDB modulates the composition of the gut microbiota during T2DM treatment, 24 BKS db diabetic mice were randomly grouped to receive BDB (n = 6), metformin (n = 6), or the vehicle (n = 6) for 7 weeks in a blinded manner. Non-diabetic BKS mice (n = 6) were used as normal control. Diabetic mice treated with BDB or metformin demonstrated significant reductions in fasting blood glucose (FBG) levels compared with the vehicle-treated mice in the 7th week. Pyrosequencing of the V3-V4 regions of the 16S rRNA gene revealed the changes of gut microbiota in response to BDB treatment. The result demonstrated short-chain acid (SCFA) producing bacteria Lachnospiraceae and Bacteroides were found to be significantly more abundant in the BDB and metformin treated group than the vehicle-treatment diabetic group. Remarkably, at the genus levels, Akkermansia elevated significantly in the BDB-treatment group. Metagenomic results indicated that BDB may alleviate the metabolic disorder of diabetic mice by promoting propanoate metabolism and inhibiting starch and sucrose metabolism, amino sugar and nucleotide sugar metabolism. In conclusion, our study suggests that the anti-diabetic effect of BDB is closely related to the modulating structure of gut microbiota and the improvement of functional metabolism genes of intestinal microorganisms.

Antidiabetic activity in vitro and in vivo of BDB, a selective inhibitor of protein tyrosine phosphatase 1B, from Rhodomela confervoides.

BACKGROUND AND PURPOSE: Protein tyrosine phosphatase (PTP) 1B (PTP1B) plays a critical role in the regulation of obesity, Type 2 diabetes mellitus and other metabolic diseases. However, drug candidates exhibiting PTP1B selectivity and oral bioavailability are currently lacking. Here, the enzyme inhibitory characteristics and pharmacological benefits of 3-bromo-4,5-bis(2,3-dibromo-4,5-dihydroxybenzyl)-1,2-benzenediol (BDB) were investigated in vitro and in vivo. EXPERIMENTAL APPROACH: Surface plasmon resonance (SPR) assay was performed to validate the direct binding of BDB to PTP1B, and Lineweaver-Burk analysis of the enzyme kinetics was used to characterise the inhibition by BDB. Both in vitro enzyme-inhibition assays and SPR experiments were also conducted to study the selectivity exhibited by BDB towards four other PTP-family proteins: TC-PTP, SHP-1, SHP-2, and LAR. C2C12 myotubes were used to evaluate cellular permeability to BDB. Effects of BDB on insulin signalling, hypoglycaemia and hypolipidaemia were investigated in diabetic BKS db mice, after oral gavage. The beneficial effects of BDB on pancreatic islets were examined based on insulin and/or glucagon staining. KEY RESULTS: BDB acted as a competitive inhibitor of PTP1B and demonstrated high selectivity for PTP1B among the tested PTP-family proteins. Moreover, BDB was cell-permeable and enhanced insulin signalling in C2C12 myotubes. Lastly, oral administration of BDB produced effective antidiabetic effects in spontaneously diabetic mice and markedly improved islet architecture, which was coupled with an increase in the ratio of ß-cells to α-cells. CONCLUSION AND IMPLICATIONS: BDB application offers a potentially practical pharmacological approach for treating Type 2 diabetes mellitus by selectively inhibiting PTP1B.

Binding properties of marine bromophenols with human protein tyrosine phosphatase 1B: Molecular docking, surface plasmon resonance and cellular insulin resistance study.

Protein tyrosine phosphatase 1B (PTP1B) is a highly validated target for the treatment of type 2 diabetes and obesity. Previous studies have shown that bromophenols from marine red alga Rhodomela confervoides can inhibit PTP1B activity. However, traditional in vitro enzymatic assays may result in false positive activity. Here, we reported a successful application of molecular docking and surface plasmon resonance (SPR) assay for the characterization of small-molecule PTP1B inhibitors with high affinity. First, molecular docking study indicated that six bromophenol compounds preferred to bind PTP1B with open conformation rather than one with closed conformation. Next, SPR study indicated that compound 3 was the most potent and stable PTP1B inhibitor at the nanomolar level. Then Lineweaver-Burk plot data showed that compound 3 was a competitive PTP1B inhibitor. Moreover, compound 3 could improve palmitate-induced insulin resistance in HepG2 cells. Taken together, molecular docking and SPR-based methodology could apply in the development of PTP1B inhibitors with high affinity.

The Fluoro-Thiazolylhydrazone Compound TSC-3C Inhibits Triple Negative Breast Cancer (TNBC) Cell Line Activity by Promoting Apoptosis, Regulating the MAPK Pathway and Inducing Mitochondrial Dysfunction.

Triple negative breast cancer (TNBC) is the most aggressive cancer in women, and despite improved treatments, it remains a major cause of morbidity and mortality. We and others have demonstrated that different hybrid compounds targeting PARP/MAPK or other pathways to inhibit cancer progression may lead to promising therapeutic results. We introduced fluorine to alter the physical properties of the compounds. TSC-3C was one of the generated compounds. Upon treatment with TSC-3C, MDA-MB-231 cell proliferation, invasion, and migration were inhibited. TSC-3C induced MDA-MB-231 cell mitochondrial dysfunction and apoptosis, which may be caused by reducing the level of phosphorylated p44/42 MAPK (ERK1/2) and increasing the level of p-JNK. The present study may help to elucidate the role of the MAPK pathway in the development of breast cancer and may promote further research on halogenated heterocyclic compounds for the treatment of breast cancer.

Effects of a natural PTP1B inhibitor from Rhodomela confervoides on the amelioration of fatty acid-induced insulin resistance in hepatocytes and hyperglycaemia in STZ-induced diabetic rats.

PTP1B is a key negative regulator of insulin signaling transduction, and the inhibition of PTP1B has emerged as a potential therapeutic strategy to treat T2DM. 3,4-Dibromo-5-(2-bromo-6-(ethoxymethyl)-3,4-dihydroxybenzyl)benzene-1,2-diol (BPN), a natural bromophenol isolated from marine red alga Rhodomela confervoides, was found to inhibit PTP1B activity in our previous study. Herein, we identified that BPN functioned as a competitive PTP1B inhibitor and enhanced phosphorylation of IRß, IRS-1 and Akt in palmitate acid-induced insulin-resistant HepG2 cells. Moreover, 2-deoxyglucose uptake technology-based characterization demonstrated that BPN could stimulate glucose uptake in HepG2 cells. Furthermore, the effects of BPN against oxidative stress were investigated and showed that BPN attenuated oxidative stress by attenuating ROS generation. Finally, long-term oral administration of BPN at dose of 20 mg kg-1 significantly reduced blood glucose levels in streptozotocin-induced diabetic mice and no visible toxic effects were observed. Our work is thus expected to provide a natural uncharged PTP1B inhibitor that could be used as a potential lead compound for further research.

Chalcone-analogue fluorescent probes for detecting thiophenols in seawater samples.

Two efficient chalcone fluorescent probes (probe-KCN1 and probe-KCN2) were developed for the detection of thiophenols. Upon gradual addition of thiophenols to the fluorescent probes, the fluorescence intensity of the emission band at 550 nm is enhanced about 40-fold, with a large Stokes shift (130 nm). Probe-KCN1 responds to thiophenols with a good range of linearity and a detection limit of 79 nΜ (R2 = 0.9915), and Probe-KCN2 responds selectively to thiophenols over other amino acids, common metal ions and other potential interferents with a detection limit of 96 nM (R2 = 0.9978). The low-toxicity probe has been successfully used to detect thiophenols in samples of seawater. These results demonstrate that Probe-KCN is a class of specific probes that might provide a simple way to monitor changes in thiophenols at low concentrations in seawater samples.

Discovery of Natural Dimeric Naphthopyrones as Potential Cytotoxic Agents Through ROS-Mediated Apoptotic Pathway.

A study on the secondary metabolites of Aspergillus sp. XNM-4, which was derived from marine algae Leathesia nana (Chordariaceae), led to the identification of one previously undescribed (1) and seventeen known compounds (2-18). Their planar structures were established by extensive spectroscopic analyses, while the stereochemical assignments were defined by electronic circular dichroism (ECD) calculations. The biological activities of the compounds were assessed on five human cancer cell lines (PANC-1, A549, MDA-MB-231, Caco-2, and SK-OV-3), and one human normal cell line (HL-7702) using an MTT [3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl tetrazolium bromide] assay. Among them, the dimeric naphthopyrones 7, 10 and 12 exhibited potent cytotoxicity. Further mechanism studies showed that 12 induced apoptosis, arrested the cell cycle at the G0/G1 phase in the PANC-1 cells, caused morphological changes and generated ROS; and it induces PANC-1 cells apoptosis via ROS-mediated PI3K/Akt signaling pathway.

Highly Selective Protein Tyrosine Phosphatase Inhibitor, 2,2',3,3'-Tetrabromo-4,4',5,5'-tetrahydroxydiphenylmethane, Ameliorates Type 2 Diabetes Mellitus in BKS db Mice.

Protein tyrosine phosphatase 1B (PTP1B) is a widely confirmed target of the type 2 diabetes mellitus (T2DM) treatment. Herein, we reported a highly specific PTP1B inhibitor 2,2',3,3'-tetrabromo-4,4',5,5'-tetrahydroxydiphenylmethane (compound 1), which showed promising hypoglycemic activity in diabetic BKS db mice. With the IC50 value of 2.4 µM, compound 1 could directly bind to the catalytic pocket of PTP1B through a series of hydrogen bonds. Surface plasmon resonance analysis revealed that the target affinity [KD (equilibrium dissociation constant) value] of compound 1 binding to PTP1B was 2.90 µM. Moreover, compound 1 could activate the insulin signaling pathway in C2C12 skeletal muscle cells. We further evaluated the long-term effects of compound 1 in diabetic BKS db mice. Notably, oral administration of compound 1 significantly reduced the blood glucose levels of diabetic mice with increasing insulin sensitivity. In addition, the dyslipidemia of diabetic mice was also significantly improved by compound 1 gavage. The histological experiments showed that compound 1 treatment significantly ameliorated the disordered hepatic and pancreatic architecture and increased the glycogen content in the liver tissues as well as improved the insulin secretion function of pancreas. Taken together, our results manifested that the natural product compound 1 was a highly specific PTP1B inhibitor, which could activate insulin signaling pathway and ameliorate hyperglycemia and dyslipidemia in diabetic BKS db mice.

Design and Synthesis of a Fluorescent Probe with a Large Stokes Shift for Detecting Thiophenols and Its Application in Water Samples and Living Cells.

A turn-on florescent probe (probe-KCP) was developed for highly selective detection of thiophenols based on a donor-excited photo-induced electron transfer mechanism. Herein, the synthesis of the probe, a chalcone derivative, through a simple straightforward combination of a carbazole-chalcone fluorophore with a 2,4-dinitrophenyl functional group. In a kinetic study of the probe-KCP for thiophenols, the probe displayed a short response time (~30 min) and significant fluorescence enhancement. In selection and competition experiments, the probe-KCP exhibited excellent selectivity for thiophenols over glutathione (GSH), cysteine (Cys), sodium hydrosulfide (NaSH), and ethanethiol (C2H5SH) in addition to common anions and metal ions. Using the designed probe, we successfully monitored and quantified thiophenols, which are highly toxic. This turn-on fluorescence probe features a remarkably large Stokes shift (130 nm) and a short response time (30 min), and it is highly selective and sensitive (~160-fold) in the detection of thiophenols, with marked fluorescence in the presence of thiophenols. probe-KCP responds to thiophenols with a good range of linearity (0⁻15 µM) and a detection limit of 28 nM (R² = 0.9946) over other tested species mentioned including aliphatic thiols, thiophenol analogues, common anions, and metal ions. The potential applications of this carbazole-chalcone fluorescent probe was successfully used to determine of thiophenols in real water samples and living cells with good performance and low cytotoxicity. Therefore, this probe has great potential application in environment and biological samples.

Design, synthesis and biological evaluation of novel pyrimidinedione derivatives as DPP-4 inhibitors.

A series of novel pyrimidinedione derivatives were designed and evaluated for in vitro dipeptidyl peptidase-4 (DPP-4) inhibitory activity and in vivo anti-hyperglycemic efficacy. Among them, the representative compounds 11, 15 and 16 showed excellent inhibitory activity of DPP-4 with IC50 values of 64.47 nM, 188.7 nM and 65.36 nM, respectively. Further studies revealed that compound 11 was potent in vivo hypoglycemic effect. The structure-activity relationships of these pyrimidinedione derivatives had been discussed, which would be useful for developing novel DPP-4 inhibitors as treating type 2 diabetes.

Recent progress of the development of dipeptidyl peptidase-4 inhibitors for the treatment of type 2 diabetes mellitus.

Diabetes is a fast growing chronic metabolic disorder around the world. Dipeptidyl peptidase-4 (DPP-4) is a new promising target during type 2 diabetes glycemic control. Thus, a number of potent DPP-4 inhibitors were developed and play a rapidly evolving role in the management of type 2 diabetes in recent years. This article reviews the development of synthetic and natural DPP-4 inhibitors from 2012 to 2017 and provides their physico-chemical properties, biological activities against DPP-4 and selectivity over dipeptidyl peptidase-8/9. Moreover, the glucose-lowering mechanisms and the active site of DPP-4 are also discussed. We also discuss strategies and structure-activity relationships for identifying potent DPP-4 inhibitors, which will provide useful information for developing potent DPP-4 drugs as type 2 diabtes treatments.

A Novel Bromophenol Derivative BOS-102 Induces Cell Cycle Arrest and Apoptosis in Human A549 Lung Cancer Cells via ROS-Mediated PI3K/Akt and the MAPK Signaling Pathway.

Bromophenol is a type of natural marine product. It has excellent biological activities, especially anticancer activities. In our study of searching for potent anticancer drugs, a novel bromophenol derivative containing indolin-2-one moiety, 3-(4-(3-([1,4'-bipiperidin]-1'-yl)propoxy)-3-bromo-5-methoxybenzylidene)-N-(4-bromophenyl)-2-oxoindoline-5-sulfonamide (BOS-102) was synthesized, which showed excellent anticancer activities on human lung cancer cell lines. A study of the mechanisms indicated that BOS-102 could significantly block cell proliferation in human A549 lung cancer cells and effectively induce G0/G1 cell cycle arrest via targeting cyclin D1 and cyclin-dependent kinase 4 (CDK4). BOS-102 could also induce apoptosis, including activating caspase-3 and poly (ADP-ribose) polymerase (PARP), increasing the Bax/Bcl-2 ratio, enhancing reactive oxygen species (ROS) generation, decreasing mitochondrial membrane potential (MMP, ΔΨm), and leading cytochrome c release from mitochondria. Further research revealed that BOS-102 deactivated the PI3K/Akt pathway and activated the mitogen-activated protein kinase (MAPK) signaling pathway resulting in apoptosis and cell cycle arrest, which indicated that BOS-102 has the potential to develop into an anticancer drug.

Discovery of Novel Bromophenol Hybrids as Potential Anticancer Agents through the Ros-Mediated Apoptotic Pathway: Design, Synthesis and Biological Evaluation.

A series of bromophenol hybrids with N-containing heterocyclic moieties were designed, and their anticancer activities against a panel of five human cancer cell lines (A549, Bel7402, HepG2, HCT116 and Caco2) using MTT assay in vitro were explored. Among them, thirteen compounds (17a, 17b, 18a, 19a, 19b, 20a, 20b, 21a, 21b, 22a, 22b, 23a, and 23b) exhibited significant inhibitory activity against the tested cancer cell lines. The structure-activity relationships (SARs) of bromophenol derivatives were discussed. The promising candidate compound 17a could induce cell cycle arrest at G0/G1 phase and induce apoptosis in A549 cells, as well as caused DNA fragmentations, morphological changes and ROS generation by the mechanism studies. Furthermore, compound 17a suppression of Bcl-2 levels (decrease in the expression of the anti-apoptotic proteins Bcl-2 and down-regulation in the expression levels of Bcl-2) in A549 cells were observed, along with activation caspase-3 and PARP, which indicated that compound 17a induced A549 cells apoptosis in vitro through the ROS-mediated apoptotic pathway. These results might be useful for bromophenol derivatives to be explored and developed as novel anticancer drugs.

A novel fluorinated thiosemicarbazone derivative- 2-(3,4-difluorobenzylidene) hydrazinecarbothioamide induces apoptosis in human A549 lung cancer cells via ROS-mediated mitochondria-dependent pathway.

Thiosemicarbazone, a class of compounds with excellent biological activity, especially antitumor activity, have attracted wide attention. In this study, a novel fluorinated thiosemicarbazone derivative, 2-(3,4-difluorobenzylidene) hydrazinecarbothioamide (compound 1) was synthesized and its antitumor activities were further investigated on a non-small cell lung cancer cell line (A549) along with its underlying mechanisms. Compound 1 showed significant anti-proliferative activity on A549 cells, which was further proved by colony formation experiment. Compound 1 also inhibits the invasion of A549 cells in a trans-well culture system. Moreover, compound 1 markedly induced apoptosis on A549 cells, and the ratio of Bcl-2/Bax was decreased while the amount of p53, Cleaved-Caspase 3 and Cleaved-PARP expression were increased significantly. Compound 1 decreased the mitochondrial membrane potential, while the content of reactive oxygen was increased obviously. It is revealed that compound 1 mediated cell cycle arrest in G0/G1 phase by reducing G1 phase dependent proteins, CDK4 and Cyclin D1. As a result, it is indicated that compound 1 induced apoptosis on A549 cells was realized by regulating ROS-mediated mitochondria-dependent signaling pathway.

Design of antitumor agents containing carbohydrate based on GLUT1, and evaluation of antiproliferative activity.

A series of novel carbohydrate-modified antitumor compounds were designed based on glucose transporter 1 (GLUT1), and evaluated for their anticancer activities against four cancer cell lines. The ribose derivatives (compound 9 and 10) exhibited modest inhibitory activity. The compound 9 significantly inhibited the migration of A549 cell and induced A549 cell apoptosis in a concentration-dependent manner. Moreover, compound 9 blocked A549 cells at the G0/G1 phase. The cellular uptake studies suggested that ribose-modified compound 9 could be taken through GLUT1 in A549 cell line.

Discovery and evaluation of the hybrid of bromophenol and saccharide as potent and selective protein tyrosine phosphatase 1B inhibitors.

Protein tyrosine phosphatase 1B (PTP1B) is a key negative regulator of insulin signaling pathway. Inhibition of PTP1B is expected to improve insulin action. Appropriate selectivity and permeability are the gold standard for excellent PTP1B inhibitors. In this work, molecular hybridization-based screening identified a selective competitive PTP1B inhibitor. Compound 10a has IC50 values of 199 nM against PTP1B, and shows 32-fold selectivity for PTP1B over the closely related phosphatase TCPTP. Molecule docking and molecular dynamics studies reveal the reason of selectivity for PTP1B over TCPTP. Moreover, the cell permeability and cellular activity of compound 10a are demonstrated respectively.