Peniditerpenoids A and B: Oxidized Indole Diterpenoids with Osteoclast Differentiation Inhibitory Activity from a Mangrove-Sediment-Derived Penicillium sp.

An unprecedented di-seco-indole diterpenoid, peniditerpenoid A (1), and a rare N-oxide-containing indole diterpenoid derivative, peniditerpenoid B (2), together with three known ones (3-5), were obtained from the mangrove-sediment-derived fungus Penicillium sp. SCSIO 41411. Their structures were determined by the analysis of spectroscopic data, quantum chemical calculations, and X-ray diffraction analyses. Peniditerpenoid A (1) inhibited lipopolysaccharide-induced NF-κB with an IC50 value of 11 µM and further effectively prevented RANKL-induced osteoclast differentiation in bone marrow macrophages. In vitro studies demonstrated that 1 exerted significant inhibition of NF-κB activation in the classical pathway by preventing TAK1 activation, IκBα phosphorylation, and p65 translocation. Furthermore, 1 effectively reduced the level of NFATc1 activation, resulting in the attenuation of osteoclast differentiation. Our findings suggest that 1 holds promise as an inhibitor with significant potential for the treatment of diseases related to osteoporosis.

6-O-angeloylplenolin inhibits osteoclastogenesis in vitro via suppressing c-Src/NF-κB/NFATc1 pathways and ameliorates bone resorption in collagen-induced arthritis mouse model.

One of the effective therapeutic strategies to treat rheumatoid arthritis (RA)-related bone resorption is to target excessive activation of osteoclasts. We discovered that 6-O-angeloylplenolin (6-OAP), a pseudoguaianolide from Euphorbia thymifolia Linn widely used for the treatment of RA in traditional Chinese medicine, could inhibit RANKL-induced osteoclastogenesis and bone resorption in both RAW264.7 cells and BMMs from 1 µM and protect a collagen-induced arthritis (CIA) mouse model from bone destruction in vivo. The severity of arthritis and bone erosion observed in paw joints and the femurs of the CIA model were attenuated by 6-OAP administered at both dosages (1 or 5 mg/kg, i.g.). BMD, Tb.N and BV/TV were also improved by 6-OAP treatment. Histological analysis and TRAP staining of femurs further confirmed the protective effects of 6-OAP on bone erosion, which is mainly due to reduced osteoclasts. Molecular docking indicated that c-Src might be a target of 6-OAP and phosphorylation of c-Src was suppressed by 6-OAP treatment. CETSA and SPR assay further confirmed the potential interaction between 6-OAP and c-Src. Three signaling molecules downstream of c-Src that are vital to the differentiation and function of osteoclasts, NF-κB, c-Fos and NFATc1, were also suppressed by 6-OAP in vitro. In summary, the results demonstrated that the function of c-Src was disrupted by 6-OAP, which led to the suppression of downstream signaling vital to osteoclast differentiation and function. In conclusion, 6-OAP has the potential to be further developed for the treatment of RA-related bone erosion.

Erianin serves as an NFATc1 inhibitor to prevent breast cancer-induced osteoclastogenesis and bone destruction.

INTRODUCTION: Breast cancer-related bone metastasis can lead to skeletal-related events (SREs), which decrease patient quality of life. Inhibition of osteoclastogenesis is a key treatment for SREs; however, the availability of clinical drugs remains limited, and all existing ones disrupt physiological bone formation, while exhibiting no effect on patient survival time. OBJECTIVES: This study aimed to identify a novel osteoclast inhibitor for the treatment of breast cancer-induced SREs. METHODS: The MDA-MB-231 breast cancer cell-induced bone loss model was used to investigate the therapeutic effects of erianin in vivo. Then, we evaluated the inhibitory effects of erianin on osteoclastogenesis and signalling in bone marrow-derived macrophages (BMMs) induced by conditioned medium from MDA-MB-231 breast cancer cells (231 CM) and receptor activator of nuclear factor-κB ligand (RANKL) in vitro. Next, a Cellular Thermal Shift Assay and siRNA-mediate knockdown were performed, to investigate the target of erianin during osteoclast formation. The effects of erianin on human osteoclastogenesis were evaluated using CD14+ monocytes obtained from patients with breast cancer. RESULTS: Erianin effectively improved breast cancer cells-induced bone destruction at doses of 2 and 20 mg/kg/day in vivo, while suppressing osteoclastogenesis and the upregulation of SRC-NFATc1, INTEGRIN ß3-MMP9 signals induced by 231 CM and RANKL in vitro. Furthermore, erianin interacted with NFATc1 but not SRC, and Nfatc1 knockdown eliminated the inhibitory effects of erianin on osteoclastogenesis. Notably, lower expression of NFATc1 positively correlated with longer survival in patients with cancer and a high risk of bone metastasis. We further revealed that 62.5-250 nM erianin suppresses NFATc1 and excessive osteoclastogenesis in CD14+ monocytes from patients with breast cancer. CONCLUSION: Erianin acts as an NFATc1 inhibitor that attenuates breast cancer-induced osteoclastogenesis and bone destruction.

Identifying Marine-Derived Tanzawaic Acid Derivatives as Novel Inhibitors against Osteoclastogenesis and Osteoporosis via Downregulation of NF-κB and NFATc1 Activation.

To discover novel osteoclast-targeting antiosteoporosis leads from natural products, we identified 40 tanzawaic acid derivatives, including 22 new ones (1-8, 14-19, 27-32, 37, and 38), from the South China Sea mangrove-derived fungus Penicillium steckii SCSIO 41025. Penicisteck acid F (2), one of the new derivatives showing the most potent NF-κB inhibitory activity, remarkably inhibited osteoclast generation in vitro. Mechanistically, 2 reduced RANKL-induced IκBα degradation, NF-κB p65 nuclear translocation, the activation and nuclear translocation of NFATc1, and the relevant mRNA expression. NF-κB p65 could be a potential molecular target for 2, which has been further determined by the cellular thermal shift assay, surface plasmon resonance, and the gene knock-down assay. Moreover, 2 could also alleviate osteoporosis in ovariectomized mice by reducing the quantities of osteoclasts. Our finding offered a novel potential inhibitor of osteoclastogenesis and osteoporosis for further development of potent antiosteoporosis agents.

Discovery of a novel anti-osteoporotic agent from marine fungus-derived structurally diverse sirenins.

Thirteen new sirenin derivatives named eupenicisirenins C-O (1-13), along with a biosynthetically related known one (14), were isolated from the mangrove sediment-derived fungus Penicillium sp. SCSIO 41410. The structures, which possessed a rare cyclopropane moiety, were confirmed by extensive analyses of the spectroscopic data, quantum chemical calculations, and X-ray diffraction. Among them, eupenicisirenin C (1) exhibited the strongest NF-κB inhibitory activities, as well as suppressing effects on cGAS-STING pathway. Moreover, 1 showed the significant inhibitory effect on RANKL-induced osteoclast differentiation in bone marrow macrophages cells, and also displayed the therapeutic potential on prednisolone-induced zebrafish osteoporosis. Transcriptome analysis and the following verification tests suggested that its anti-osteoporotic mechanism is related to the extracellular matrix receptor interaction-related pathways. This study provided a promising marine-derived anti-osteoporotic agent for the treatment of skeletal disease.

New Fusarin Derivatives from the Marine Algicolous Fungus Penicillium steckii SCSIO41040.

Five new fusarin derivatives, steckfusarins A-E (1-5), and two known natural products (6, 7), were isolated and identified from the marine algicolous fungus Penicillium steckii SCSIO 41040. The new compounds, including absolute configurations, were determined by spectroscopic analyses and calculated electronic circular dichroism (ECD). All new compounds were evaluated for their antioxidant, antibacterial, antifungal, antiviral, cytotoxic, anti-inflammatory, antioxidant, cholesterol-lowering, acetyl cholinesterase (AChE) enzyme and 6-phosphofructo-2-kinase (PFKFB3) and phosphatidylinositol-3-kinase (PI3K) inhibitory activities. The biological evaluation results revealed that compound 1 exhibited radical scavenging activity against 2,2-diphenyl-1-picrylhydrazylhydrate (DPPH), with an IC50 value of 74.5 µg/mL. In addition, compound 1 also showed weak anti-inflammatory activity at a concentration of 20 µM.

Coupling a Virulence-Targeting Moiety with Ru-Based AMP Mimics Efficiently Improved Its Anti-Infective Potency and Therapeutic Index.

The surge of antibiotic resistance in Staphylococcus aureus calls for novel drugs that attack new targets. Developing antimicrobial peptides (AMPs) or antivirulence agents (AvAs) is a promising strategy to tackle this challenge. However, AMPs, which kill bacteria by disrupting cell membranes, suffer from low stability and high synthesis cost, while AvAs, which inhibit toxin secretion, have relatively poor bactericidal activity. Here, to address their respective shortcomings, we combined these two different antibacterial activities on the same molecular scaffold and developed a Ru-based metalloantibiotic, termed Ru1. Notably, Ru1 exerted remarkable bactericidal activity (MICS = 460 nM) and attenuated bacterial virulence as well. Mechanistic studies demonstrated that Ru1 had two independent targets: CcpA and bacterial membrane integrity. Based on its dual mechanism of action, Ru1 effectively overcame S. aureus resistance and showed high efficacy in a mouse infection model against S. aureus. This study provides a promising approach to confronting bacterial infections.

New Meroterpenoids and Anti-Osteoclastogenic Polyketides from the Mangrove-Derived fungus Arthrinium sp. SCSIO 41306.

Two new meroterpenoids, arthrinones A and B (1 and 2), along with six known compounds (3-8), were obtained from the fungus Arthrinium sp. SCSIO 41306. Comprehensive methods such as chiral-phase HPLC analysis and ECD calculations were applied to determine the absolute configurations. Griseofulvin (5), kojic acid (6), and 1H-indole-3-carboxaldehyde (8) showed inhibition of NF-κB in RAW 264.7 macrophages induced by lipopolysaccharide (LPS) with IC50 values of 22.21, 13.87 and 19.31 µM, respectively. In addition, griseofulvin (5) inhibited receptor activator of NF-κB ligand (RANKL)-induced osteoclast differentiation in a dose-dependent manner without visible evidence of cytotoxicity in bone marrow macrophages (BMMs). This is the first report on the activity of griseofulvin (5) to inhibit osteoclast formation (IC50 10.09±0.21 µM).

Tanzawaic Acid Derivatives from the Marine-Derived Penicillium steckii as Inhibitors of RANKL-Induced Osteoclastogenesis.

Seven new tanzawaic acid derivatives, steckwaic acids E-K (1-7), and one new benzene derivate (8), together with seven known tanzawaic acid analogues (9-16) were isolated from the marine algicolous fungus Penicillium steckii SCSIO 41040. The structures and absolute configurations of these new compounds (1-8) were determined by spectroscopic analyses, X-ray diffraction, and comparison of ECD spectra to calculations. Compounds 2, 10, and 15 inhibited lipopolysaccharide (LPS)-induced nuclear factor kappa-B (NF-κB) with IC50 values of 10.4, 18.6, and 15.2 µM, respectively. Compound 2 could suppress the receptor activator of NF-κB ligand (RANKL)-induced osteoclast differentiation in bone marrow macrophage cells (BMMCs). To the best of our knowledge, this is the first report of osteoclastogenesis inhibitory activity for tanzawaic acid derivatives.

Loss of LXN promotes macrophage M2 polarization and PD-L2 expression contributing cancer immune-escape in mice.

Latexin (LXN) plays an important role in tumorigenesis and inflammatory response and as a tumor suppressor in many tumors. However, whether LXN regulates tumorigenesis through immune regulation remains uncertain. Here, we demonstrate that LXN deficiency increases hematopoietic stem cells, as well as affects the proportion of immune cells in the peripheral system. Animal studies show that mice loss of LXN promotes tumor growth in subcutaneous tumor model and AOM/DSS-induced colorectal cancer model. We found that loss of LXN promotes macrophage M2 polarization and PD-L2 expression in macrophage, thus, inhibits the function of T cells. Adoptive transfer of wild-type macrophage rescues the function of T cells in LXN-deficient mice. LXN deficiency in hematopoietic lineage exacerbates colorectal carcinogenesis, and targeted inhibition of PD-L2 ameliorates cancer growth in LXN-deficient mice. Mechanistically, we demonstrate that LXN inhibits STAT3 transcriptional activity by targeting inhibition of JAK1 in macrophages. LXN deficiency enhances PD-L2 expression rather than PD-L1 in macrophages, which lead to inhibition of T cells in tumor microenvironment. Collectively, we define a critical role of LXN/JAK1/STAT3 signal in macrophage and highlights the potential role of LXN in tumor immune-escape by regulating macrophage polarization, as well as the expression of immune checkpoint PD-L2.

Ruthenium polypyridine complexes with triphenylamine groups as antibacterial agents against Staphylococcus aureus with membrane-disruptive mechanism.

Due to the emergence and wide spread of methicillin-resistant Staphylococcus aureus, the treatment of this kind of infection becomes more and more difficult. To solve the problem of drug resistance, it is urgent to develop new antibiotics to avoid the most serious situation of no drug available. Three new Ru complexes [Ru (dmob)2PMA] (PF6)2 (Ru-1) [Ru (bpy)2PMA] (PF6)2 (Ru-2) and [Ru (dmb)2PMA] (PF6)2 (Ru-3) (dmob = 4,4'-dimethoxy-2,2'-bipyridine, bpy = 2,2'-bipyridine, dmb = 4,4'-dimethyl-2,2'-bipyridine and PMA = N-(4-(1H-imidazo [4,5-f] [1,10] phenanthrolin-2-yl) -4-methyl-N-(p-tolyl) aniline) were synthesized and characterized by 1H NMR, 13C NMR and HRMS. The detailed molecular structure of Ru-3 was determined by single crystal X-ray diffraction. Their antibacterial activities against Staphylococcus aureus (Staphylococcus aureus) were obvious and Ru-3 showed the best antibacterial effect with the minimum inhibitory concentration value of 4 µg ml-1. Therefore, further study on its biological activity showed that Ru-3 can effectively inhibit the formation of biofilm and destroy cell membrane. In vitro hemolysis test showed that Ru-3 has almost negligible cytotoxicity to mammalian red blood cells. In the toxicity test of wax moth insect model, Ru-3 exhibited low toxicity in vivo. These results, combined with histopathological studies, strongly suggest that Ru-3 was almost non-toxic. In addition, the synergistic effect of Ru-3 with common antibiotics such as ampicillin, chloramphenicol, tetracycline, kanamycin and gentamicin on Staphylococcus aureus was detected by chessboard method. Finally, in vivo results revealed that Ru-3 could obviously promote the wound healing of Staphylococcus aureus infected mice.

Synthesis of ruthenium polypyridine complexes with benzyloxyl groups and their antibacterial activities against Staphylococcus aureus.

Four new ruthenium polypyridyl complexes, [Ru(bpy)2(BPIP)](PF6)2 (Ru(II)-1), [Ru(dtb)2(BPIP)](PF6)2 (Ru(II)-2), [Ru(dmb)2(BPIP)](PF6)2 (Ru(II)-3) and [Ru(dmob)2(BPIP)](PF6)2 (Ru(II)-4) (bpy = 2,2'-bipyridine, dtb = 4,4'-di-tert-butyl-2,2'-bipyridine, dmb = 4,4'-dimethyl-2,2'-bipyridine, dmob = 4,4'-dimethoxy-2,2'-bipyridine and BPIP = 2-(3,5-bis(benzyloxyl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline) had been synthesized and characterized. Their antimicrobial activities were investigated against Staphylococcus aureus (S. aureus) and four complexes showed obvious antibacterial effect, especially the minimum inhibition concentration (MIC) value of Ru(II)-3 was only 4 µg/mL. In addition, Ru(II)-3 was able to kill bacteria quickly and inhibit the formation of biofilm. Meanwhile, the cooperative effect between Ru(II)-3 and general antibiotics were tested and the results showed that Ru(II)-3 could enhance the susceptibility of S. aureus to different types of antibiotics. Most importantly, Ru(II)-3 hardly showed cytotoxicity to mammalian erythrocytes both in homelysis experiment and G. mellonella model. After being injected with high doses of the Ru(II)-3in vivo, the G. mellonella worms still exhibited high survival rates. Finally, a mouse skin infection model and G. mellonella infection model was built to determine the antibacterial activity of Ru(II)-3in vivo. The antibacterial mechanism of Ru(II)-3 was probably related to the membrane-disruption. Taken together, ruthenium polypyridine complexes with benzyloxyl groups had the potential to develop an attractive and untraditional antibacterial agent with new mode of action.

Ruthenium(II) complexes targeting membrane as biofilm disruptors and resistance breakers in Staphylococcus aureus bacteria.

The development of ruthenium-based complexes or antimicrobial peptides are identified as a promising strategy for combating drug-resistant bacteria. In this work, four biphenyl-based antibacterial ruthenium complexes by targeting membrane integrity, which act as antimicrobial peptides mimics, were designed and synthesized. In vitro antimicrobial screening demonstrated that four complexes could absolutely inhibit the growth of Staphylococcus aureus (S. aureus) with MIC values ranging from 15.6 to 100 µg/mL. The most active complex Ru(Ⅱ)-1 (MIC = 15.6 µg/mL) could kill S. aureus through targeting the membrane integrity without detectably resistance frequencies. Further investigation including bacteria biofilm formation, hemolysin activity and checkerboard assay were performed as well. The results revealed that Ru(Ⅱ)-1 could inhibit the biofilm formation and α-hemolysis secretion in S. aureus at subinhibitory concentration. More interestingly, the combination use of Ru(Ⅱ)-1 and five traditional antibiotics showing synergistic effect. Finally, based on the mouse model of S. aureus skin infection, Ru(Ⅱ)-1 showed important antibacterial efficacy against S. aureus in vivo, and almost non-toxic against mouse tissue. Our study indicates that introducing membrane targeting ligands onto ruthenium complexes may be an underappreciated strategy for developing antibacterial agents.

New 3-Acyl Tetramic Acid Derivatives from the Deep-Sea-Derived Fungus Lecanicillium fusisporum.

Seven rare C3-C6 reduced 3-acyl tetramic acid derivatives, lecanicilliumins A-G (1-7), along with the known analogue cladosporiumin D (8), were obtained from the extract of the deep-sea-derived fungus Lecanicillium fusisporum GXIMD00542 within the family Clavipitacae. Their structures were elucidated by extensive spectroscopic data analysis, quantum chemistry calculations and chemical reaction. Compounds 1, 2, 5-7 exhibited moderate anti-inflammatory activity against NF-κB production using lipopolysaccharide (LPS) induced RAW264.7 cells with EC50 values range of 18.49-30.19 µM.

Thiodiketopiperazines and Alkane Derivatives Produced by the Mangrove Sediment-Derived Fungus Penicillium ludwigii SCSIO 41408.

A new trithiodiketopiperazine derivative, adametizine C (1), and five new alkane derivatives (7-11), were isolated from the mangrove sediment-derived fungus Penicillium ludwigii SCSIO 41408, together with five known dithiodiketopiperazine derivatives (2-6). Their structures were elucidated on the basis of spectroscopic analysis, and the absolute configuration of 1 was determined by X-ray crystallographic analysis. In a variety of bioactivity screening, 1-5 exhibited some selective antifungal or antibacterial activities. Compounds 1-3 showed cytotoxicity against prostate cancer cell line 22Rv1 with half maximal inhibitory concentration (IC50) values of 13.0-13.9 µM; moreover, 3 showed obvious activity against another prostate cancer PC-3 cells with an IC50 value of 5.1 µM. Further experiments revealed that 3 could significantly reduce PC-3 cells colony formation and induce apoptosis in a dose-dependent manner. Several compounds also exhibited obvious inhibitory activities of lipopolysaccharide-induced nuclear factor-κB with IC50 values range from 8.2 to 21.5 µM, and 1, 5, and 9 were further evaluated for their effects on receptor activator of NF-κB ligand (RANKL)-induced osteoclastogenesis. Adametizine C (1), with the strongest inhibitory activity against RANKL-induced osteoclast differentiation in bone marrow macrophage cells with 10 µM, was suggested to be the promising lead compound for the treatment of osteoclast-related diseases.

Osteoclastogenesis inhibitory phenolic derivatives produced by the Beibu Gulf coral-associated fungus Acremonium sclerotigenum GXIMD 02501.

Three new chlorinated orsellinic aldehyde derivatives, orsaldechlorins A - C (1-3) and a naturally new brominated orsellinic acid (7), along with ten known biosynthetically related phenolic (4-6, 8-13) and cyclohexanone (14) derivatives, were identified from the Beibu Gulf coral-derived fungus Acremonium sclerotigenum GXIMD 02501. Their structures were determined by spectroscopic data interpretation and comparison with those reported in the literature. Several of them showed inhibition of lipopolysaccharide (LPS)-induced NF-κB activation in RAW 264.7 macrophages at 20 µM. Moreover, the two new potent inhibitors (1 and 2) suppressed RANKL-induced osteoclast differentiation without cytotoxicity in bone marrow macrophages cells (BMMs). Our findings reveal that the phenolic compounds could be potential candidates for the prevention and treatment of osteolytic bone diseases.

Anti-Osteoclastogenic and Antibacterial Effects of Chlorinated Polyketides from the Beibu Gulf Coral-Derived Fungus Aspergillus unguis GXIMD 02505.

One new depsidone derivative, aspergillusidone H (3), along with seven known biosynthetically related chlorinated polyketides, were obtained from the Beibu Gulf coral-derived fungus Aspergillus unguis GXIMD 02505. Their structures were determined by comprehensive physicochemical and spectroscopic data interpretation. Notably, the X-ray crystal structure of 2 and the previously unknown absolute configuration of 8, assigned by ECD calculations, are described here for the first time. Compounds 1-5, 7 and 8 exhibited inhibition of lipopolysaccharide (LPS)-induced NF-κB in RAW 264.7 macrophages at 20 µM. In addition, the two potent inhibitors (2 and 7) dose-dependently suppressed RANKL-induced osteoclast differentiation without any evidence of cytotoxicity in bone marrow macrophages cells (BMMs). This is the first report of osteoclastogenesis inhibitory activity for the metabolites of these kinds. Besides, compounds 1, 2, 4, and 6-8 showed inhibitory activity against marine biofilm-forming bacteria, methicillin-resistant Staphylococcus aureus, Microbulbifer variabilis, Marinobacterium jannaschii, and Vibrio pelagius, with their MIC values ranging from 2 to 64 µg/mL. These findings provide a basis for further development of chlorinated polyketides as potential inhibitors of osteoclast differentiation and/or for use as anti-fouling agents.

Latexin deficiency attenuates adipocyte differentiation and protects mice against obesity and metabolic disorders induced by high-fat diet.

Obesity is a risk factor for many chronic diseases, and is associated with increased incidence rate of type 2 diabetes, hypertension, dyslipidemia and cardiovascular diseases. Adipocyte differentiation play critical role during development of obesity. Latexin (LXN), a mammalian carboxypeptidase inhibitor, plays important role in the proliferation and differentiation of stem cells, and highlights as a differentiation-associated gene that was significantly downregulated in prostate stem cells and whose expression increases through differentiation. However, it is unclear whether LXN is involved in adipocyte differentiation. The aim of this study was to evaluate the role of LXN on adipocyte differentiation, as well as its effects on high fat-induced obesity and metabolic disorders. In this study, we determine the expression of LXN in adipose tissue of lean and fat mice by Western blot, qPCR and immunohistochemistry. We found that LXN in fat tissues was continuous increased during the development of diet-induced obesity. We fed wild-type (WT) and LXN-/-mice with high-fat diet (HFD) to study the effects of LXN on obesity and related metabolic functions. We found that mice deficient in LXN showed resistance against high-fat diet (HFD)-induced obesity, glucose tolerance, insulin tolerance and hepatic steatosis. In vitro studies indicated that LXN was highly induced during adipocyte differentiation, and positively regulated adipocyte differentiation and adipogenesis in 3T3-L1 cells and primary preadipocytes. Functional analysis revealed that the expression of LXN was positively regulated by mTOR/RXR/PPARɤ signaling pathway during the differentiation of adipocytes, while LXN deletion decreased the protein level of PPARɤ in adipocyte through enhancing FABP4 mediated ubiquitination, which led to impaired adipocyte differentiation and lipogenesis. Collectively, our data provide evidence that LXN is a key positive regulator of adipocyte differentiation, and therapeutics targeting LXN could be effective in preventing obesity and its associated disorders in clinical settings.

A ratiometric electrochemical biosensor via alkaline phosphatase mediated dissolution of nano-MnO2 and Ru(III) redox recycling for the determination of dimethoate.

A sensitive and ratiometric electrochemical biosensor was developed for the determination of dimethoate via alkaline phosphatase (ALP) mediated dissolution of nano-MnO2 and [Ru(NH3)6]3+(Ru(III)) redox recycling. The electroactive probe Ru(III) was adsorbed on the nano-MnO2 with the high specific surface area through electrostatic interaction to form the MnO2-Ru(III) nanocomposite, which was then fixed on the surface of the glassy carbon electrode. When the dimethoate inhibited the catalytic activity of ALP in a homogeneous system, the hydrolysate L-ascorbic acid (AA) produced by ALP hydrolysis of L-ascorbic acid-trisodium 2-phosphate (AAP) decreased. The solution was then incubated with a glassy carbon electrode modified by MnO2-Ru(III). At this time, only a small amount of MnO2-Ru(III) was decomposed and Ru(III) was rapidly electroreduced to Ru(II) on the surface of the electrode. The in-situ produced Ru(II) was chemically oxidized back to Ru(III) by Fe(III). The redox recycling of Ru(III) was completed and the Ru(III) reduction current signal was amplified. The process consumed part of Fe(III) to reduce the reduction current signal of Fe(III), and the ratio of the two reduction currents (IRu(III)/IFe(III)) increased significantly. The IRu(III)/IFe(III) value increased with the increase of dimethoate concentration in the linear range of 0.01-300 ng mL-1, and the detection limit was 6.3 pg mL-1. It has been successfully applied to the determination of dimethoate in oilseed rape and lettuce with a satisfactory result.

Synthesis and biological evaluation of ruthenium polypyridine complexes with 18ß-glycyrrhetinic acid as antibacterial agents against Staphylococcus aureus.

Four new ruthenium(II) polypyridine complexes bearing 18ß-glycyrrhetinic acid derivatives, [Ru(bpy)2L](PF6)2 (Ru1), [Ru(dmb)2L](PF6)2 (Ru2), [Ru(dtb)2L](PF6)2 (Ru3) and [Ru(phen)2L](PF6)2 (Ru4) (bpy = 2,2-bipyridine, dmb = 4,4'-dimethyl-2,2'-bipyridine, dtb = 4,4'-di-tert-butyl-2,2'-bipyridine, phen = 1,10-phenanthroline and L is the GA modified new ligand) were designed and synthesized. Their antimicrobial activities against Staphylococcus aureus (S. aureus) were evaluated and all complexes showed an obvious inhibitory effect, especially, the minimum inhibitory concentration (MIC) value of Ru2 was 3.9 µg mL-1. Moreover, Ru2 was found to significantly inhibit the formation of biofilms. The membrane-compromising action mode was suggested to be their potential antibactericidal mechanism. In hemolysis experiments, Ru2 hardly showed cytotoxicity to mammalian erythrocytes. Furthermore, the synergism between Ru2 and common antibiotics, such as ampicillin, chloramphenicol, tetracyclines and ofloxacin, against S. aureus was also detected using the checkerboard method. Finally, a mouse skin infection model was established to evaluate the antibacterial activity of Ru2in vivo, and the results showed that Ru2 could effectively promote wound healing in mice infected with S. aureus. Moreover, the results of histopathological research were consistent with the results of the hemolysis test, indicating that the Ru2 complex was almost non-toxic. Thus, it was demonstrated that the polypyridine ruthenium complexes modified with glycyrrhetinic acid (GA) are a promising strategy for developing interesting antibacterial agents.