Phosphorus-Ligand Redox Cooperative Catalysis: Unraveling Four-Electron Dioxygen Reduction Pathways and Reactive Intermediates.

The reduction of dioxygen to water is crucial in biology and energy technologies, but it is challenging due to the inertness of triplet oxygen and complex mechanisms. Nature leverages high-spin transition metal complexes for this, whereas main-group compounds with their singlet state and limited redox capabilities exhibit subdued reactivity. We present a novel phosphorus complex capable of four-electron dioxygen reduction, facilitated by unique phosphorus-ligand redox cooperativity. Spectroscopic and computational investigations attribute this cooperative reactivity to the unique electronic structure arising from the geometry of the phosphorus complex bestowed by the ligand. Mechanistic study via spectroscopic and kinetic experiments revealed the involvement of elusive phosphorus intermediates resembling those in metalloenzymes. Our result highlights the multielectron reactivity of phosphorus compound emerging from a carefully designed ligand platform with redox cooperativity. We anticipate that the work described expands the strategies in developing main-group catalytic reactions, especially in small molecule fixations demanding multielectron redox processes.

Identification and Characterization of Baicalin as a Phosphodiesterase 4 Inhibitor.

Asthma is a chronic inflammatory disease of lung airways, and pharmacological inhibitors of cyclic adenosine monophosphate-specific phosphodiesterase 4 (PDE4) have been considered as therapeutics for the treatment of asthma. However, development of PDE4 inhibitors in clinical trials has been hampered because of the severe side effects of non-selective PDE4 inhibitors. Here, screening of a plant extract library in conjunction with dereplication technology led to identification of baicalin as a new type of PDE4-selective inhibitor. We demonstrated that while rolipram inhibited the enzyme activity of a range of PDE4 subtypes in in vitro enzyme assays, baicalin selectively inhibited the enzyme activity of PDE4A and 4B. In addition, baicalin suppressed lipopolysaccharide-induced TNF-α expression in macrophage where PDE4B plays a key role in lipopolysaccharide-induced signaling. Furthermore, baicalin treatment in an animal model of allergic asthma reduced inflammatory cell infiltration and TNF-α levels in bronchoalveolar lavage fluids, indicating that the antiinflammatory effects of baicalin in vivo are attributable, in part, to its ability to inhibit PDE4.

The roots of Nardostachys jatamansi inhibits lipopolysaccharide-induced endotoxin shock.

Nardostachys jatamansi (NJ) has been used in the treatment of inflammatory diseases. However, it is not clear how NJ produces anti-inflammatory effects. In the present study, using an experimental model of lipopolysaccharide (LPS)-induced endotoxin shock, the protective effects and mechanisms of action of NJ were investigated. The water extract of roots of NJ was administrated to mice orally (1, 5, and 10 mg/kg) 1 h after or before LPS challenge. The administration of NJ inhibited LPS-induced endotoxin shock and the production of inflammatory mediators, such as interleukin (IL)-1ß, IL-6, tumor necrosis factor (TNF)-α, and interferon (IFN)-α/ß. Murine peritoneal macrophages were used to determine the production of inflammatory mediators. In peritoneal macrophages, NJ also inhibited LPS-induced production of inflammatory mediators, such as IL-1ß, IL-6, TNF-α, and IFN-α/ß. In addition, NJ reduced the activation of mitogen-activated protein kinases (MAPKs) and the level of expression of interferon regulatory factor (IRF)-1 and IRF-7 mRNA. Furthermore, post-treatment with NJ reduced LPS-induced endotoxin shock and the production of inflammatory mediators. These results suggest that NJ inhibits endotoxin shock by inhibiting the production of IL-1ß, IL-6, TNF-α, and IFN-α/ß through the inhibition of MAPKs activation and IRF induction.

Protective effects of Curcuma longa against cerulein-induced acute pancreatitis and pancreatitis-associated lung injury.

Curcuma longa (CL) has been reported to possess a variety of pharmacological activities. However, the effects of CL on acute pancreatitis (AP) have not yet been determined. To this end, we examined the effects of CL on cerulein-induced AP. Cell viability and cytokine productions were measured in pancreatic acini. Mice were divided into 3 groups: i) Normal group, ii) normal saline-treated group, iii) group treated with CL at a dose of 0.05, 0.1, 0.5 and 1 g/kg. CL was administered orally to mice for 7 days. The mice were intraperitoneally injected with the stable cholecystokinin analogue, cerulein (50 µg/kg), every hour for a total of 6 h. The mice were sacrificed 6 h after the completion of the cerulein injections. Blood samples were obtained to determine serum amylase, lipase and cytokine levels. The pancreas was rapidly removed for morphological examination, measurement of tissue myeloperoxidase activity, as well as the level of cytokines and heme oxygenase-1 (HO-1). The CL treatment reduced cerulein-induced cell death and cytokine production in pancreatic acini. The administration of CL significantly ameliorated the severity of pancreatitis and pancreatitis-associated lung injury, as was shown by the reduction in pancreatic edema, neutrophil infiltration, vacuolization, necrosis, serum amylase, lipase and cytokine levels, and mRNA expression of multiple inflammatory mediators such as interleukin (IL)-1ß and -6 and tumor necrosis factor (TNF)-α. In order to identify the regulatory mechanism of CL on cerulein-induced pancreatitis, we examined the level of HO-1 in the pancreas. We found that the administration of CL induced HO-1. Our results suggest that CL plays a protective role in the development of AP and pancreatitis-associated lung injury.

Inhibition of lipopolysaccharide-induced inflammatory responses by piperine.

Piperine, a main component of Piper longum Linn. and Piper nigrum Linn., is a plant alkaloid with a long history of medical use. Piperine exhibits anti-inflammatory activity; however, the underlying mechanism remains unknown. We examined the effects of piperine on lipopolysaccharide (LPS)-induced inflammatory responses. Administration of piperine inhibited LPS-induced endotoxin shock, leukocyte accumulation and the production of tumor necrosis factor-alpha (TNF-alpha), but not of interleukin (IL)-1beta and IL-6. In peritoneal macrophages, piperine inhibited LPS/poly (I:C)/CpG-ODN-induced TNF-alpha production. Piperine also inhibited LPS-induced endotoxin shock in TNF-alpha knockout (KO) mice. To clarify the inhibitory mechanism of LPS-induced endotoxin shock, type 1 interferon (IFN) mRNA expression was determined. Piperine inhibited LPS-induced expression of type 1 IFN mRNA. Piperine inhibited the levels of interferon regulatory factor (IRF)-1 and IRF-7 mRNA, and the phosphorylation and nuclear translocation of IRF-3. Piperine also reduced activation of signal transducer and activator of transcription (STAT)-1. In addition, activation of STAT-1 was inhibited in IFN-alpha/beta-treated cells by piperine. These results suggest that piperine inhibits LPS-induced endotoxin shock through inhibition of type 1 IFN production.

Synthesis and biological evaluation of homopiperazine derivatives with beta-aminoacyl group as dipeptidyl peptidase IV inhibitors.

Compounds with homopiperazine skeleton are designed to find a potent DPP-IV inhibitor without inhibiting CYP. Thus a series of beta-aminoacyl-containing homopiperazine derivatives was synthesized and evaluated. Compounds with acid moiety were found to be potent inhibitors of DPP-IV without inhibiting CYP 3A4. More specifically, compound 7m showed nanomolar activity with no inhibition towards five subtypes of CYPs, was considered as a prototype for further derivatization. Based on its X-ray co-crystal structure with human DPP-IV, we identified compounds 7s and 7t which showed good in vitro activity, no CYP inhibition, and good selectivity.

Synthesis and biological evaluation of pyrazoline analogues with beta-amino acyl group as dipeptidyl peptidase IV inhibitors.

A series of pyrazoline derivatives with beta-amino acyl group were synthesized and evaluated for their ability to inhibit dipeptidyl peptidase IV. Several pyrazoline derivatives exhibited submicromolar inhibitory activities against DPP-IV. X-ray co-crystal structure of initial hit compound 1h was determined. Among this series, carboxylic acid substituted pyrazoline derivative 2u was the most active and greatly decreased the inhibitory activity toward CYP3A4 enzyme.

Synthesis, biological evaluation and structural determination of beta-aminoacyl-containing cyclic hydrazine derivatives as dipeptidyl peptidase IV (DPP-IV) inhibitors.

Inhibitors of dipeptidyl peptidase IV (DPP-IV) have been shown to be effective treatments for type 2 diabetes. A series of beta-aminoacyl-containing cyclic hydrazine derivatives were synthesized and evaluated as DPP-IV inhibitors. One member of this series, (R)-3-amino-1-(2-benzoyl-1,2-diazepan-1-yl)-4-(2,4,5-trifluorophenyl)butan-1-one (10f), showed potent in vitro activity, good selectivity and in vivo efficacy in mouse models. Also, the binding mode of compound 10f was determined by X-ray crystallography.

[Prevalence Of Intestinal Helminthic Infections And Skin Tests For Paragonimus And Clonorchis In Tuberculosis Patients]

This study was conducted to evaluate prevalence of intestinal helminthic infections and skin tests and Paragonimus and Clonorchis in tuberculosis(TB) patients in Korea. Stool examinations by formalin-ether technique and intradermal tests were carried out in 2 areas; Masan TB hospital and Kong-Ju TB hospital. 1. The positive rate of intestinal helminths of any kind was 51.7 % among 329 patients in Masan hospital, but 18.1 % among 215 patients in Kong-Ju hospital. 2. The infection rates of Trichocephalus trichiurus and Clonorchis sinensis were 20.7 % and 17.6 % respectively in Masan hospital patients, but the infection rates of T. trichiurus and C. sinensis were 6.5 % and 6.0 % respectively in Kong-Ju hospital patients. 3. In skin tests, positive reactions to Paragonimus and Clonorchis antigens were 22.0 % and 37.6 % respectively in Masan hospital patients. On the contrary, Kong-Ju hospital patients showed the positive rates of 15.2 % for Paragonimus and 27.2 % for Clonorchis respectively.