The Structural Revision and Total Synthesis of Carambolaflavone A.

The synthesis of both enantiomers of carambolaflavone A, the antidiabetic and flavonoid C-glycoside, was achieved for the first time via a 12-longest-linear-step with 16% (l-fucose) and 11% (d-fucose) overall yields. Through the synthetic investigation, the adverse effect of 4A MS in Suzuki C-glycosylation was disclosed, the mechanism of hydrogen-bonded-phenol involved Suzuki C-glycosylation was clarified, and the authentic structure of carambolaflavone A was also determined.

Metal-independent decomposition of hydroperoxides by halogenated quinones: detection and identification of a quinone ketoxy radical.

We have shown recently that halogenated quinones could enhance the decomposition of hydroperoxides and formation of alkoxyl/hydroxyl radicals through a metal-independent mechanism. However, neither the proposed quinone enoxy radical intermediate, nor the major reaction products were unambiguously identified. In the present study, one of the major reaction products between 2,5-dichloro-1,4-benzoquinone (DCBQ) and t-butylhydroperoxide (t-BuOOH) was isolated and purified by semipreparative HPLC, and identified as 2-hydroxy-3-t-butoxy-5-chloro-1,4-benzoquinone [CBQ(OH)-O-t-Bu], which is the rearranged isomer of the postulated quinone-peroxide reaction intermediate. The formation of CBQ(OH)-O-t-Bu was found to be inhibited by the spin trapping agent 5,5-dimethyl-1-pyrroline N-oxide (DMPO), and concurrently, a new DMPO adduct with 1-chlorine isotope peak clusters at m/z 268 was observed. Further electron spin resonance (ESR) spin-trapping, (1)H-NMR and HPLC/Fourier transform ion cyclotron resonance (FTICR) mass spectrometric studies with oxygen-17-labeled and unlabeled hydrogen peroxide strongly suggest that the radical trapped by DMPO is a carbon-centered quinone ketoxy radical, which is the spin isomer of the proposed oxygen-centered quinone enoxy radical. Analogous results were observed when DCBQ was substituted by other halogenated quinones. This study represents the first detection and identification of an unusual carbon-centered quinone ketoxy radical, which provides direct experimental evidence to further support and expand our previously proposed mechanism for metal-independent decomposition of hydroperoxides by halogenated quinones.

[Evaluation Parameters and System for Reclaimed Water Quality Stability].

Wastewater reclamation and reuse are an effective measure to alleviate water shortages. Water quality stability is the premise for safe utilization of reclaimed water and other water resources. Stable water quality can prevent the frequent occurrence of corrosion and scaling, which not only improves the sensory properties of water quality but also reduces secondary pollution and energy consumption. In order to promote the utilization of wastewater resources, it is important to evaluate and manage reclaimed water quality stability. Based on substantial literature and research, the characteristics and scopes of evaluation parameters for both chemical stability and biological stability were summarized, and a set of evaluation parameters and a system for reclaimed water quality stability were comprehensively established in this study. The evaluation procedure was mainly divided into four steps including:① determine the influencing factors of reclaimed water quality stability; ② select corresponding evaluation parameters based on reclaimed water quality characteristics, the materials of pipelines, and equipment; ③ evaluate the reclaimed water quality stability; and ④ examine whether the evaluation results were appropriate. Finally, the potential challenges for the stability evaluation of water quality were analyzed. This study is expected to provide a theoretical foundation for the scientific evaluation of water quality stability and safe utilization of reclaimed water.

Potential mechanisms involved in ceramide-induced apoptosis in human colon cancer HT29 cells.

OBJECTIVE: To investigate the potential mechanisms of cell death after the treatment with ceramide. METHODS: MTT assay, DNA ladder, reporter assay, FACS and Western blot assay were employed to investigate the potential mechanisms of cell death after the treatment with C2-ceramide. RESULTS: A short-time treatment with C2-ceramide induced cell death, which was associated with p38 MAP kinase activation, but had no links with typical caspase activation or PARP degradation. Rather than caspase inhibitor, Inhibitor of p38 MAP kinase blocked cell death induced by a short-time treatment with ceramide (<12 h). However, inhibition of p38 MAP kinase could not block cell death induced by a prolonged treatment with ceramide (>12 h). Moreover, incubation of cells with ceramide for a long time (>12 h) increased subG1, but reduced S phase accompanied by caspase-dependent and caspase-independent changes including NFkappaB activation. CONCLUSION: Ceramide-induced cell apoptosis involves both caspase-dependent and -independent signaling pathway. Caspase-independent cell death occurring in a relatively early stage, which is mediated via p38 MAP kinase, can progress into a stage involving both caspase-dependent and -independent mechanisms accompanied by cell signaling of MAPKs and NFkappaB.

[A new "turn-on" fluorescent probe for visual detection of hydrogen sulfide].

Hydrogen sulfide (H2S) is one of the important parameters for characterizing water pollution. Therefore, fast and effective detection method is in great need. Fluorescence analysis method gains wide attention because of unparalleled advantages. A new colorimetric and fluorescent "turn-on" probe for H2S detection based on thiolysis by H2S was reported. 2-(2'-Hydroxyphenyl) benzimidazole (HBI), a kind of excited-state intramolecular proton transfer dye was chosen as the fluorophore because of large Stokes shift and high fluorescence quantum yield. It was found that the fluorescence intensity of testing system increased with the addition of H2S and accompanied with a color change from pale yellow to purple. The visual detection limit was 3 micromol x L(-1). The new fluorescent probe showed a good selectivity for H2S over other anions and a good fluorescence response in a relatively wide pH range. The response process was finished in five minutes with a 100-fold fluorescence enhancement. The probe provides a new method for the detection of H2S.

Characterization of Three Tetrabromobisphenol-S Derivatives in Mollusks from Chinese Bohai Sea: A Strategy for Novel Brominated Contaminants Identification.

Identification of novel brominated contaminants in the environment, especially the derivatives and byproducts of brominated flame retardants (BFRs), has become a wide concern because of their adverse effects on human health. Herein, we qualitatively and quantitatively identified three byproducts of tetrabromobisphenol-S bis(2,3-dibromopropyl ether) (TBBPS-BDBPE), including TBBPS mono(allyl ether) (TBBPS-MAE), TBBPS mono(2-bromoallyl ether) (TBBPS-MBAE) and TBBPS mono(2,3-dibromopropyl ether) (TBBPS-MDBPE) as novel brominated contaminants. Meanwhile, the mass spectra and analytical method for determination of TBBPS-BDBPE byproducts were presented for the first time. The detectable concentrations (dry weight) of TBBPS-MAE, TBBPS-MBAE and TBBPS-MDBPE were in the ranges 28-394 µg/g in technical TBBPS-BDBPE and 0.1-4.1 ng/g in mollusks collected from the Chinese Bohai Sea. The detection frequencies in mollusk samples were 5%, 39%, 95% for TBBPS-MAE, TBBPS-MBAE and TBBPS-MDBPE, respectively, indicating their prevailing in the environment. The results showed that they could be co-produced and leaked into the environment with production process, and might be more bioaccumulative and toxic than TBBPS-BDBPE. Therefore, the production and use of TBBPS derivatives lead to unexpected contamination to the surrounding environment. This study also provided an effective approach for identification of novel contaminants in the environment with synthesized standards and Orbitrap high resolution mass spectrometry.

Mechanism of metal-independent decomposition of organic hydroperoxides and formation of alkoxyl radicals by halogenated quinones.

The metal-independent decomposition of organic hydroperoxides and the formation of organic alkoxyl radicals in the absence or presence of halogenated quinones were studied with electron spin resonance (ESR) and the spin-trapping agent 5,5-dimethyl-1-pyrroline N-oxide (DMPO). We found that 2,5-dichloro-1,4-benzoquinone (DCBQ) markedly enhanced the decomposition of tert-butylhydroperoxide (t-BuOOH), leading to the formation of the DMPO adducts with t-butoxyl radicals (t-BuO* and methyl radicals *CH(3)). The formation of DMPO/t-BuO* and DMPO/*CH(3) was dose-dependent with respect to both DCBQ and t-BuOOH and was not affected by iron- or copper-specific metal chelators. Comparison of the data obtained with DCBQ and t-BuOOH with those obtained in a parallel study with ferrous iron and t-BuOOH strongly suggested that t-BuO* was produced by DCBQ and t-BuOOH through a metal-independent mechanism. Other halogenated quinones were also found to enhance the decomposition of t-BuOOH and other organic hydroperoxides such as cumene hydroperoxide, leading to the formation of the respective organic alkoxyl radicals in a metal-independent manner. Based on these data, we propose a mechanism for DCBQ-mediated t-BuOOH decomposition and formation of t-BuO*: a nucleophilic attack of t-BuOOH on DCBQ, forming a chloro-t-butylperoxyl-1,4-benzoquinone intermediate, which decomposes homolytically to produce t-BuO*. This represents a mechanism of organic alkoxyl radical formation not requiring the involvement of redox-active transition metal ions.

[Inducement effect of synthetic indiosides from Solanum indicum L.on apoptosis of human hepatocarcinoma cell line Bel-7402 and its mechanism].

BACKGROUND & OBJECTIVE: Solanum indicum L., an anti-inflammatory and wound-healing herb in traditional Chinese medicine, is enriched of unique dioscins, that is, indiosides. Our previous studies revealed that several synthetic indiosides from Solanum indicum L. have potent anticancer effects. This study was to investigate the anticancer mechanism of synthetic indiosides I from Solanum indicum L. METHODS: Human hepatocarcinoma Bel-7402 cells were treated with different concentrations of indiosides. The inhibitory rate of cell proliferation and 50% inhibitory concentration (IC50) of indiosides were detected by the acid phosphatase assay (APA). Cell morphology was observed under optical microscope with crystal violet staining. The expression of apoptosis-related proteins was detected by Western blot. RESULTS: Indiosides significantly inhibited proliferation of Bel-7402 cells: when treated with indioside I for 72 h, the IC50 value was 4.2 microg/ml, cell density was decreased, and bubbles were observed in cytoplasm. Western blot showed that the cytoplasmic level of cytochrome c was increased significantly, Caspase-3 was activated, and poly (ADR-ribose) polymerase (PARP) was cleavaged after indioside I treatment. CONCLUSION: Indiosides have dose-dependent inhibitory effect on proliferation of Bel-7402 cells, and can induce cell apoptosis through mitochondria-dependent pathway.