Hua Fang

Comparative evaluation of the radical-scavenging activities of fucoxanthin and its stereoisomers.

Fucoxanthin (Fuco) is a characteristic carotenoid of brown seaweeds. In the present study, Fuco and its stereoisomers 9Z-Fuco, 13Z- and 13Z-Fuco were extracted from Laminaria japonica Aresch. They were isolated and purified by silica gel column chromatography, Sephadex LH-20, and reversed-phase HPLC. The radical-scavenging activities of the three stereoisomers were evaluated toward 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, 2-2-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical, hydroxyl radical, and superoxide radical. The order of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity was 13Z- and 13Z-Fuco > (all-E)-Fuco > 9Z-Fuco. The order of 2-2-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and hydroxyl radical-scavenging activities were 9Z-Fuco > (all-E)-Fuco > 13Z-and 13Z-Fuco. The order of superoxide radical-scavenging activity was 13Z- and 13Z-Fuco > (all-E)-Fuco > 9Z-Fuco. The scavenging activities of Fuco and its stereoisomers toward the four radical types were all dose-dependent. The ABTS, DPPH, and superoxide radical-scavenging activities were all weaker than that of tocopherol (VE), while their hydroxyl radical-scavenging activities were stronger than that of VE. The results confirmed that Fuco and its stereoisomers have potent antioxidant activities.

On-line comprehensive two-dimensional normal-phase liquid chromatography × reversed-phase liquid chromatography for preparative isolation of toad venom ☆

An on-line comprehensive preparative two-dimensional normal-phase liquid chromatography×reversed-phase liquid chromatography (2D NPLC×RPLC) system was constructed with a newly developed vacuum evaporation assisted adsorption (VEAA) interface, allowing fast removal of NPLC solvent in the vacuum condition and successfully solving the solvent incompatibility problem between NPLC and RPLC. The system achieved on-line solvent exchange within the two dimensions and its performance was illustrated by gram-scale isolation of crude extract from the venom of Bufo bufo gargarizans. Within separation time of ∼20h, 19 compounds were obtained with high purity in a single run. With the VEAA interface, the 2D system exhibited apparent advantages in separation efficiency and automation compared with conventional methods, indicating its promising application in the routine separation process for complicated natural products.

Copper (I) Iodide-Catalyzed Solvent-Free Synthesis of α-Aminophosphonates

Abstract A method for the synthesis of α-aminophosphonates through the three-component coupling reaction of aldehydes, amines, and diisopropyl phosphite using copper (I) iodide salt catalyst is demonstrated, The reaction is highly efficient, economic, and also environment friendly. [Supplemental materials are available for this article. Go to the publishers online edition of Phosphorus, Sulfur, and Silicon and the Related Elements for the following free supplemental resource: Table S1, Figures S1–S9.] GRAPHICAL ABSTRACT

A new diphenyl ether from Phoma sp. strain, SHZK-2

A new diphenyl ether methyl 2-(2-formyl-3-hydroxy-5-methylphenoxy)-5-hydroxy-3-methoxybenzoate (3), together with four known compounds, asterric acid (1), methyl asterrate (2), 9(Z),12(Z)-nonadecadienoic acid (4) and orsellinic acid (5), were isolated from the Phoma sp. strain SHZK-2, which was isolated from a polluted environment in southern China. The structures of these compounds were determined by spectroscopic methods. Cytotoxicities of compounds against HEPG2 cell and Raji cell lines were preliminarily evaluated by the MTT method.

Diisopropyl [(benzoyl­amino)­(phen­yl)meth­yl]phospho­nate

The title compound, C20H26NO4P, has been obtained by the reaction of benzoyl chloride and diisopropyl[amino(phenyl)methyl]phosphonate. The dihedral angle between the planes of the benzoylamino group and the phenyl ring is 77.0u2005(2)°. The crystal structure is stabilized by strong intermolecular N—H⋯O hydrogen bonds between the doubly bonded phosphoryl O atom and the amide N atom which link the molecules into pairs about a center of symmetry.

Simultaneous Determination of Fucoxanthin and Its Deacetylated Metabolite Fucoxanthinol in Rat Plasma by Liquid Chromatography-Tandem Mass Spectrometry

Fucoxanthin and its deacetylated metabolite fucoxanthinol are two major carotenoids that have been confirmed to possess various pharmacological properties. In the present study, fucoxanthinol was identified as the deacetylated metabolite of fucoxanthin, after intravenous (i.v.) and intragastric gavage (i.g.) administration to rats at doses of 2 and 65 mg/kg, respectively, by liquid chromatography-tandem mass spectrometric (LC-MS/MS) analysis. Next, an accurate and precise LC-MS/MS method was developed to quantitatively determine fucoxanthin and fucoxanthinol in rat plasma. Plasma samples were resolved by LC-MS/MS on a reverse-phase SB-C18 column that was equilibrated and eluted with acetonitrile (A)/aqueous 0.1% formic acid (B; 92/8, v/v) at a flow rate of 0.5 mL/min. Analytes were monitored by multiple-reaction monitoring (MRM) under positive electrospray ionization mode. The precursor/product transitions (m/z) were 659.3→109.0 for fucoxanthin, 617.2→109.0 for fucoxanthinol, and 429.4→313.2 for the internal standard (IS). Calibration curves for fucoxanthin and fucoxanthinol were linear over concentrations ranging from 1.53 to 720 and 1.17 to 600 ng/mL, respectively. The inter- and intraday accuracy and precision were within ±15%. The method was applied successfully in a pharmacokinetic study and the resulting oral fucoxanthin bioavailability calculated.

Using positive-ion electrospray ionization mass spectrometry and H/D exchange study phosphoryl group transfer reactions involved in amino acid ester isopropyl phosphoramidates of Brefeldin A.

As mini-chemical models, amino acid ester isopropyl phosphoramidates of Brefeldin A (compounds 2a-2d) were synthesized and investigated by electrospray ionization tandem mass spectrometry in combination with H/D exchange. To further confirm the fragmentss structures, off-line Fourier transform resonance tandem mass spectrometry (FT-ICR-MS/MS) was also performed. The fragmentation rules of compounds 2a-2d have been summarized and the plausible schemes for the fragmentation pathways were proposed. In this study, one dephosphorylated ion and two phosphorylated ions were observed in ESI-MS(2) spectra of [M+Na](+) ions for compounds 2a-2d. The possible mechanisms about phosphorylation and dephosphorylation were proposed and confirmed by H/D exchange. For the dephosphorylation rearrangement, a nitrogen atom was migrated from the phosphoryl group to the carbon atom of Brefeldin As backbone with losing a molecule of C3H7PO3 (122 Da). For the phosphorylation rearrangement, an oxygen atom of one phosphoryl group attacked the sideward phosphorus atom to form a nine-member ring intermediate, then two steps of CH covalent bond cleavage with consecutive migration of hydrogen atom to lose a molecule of C16H20O2 (244 Da). The two proposed rearrangement mechanisms about phosphoryl group transfer might be valuable for the structure analysis of other analogs and provide insights into elucidating the dynamic process of the phosphorylation-dephosphorylation of proteins.

Disopropyl {[(2S,3S)-2-amino-3-methyl­penta­namido](phen­yl)meth­yl}phosphinate

There are two independent molecules in the asymmetric unit of the title compound, C19H33N2O4P. In the crystal, the two independent molecules are linked via N—H⋯O=P hydrogen bonds, forming dimers.

Synthesis, Characterizations, and Crystal Structures of α-Hydroxyphosphonic Acid Esters

This article describes the synthesis of α-hydroxyphosphonic acid esters using the Pudovik reaction. IR, 1H NMR, 13C NMR, 31P NMR, MS, and elemental analysis were employed to confirm their structures. X-ray structure analysis is reported for six compounds. The antibacterial activities of these compounds are also reported. Supplemental materials are available for this article. Go to the publishers online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

Electrospray ionization tandem mass spectrometry of phosphonate peptides

Phosphonate peptides were synthesized and investigated by positive ion electrospray ionization mass spectrometry in conjunction with tandem mass spectrometry. It was found that, for the sodiated adduct, there were two rearrangement reactions. In path A, there was C–C covalent bond cleavage with consecutive migration of a hydrogen atom to lose the amino alcohol molecule. In path B, two consecutive covalent cleavages of the C–N and P–O bonds occurred.