Qingzhi Zhang

The pharmacokinetics of anthocyanins and their metabolites in humans.

Anthocyanins are phytochemicals with reported vasoactive bioactivity. However, given their instability at neutral pH, they are presumed to undergo significant degradation and subsequent biotransformation. The aim of the present study was to establish the pharmacokinetics of the metabolites of cyanidin‐3‐glucoside (C3G), a widely consumed dietary phytochemical with potential cardioprotective properties.

Bioavailability of Sulforaphane from Two Broccoli Sprout Beverages: Results of a Short-term, Cross-over Clinical Trial in Qidong, China

One of several challenges in design of clinical chemoprevention trials is the selection of the dose, formulation, and dose schedule of the intervention agent. Therefore, a cross-over clinical trial was undertaken to compare the bioavailability and tolerability of sulforaphane from two of broccoli sprout–derived beverages: one glucoraphanin-rich (GRR) and the other sulforaphane-rich (SFR). Sulforaphane was generated from glucoraphanin contained in GRR by gut microflora or formed by treatment of GRR with myrosinase from daikon (Raphanus sativus) sprouts to provide SFR. Fifty healthy, eligible participants were requested to refrain from crucifer consumption and randomized into two treatment arms. The study design was as follows: 5-day run-in period, 7-day administration of beverages, 5-day washout period, and 7-day administration of the opposite intervention. Isotope dilution mass spectrometry was used to measure levels of glucoraphanin, sulforaphane, and sulforaphane thiol conjugates in urine samples collected daily throughout the study. Bioavailability, as measured by urinary excretion of sulforaphane and its metabolites (in approximately 12-hour collections after dosing), was substantially greater with the SFR (mean = 70%) than with GRR (mean = 5%) beverages. Interindividual variability in excretion was considerably lower with SFR than with GRR beverage. Elimination rates were considerably slower with GRR, allowing for achievement of steady-state dosing as opposed to bolus dosing with SFR. Optimal dosing formulations in future studies should consider blends of sulforaphane and glucoraphanin as SFR and GRR mixtures to achieve peak concentrations for activation of some targets and prolonged inhibition of others implicated in the protective actions of sulforaphane. Cancer Prev Res; 4(3); 384–95. ©2011 AACR.

Anthocyanins and their physiologically relevant metabolites alter the expression of IL-6 and VCAM-1 in CD40L and oxidized LDL challenged vascular endothelial cells

Scope In vitro and in vivo studies suggest that dietary anthocyanins modulate cardiovascular disease risk; however, given anthocyanins extensive metabolism, it is likely that their degradation products and conjugated metabolites are responsible for this reported bioactivity. Methods and results Human vascular endothelial cells were stimulated with either oxidized LDL (oxLDL) or cluster of differentiation 40 ligand (CD40L) and cotreated with cyanidin‐3‐glucoside and 11 of its recently identified metabolites, at 0.1, 1, and 10 μM concentrations. Protein and gene expression of IL‐6 and VCAM‐1 was quantified by ELISA and RT‐qPCR. In oxLDL‐stimulated cells the parent anthocyanin had no effect on IL‐6 production, whereas numerous anthocyanin metabolites significantly reduced IL‐6 protein levels; phase II conjugates of protocatechuic acid produced the greatest effects (>75% reduction, p ≤ 0.05). In CD40L‐stimulated cells the anthocyanin and its phase II metabolites reduced IL‐6 protein production, where protocatechuic acid‐4‐sulfate induced the greatest reduction (>96% reduction, p ≤ 0.03). Similarly, the anthocyanin and its metabolites reduced VCAM‐1 protein production, with ferulic acid producing the greatest effect (>65% reduction, p ≤ 0.04). Conclusion These novel data provide evidence to suggest that anthocyanin metabolites are bioactive at physiologically relevant concentrations and have the potential to modulate cardiovascular disease progression by altering the expression of inflammatory mediators.

Methods for Isolating, Identifying, and Quantifying Anthocyanin Metabolites in Clinical Samples

The metabolic fate of anthocyanins until recently was relatively unknown, primarily as a result of their instability at physiological pH and a lack of published methods for isolating and identifying their metabolites from biological samples. The aim of the present work was to establish methods for the extraction and quantification of anthocyanin metabolites present in urine, serum, and fecal samples. 35 commercial and 10 synthetic analytes, including both known and predicted human and microbial metabolites of anthocyanins, were obtained as reference standards. HPLC and MS/MS conditions were optimized for organic modifier, ionic modifier, mobile phase gradient, flow rate, column type, MS source, and compound dependent parameters. The impact of sorbent, solvent, acid, preservative, elution, and evaporation on solid phase extraction (SPE) efficiency was also explored. The HPLC-MS/MS method validation demonstrated acceptable linearity (R(2), 0.997 ± 0.002) and sensitivity (limits of detection (LODs): urine, 100 ± 375 nM; serum, 104 ± 358 nM; feces 138 ± 344 nM), and the final SPE methods provided recoveries of 88.3 ± 17.8% for urine, 86.5 ± 11.1% for serum, and 80.6 ± 20.9% for feces. The final methods were applied to clinical samples derived from an anthocyanin intervention study, where 36 of the 45 modeled metabolites were detected within urine, plasma, or fecal samples. The described methods provide suitable versatility for the identification and quantification of an extensive series of anthocyanin metabolites for use in future clinical studies exploring absorption, distribution, metabolism, and elimination.

Flavonoid metabolites reduce tumor necrosis factor‐α secretion to a greater extent than their precursor compounds in human THP‐1 monocytes

1 Scope Flavonoids are generally studied in vitro, in isolation, and as unmetabolized precursor structures. However, in the habitual diet, multiple flavonoids are consumed together and found present in the circulation as complex mixtures of metabolites. Using a unique study design, we investigated the potential for singular or additive anti‐inflammatory effects of flavonoid metabolites relative to their precursor structures.2 Methods and results Six flavonoids, 14 flavonoid metabolites, and 29 combinations of flavonoids and their metabolites (0.1–10 μM) were screened for their ability to reduce LPS‐induced tumor necrosis factor‐α (TNF‐α) secretion in THP‐1 monocytes. One micromolar peonidin‐3‐glucoside, cyanidin‐3‐glucoside, and the metabolites isovanillic acid (IVA), IVA‐glucuronide, vanillic acid‐glucuronide, protocatechuic acid‐3‐sulfate, and benzoic acid‐sulfate significantly reduced TNF‐α secretion when in isolation, while there was no effect on TNF‐α mRNA expression. Four combinations of metabolites that included 4‐hydroxybenzoic acid (4HBA) and/or protocatechuic acid also significantly reduced TNF‐α secretion to a greater extent than the precursors or metabolites alone. The effects on LPS‐induced IL‐1β and IL‐10 secretion and mRNA expression were also examined. 4HBA significantly reduced IL‐1β secretion but none of the flavonoids or metabolites significantly modified IL‐10 secretion.3 Conclusion This study provides novel evidence suggesting flavonoid bioactivity results from cumulative or additive effects of circulating metabolites.

Common Phenolic Metabolites of Flavonoids, but Not Their Unmetabolized Precursors, Reduce the Secretion of Vascular Cellular Adhesion Molecules by Human Endothelial Cells

Background: Flavonoids have been implicated in the prevention of cardiovascular disease; however, their mechanisms of action have yet to be elucidated, possibly because most previous in vitro studies have used supraphysiological concentrations of unmetabolized flavonoids, overlooking their more bioavailable phenolic metabolites. Objective: We aimed to explore the effects of phenolic metabolites and their precursor flavonoids at physiologically achievable concentrations, in isolation and combination, on soluble vascular cellular adhesion molecule-1 (sVCAM-1). Method: Fourteen phenolic acid metabolites and 6 flavonoids were screened at 1 μM for their relative effects on sVCAM-1 secretion by human umbilical vein endothelial cells stimulated with tumor necrosis factor alpha (TNF-α). The active metabolites were further studied for their response at different concentrations (0.01 μM–100 μM), structure-activity relationships, and effect on vascular cellular adhesion molecule (VCAM)-1 mRNA expression. In addition, the additive activity of the metabolites and flavonoids was investigated by screening 25 unique mixtures at cumulative equimolar concentrations of 1 μM. Results: Of the 20 compounds screened at 1 μM, inhibition of sVCAM-1 secretion was elicited by 4 phenolic metabolites, of which protocatechuic acid (PCA) was the most active (−17.2%, P = 0.05). Investigations into their responses at different concentrations showed that PCA significantly reduced sVCAM-1 15.2–36.5% between 1 and 100 μM, protocatechuic acid-3-sulfate and isovanillic acid reduced sVCAM-1 levels 12.2–54.7% between 10 and 100 μM, and protocatechuic acid-4-sulfate and isovanillic acid-3-glucuronide reduced sVCAM-1 secretion 27.6% and 42.8%, respectively, only at 100 μM. PCA demonstrated the strongest protein response and was therefore explored for its effect on VCAM-1 mRNA, where 78.4% inhibition was observed only after treatment with 100 μM PCA. Mixtures of the metabolites showed no activity toward sVCAM-1, suggesting no additive activity at 1 μM. Conclusions: The present findings suggest that metabolism of flavonoids increases their vascular efficacy, resulting in a diversity of structures of varying bioactivity in human endothelial cells.

Synthesis and Coordination Chemistry of the New Unsymmetrical Ligand Ph2PCH2NHC6H4PPh2

Condensation of Ph2PCH2OH with 2-(diphenylphosphanyl)aniline in toluene gave the new unsymmetrical ligand Ph2PCH2NHC6H4PPh2 (1) in good yield. Oxidation of 1 with H2O2 or elemental sulfur led to the oxidised products Ph2P(O)CH2NHC6H4P(O)Ph2 (2) and Ph2P(S)CH2NHC6H4P(S)Ph2 (3). The new ligand 1 demonstrates three distinct modes of coordination. Reaction of compound 1 with [MX2(cod)] (M = Pd, Pt; X = Cl, Br, Me) or [Mo(CO)4(pip)2] gave the chelate complexes [PdCl2(Ph2PCH2NHC6H4PPh2-PX,PA)] (4), [PdBr2(Ph2PCH2NHC6H4PPh2-PX,PA)] (5), [PtCl2(Ph2PCH2NHC6H4PPh2-PX,PA)] (6), [PtMe2(Ph2PCH2NHC6H4PPh2-PX,PA)] (7) and [Mo(CO)4(Ph2PCH2NHC6H4PPh2-PX,PA)] (8). Coordination of 1 with [{RuCl(μ-Cl)(η3:η3-C10H16)}2] or [{RhCl(μ-Cl)(η5-C5Me5)}2] gave the monodentate complexes [RuCl2(η3:η3-C10H16)(Ph2PCH2NHC6H4PPh2-PX)] (9) and [RhCl2(η5-C5Me5)(Ph2PCH2NHC6H4PPh2-PX)] (10). Reaction of 1 with [{IrCl(μ-Cl)(η5-C5Me5)}2] led to a mixture from which the monodentate complex [IrCl2(η5-C5Me5)(Ph2PCH2NHC6H4PPh2-PX)] (11) and the chelate cationic complex [IrCl(η5-C5Me5)(Ph2PCH2NHC6H4PPh2-PX,PA)][Cl] (12) were separated. Abstraction of the chloride ligands from complexes 9 and 10 with AgClO4 gave the cationic chelate complexes [RuCl(η3:η3-C10H16)(Ph2PCH2NHC6H4PPh2-PX,PA)][ClO4] (13) and [RhCl(η5-C5Me5)(Ph2PCH2NHC6H4PPh2-PX,PA][ClO4] (14). Compound 1 also functions as a bridging ligand when reacted with two molar equivalents of [AuCl(tht)] or one molar equivalent of [{RhCl(μ-Cl)(η5-C5Me5)}2] to give the bimetallic complexes [Ph2P{AuCl}CH2NHC6H4PPh2{AuCl}] (15) and [{RhCl2(η5-C5Me5)}2(Ph2PCH2NHC6H4PPh2)] (16). The dioxidised compounds 2 and 3 and several typical complexes 8, 9, 11 and 14 were structurally characterised by X-ray diffraction. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

A novel alanine derivatised phosphine

Abstract Reaction of Ph2PCl with alanine methyl ester affords the chiral aminophosphine Ph2NHCH(CH3)C(O)OCH3 (dppal) which reacts with M(COD)Cl2 to give Pt(dppal)2Cl2 (1) and Cl(dppal)PdCl2Pd(dppal)Cl (2). The X-ray structures of dppalO, 1 and 2 are reported. The amino acid containing ligand forms intramolecular H bonds with the C–O–C or CO oxygen atoms within the ligand and with the cis chlorides in the complexes.

Novel non-aqueous Fe(III)/Fe(II) redox couple for the catalytic oxidation of hydrogen sulfide to sulfur by air

A series of Fe(III) salts and organic solvents have been screened to develop novel non-aqueous catalysts for the conversion of H2S to sulfur. FeCl3/95% N-methylpyrrolidinone/5% H2O was found to be a most efficient non-aqueous system. The process chemistry, the proposed mechanism of catalytic oxidation of H2S, and the electrochemistry are discussed.

Signatures of anthocyanin metabolites identified in humans inhibit biomarkers of vascular inflammation in human endothelial cells

Scope The physiological relevance of contemporary cell culture studies is often perplexing, given the use of unmetabolized phytochemicals at supraphysiological concentrations. We investigated the activity of physiologically relevant anthocyanin metabolite signatures, derived from a previous pharmacokinetics study of 500 mg 13C5‐cyanidin‐3‐glucoside in eight healthy participants, on soluble vascular adhesion molecule‐1 (VCAM‐1) and interleukin‐6 (IL‐6) in human endothelial cells. Methods and results Signatures of peak metabolites (previously identified at 1, 6, and 24 h post‐bolus) were reproduced using pure standards and effects were investigated across concentrations ten‐fold lower and higher than observed mean (<5 μM) serum levels. Tumor necrosis factor‐α (TNF‐α)‐stimulated VCAM‐1 was reduced in response to all treatments, with maximal effects observed for the 6 and 24 h profiles. Profiles tested at ten‐fold below mean serum concentrations (0.19–0.44 μM) remained active. IL‐6 was reduced in response to 1, 6, and 24 h profiles, with maximal effects observed for 6 h and 24 h profiles at concentrations above 2 μM. Protein responses were reflected by reductions in VCAM‐1 and IL‐6 mRNA, however there was no effect on phosphorylated NFκB‐p65 expression. Conclusion Signatures of anthocyanin metabolites following dietary consumption reduce VCAM‐1 and IL‐6 production, providing evidence of physiologically relevant biological activity.