A Dipeptide Isolated from Aster tataricus L.f

从紫菀AastertataricusL.f的根及根茎中分离鉴定出6个化合物，分别为auraniamideacetate;shionone,triedelm,epitrriedelanol,triedel-3-ene和stigmasterol.其中aurantiamideacetate和triedel-3-ene为首次从菊科植物中分得。

Glutamine dipeptide for parenteral nutrition in abdominal surgery:A meta-analysis of randomized controlled trials

AIM: To assess the clinical and economical validity of glutamine dipeptide supplemented to parenteral nutrition (PN) in patients undergoing abdominal surgery. METHODS: A meta-analysis of all the relevant randomized controlled trials (RCTs) was performed. The trials compared the standard PN and PN supplemented with glutamine dipeptide in abdominal surgery. RCTs were identified from the following electronic databases: the Cochrane Library, MEDLINE, EMBASE and ISI web of knowledge (SCI). The search was undertaken in April 2006. Literature references were checked by computer or hand at the same time. Clinical trials were extracted and evaluated by two reviewers independently. Statistical analysis was performed by RevMan4.2 software from Cochrane Collaboration. A P value of < 0.05 was considered statistically significant. RESULTS: Nine RCTs involving 373 patients were included. The combined results showed that glutamine dipeptide has a positive effect in improving postoperative cumulative nitrogen balance (weighted mean difference (WMD = 8.35, 95% CI [2.98, 13.71], P = 0.002), decreasing postoperative infectious morbidity (OR = 0.24, 95% CI [0.06, 0.93], P = 0.04), shortening the length of hospital stay (WMD= -3.55, 95% CI [-5.26, -1.84], P < 0.00001). No serious adverse effects were found. CONCLUSION: Postoperative PN supplemented with glutamine dipeptide is effective and safe to decrease the infectious rate, reduce the length of hospital stay and improve nitrogen balance in patients undergoing abdominal surgery. Further high quality trials in children and severe patients are required, and mortality and hospital cost should be considered in future RCTs with sufficient size and rigorous design.

Alanyl-glutamine dipeptide inhibits hepatic ischemiareperfusion injury in rats

AIM： To investigate the protective effect and mechanism of alanyl-glutamine dipeptide （Ala-GIn） against hepatic ischemia-reperfusion injury in rats. METHODS： Rats were divided into group C as normal control Group （/7=16） and group G as alanyl-glutamine pretreatment 07=16）. Rats were intravenously infused with 0.9% saline solution in group C and Ala-GIn -enriched （2% glutamine） 0.9% saline solution in group G via central venous catheter for three days. Then all rats underwent hepatic warm ischemia for 30 min followed by different periods of reperfusion. Changes in biochemical parameters, the content of glutathione （GSH） and the activity of superoxide dismutase （SOD） in liver tissue, Bcl-2 and Bax protein expression and morphological changes of liver tissue were compared between both groups. RESULTS： One hour after reperfusion, the levels of liver enzymes in group G were significantly lower than those in group C （P〈0.05）. Twenty-four hours after reperfusion, the levels of liver enzymes in both groups were markedly recovered and the levels of liver enzyme in group G were also significantly lower than those in group C （P〈0.01）. One and 24 h after reperfusion, GSH content in group G was significantly higher than that in group C （P 〈0.05）. There was no statistical difference in activities of SOD between the two groups. One and 24 h after reperfusion, the positive expression rate of Bcl-2 protein was higher in group G than in group C （P〈0.05） and the positive expression rate of Bax protein was lower in group G than in group C （P〈0.05）. Histological and ultrastructural changes of liver tissue were inhibited in group C compared to group G. CONCLUSION： Our results suggest that Ala-GIn pretreatment provides the rat liver with significant tolerance to warm ischemia-reperfusion injury, which may be mediated partially by enhancing GSH content and regulating the expression of Bcl-2 and Bax proteins in the liver tissue.

Simultaneous determination of doxorubicin and its dipeptide prodrug in mice plasma by HPLC with fluorescence detection

A simple and sensitive high performance liquid chromatography with fluorescence detection （HPLC-FD） has been developed for simultaneous quantification of doxorubicin （DOX） and its dipeptide conjugate prodrug （PDOX） in mice plasma. The chromatographic separation was carried out on an Amethyst C18-H column with gradient mobile phase of 0.1% formic acid and 0.1% formic acid in acetonitrile at a flow rate of 1.0 mL/min. The excitation and emission wavelengths were set at 490 and 550 nm, respectively. The method was comprehensively validated. The limits of detection were low up to 5.0 ng/mL for DOX and 25.0 ng/mL for PDOX. And the limits of quantification were low up to 12.5 ng/mL for DOX and 50 ng/mL for PDOX, which were lower than those for most of the current methods. The calibration curves showed good linearity （R2 〉 0.999） over the concentration ranges. The extraction recoveries ranged from 84.0% to 88.2% for DOX and from 85.4% to 89.2% for PDOX. Satisfactory intra-day and inter-day precisions were achieved with RSDs less than 9.1%. The results show that the developed HPLC-FD method is accurate, reliable and will be helpful for preclinical pharmacokinetic study of DOX and PDOX.

The Effect of Glycyl-Glutamine Dipeptide Concentration on Enzyme Activity, Cell Proliferation and Apoptosis of Jejunal Tissues from Weaned Piglets

An experiment was conducted in a singly factorial design to study the effect of glycyl-glutamine dipeptide on enzyme activity, cell proliferation and apoptosis of jejunal tissues from weaned piglets at different glycyl-glutamine concentration levels of 2, 4, 10, 20, and 30 mmol L-1, respectively. The glutaminase activity, diamine oxidase （DAO） activity, cell peoliferation, apoptosis, and perotein metabolism were measured by the tissue culture method in vitro using jejunal tissues. The immunohistochemical method was used to study the cell proliferation and apoptosis of jejunal tissues. The results showed that compared to the blank control, the percentage and MOD value of BrdU-positicve cells incubated with glycyl-glutamine dipeptide solution were significantly （P0.05） increased. Accordingly, the percentage and MOD value of caspase-3-positive cells from tissue incubated with glycyl-glutamine dipeptide were notably lower （P0.05） than that from the control treatment. The glycyl-glutamine dipeptide increased the glutaminase activity, DAO activity and protein content of jejunal tissues, as the dipeptide concentration was on the rise （P0.05）. These results indicated that glycyl-glutamine dipeptide affected the jejunum development and adaptation of weaned piglets, and the function might be fulfilled by enhancing the glutamine-related enzyme activity, thereby increasing the consumption of glutamine, and then improving the jejunal cell proliferation and suppressing cell apoptosis. The effects of glycyl-glutamine dipeptide relied in a dose-dependent manner, and the maximum effect was achieved at 20-30 mmol L-1 glycyl-glutamine dipeptide.

Antiproliferative Properties of Vinyl Dipeptides: Synthesis and MCF-7 Cell Line Testing

Peptide mimics derived with close structure to peptide have vast utility because they are expected to interfere with biological targets while having superior drug-like properties if compared to peptides. In this work, novel vinyl dipeptides which are different in a double bond between the α-carbon of peptide and C1 of its side chain. Added to that, suitable substituents were selected to harness drug-like properties. The compounds were found to have moderate activities when tested against MCF-7 breast cancer cell line. For instance, the adamantyl analogue 2-(benzoylamino)-3-(2-furyl)-N-(1-adamantyl) propenamide (1c) and the heterocyclic analogue 2-(Benzoylamino)-3-(2-furyl)-N-[2-(5-cyanothia-zol-2-yl)] propenamide (1o) exhibited inhibition potency at 27.4 and 37.8 μM, respectively.

Synthesis of Muramyl dipeptide Analogs by Incorporation of 3,3,3-Trifluoroalanine

Carbobenzoxy-L-3, 3, 3-trifluoroalanine was synthesized and it was incorporated into MDP for replacement of L-alanine.

Asymmetric Reformatsky Reaction Induced by Dipeptides

For the first time, synthetic dipeptides were applied to the catalysis of asymmetric Reformatsky reaction. Review in this domain & factors influencing enantioselectivity were discussed.

Design and Solid-Phase Synthesis of Multiple Muramyl Dipeptide (MMD)

As a non-specific modulator of macrophage, multiplied muramyl dipeptide (MMD) is solid-phase synthesized by application of standard Fmoc chemistry strategy. Tarn's multiple antigen system (MAS) is used as our four branched-linker on Lysine.

Synthesis of a Dopamimetic Thionated Dipeptide Prodrug of L-DOPA

L-DOPA has gained widespread credit over the past decades as being the mainstay of the pharmacological treatment of Parkinson’s disease. However, there are many adverse effects associated with the use of L-DOPA. The prodrug approach is the most promising way to solve the problem. In this article, a thionated dipeptide prodrug of L-DOPA 11 was synthesized via 10 steps in a total yield of 26.5% from L-DOPA.

Dipeptide transport: an active process with energy-and proton-dependence in the human intestinal cell line,Caco-2

Objective: To determine the active process on dipeptide transport with proton-and energy-dependence in Caco-2 cells.Methods: A human intestinal cell monolayer(Caco-2) was used as the in vitro model of human small intestine and cephalexin as the model substrate for dipeptide transporter(PepT1).Caco-2 cells grown on multiwell dishes(24 wells) and Transwell membrane filters were incubated in the culture medium. The transport and uptake experiments of cephalexin across apical membranes were then conducted with different temperature and different pH values.Uptake of cephalexin in Caco-2 cells gsown on multiple well dishes with addition of energy inhibitors(sodium azide,SA and 2,4-dinitrophenol,DNP) were then measured. Results: The accumulation of cephalexin into Caco-2 monolayers increased with the duration of culture.The uptake from the apical surface was markedly influenced by the pH of the apical medium,and the maximal uptake was achieved at pH 5.5;further acidification of the incubation medium may decrease transport of cephalexin despite an increase inward H+ gradient.Cephalexin uptake was linear over the concentration range when the cells were incubated at 4℃ while the uptake rate was enhanced and tended to be saturated as the cephalexin concentration increased when the cells were incubated at 37℃.The kinetic parameters for the cephalexin transport carrier were determined to be: Vmax of(22.173±1.9) nmol/min per mg protein,Km of(2.069±0.9)mol/L,the Kd was estimated to be(0.07±0.02) nmol/min per mg protein per mmol/L.Uptake of cephalexin was markedly inhibited by sodium azide(SA) and 2,4-dinitrophenol(DNP). Conclusion: Cephalexin was transported actively across Caco-2 cells,and the transport process was proton-and energy-dependent.In addition, Caco-2 cells taked up cephalexin by dipeptide transporters that closely resembled the transporters present in the intestine.Caco-2 cells represented an ideal cellular model for future studies of the dipeptide transporter.

Synthesis and Characterization of Dipeptide Schiff Base Complexes of Copper(Ⅱ), Zinc(Ⅱ), Nickel(Ⅱ) and Cobalt(Ⅱ)

A new Schiff base (LK) obtained from 2, 4, -dihydroxybenzaldehyde and glycly-DL- phenylalanine reacted with Cu(II), Zn(II), Ni(II) and Co(II) to yield new complexes. The complexes were characterized by elemental analyses, molar conductance, 1H NMR DTA, TG, IR and UV spectroscopy. In these complexes the ligand is coordinated to the metal through its phenolic oxygen, carboxyl oxygen, imino nitrogen and amide nitrogen. All complexes are non-electrolytes and four coordinated with 1:1(metal; ligand) stoichiometry. The probable structure of the complexes is suggested

Systematic screening and structural characterization of dipeptides using offline 2D LC-LTQ-Orbitrap MS:A case study of Cordyceps sinensis

Cordyceps sinensis(C.sinensis)is a widely used and highly valuable traditional Chinese medicine.Several dipeptides have been detected in C.sinensis,but current scientific knowledge of its chemical makeup remains limited.In this study,an improved approach that integrates offline two-dimensional liquid chromatography(2D LC)separation,precursor ion list,library screening,and diagnostic ion filtering was established to systematically screen and characterize dipeptides in C.sinensis.Offline 2D LC integrating hydrophilic interaction LC and reverse phase separations was established to eliminate interference and identify the target dipeptides.A library containing the potential 400 dipeptides was created,and a precursor ion list with all theoretical precursor ions was adopted to trigger the MS/MS scan with high sensitivity.To identify dipeptides,the type and connection sequence of amino acids were determined according to the product ions.Ile and Leu residues were differentiated for the first time according to the characteristic ion at m/z 69.07.Ultimately,170 dipeptides were identified or tentatively characterized from C.sinensis,and most are reported for the first time in this species herein.In addition,the identified dipeptides were also applied for discrimination among the three Cordyceps species,and 11 markers were identified.The obtained results provide a deeper understanding of the chemical basis of C.sinensis.

SYNTHESIS OF DIPEPTIDE THROUGH A TWO-LIQUID-PHASE ENZYME MEMBANE REACTOR

The synthesis of dipeptide AcPheLeuNH2 catalyzed by immobilized pancreatic lipase was carried out in a two- liquid-phase hollow-fiber membrane reactor, operated in a batch mode. Kinetic properties of free and immobilized enzyme, partition behavior between aqueous buffer phase and organic solvent phase, and effective diffusion coefficients of substrates and products through the membrane were investigated respectively. Based on the preliminary experimental results, the performance of the enzyme membrane reactor, which is evaluated by the purity and the yield, is discussed.

Hydrolysis of Dipeptide Heptyl Esters with Newlase F

Newlase F is a rude enzyme which contains triacylglycerol lipase and acid protease. Hydrolysis of dipeptide heptyl esters with Newlase F was studied in phosphate buffer-organic solvent by HPLC. When the Newlase F's level reached 5 mg/mL under mild condition (PH 7.0, 30 degreesC), the lipase had the highest activity. The reaction was also affected greatly by organic solvents and their concentrations. It is found that protease in Newlase F does not hydrolyze amide bond under this condition (pH 7.0, r.t.).

Proline-based Amino Pyridine Dipeptides as Efficient Organocatalysts for Direct Aldol Reaction

A series of proline-based amino pyridine dipeptide organocatalysts was synthesized and applied in direct asymmetric intermolecular aldol reaction. These catalysts showed good solubility in organic solvents, good yields （73%--97%） and enantioselectivitives（74%--94%）. Among them, dipeptide organocatalyst（2） was found to be the most efficient one for the asymmetric aldol reaction between cyclohexanone and 4-nitrobeznaldehyde. After optimizing the catalytic reaction conditions, we found that the catalyst showed high yield（97%）, enantioselectivity（e.e., up to 92%） and anti-diastcreoselectivity（up to 95：5） at mild room temperature without any additives.

Regulation of Cleavage Activity of Ser-His Dipeptide on DNA by Phosphorylation

The cleavage reactions of Ser-His and its N-terminal phosphorylated form - N-(O,O-diisopropyl) phosphoryl seryl-histidine (DIPP-Ser-His) were studied on DNA. It was found that the phosphorylation of Ser-His caused the lost of the cleavage activity on DNA. The result might give some clue on the regulation of the activity of protein by phosphorylation.

Kinetically Controlled Carboxypeptidase-Catalyzed Synthesis of Novel Antioxidant Dipeptide Precursor BOC-Tyr-Ala

Recently, enzymatic peptide synthesis has drawn increasing attention due to its eco-friendly reagents and mild conditions, as compared to traditional chemical peptide synthesis. In this study, we successfully produced an important antioxidant dipeptide precursor, BOC-Tyr-Ala, via a kinetically controlled enzymatic peptide synthesis reaction, catalyzed by the recombinant car- boxypeptidase Y （CPY） expressed in P. pastoris GS 115. In this reaction, the enzyme activity was 95.043 U/mL, and we used t-butyloxycarbonyl-L-tyrosine-methyl ester （BOC-Tyr-OMe） as the acyl donor and L-alanine （L-Ala） was the amino donor. We optimized the reaction conditions to be： 30 ℃, pH 9.5, organic phase （methanol）/aqueous phase = 1：20, BOC-Tyr-OMe 0.05 mol/L, Ala 0.5 mol/L, and a reaction time of 12 h. Under these conditions, the dipeptide yield reached 49.84%. Then, we established the kinetic model of the synthesis reaction in the form of Michaelis-Menten equation according to the con-centration-time curve during the process and the transpeptidation mechanism. We calculated the apparent Michaelis constant K^（app）mand the apparent maximum reaction rate r^（app）max to be 2.9946 x 10^-2 mol/L and 2.0406 x 10.2 mmol/（mL h）, respectively.

Dimeric Dipeptide Mimetics of NGF and BDNF Are Promising Agents for Post-Stroke Therapy

The dimeric dipeptide mimetics of the brain derived neurotrophic factor (BDNF) loops 1 and 4 and nerve growth factor (NGF) loop 4 were designed and synthesized at the Zakusov Research Institute of Pharmacology. There are respectively bis-(N-monosuccinyl-L-methionyl-L-serine) heptamethylenediamide(GSB-214), bis-(N-monosuccinyl-L-seryl-L-lysine) hexamethylenediamide (GSB-106) and bis-(N-monosuccinyl-L-glutamyl-L-lysine) hexamethylenediamide (GK-2). All of the ob-tained compounds activated a corresponding specific NGF or BDNF tyrosine kinase receptor (TrkA or TrkB), but had different postreceptor signaling patterns. GSB-106 activated the ERK and AKT, whereas GSB-214 and GK-2 only activated the AKT kinase. Here we report a comparative analysis of neuroprotective activity of these dipeptides in a model of ischemic stroke induced by transient middle cerebral artery occlusion (MCAO). The all three dimeric dipeptides showed a statistically significant decrease of infarct volumes with the treatment beginning 4 hour after surgery. In the experiment with BDNF mimetics, GSB-106 reduced this volume by 66% and GSB-214 by 26%. NGF GK-2 reduced the cerebral infarct volume by 45%. Thus, BDNF mimetic, which activated both the ERK and AKT, and NGF mimetic, which selectively activated PI3K/AKT, showed high neuroprotective efficacy. In addition, we studied neuroprotective effects of GK-2 at the beginning of the treatment 6, 8 and 24 hours after reperfusion. The neuroprotective effect of GK-2 persisted in all these conditions. The effectiveness of GK-2 at a delayed start of administration suggests that the dipeptide has neuroregenerative properties. The results obtained suggest a potential role for the dimeric dipeptide NGF and BDNF mimetics as therapeutic agents useful in the treatment of a stroke.

DETERM INATION OF THE STABILITY CONSTANTS OF COMPLEXES OF HISTIDINE,SOME DIPEPTIDES AND TRIGLYCINE WITH Zn(Ⅱ)AND Cd(Ⅱ)USING SMALL-SCALE PH-METRIC TITRATIONS

A potentiometric study on the complexes of His,Gly-His,ALa-His,Gly-Gly and Gly—Gly—Gly with Zn(Ⅱ)and Cd(Ⅱ)has been reported.Small-scale potentiometric titrations were car- ried out to determine stabil ity constants of complexes at 25℃ with I=0.10 mol dm^(-3)(KNO_3).The com- puter programs SUPERQUAD were applied for data treatment with satisfactory results.