The Nucleosides Contents and Their Variation in Natural Cordyceps sinensis and Cultured Cordyceps Mycelia

Aim: To compare the contents of nucleosides from natural Cordyceps sinensis and cultured Cordyceps mycelia, and to study the effect of humidity and heat on the content of nucleosides. Methods: The contents of nucleosides were determined by using high performance capillary electrophoresis (HPCE). Beckman P/ACE System 5010 apparatus equipped with a UV detector and a Beckman untreated fused-silica capillary (57 cm 75 mm, 50 cm effective length) was used. Before sample injection, the capillary was rinsed with 1 molL-1 sodium hydroxide solution and running buffer for 5 min, respectively. A voltage of 20 kV was applied for the separation. Pressure injection was 586 kPa for 6 seconds, and the wavelength of detector was 254 nm. The running time was 20 min at 20 oC. The effect of humidity and heat on the contents of nucleosides from natural Cordyceps sinensis and cultured Cordyceps mycelia was observed for 1, 3, 5 and 10 days at temperature 40 oC, and relative humidity 75%. Results: The content of nucleosides from natural Cordyceps sinensis was higher than that from cultured Cordyceps mycelia. But the contents of nucleosides from freshly collected natural Cordyceps sinensis were very low, even below the limit of quantitation. The contents of nucleosides from natural Cordyceps sinensis were significantly increased by humidity and heat, but this phenomenon was not observed in cultured Cordyceps mycelia. Conclusion: There are differences between the nucleosides from natural Cordyceps sinensis and cultured Cordyceps mycelia. The nucleosides in natural Cordyceps sinensis may be derived from the degradation of nucleic acids. This implies that adenosine being used for the quality control of natural Cordyceps sinensis may have to be reconsidered.

Role of human nucleoside transporters in pancreatic cancer and chemoresistance

The prognosis of pancreatic cancer is poor with the overall 5-year survival rate of less than 5%changing minimally over the past decades and future projections predicting it developing into the second leading cause of cancer related mortality within the next decade.Investigations into the mechanisms of pancreatic cancer development,progression and acquired chemoresistance have been constant for the past few decades,thus resulting in the identification of human nucleoside transporters and factors affecting cytotoxic uptake via said transporters.This review summaries the aberrant expression and role of human nucleoside transports in pancreatic cancer,more specifically human equilibrative nucleoside transporter 1/2(hENT1,hENT2),and human concentrative nucleoside transporter 1/3(hCNT1,hCNT3),while briefly discussing the connection and importance between these nucleoside transporters and mucins that have also been identified as being aberrantly expressed in pancreatic cancer.The review also discusses the incidence,current diagnostic techniques as well as the current therapeutic treatments for pancreatic cancer.Furthermore,we address the importance of chemoresistance in nucleoside analogue drugs,in particular,gemcitabine and we discuss prospective therapeutic treatments and strategies for overcoming acquired chemoresistance in pancreatic cancer by the enhancement of human nucleoside transporters as well as the potential targeting of mucins using a combination of mucolytic compounds with cytotoxic agents.

Syntheses of Nucleoside Derivatives Containing Fmocor Trityl-protected Amino Acids

Facile direct esterification reactions between 2′,3′-O-isopropylidene-nucleosides and Fmoc- or trityl-protected amino acids %via% N,N-dicyclohexyl-carbodiimide(DCC) mediated condensation are described. These reactions offer a mild and convenient method to synthesize aminoacylated nucleoside derivatives.

Simultaneous determination of five nucleosides and nucleobases in Panax notoginseng using high-performance liquid chromatography

Aim To quantitatively determine five nucleosides and nucleobases, including cytidine, uridine, guanosine, adenosine and uracil in different parts of Panax notoginseng. Methods Separation was performed on a Zorbax SB-Aq column using a gradient elution with mobile phase of 8 mmol^L-1 ammonium acetate aqueous solution （A） and methanol （B）. The assay was carried out at a flow rate of 1 mL·min^-1 at 25 ℃ with the diode-array detection at 260 nm. Results Cytidine, uridine, guanosine, adenosine and uracil had good linearity in the ranges of 1.79 - 57.40 μg·mL^-1 （r^2 = 1.0000）, 3.30 - 105.60 μg·mL^-1 （r^2 = 1.0000）, 3.09 - 98.80 μg·mL^ -1（r^2 = 0.9999）, 2.77 - 88.60 μg·mL^-1 （r^2 = 1.0000） and 0.38 - 12.30 μg·mL ^-1 （r^2 = 1.0000） with average recoveries of 93.9%, 96.5%, 92.7%, 93.2% and 98.8%, respectively. The content of cytidine, uridine, guanosine, adenosine and uracil in different parts of P. notogingeng were significantly different. Conclusion This is the first report on quantitative determination of nucleosides and nucleobases in P notoginseng.

Viral infection parameters not nucleoside analogue itself correlates with host immunity in nucleoside analogue therapy for chronic hepatitis B

AIM: To determine the relationship between host immunity and the characteristics of viral infection or nucleoside analogues (NAs) themselves in patients with chronic hepatitis B (CHB) receiving NA therapy.

Induction of nucleoside phosphorylase in Enterobacter aerogenes and enzymatic synthesis of adenine arabinoside

Nucleoside phosphorylases (NPases) were found to be induced in Enterobacter aerogenes DGO-04, and cytidine and cytidine 5′-monophosphate (CMP) were the best inducers. Five mmol/L to fifteen mmol/L cytidine or CMP could distinctly increase the activities of purine nucleoside phosphorylase (PNPase), uridine phosphorylase (UPase) and thymidine phosphorylase (TPase) when they were added into medium from 0 to 8 h. In the process of enzymatic synthesis of adenine arabinoside from adenine and uracil arabinoside with wet cells of Enterobacter aerogenes DGO-04 induced by cytidine or CMP, the reaction time could be shortened from 36 to 6 h. After enzymatic reaction the activity of NPase in the cells induced remained higher than that in the cells uninduced.

Nucleoside diphosphate-linked moiety X-type motif 15 R139C genotypes impact 6-thioguanine nucleotide cut-off levels to predict thiopurine-induced leukopenia in Crohn’s disease patients

BACKGROUND Thiopurine-induced leukopenia(TIL)is a life-threatening toxicity and occurs with a high frequency in the Asian population.Although nucleoside diphosphate-linked moiety X-type motif 15(NUDT15)variants significantly improve the predictive sensitivity of TIL,more than 50%of cases of this toxicity cannot be predicted by this mutation.The potential use of the 6-thioguanine nucleotide(6TGN)level to predict TIL has been explored,but no decisive conclusion has been reached.Can we increase the predictive sensitivity based on 6TGN by subgrouping patients according to their NUDT15 R139C genotypes?AIM To determine the 6TGN cut-off levels after dividing patients into subgroups according to their NUDT15 R139C genotypes.METHODS Patients’clinical and epidemiological characteristics were collected from medical records from July 2014 to February 2017.NUDT15 R139C,thiopurine S methyltransferase,and 6TGN concentrations were measured.RESULTS A total of 411 Crohn’s disease patients were included.TIL was observed in 72 individuals with a median 6TGN level of 323.4 pmol/8×10^8 red blood cells(RBC),which was not different from that of patients without TIL(P=0.071).Then,we compared the 6TGN levels based on NUDT15 R139C.For CC(n=342)and CT(n=65)genotypes,the median 6TGN level in patients with TIL was significantly higher than that in patients without(474.8 vs 306.0 pmol/8×10^8 RBC,P=9.4×10-^5;291.7 vs 217.6 pmol/8×10^8 RBC,P=0.039,respectively).The four TT carriers developed TIL,with a median 6TGN concentration of 135.8 pmol/8×10^8 RBC.The 6TGN cut-off levels were 411.5 and 319.2 pmol/8×108 RBC for the CC and CT groups,respectively.CONCLUSION The predictive sensitivity of TIL based on 6TGN is dramatically increased after subgrouping according to NUDT15 R139C genotypes.Applying 6TGN cut-off levels to adjust thiopurine therapies based on NUDT15 is strongly recommended.

Application of nucleoside analogues to liver transplant recipients with hepatitis B

Hepatitis B is a common yet serious infectious disease of the liver, affecting millions of people worldwide. Liver transplantation is the only possible treatment for those who advance to end-stage liver disease. Donors positive for hepatitis B virus(HBV) core antibody(HBc Ab) have previously been considered unsuitable for transplants. However, those who test negative for the more serious hepatitis B surface antigen can now be used as liver donors, thereby reducing organ shortages. Remarkable improvements have been made in the treatment against HBV, most notably with the development of nucleoside analogues(NAs), which markedly lessen cirrhosis and reduce post-transplantation HBV recurrence. However, HBV recurrence still occurs in many patients following liver transplantation due to the development of drug resistance and poor compliance with therapy. Optimized prophylactic treatment with appropriate NA usage is crucial prior to liver transplantation, and undetectable HBV DNA at the time of transplantation should be achieved. NA-based and hepatitis B immune globulin-based treatment regimens can differ between patients depending on the patients' condition, virus status, and presence of drug resistance. This review focuses on the current progress in applying NAs during the perioperative period of liver transplantation and the prophylactic strategies using NAs to prevent de novo HBV infection in recipients of HBc Ab-positive liver grafts.

Effects of two novel nucleoside analogues on different hepatitis B virus promoters

AIM： To explore the effects of the nucleoside analogues β-L-D4A and β-LPA on hepatitis B virus （HBV） promoters. METHODS： Four HBV promoters were amplified by polymerase chain reaction （PCR） and subcloned into the expression vector pEGFP-1. The four recombinants controlled by HBV promoters were confirmed by restriction analysis and sequencing. Human hepatoma HepG2 cells transfected with the recombinant plasmids were treated with various concentrations of β-L-D4A and β-LPA. Then, enhanced green fluorescent protein （EGFP）-positive cells were detected by fluorescence microscopy and using a fluorescence activated cell sorter RESULTS： Four HBV promoters were separately obtained and successfully cloned into pEGFP-1, Expression of EGFP under the control of the surface promoter （Sp） and the X promoter （Xp） was inhibited by β-L-D4A in a dosedependent manner, while expression of EGFP under the control of the core promoter （Cp） and Xp was inhibited by β-LPA in a dose-dependent manner. CONCLUSION： The two novel nucleoside analogues investigated here can inhibit the activities of HBV promoters in a dose-dependent manner. These findings may explain the mechanisms of action by which these two novel compounds inhibit HBV DNA replication.

Current prodrug strategies for improving oral absorption of nucleoside analogues

Nucleoside analogues are first line chemotherapy in various severe diseases:AIDS(acquired immunodeficiency disease syndrome),cytomegalovirus infections,cancer,etc.However,many nucleoside analogues exhibit poor oral bioavailability because of their high polarity and low intestinal permeability.In order to get around this drawback,prodrugs have been utilized to improve lipophilicity by chemical modification of the parent drug.Alternatively,prodrugs targeting transporters present in the intestine have been applied to promote the transport of the nucleoside analogues.Valacyclovir and valganciclovir are two classic valine ester prodrugs transported by oligopeptide transporter 1.The ideal prodrug achieves delivery of a parent drug by attaching a non-toxic moiety that is stable during transport,but is readily degraded to the parent drug once at the target.This article presents advances of prodrug approaches for enhancing oral absorption of nucleoside analogues.

Induction of Recombinant Uridine Phosphorylase and Its Application in Biosynthesis of Pyrimidine Nucleosides

Recombinant Escherichia coli pUDP,which overexpressed uridine phosphorylase（UPase）,was constructed.0.5 mmol·L 1lactose had a similar induction effect as the commonly used inducer IPTG during 2.5-5.5 h of cell growth.The lactose-induced UPase was stable at 50°C.Wet cells of pUDP was used as catalyst to biosynthesize 5-fluorouridine from 30 mmol·L 1uridine and 5-fluorouracil in phosphate buffer（pH 7.0）catalyzed at 50°C for 1.5 h and the yield of 5-fluorouridine was higher than 68%.Under the optimum reaction conditions for production of 5-fluorouridine,5-methyluridine and azauridine were synthesized from uridine by pUDP,the yield was 61.7%and 47.2%respectively.Deoxynucleosides were also synthesized by pUDP,but the yield was only about 20%.

Effects of Bases on the Stabilities of Nucleoside C4'Radicals

C4'-H bond dissociation enthalpies of nucleosides were predicted using theoretical methods to a precision of 1-2 Kcal/mol. It was found that the stability of the C4' nucleoside radical is slightly dependent on the base. The orders of stability are dA < dG < dT < dC for deoxynucleosides and U < G < A = C for nucleosides.

Design, synthesis and in vitro evaluation of L-amino acid esters prodrugs of acyclic nucleoside phosphonates as anti-HBV agent

A series of novel L-amino acid esters prodrugs of acyclic nucleoside phosphonates was synthesized and their anti-HBV activity was evaluated in HepG2 2.2.15 cells. Compound 1d exhibited more potent anti-HBV activity and lower cytotoxicity than those of adefovir dipivoxil with EC50 and CC50 values of 0.207 μmol/L and 2530 μmol/L, respectively.

An efficient and green preparation of 5-aminophosphonate substituted pyrimidine nucleosides under solvent-free conditions

An environmentally benign and highly efficient one-pot preparation of α-aminophosphonates under solvent-free conditions was developed. By employing this method, 5-aminophosphonate substituted pyrimidine nucleosides were synthesized in good to excellent yields starting from 5-forrnyl-2＇-deoxyuridine, aniline and dimethylphosphite.

Simultaneous determination of ten nucleosides and bases in Ganoderma by micellar electrokinetic chromatography

Ganoderma(lingzhi)is a famous herbal medicine and edible supplement in oriental countries for a long history.In this study,a simple micellar electrokinetic chromatography(MEKC)method was established for the analysis of nucleosides and bases,the major bioactive components in Ganoderma for the first time.By optimizing the borate concentration,the sodium dodecyl sulfate(SDS)concentration and the pH value of running buffer,10 nucleosides and bases achieved an ideal separation.In real sample analysis,the developed method was successfully used to determine the 10 target analytes in 23 batches of Ganoderma samples from different regions.Results indicated that contents of 10 investigated analytes in each sample showed obvious variation.The principal components analysis(PCA)and hierarchical cluster analysis(HCA)analysis classified the samples into three groups,and the HCA tree visualized the relationships which was mainly contributed by geographical partition.The results indicated geographical origin to be an important factor that affect the accumulation of nucleosides and bases in Ganoderma.In summary,this study provides a simple and practical strategy for quality assessment and cultivation reference of Ganoderma.

Synthesis and X-Ray Structure of New Anticancer Nucleosides Based on 1-((2-Hydroxyethoxy)methyl)-5-(phenylthio)-1H-1,2,4-triazole-3-carboxamide

A pair of new anticancer nucleosides based on 1,2,4-triazole nucleosides and 1-((2-hydroxyethoxy) methyl)-5-(phenylthio)-1H-1,2,4-triazole-3-carboxamide have been synthesized, and have given the corresponding products in excellent yields. Its structures and conformations were confirmed by single crystal X-ray diffraction.

Clinical efficacy and safety of TCM prescriptions combined with nucleoside(acid)analogues in treating chronic hepatitis B:a meta-analysis

Objective There are many clinical reports on traditional Chinese medicine(TCM)combined with nucleoside(acid)analogues(NAs)for the treatment of chronic hepatitis B(CHB),but its efficacy and safety are not completely clear.This meta-analysis aims to evaluate the clinical efficacy and safety thus providing evidence for clinical applications.Methods We searched Chinese databases the China National Knowledge Infrastructure(CNKI),Wanfang Data,and China Science and Technology Journal Database(VIP),as well as English databases Pub Med and Cochrane Library,from time of establishment to April 14,2021.Literature quality was evaluated according to the bias risk assessment criteria of Cochrane Collaboration network.Rev Man 5.3 and Stata 12.0 software were used to perform this research.Results A total of 23 articles,3282 patients,and 25 TCM prescriptions were included in this study.NAs plus TCM remarkably improved the clinical total effective rate[Odds ratio(OR)=3.92,P<0.00001],TCM syndrome score(Mean difference=-3.73,P<0.00001),hepatitis B virus(HBV)DNA negative conversion rate(OR=1.49,P=0.0001),hepatitis Be antigen(HBe Ag)negative conversion rate(OR=2.03,P<0.00001),alanine aminotransferase levels[Std mean difference(SMD)=-0.95,P<0.00001],and aspartate aminotransferase levels(SMD=-0.70,P=0.0004).Adverse reaction rates did not increase in the combined treatment group(OR=0.97,P=0.84).A comprehensive analysis of the 25 TCM prescriptions suggested that the combination of spleen-strengthening prescriptions with NAs showed better effects than other prescriptions.Conclusion TCM in combination with NAs,demonstrated better clinical efficacy against CHB than NAs alone.In addition,the combination of spleen-strengthening prescriptions and NAs was identified as the best therapeutic strategy.However,more randomized controlled trials of high quality are needed to provide more reliable clinical basis for the application of TCM.

Preparation of nucleoside-pyridine hybrids and pyridine attached acylureas from an unexpected uracil ring-opening and pyridine ring-forming sequence

Novel pyrimidine nucleoside-3,5-dicyanopyridine hybrids （4） or pyridine attached acylureas （5） were selectively and efficiently prepared from the reaction of 2′-deoxyuddin-5-yl-methylene malononitrile （1）, malononitrile （2） and thiophenol （3） or from an unexpected uracil ring-opening and pyddine ring-forming sequence via the reaction of 1 and 3. It is the first time such a sequence has ever been reported.

Interaction between N-Phospho-Amino Acids and Nucleoside in Aqueous Medium

Nucleosides were phosphorylated with different N- (O, O-diisopropyl) phosphoryl amino acids to give nucleoside mono phosphates in aqueous solution. 2', 3', and 5'-isomers had been confirmed by comparison with authentic samples on the basis of HPLC analysis. The conversion percentage of nucleoside indicated that N- (O, O-diisopropyl) phosphoryl aspartic acid reacted with adenosine and guanosine at a much higher rate than other kinds of N- phosphoryl amino acids. while phosphorylation of cytidine and uridine was relatively easy by using N- (O, O-diisopropyl) phosphoryl threonine. The result could give some clue to the prebiotic code origin of nucleic acid and protein.

Design and Synthesis of Lipids Bearing Nucleosides as Gene Vectors

Some novel lipids bearing nucleosides were designed and synthesized as gene vectors, and the structures of these compounds were characterized by UV, IR, 1HNMR, 13CNMR and elemental analysis.