Patterns of adenine metabolism and caffeine biosynthesis in different parts of tea seedlings

Contents of purine alkaloids in different parts of tea ( Camellia sinensis L. cv. Yabukita ) seedlings, seeds and tissue cultures were determined with high-performance liquid chromatography. More than 99% of the caffeine detected was in the leaves of the 4-month-old seedlings. The amount expressed per g fresh weight was higher in older leaves. Theobromine, a precursor of caffeine biosynthesis, was found only in younger leaves. Zero or only trace amounts of theophylline, a degradation product of caffeine, were found in the seedlings. Almost all the caffeine in tea seeds was found in the seed coats. Theobromine and theophilline could not be detected in any part of the seeds.
Tracer experiments using [8-¹⁴C]-adenine indicate that (i) caffeine biosynthesis from [8-¹⁴C]-adenine occurs only in younger leaves,(ii) "salvage" of [8-¹⁴C]-adenine for nucleic acid synthesis takes place in all parts of the seedlings, (iii) considerable degradation of [8-¹⁴C]-adenine by conventional purine degradation pathway via uric acid takes place in roots and lower parts of stem tissue.
The results strongly suggest that caffeine is synthesized in younger leaves and accumulated within the leaves. Both caffeine contents and its synthetic activity from adenine were extremely low in tissue culture of tea.     

Effect of Acarbose on the Increased Plasma Concentration of Uric Acid Induced by Sucrose Ingestion

Sucrose is converted fructose and glucose, which may increase plasma uric acid concentration (pUA) through increased purine degradation and/or decreased uric acid (UA) excretion. To investigate effects of acarbose, an inhibitor of alpha-glucosidase, on the increased pUA from sucrose administration, we measured pUA and urinary UA excretion in 6 healthy subjects before and after administering sucrose, with and without co-administration of acarbose. Sucrose raised pUA by 10% (p < 0.01). However, excretion and fractional clearance of UA were unchanged. Sucrose and acarbose coadministration also increased pUA, but less than did sucrose alone (sucrose: 4.9 to 5.4 mg/dl; sucrose + acarbose, 4.7 to 4.9 mg/dl, p < 0.05) without changes in urinary excretion and fractional clearance of UA. Acarbose appears to attenuate the rise in pUA by sucrose ingestion by inhibiting sucrose absorption.     

Review: Markers and proxies to monitor ruminal function and feed efficiency in young ruminants

Developing the rumen’s capacity to utilise recalcitrant and low-value feed resources is important for ruminant production systems. Early-life nutrition and management practices have been shown to influence development of the rumen in young animals with long-term consequences on their performance. Therefore, there has been increasing interest to understand ruminal development and function in young ruminants to improve feed efficiency, health, welfare, and performance of both young and adult ruminants. However, due to the small size, rapid morphological changes and low initial microbial populations of the rumen, it is difficult to study ruminal function in young ruminants without major invasive approaches or slaughter studies. In this review, we discuss the usefulness of a range of proxies and markers to monitor ruminal function and nitrogen use efficiency (a major part of feed efficiency) in young ruminants. Breath sulphide and methane emissions showed the greatest potential as simple markers of a developing microbiota in young ruminants. However, there is only limited evidence for robust indicators of feed efficiency at this stage. The use of nitrogen isotopic discrimination based on plasma samples appeared to be the most promising proxy for feed efficiency in young ruminants. More research is needed to explore and refine potential proxies and markers to indicate ruminal function and feed efficiency in young ruminants, particularly for neonatal ruminants.     

Solid-phase Parallel Synthesis of 4-β-D-Ribofuranosylpyrazolo[4,3-d]pyrimidine Nucleosides

The synthesis of pyrazolo[4,3-d]pyrimidine nucleoside library using solid-phase parallel synthesis methodology is described. Glycosylation of the trimethylsilyl (TMS) derivative of 1- and 2-(methyl)-1H and 2H-pyrazolo[4,3-d]pyrimidine-5,7-(4H,6H)-dione (5) with 1-O-acetyl-2,3,5-tri-O-benzoyl-D-ribofuranose in the presence of TMS triflate provided two novel protected nucleosides 6 and 7. The structures of 6 and 7 were assigned by 1H and 2D NMR experiments. Nucleosides 6 and 7 were then transformed to the key intermediates 12 and 15 respectively. Reaction of 12 and 15 with MMTCl resin in the presence of 2,6-lutidine afforded the necessary scaffolds B and C. Different amines (96) were introduced selectively by nucleophilic substitution on scaffolds B and C using solid-phase parallel semi-automated synthesizer. Cleavage of the products from the solid support with 30% HFIP in a parallel fashion yielded nucleoside libraries simultaneously, and they were analyzed and characterized by high-throughput LC-MS.     

Synthesis and NMR Assignment of the Two Diastereomers of 8,6′-Cyclo-2′,6′-Dideoxyadenosine

We herein present the first synthesis and characterization of the two C5′ diastereomers of 8,6′-cyclo-2′,6′-dideoxyadenosine. Starting from commercially available 2′-deoxyadenosine, the target cyclonucleosides were synthesized in 11 linear steps. Following a zinc-mediated cyclization reaction to form the seven-membered ring, the stereochemistry of the newly formed chiral center was established using two-dimensional NOESY NMR experiments.

[Supplemental materials are available for this article. Go to the publisher's online edition of Nucleosides, Nucleotides & Nucleic Acids for the free supplemental resource.]     

Novel 5-Arylcarbamoyl-2-methylisoxazolidin-3-yl-3-phosphonates as Nucleotide Analogues

A series of 5-substituted 3-phosphonylated isoxazolidines have been obtained via cycloaddition of N-methyl-C-(diethoxyphosphoryl)nitrone with N-heteroaromatic acrylamides. Good trans/cis diastereoselectivities (d.e. 58–76%) of isomeric (3-diethoxyphosphoryl)isoxazolidines were observed. cis- and trans-Isoxazolidine phosphonates were evaluated for their antiviral activity against a broad range of DNA and RNA viruses but were found inactive. Their cytostatic activity toward L1210, CEM, and HeLa cells was also established, and compounds cis-12r and trans-11r having a 2,2-difluorobenzo[d][1,3]dioxole moiety slightly inhibited proliferation of HeLa cells at IC₅₀ values of 186 and 179 μM, respectively.     

Synthesis of the first example of a nucleoside analogue bearing a 5′-deoxy-β-d-allo-septanose as a seven-membered ring sugar moiety

The first example of a nucleoside analogue bearing a 5′-deoxy-β-d-allo-septanose as a seven-membered ring sugar moiety, namely 9-(5-deoxy-β-d-allo-septanosyl)-adenine, is reported. This compound was synthesized in 14 steps from the commercially available d-glycero-d-gulo-1,4-lactone. When evaluated in cell culture experiments against a broad range of viruses, it did not exhibit any significant antiviral effect or cytotoxicity.     

New carbocyclic nucleoside analogues with a bicyclo[2.2.1]heptane fragment as sugar moiety; Synthesis,X-ray crystallography and anticancer activity

An amine group was synthesized starting from an optically active bicyclo[2.2.1]heptane compound, which was then used to build the 5 atoms ring of a key 6-chloropurine intermediate. This was then reacted with ammonia and selected amines obtaining new adenine- and 6-substituted adenine conformationally constrained carbocyclic nucleoside analogues with a bicyclo[2.2.1]heptane skeleton in the sugar moiety. X-ray crystallography confirmed an exo-coupling of base to the ring and a L configuration of the nucleoside analogues. The compounds were tested for anticancer activity.     

Synthesis and antiviral activities of 3-deaza-3-fluoroaristeromycin and its 5′ analogues

The naturally occurring adenine based carbocyclic nucleosides aristeromycin and neplanocin A and their 3-deaza analogues have found a prominent place in the search for diverse antiviral activity agent scaffolds because of their ability to inhibit S-adenosylhomocysteine (AdoHcy) hydrolase. Following the lead of these compounds, their 3-deaza-3-fluoroaristeromycin analogues have been synthesized and their effect on S-adenosylhomocysteine hydrolase and RNA and DNA viruses determined.