Synthesis and biological evaluation of halo-neplanocin A as novel mechanism-based inhibitors of S-adenosylhomocysteine hydrolase

Halogenated analogues of neplanocin A were synthesized from the key intermediate 1, among which fluoro-neplanocin A was found to be novel mechanism-based irreversible inhibitor of S-Adenosylhomocysteine hydrolase.     

Design, synthesis, and in vitro evaluation of APIO analogue of neplanocin A

A novel apio analogue of neplanocin A was efficiently synthesized from D-ribose via stereoselective aldol-retroaldol reaction for introducing hydroxymethyl group and RCM reaction for synthesizing carbocycle, and its inhibitory activity against SAH hydrolase was assayed.     

Synthesis and biological evaluation of novel thioapio dideoxynucleosides

On the basis of the bioisosteric rationale to apio dideoxynucleosides, novel thioapio dideoxynucleosides have been synthesized, starting from 1,3-dihydroxyacetone via thioapio sugar acetate as a key intermediate. The intermediate was condensed with silylated pyrimidine bases such as N(4)-benzoylcytosine, uracil or thymine in the presence of TMSOTf to give the beta-anomers and alpha-anomers, respectively. The intermediate was also condensed with silylated 6-chloropurine to give the 6-chloropurine derivatives and which were converted to adenine derivatives and, N(6)-methyladenine derivatives and, and hypoxanthine derivatives and, respectively. The guanine analogues and were also synthesized from the condensation of sugar acetate with 2-acetamido-6-chloropurine. All synthesized final compounds were tested against HIV-1. Most of the synthesized compounds exhibited toxicity-dependent anti-HIV-1 activity, among which 6-chloropurine derivative was found to be the most cytotoxic and showed good cytotoxicity against colon cancer cell lines. Although we could not find good anti-HIV agents in this study, findings of some anticancer activity in this series will allow this class of nucleosides to be the new template for the development of new anticancer agents (Fig. 1).     

Cultivar variability in the Agrobacterium-rice cell interaction and plant regeneration

Thirteen cultivars of rice ( Oryza sativa ) were tested for plant regeneration from calli initiated from the scutella of mature seeds by water stress treatment using a high concentration of agarose, and examined for their response to Agrobacterium tumefaciens LBA4404, carrying a plasmid pTOK233, harboring genes for kanamycin resistance ( npt II), hygromycin resistance ( hpt ) and β -glucuronidase ( gus ). Plant regeneration frequency was considerably increased in most of the cultivars when the calli were treated with water stress, as compared with untreated controls. In particular, the cultivars Dongjinbyeo, IR43, Nagdongbyeo and Sinseonchalbyeo showed an increased frequency of shoot regeneration. Expression of GUS was detected in all of the co-cultivated cultivars. Based on GUS expression at 3 days after co-cultivation with A. tumefaciens , three rice cultivars (Dongjinbyeo, Hwayoungbyeo and Nagdongbyeo) were judged highly susceptible to A. tumefaciens , while Milyang 23, Nonganbyeo and Samgangbyeo cultivars were weakly susceptible. Plantlets were readily regenerated when the hygromycin-resistant calli were transferred to a regeneration medium containing hygromycin. Intense blue staining was observed in GUS assays of leaf segments, roots and flower organs from regenerated plants. Stable integration and expression of the introduced hpt and gus genes were confirmed by Southern blot analysis of the transformants. Therefore, Dongjinbyeo and Nagdongbyeo cultivars proved to be both highly susceptible to A. tumefaciens and highly responsive to plant regeneration.     

Synthesis of D- and L-apio nucleoside analogues with 2'-hydroxyl group as potential anti-HIV agents

The present work describes the asymmetric synthesis of D- and L-apio-2',3'-dideoxynucleoside analogues, 4 and 5 with 2'-hydroxyl group via a common intermediate 9, starting from D-galactose. Stereoselective dihydroxylation and deoxygenation through radical inversion were successfully employed to synthesize the key intermediate 12 with D-apio structure, while stereoselecetive hydroboration-oxidation was used for the synthesis of another key intermediate 18 with L-apio structure.     

Synthesis of 5'-substituted fluoro-neplanocin A analogues: importance of a hydrogen bonding donor at 5'-position for the inhibitory activity of S-adenosylhomocysteine hydrolase

Four 5'-substituted fluoro-neplanocin A analogues 1a-d were designed and synthesized, using cyclopentenone derivative 2 as a key intermediate. The inhibitory activity against SAH was in the following order: NH(2)>SH>F, N(3), indicating a hydrogen bonding donor such as OH or NH(2) was essential for inhibitory activity. All the final compounds showed much less decreased cytotoxicity in two cancer cell lines (Col2 and A549), implying that phosphorylation of the 5'-hydroxyl group of fluoro-neplanocin A is closely related to its high cytotoxicity.     

Stereoselective synthesis of 3-hydroxymethyl-D-cyclopentenone, the versatile intermediate for the synthesis of carbocyclic nucleosides

The preparative and stereoselective synthesis (45- 50% overall yields, >50 g scale) of the key carbasugars 7a-d was achieved from D-ribose via stereoselective Grignard reaction and oxidative rearrangement as key reactions.     

Analysis of carbon metabolism in transgenic<Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> transformed with the cyanobacterial sucrose phosphate synthase gene

To investigate the effects of sucrose-phosphate synthase (SPS) on carbon partitioning, transgenicArabidopsis plants transformed withSynechocystis SPS were constructed. The integration, copy number and expression level were confirmed by Southern and Northern blot analyses. SPS activity in leaves from the transgenic and wild type plants was not significantly different. The level of sucrose and starch in the leaves of transgenic plant were slightly decreased compared to wild type. The glucose and fructose contents were increased up to two-fold compared to wild type during the light period. It is our speculation that the decreased sucrose level of the transgenic plant might be caused by the high acid invertase. These authors contributed equally to this work     

Association between Self-Reported Smoking and Hemoglobin A1c in a Korean Population without Diabetes: The 2011–2012 Korean National Health and Nutrition Examination Survey

BackgroundSeveral Western studies have revealed that among non-diabetics, glycosylated hemoglobin A1c (HbA1c) levels are higher in smokers than non-smokers. While studies conducted in Western populations consistently support this association, a recent meta-analysis reported that studies carried out in non-Western populations, including studies of Chinese, Egyptian, and Japanese-Americans, did not detect any significant differences in HbA1c levels between smokers and non-smokers.ObjectivesWe assessed the association between smoking habits and HbA1c levels in the general Korean adult population using data from the Korean National Health and Nutrition Examination Survey (KNHANES) performed in 2011–2012.MethodsA total of 10,241 participants (weighted n=33,946,561 including 16,769,320 men and 17,177,241 women) without diabetes were divided into four categories according to their smoking habits: never smokers (unweighted n/ weighted n= 6,349/19,105,564), ex-smokers (unweighted n/ weighted n= 1,912/6,207,144), current light smokers (<15 cigarettes per day, unweighted n/ weighted n=1,205/5,130,073), and current heavy smokers (≥15 cigarettes per day, unweighted n/ weighted n=775/3,503,781).ResultsIn age- and gender-adjusted comparisons, the HbA1c levels of each group were 5.52 ± 0.01% in non-smokers, 5.49 ± 0.01% in ex-smokers, 5.53 ± 0.01% in light smokers, and 5.61 ± 0.02% in heavy smokers. HbA1c levels were significantly higher in light smokers than in ex-smokers (p = 0.033), and in heavy smokers compared with light smokers (p < 0.001). The significant differences remained after adjusting for age, gender, fasting plasma glucose, heavy alcohol drinking, hematocrit, college graduation, and waist circumference. Linear regression analyses for HbA1c using the above-mentioned variables as covariates revealed that a significant association between current smoking and HbA1c (coefficient 0.021, 95% CI 0.003–0.039, p = 0.019).ConclusionsCurrent smoking was independently associated with higher HbA1c levels in a cigarette exposure-dependent manner in a representative population of Korean non-diabetic adults. In this study, we have observed an association between smoking status and HbA1c levels in non-diabetics drawn from a non-Western population, consistent with previous findings in Western populations.     

Novel method for isolating human melanoblasts from keratinocyte culture

The characterization of melanoblasts is important for understanding their in vivo development, melanoma formation, and pigment‐related disorders. However, no methods have been reported for the isolation of melanoblasts from human skin. Using a ‘calcium‐pulse’ technique, involving the differentiation of human keratinocytes with high calcium and the subsequent spontaneous separation of the epidermal sheets, we effectively isolated human melanoblasts (keratinocyte‐adapted melanoblasts, KaMBs) from keratinocyte culture. The KaMBs expressed early melanogenesis‐related genes, including BRN2, which is a known melanoblast marker. Moreover, the KaMBs displayed much higher proliferative and growth capacities than the primary melanocytes. Considering that keratinocytes might provide an in vivo‐like environment for KaMBs during isolation and in vitro culture, the ‘calcium‐pulse’ technique offers an unprecedented, easy, and efficient method for the isolation of human melanoblasts, retaining the original characteristics of these cells.