Synthesis And Biochemistry Of Ascorbic Acid Analogues

抗坏血酸对癌细胞的选择性体内毒性的一种解释是，与血液相比，抗坏血酸是血管外空间优先稳定形成抗坏血酸自由基和过氧化氢的前体药物。为了测试这一假设，开发了一种直接测量细胞外液中抗坏血酸浓度和过氧化氢之间关系的方法，该方法使用合成的硼酸盐荧光基团过氧苯甲酮，并结合过氧化氢酶控制。用最近一篇文献报道的改良法制备的过氧杂蒽酮，通过通常的？ATE？与过氧化氢反应。产生荧光分子的机制。基于硼化合物独特的化学特性，该反应是针对过氧化氢的。 按典型的人体药理剂量(0.25-0.5 mg/g)静脉、口服或腹腔注射抗坏血酸。在微透析细胞外液和血液中，用高效液相色谱-库仑电化学法测定抗坏血酸，用电子顺磁共振测定抗坏血酸自由基。静脉注射后，血液和细胞外液中的抗坏血酸浓度从50-100微米的基线增加到大约8 mM的峰值，而腹膜内注射产生血液和细胞外液中抗坏血酸的峰值浓度接近3 mM。细胞外液中的抗坏血酸自由基浓度比血液中的高9倍，尽管两个隔室中的抗坏血酸浓度相同。在细胞外液中，抗坏血酸自由基浓度高达250 nm，是抗坏血酸浓度的指数函数。当细胞外液中抗坏血酸自由基浓度超过100 nM时，检测到细胞外液中的过氧化氢，这仅在非肠道给药时发生。胞外液中20-30微米的过氧化氢浓度与最高的抗坏血酸自由基浓度相对应，约为250毫微米。综上所述，这些数据证实了药理抗坏血酸是促进抗坏血酸自由基和过氧化氢在血管外空间优先稳定形成的假设，而不是在血液中。 我们正在继续合成工作，以制备新的类黄酮类类似物，以研究这些抗坏血酸和葡萄糖转运抑制剂的结构参数。被包含的将是运输蛋白的潜在亲和标记(S)。此外，还将考察类黄酮类化合物的氟代换生物效应。一系列氟化查尔酮已经被制备出来，并将在产生类黄酮结构的条件下进行环化。

One explanation for selective in vivo toxicity of ascorbic acid to cancer cells is that ascorbic acid serves as a pro-drug for preferential steady state formation of ascorbate radical and hydrogen peroxide in the extravascular space compared to blood. To test this hyptothesis, a procedure was developed for direct measurement of the relationship between ascorbic acid concentration and hydrogen peroxide in extracellular fluid using a synthetic boronate fluorophore peroxyanthone, coupled to catalase controls. The peroxyxanthone, prepared using a modification of a recent literature report, reacts with hydrogen peroxide through the usual ?ate? mechanism to produce a fluorescent molecule. Based on the unique chemistry of boron compounds, the reaction is specific for hydrogen peroxide. Rats were administered intravenous, oral, or intraperitoneal ascorbic acid using typical human pharmacologic doses (0.25-0.5 mg/g). In extracellular fluid obtained by microdialysis and in blood, ascorbic acid was measured by HPLC with coulometric electrochemical detection and ascorbate radical was measured by electron paramagnetic resonance. Upon intravenous injection, ascorbic acid concentrations in blood and extracellular fluid increased from baselines of 50-100 uM to peaks of approximately 8 mM, and intraperitoneal injections produced peak ascorbic acid concentrations approaching 3 mM in blood and extracellular fluid. Ascorbate radical concentrations in extracellular fluid were as much as 9 fold higher than those in blood, even though ascorbic acid concentrations in both compartments were equivalent. In extracellular fluid, ascorbate radical concentrations as high as 250 nM occurred and were an exponential function of ascorbic acid concentrations. Hydrogen peroxide in extracellular fluid was detected when ascorbate radical concentrations in extracellular fluid exceeded 100 nM, and this occurred only with parenteral administration. Hydrogen peroxide concentrations of 20-30 uM in extracellular fluid corresponded to the highest ascorbate radical concentrations of approximately 250 nM. Taken together, these data validate the hypothesis that pharmacologic ascorbic acid is a pro-drug for preferential steady state formation of ascorbate radical and hydrogen peroxide in the extravascular space but not blood. We are continuing synthetic work to prepare new flavonoid analogues to study sturtural parameters of these inhibitors of ascorbate and glucose transport. Inculded will be potential affinity labels for the transport protein(s). Effects of fluorine substitution biolgical begavior of the flavonoids also will be examined. A series of fluorinated chalcones have been prepared and will be cyclized under conditions that produce the flavonoid structures.