The application of nuclear magnetic resonance spectroscopy to drug metabolism studies

1. The applications of n.m.r. spectroscopy studies to drug metabolism, both in vitro (biofluids, isolated cells, excised tissue samples, isolated organs) and in vivo (animals, humans) are reviewed. 2. N.m.r. is a relatively insensitive technique, but it has the great advantage of being non-invasive and non-destructive, i.e. it allows a direct study of intact biological samples. 3. The majority of studies examined deal with 19F-n.m.r. spectroscopy mainly because of the favourable n.m.r. characteristics of this nucleus, and the low level of endogenous fluorine which gives no detectable 19F signal. However, the potential utility of 1H-31P- and 13C-n.m.r. is also emphasized.     

核磁共振谱技术在药物代谢研究中的应用

核磁共振谱技术在药物代谢研究中的应用司伊康（中国医学科学院、中国协和医科大学药物研究所，北京１０００５０）核磁共振谱（ＮＭＲＳ）是一种无损伤的物理测试方法，它可直接用于体内和体外的生物样品测定，提供分子水平的信息。近二十年来，这种生物核磁技术有很快发...     

Nuclear magnetic resonance (NMR) spectroscopy and its application to biomedical research

The principles of nuclear magnetic resonance (NMR) spectroscopy were explained and its application to biomedical research discussed. With 31P-NMR, it is feasible to conduct a continuous, non-invasive measurement of the contents of myocardial high-energy phosphate compounds and the intracellular pH (determined by monitoring the pH dependent shift of the inorganic phosphate peak relative to that of creatine phosphate), and to correlate them with the mechanical function. The determination of the free magnesium concentration is also possible on a similar principle to that for pH determination (the shift of MgATP peaks relative to ATP is utilized in this case). It is estimated to be 0.3 mM and was found not to be changed during ischemia. Several examples of studies including our own conducted to delineate the ischemic derangements of the myocardial energy metabolism and the effects of various interventions thereupon were illustrated. Finally a brief mention was made of the saturation transfer technique. This is the only method with which one can study the kinetics of the enzyme reactions under in vivo conditions. The application of the method for analysis of the creatine kinase reaction and the ATP synthesis was demonstrated.     

~(19)F体内核磁共振技术观测5-氟尿嘧啶在小鼠肝脏中的代谢

应用１９Ｆ体内核磁共振技术（１９ＦＮＭＲ）直接观测了５－氟尿嘧啶（５－ＦＵ）在小鼠肝脏中的代谢产物和代谢动力学，昆明种（ＫＭ）小鼠和Ｃ５７小鼠ｉｖ５－ＦＵ２００ｍｇ·ｋｇ－１后，用１９Ｆ表面线圈测得５－ＦＵ在肝脏中依次代谢为α－氟－β－脲基丙酸（ＦＵＰＡ）和α－氟－β－丙氨酸（ＦＢＡＬ）．在荷Ｓ１８０瘤ＫＭ小鼠肝脏中还可检测到活化产物氟代核苷／核苷酸（ＦＮＵＣ）．５－ＦＵ在ＫＭ和Ｃ５７小鼠肝脏中清除较快，消除半衰期分别为１６．７±３．０和３６．６±２．４ｍｉｎ，其主要产物ＦＢＡＬ的最大生成ｒｍａｘ（相对强度比）分别为８４±１４和９２±１０．但在ＫＭ小鼠肝脏中由ＦＵＰＡ进一步降解为ＦＢＡＬ的速率明显快于Ｃ５７小鼠，ｔ１／２ｒ分别为３１±８和５７±１３ｍｉｎ．相应地，在Ｃ５７小鼠肝脏中ＦＵＰＡ能维持一定的水平并达到ｒｍａｘ２６．２±２．２．     

Utilizing nuclear magnetic resonance (NMR) spectroscopy for assessing nadolol racemat composition

NMR methods were developed for the determination of the racemate composition in nadolol raw materials. With high-field instruments (400 MHz or greater) the racemate ratio may be determined by the relative heights of the t-butyl peaks, which are well enough resolved for this determination. For lower field spectrometers, the t-butyl peaks are not resolved. An NMR method has been developed which involves preparation of the tribenzoate derivative of the drug. Seven lots of nadolol raw material, as well as several standards, were analysed for their racemate content. Three lots of raw material did not meet the USP limits of 40–60% for racemate A. Of these, two were granular in appearance and were found to vary markedly in racemate composition in successive analyses. The results for all the materials of uniform content agree very well with those from the HPLC method, as well as for the USP IR method using the absorbance at the corrected wavelength.     

In vivo 19F nuclear magnetic resonance spectroscopy: a potential monitor of 5-fluorouracil pharmacokinetics and metabolism

Summary In vivo ¹⁹F nuclear magnetic resonance (NMR) spectroscopy has the potential to non-invasively measure the concentration of 5-fluorouracil (FUra) and some of its metabolites in humans. Such a measure could be useful in predicting and optimizing the response of individual patients treated with FUra. The ability of ¹⁹F NMR to monitor FUra metabolism in situ in rodent tumors and liver and in human liver has been demonstrated. However, the potential impact of this technique as a predictor of FUra response in individual patients is limited by both the sensitivity (i.e., limit of detection) and the resolution (i.e., ability to distinguish among magnetically similar metabolites) of NMR. To date, the ability of in vivo ¹⁹F NMR spectroscopy to provide information that can distinguish FUra-sensitive from FUra-insensitive tumors has not been established. This crucial point should be addressed in the immediate future in studies using the best of experimental conditions (i.e., optimum sensitivity and resolution in well-defined rodent tumor models with NMR methodology appropriate for measurement of absolute metabolite concentrations). The information gained from such studies and any new technical developments to enhance in vivo NMR sensitivity should be directly applicable to any future application of ¹⁹F NMR spectroscopy in clinical FUra therapy.     

氢核磁共振定量法测定恩替卡韦

目的 建立氢核磁共振定量法测定恩替卡韦含量的方法.方法 以氘代DMSO为溶剂,恩替卡韦为样品,1,4-二硝基苯为内标测定氢核磁共振谱,通过比较样品定量峰与内标物质响应峰面积,计算恩替卡韦的量.结果 同一样品在相同条件下测定6次,定量峰与内标响应峰比值的RSD值为1.1%;平行配制3份样品,恩替卡韦质量分数93.8%,RSD值为0.70%,与质量平衡法测定结果93.8%一致.结论 氢核磁共振定量法与质量平衡法相比样品用量少,不需要对照品,测定快速准确,是一种有效地化学样品含量测定手段.     

19F and 1H magnetic resonance strategies for metabolic studies on fluorinated xenobiotics: application to flurbiprofen [2-(2-fluoro-4-biphenylyl)propionic acid

Strategies for the use of 1H and 19F nuclear magnetic resonance (NMR) spectroscopy as an aid to the study of the metabolic fate of fluorinated drugs are discussed with reference to the application of these methods to flurbiprofen metabolism in man. 1H and 19F NMR analysis of untreated urine enabled the detection of two major and eight minor metabolites of the drug. The two major metabolites were identified using a combination of NMR spectroscopy, solid-phase extraction chromatography with 19F and 1H NMR detection and chemical hydrolysis to a flurbiprofen glucuronide and the glucuronide of the 4-hydroxy metabolite. 1H-19F 2D shift correlated spectroscopy and spin-echo difference experiments are discussed in relation to their use in the structural identification of drug metabolites.     

~(19)F体内核磁共振技术观测5-氟尿嘧啶在小鼠植入肿瘤中的摄取与代谢

应用体内１９ＦＮＭＲ谱观察并定量评价了５－氟尿嘧啶（５－ＦＵ）在荷Ｓ１８０瘤和Ｂ１６瘤小鼠肿瘤内的摄取和代谢动力学过程．５－ＦＵ２００ｍｇ·ｋｇ－１ｉｖ后，药物在Ｓ１８０和Ｂ１６瘤内的主要产物为其活性产物氟代核苷／核苷酸（ＦＮＵＣ），同时可检测到少量的降解产物α－氟－β－丙氨酸（ＦＢＡＬ）和α－氟－β－脲基丙酸（ＦＵＰＡ）．在Ｓ１８０瘤内，５－ＦＵ摄取，消除以及ＦＮＵＣ的生成有较大的个体变异，５－ＦＵ的消除半衰期ｔ１／２ｋｅ为４１．５－８４．８ｍｉｎ，ＦＮＵＣ生成ｔ１／２ｒ为２６．０－９１．９ｍｉｎ．当甲氨蝶呤（ＭＴＸ）与５－ＦＵ合用时，５－ＦＵ在Ｓ１８０瘤内的活化代谢过程明显加快，ｔ１／２ｋｅ缩短为２９．９－４３．４ｍｉｎ，ＦＮＵＣ的生成速率显著提高，生成量增加．５－ＦＵ在Ｂ１６瘤内的摄取及代谢过程的个体波动较小，其ｔ１／２ｋｅ为３９±５ｍｉｎ，ＦＮＵＣ的生成ｔ１／２ｒ为６０±７ｍｉｎ，在Ｂ１６瘤内，ＭＴＸ的合用不能明显加快５－ＦＵ转化为ＦＮＵＣ的反应，也不改变５－ＦＵ在瘤内的消除模式．上述结果表明，５－ＦＵ对肿瘤的化疗作用与肿瘤灌注５－ＦＵ在瘤组织内的摄取和活化代谢过程密切相关，亦可受到合用药物的影响．     

Detection of new metabolites of trifluridine (F3TdR) using 19F NMR spectroscopy.

The metabolism of 5-trifluoromethyl-2'-deoxyuridine (trifluridine, F3TdR) in male BALB/C mice has been studied by 19F NMR spectroscopy. Contrary to previous reports, a number of fluorinated metabolites were observed in urine, whole livers and blood samples taken from mice after i.p. injection of F3TdR. The present study describes the identification of two new metabolites in mouse urine using the 19F NMR technique. The NMR of crude urine showed the presence of F3TdR 5-trifluorothymine (F3T), the newly-identified metabolites, 5-trifluoromethyl-5,6-dihydrouracil (DHF3T) and 5-trifluoromethyl-5,6-dihydroxyracil (DOHF3T), and several new, as yet unidentified fluorinate metabolites. These two new metabolites were characterized by comparison to authentic compounds prepared synthetically from F3T.     

19F体内核磁共振技术观测5-氟尿嘧啶在小鼠肝脏中的代谢

应用¹⁹F体内核磁共振技术(¹⁹F NMR)直接观测了5-氟尿嘧啶(5-FU)在小鼠肝脏中的代谢产物和代谢动力学，昆明种(KM)小鼠和C57小鼠iv 5-FU 200 mg·kg^-1后，用¹⁹F表面线圈测得5- FU在肝脏中依次代谢为α-氟-β-脲基丙酸(FUPA)和α-氟-β-丙氨酸(FBAL). 在荷S180瘤KM小鼠肝脏中还可检测到活化产物氟代核苷/核苷酸(FNUC). 5-FU在KM和C57小鼠肝脏中清除较快，消除半衰期分别为16.7±3.0和36.6±2.4 min，其主要产物FBAL的最大生成r_max(相对强度比)分别为84±14和92±10. 但在KM小鼠肝脏中由FUPA进一步降解为FBAL的速率明显快于C57小鼠，t_1/2r分别为31±8和57±13 min. 相应地，在C57小鼠肝脏中FUPA能维持一定的水平并达到r_max 26.2±2.2.     

Chloride ion nuclear magnetic resonance spectroscopy probe studies of copper and nickel binding to serum albumins

The binding of Cu2+ and Ni2+ to bovine, dog, and human serum albumin has been studied by the 35Cl NMR probe technique. The number of primary copper sites were estimated to be 1.3 for human serum albumin, 3.1 for bovine serum albumin, and 6.6 for dog serum albumin. A similar number of primary nickel sites was determined for each of these albumins. On the basis of the chloride probe experiments, it appears that both copper and nickel have the same binding sites on albumin.     

The minimal metabolism of inhaled 1,1,1,2-tetrafluoroethane to trifluoroacetic acid in man as determined by high sensitivity F nuclear magnetic resonance spectroscopy of urine samples

In this work, oxidative metabolism of the new propellant, 1,1,1,2-tetrafluoroethane to trifluoroacetic acid in man is shown to be minimal. Alternative propellants and refrigerants are under development to replace the currently used chlorofluorocarbons which lead to stratospheric ozone depletion. One potentially useful replacement is the hydrofluorocarbon, 1,1,1,2-tetrafluoroethane (HFA-134a). Before it can be used, however, particularly as a propellant in an aerosol pharmaceutical formulation whereby the compound is in effect dosed to people, it is important that the safety of this compound is established. As a part of this safety evaluation it is necessary to understand the metabolism of HFA-134a. In this work the production of the potential oxidative metabolite of HFA-134a, trifluoroacetic acid (TFA) has been studied in human urine following inhalation dosing with HFA-134a. The concentrations of TFA in urine have been measured using a highly sensitive ¹⁹F nuclear magnetic resonance procedure with a limit of detection of 10 ng ml⁻¹ based on an acquisition time of only 2.25 h per sample. TFA is the only fluorinated species observed in the urine samples and only at very low levels, indicating that the oxidative route of metabolism can occur in vivo in man, but this metabolism is minimal in terms of percentage of administered dose.     

19F体内核磁共振技术观测5-氟尿嘧啶在小鼠植入肿瘤中的摄取与代谢

应用体内¹⁹F NMR谱观察并定量评价了5-氟尿嘧啶(5-FU)在荷S180瘤和B16瘤小鼠肿瘤内的摄取和代谢动力学过程. 5-FU 200 mg·kg^-1 iv后，药物在S180和B16瘤内的主要产物为其活性产物氟代核苷/核苷酸(FNUC)，同时可检测到少量的降解产物α-氟-β-丙氨酸(FBAL)和α-氟-β-脲基丙酸(FUPA). 在S180瘤内，5-FU摄取，消除以及FNUC的生成有较大的个体变异， 5-FU的消除半衰期t_1/2ke 41.5-84.8 min, FNUC生成t_1/2r为26.0-91.9 min. 当甲氨蝶呤(MTX)与5-FU合用时，5-FU在S180瘤内的活化代谢过程明显加快，t_1/2ke缩短为29.9-43.4 min, FNUC的生成速率显著提高，生成量增加. 5-FU在B16瘤内的摄取及代谢过程的个体波动较小，其t_1/2ke为39±5 min, FNUC的生成t_1/2r为60±7 min, 在B16瘤内，MTX的合用不能明显加快5-FU转化为FNUC的反应，也不改变5-FU在瘤内的消除模式. 上述结果表明，5-FU对肿瘤的化疗作用与肿瘤灌注5-FU在瘤组织内的摄取和活化代谢过程密切相关，亦可受到合用药物的影响.     

Characterization of oleic acid and propranolol oleate mesomorphism using (13)C solid-state nuclear magnetic resonance spectroscopy (SSNMR)

Lipids regularly exhibit complicated thermotropic and lyotropic phase behavior. In this study, the utility of (13)C solid-state nuclear magnetic resonance spectroscopy (SSNMR) in characterizing the phase properties of pharmaceutical lipids was investigated. Variable temperature (13)C SSNMR spectra and spin-lattice relaxation times (T(1)(C)) were obtained for high-purity oleic acid (OA) and propranolol oleate (POA). Spectral changes took place following OA gamma-to-alpha phase transition that indicated increased nuclear inequivalence of aliphatic chain carbons in the alpha phase. T(1)(C) data for the alpha phase demonstrated considerable conformational changes throughout the aliphatic chain, not solely in the methyl side chain as previously reported. These data support alpha-OA classification as a conformationally disordered crystalline phase. The prevalence of low T(1)(C) values in both POA I and II suggested the absence of a rigid crystalline molecular lattice, so both phases were described as conformationally disordered crystalline phases. A two-phase mixture of POA I and II was also identified, emphasizing the sensitivity of this technique. (13)C SSNMR provided valuable information regarding the nuclear environment of specific functional groups in lipid crystalline and mesomorphic structures. Understanding phase behavior at the molecular level can aid selection of appropriate formulation strategies for lipids by allowing prediction of processing properties, and physical and chemical stability. (13)C SSNMR is a powerful technique for pharmaceutical lipid characterization.     

Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin on 17 beta-estradiol-induced glucose metabolism in MCF-7 human breast cancer cells: 13C nuclear magnetic resonance spectroscopy studies.

The effects of 17 beta-estradiol, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and their combination on the metabolism of [1-13C] glucose were determined in cell suspensions of wild-type MCF-7 human breast cancer cells, by 13C NMR spectroscopy. Preliminary studies showed that, during the 7-hr duration of the NMR experiment, the cells maintained their viability and their aryl hydrocarbon responsiveness. Lactate was the major glucose metabolite detected in these studies, and the rate of lactate formation in the untreated (control) and 17 beta-estradiol (10(-9) M)-treated cells was 60 and 86 fmol/cell/hr, respectively; this represented a 40% increase in lactate formation in the cells treated with 17 beta-estradiol; comparable results were observed for the percentage of glucose converted into lactate. In contrast, TCDD (10(-9) M) did not significantly alter the rate of glucose metabolism or lactate formation. Co-treatment of the cells with 17 beta-estradiol (10(-9) M) plus TCDD (10(-8) to 10(-10) M) showed that TCDD completely inhibited the 17 beta-estradiol-induced metabolism of [13C] glucose to lactate in MCF-7 cells. In contrast, 2,8-dichlorodibenzo-p-dioxin (10(-8) M), a weak aryl hydrocarbon receptor agonist, did not inhibit estrogen-induced glucose-to-lactate metabolism in MCF-7 cells. In addition, it was shown that TCDD caused a significant decrease in 17 beta-estradiol-induced lactate formation within 1 hr after treatment, whereas the induction of monooxygenase activity was not observed until 3 hr after exposure of the cells to TCDD. These data indicate that TCDD-induced 17 beta-estradiol metabolism is not related to the decrease in the rate of conversion of glucose to lactate. These results further define the antiestrogenic responses elicited by TCDD and show that 13C NMR spectroscopy provides a unique method for measuring, in real time, the effects of TCDD on specific metabolic pathways.