Progress in the Application of Nuclear Magnetic Resonance Technology in Drug Detection
Nuclear magnetic resonance (NMR) spectroscopy is an analytical method based on the absorption of radio frequency field energy corresponding to the energy difference between the splitting energy levels of a specific atomic nucleus in an external magnetic field, resulting in resonance phenomena. In 1946, American physicists Purcell and Bloch elucidated the phenomenon of magnetic resonance and jointly won the Nobel Prize in Physics. In early research, the determination of drug structure was mainly achieved through various chemical reactions, such as the preparation of derivatives, chemical degradation, color reactions, etc., mainly obtaining functional groups but unable to determine the entire structure. The structural identification of a complex molecule even took decades of effort. In recent years, for molecules that are difficult to crystallize, techniques such as crystal sponge method and cryo electron microscopy have been developed for molecular structure determination. However, for amorphous and low lattice energy amorphous molecules, these methods are still inadequate and difficult to cope with. With the development and widespread application of spectroscopic technology, significant progress has been made in the study of drugs, and nuclear magnetic resonance has become the most practical and comprehensive analysis method. Its precise conformational analysis is incomparable to single crystal diffraction and electron microscopy. Compared with other analytical methods, nuclear magnetic resonance has the following advantages: ① providing rich and accurate structural information, and obtaining atomic nuclei from Larmor frequencies; Chemical displacement introduces functional groups; Spin spin coupling yields atomic correlations; Dipole coupling obtains spatial positional relationships; Relaxation phenomenon is used for dynamic research Simplicity, drugs do not require complex pre-treatment processes, can avoid errors in the processing, and have short analysis time Non destructive, in the case of a very limited sample size, after nuclear magnetic analysis, there is no damage or waste, the properties do not change, and it can be reused. In particular, the development of two-dimensional nuclear magnetic resonance has made it an extremely important tool for chemical structure research, while also opening up new windows to pharmaceutical and biomedical research, revealing the relationship between structure and function in detail. For situations where one-dimensional spectral signals overlap severely, cannot be accurately attributed, and are difficult to resolve, two-dimensional nuclear magnetic resonance spectroscopy technology is needed to solve the problem. Determine the protons at various positions in the molecule through COSY or TOCSY spectroscopy; Find the corresponding carbon signal on the HSQC spectrum through protons; Confirm the signal attribution using HMBC spectrum, and analyze the connection position and sequence between carbon and proton. Nuclear magnetic resonance spectroscopy is responding to the needs of modern drug development, providing information on drug interactions, specific molecular targets, and pharmacological action sites. With the continuous development of nuclear magnetic resonance instrument hardware and pulse methods, coupled with its multifunctionality, it has become an important tool for structural research, especially drug research. Nuclear magnetic resonance can provide a multifunctional experimental method, providing important information for drug discovery, from the characterization of synthetic products, the development of natural products to the study of molecular structures in biological systems. This article mainly reviews the application of NMR technology in drug detection and its related research progress.

 

In the past thirty years, the development of nuclear magnetic resonance technology has significantly accelerated the speed of drug research, providing unparalleled structural information and becoming the “gold standard” for structural analysis. Although HPLC-MS can detect a given analyte at the femolour level under favorable conditions, even the most modern nuclear magnetic resonance equipment requires the use of nanomolar samples for analysis within a reasonable time frame. In fact, all modern high-resolution nuclear magnetic resonance spectrometers are pulse Fourier transform instruments that can simultaneously excite all types of atomic nuclei and collect raw data in the form of free induction decay. This makes it possible to add multiple free induction decay transients to improve the signal-to-noise ratio of the high spectrum. Therefore, low sensitivity has always been (and will continue to be) the fatal weakness of nuclear magnetic resonance biological analysis applications, and improving nuclear magnetic resonance sensitivity has been the focus of most technological developments in the past forty years. At present, the world’s first 1.2GHz highest magnetic field has been installed at the Swiss Federal Institute of Technology, and it is expected that more NMR spectrometers larger than 1GHz will gradually appear in the future. By increasing the magnetic field strength of the magnet, significant breakthroughs will be made in the structural research of drug macromolecules. With the application of nuclear magnetic resonance spectroscopy in the structural analysis of biomolecules, the quantity and complexity of structural information provided by nuclear magnetic resonance technology are increasing exponentially, and three-dimensional nuclear magnetic resonance technology will be developed. Two dimensional nuclear magnetic resonance has become powerless in dealing with the conformation of three-dimensional space and the interactions between large and small molecules. Therefore, molecular modeling techniques need to be developed to use the distance information between protons in molecules provided by NOE to calculate the three-dimensional spatial structure. At the same time, it will also enhance the intrinsic sensitivity of nuclear magnetic resonance signals and the resolution of the broad and overlapping signals inherent in biomolecules above 35kDa. We hope that nuclear magnetic resonance can continue to contribute to research in the field of medicine. Especially with the development of solid-state nuclear magnetic resonance, it can provide a unique and comprehensive perspective. Its inherent quantitative properties, high sensitivity to distinguish individual chemicals, atomic resolution to elucidate local structures and complex interactions, ability to detect molecular fillers in amorphous materials, and ability to study molecular motion at different time scales make nuclear magnetic resonance a more powerful analytical tool. In the future, nuclear magnetic resonance may be combined with other analytical techniques such as mass spectrometry and X-ray crystallography to facilitate faster control, better dynamic range, and greater flexibility and scalability, providing the most advanced structural analysis methods.