Analysis of Drug Components with Very Similar Structures

The classification of drugs is mainly based on the molecular structure. If the drugs have the same molecular structure backbone, the basic components and the treatment range are basically similar, the main difference lies in the derived links. The drugs used to treat the same disease are similar in structure or vary widely. Even with the similar structure, there may be a huge difference between medicinal properties and pharmacodynamics in drugs. Therefore, it is very necessary to analyze structurally similar pharmaceutical ingredients.

The main methods of drug similar structure analysis

• Infrared spectrum

In an organic molecule, an atom constituting a chemical bond or a functional group is in a state of constant vibration, and its vibration frequency is equivalent to the vibration frequency of infrared light. Therefore, when the organic molecules are irradiated with infrared light, the chemical bonds or functional groups in the molecules can be absorbed by vibration, and the different chemical bonds or functional groups absorb different frequencies, and will be in different positions in the infrared spectrum, so that the Information of chemical bonds or functional groups contained in the molecules can be obtained.

XuHaixing et al. were performed on different medicinal parts of Baiying medicinal materials, and similarity calculation and analysis were performed by using infrared spectral fingerprinting. According to the viewpoint of chemical taxonomy, the chemical components contained therein have certain similarities, and thus the infrared spectrum has great similarity, which is clearly manifested by the spectrum. Based on the nuances of its infrared spectrum, this experiment compares the maps with computer software and similarity comparison software to find out the method of clustering and identification of similarity spectrum¹.

• Mass spectrometry

Mass spectrometry is an analytical method for measuring the mass-to-charge ratio (mass-charge ratio). The basic principle is to ionize the components in the sample in the ion source to generate charged ions with different charge-to-mass ratios. Accelerate the action of the electric field to form an ion beam into the mass analyzer. In the mass analyzer, the electric field and the magnetic field are used to make the opposite velocity dispersion, and they are respectively focused to obtain a mass spectrum to determine the mass.

Yuangu et al. found that some sex pheromone components of lepidopteran agricultural pests contain two or more double bonds, and their double bond positions and configurations are closely related to physiological activities. The content of natural insect sex pheromones is extremely small. There is great difficulty in structural identification. In particular, the identification of its double bond position has long been a hot problem in the field of organic structural analysis. The characteristics of the mass spectra of twenty aliphatic compounds were reported in detail, and similar analysis was used to identify the bismuth diene, the double bond position of the isolated diene and the mass spectrum of the geometric isomers.

• High performance liquid chromatography

High performance liquid chromatography (HPLC) is an important branch of chromatography. With a liquid as the mobile phase, a high-pressure infusion system is used to pump a mobile phase with a single solvent of different polarity or a mixture of different solvents and buffers into a stationary phase. The column is separated from the components in the column and then entered into the detector for detection, thereby realizing the analysis and separation of the sample. This method has become an important separation and analysis technology in the fields of chemistry, medicine, industry, agronomy, commodity inspection and legal inspection. Otherwise, previous study performed by LiJianping et al. had reported that four tocopherol isomers in food were determined by ultra performance liquid chromatography (UPLC) and separated on a Waters BEH Shield RP18 column through a fluorescence containing a large volume flow cell. Detector detection not only improves the selectivity, sensitivity and accuracy of tocopherol detection, but also greatly reduces the amount of mobile phase used².

References

• Haixing Xu et al.(2012) ‘Identification and similarity Analysis of IR fingerprint of Bittersweet Herb.’ Chinese Journal of Hospital Pharmacy, 32(08):590-593

• Jianping Li (2018) ‘Determination of four tocopherol isomers in food by ultra-high performance liquid chromatography-large volume flow cell fluorescence.’ Occupation and Health, 34(16):2196-2199

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