Abstract: Objective Aspirin as a commonly used antithrombotic drug has low solubility in saline. In this study the effects of different pH on the structure of aspirin were observed by using the ¹H nuclear magnetic resonance(¹HNMR) technique. Methods In order to improve the solubility of aspirin, the experiments were conducted with adding different alkaline and acidic solution dropwise into the aspirin saline solution until it is completely dissolved, and the effects of different alkaline and acidic solution on the structure of aspirin were analyzed through ¹HNMR. Results The ¹HNMR data showed that among all the alkalic solutions tested, only the 1% NaHCO₃ could improve the solubility of aspirin in saline but did not change the structure of aspirin. Conclusion ¹HNMR technique can be used in biological activity evaluation for drugs.

Key words: aspirin, drug structure, hydrogen nuclear magnetic resonance