Kupka Teobald, Makieieva Natalina, Jewgiński Michał, Witek Magdalena, Blicharska Barbara, Rahmonov Oimahmad, Doležal Karel, Pospíšil Tomáš
Faculty of Chemistry and Pharmacy, University of Opole, 48, Oleska Str., 45-052 Opole, Poland.
Department of Bioorganic Chemistry, Faculty of Chemistry, Wrocław University of Science and Technology, 27, Wybrzeże Wyspiańskiego Str., 50-370 Wrocław, Poland.
Molecules. 2024 Sep 14;29(18):4382. doi: 10.3390/molecules29184382.
Caffeine is an alkaloid with a purine structure and has been well known for centuries due to its presence in popular drinks-tea and coffee. However, the structural and spectroscopic parameters of this compound, as well as its chemical and biological activities, are still not fully known. In this study, for the first time, we report on the measured oxygen-17 NMR spectra of this stimulant. To support the assignment of our experimental NMR data, extensive quantum chemical calculations of NMR parameters, including nuclear magnetic shielding constants and indirect spin-spin coupling constants, were performed. In a theoretical study, using nine efficient density functionals (B3LYP, BLYP, BP86, CAM-B3LYP, LC-BLYP, M06, PBE0, TPSSh, wB97x), and in combination with a large and flexible correlation-consistent aug-cc-pVTZ basis set, the structure and NMR parameters were predicted for a free molecule of caffeine and in chloroform, DMSO and water. A polarized continuum model (PCM) was used to include a solvent effect. As a result, an optimal methodology was developed for predicting reliable NMR data, suitable for studies of known, as well as newly discovered, purines and similar alkaloids. The results of the current work could be used in future basic and applied studies, including NMR identification and intermolecular interactions of caffeine in various raw materials, like plants and food, as well as in the structural and spectroscopic characterization of new compounds with similar structures.
咖啡因是一种具有嘌呤结构的生物碱，由于其存在于茶和咖啡等流行饮品中，几个世纪以来一直广为人知。然而，这种化合物的结构和光谱参数，以及其化学和生物活性，仍然没有被完全了解。在本研究中，我们首次报道了这种兴奋剂的氧-17核磁共振谱测量结果。为了支持对我们实验核磁共振数据的归属，我们进行了广泛的核磁共振参数量子化学计算，包括核磁屏蔽常数和间接自旋-自旋耦合常数。在一项理论研究中，使用了九种高效密度泛函（B3LYP、BLYP、BP86、CAM-B3LYP、LC-BLYP、M06、PBE0、TPSSh、wB97x），并结合一个大的灵活的相关一致aug-cc-pVTZ基组，预测了咖啡因游离分子以及在氯仿、二甲基亚砜和水中的结构和核磁共振参数。使用极化连续介质模型（PCM）来考虑溶剂效应。结果，开发了一种最佳方法来预测可靠的核磁共振数据，适用于已知以及新发现的嘌呤和类似生物碱的研究。当前工作的结果可用于未来的基础和应用研究，包括咖啡因在各种原材料（如植物和食品）中的核磁共振鉴定和分子间相互作用，以及具有类似结构的新化合物的结构和光谱表征。
