Nano-Inspired Biomedicine Lab, Fondazione Istituto di Ricerca Pediatrica Città della Speranza, 35127, Padova, Italy.
First Surgical Clinic Section, Department of Surgical, Oncological and Gastroenterological Sciences, University of Padova, 35122, Padova, Italy.
J Mass Spectrom. 2020 Jul;55(7):e4459. doi: 10.1002/jms.4459. Epub 2019 Dec 2.
Considering the high complexity of natural extracts, because of the presence of organic molecules of different chemical nature, the possibility of formation of noncovalent complexes should be taken into account. In a previous investigation, the formation of bimolecular complexes between caffeine and catechins in green tea extracts (GTE) has been experimentally proven by means of mass spectrometric and H nuclear magnetic resonance experiments. The same approaches have been employed in the present study to evaluate the presence of bimolecular complexes in Ceylon tea and mate extracts. The obtained results show that in the case of Ceylon tea extracts, protonated theaflavin is detectable, together with theaflavin/caffein complexes, while caffeine/catechin complexes, already detected in green tea, are still present but at lower concentration. This aspect is evidenced by the comparison of precursor ion scans performed on protonated caffeine for the two extracts. The spectra obtained in these conditions for GTE and Ceylon tea show that the complexes of caffeine with epigallocatechin (EGC), epicatechin gallate (ECG), and epigallocatechin gallate (EGCG), highy abundant in the case of GTE (signal-to-chemical noise ratio in the range 50-100), are negligible (signal-to-chemical noise ratio in the range 2-3) in the case of Ceylon tea. Mate extracts show the formation of bimolecular complexes involving caffeine but not catechins, and chlorogenic acid becomes responsible for other complex formation. Under positive ion and negative ion conditions, accurate mass measurements allow the identification of malealdehyde, chlorogenic acid, caffeine, two isomers of dicaffeoylquinic acid, rutin, and kaempferol-3-O-rutinoside. These data indicate that the formation of complexes in natural extracts is a common behavior, and their presence must be considered in the description of natural extracts and, consequently, in their biological activity.
考虑到天然提取物的高度复杂性，由于存在不同化学性质的有机分子，应该考虑形成非共价复合物的可能性。在之前的一项研究中，通过质谱和 H 核磁共振实验实验证明了绿茶提取物（GTE）中咖啡因和儿茶素之间形成双分子配合物。在本研究中，同样的方法被用来评估锡兰茶和马黛茶提取物中双分子配合物的存在。所得结果表明，在锡兰茶提取物的情况下，可以检测到质子化茶黄素，以及茶黄素/咖啡因配合物，而已经在绿茶中检测到的咖啡因/儿茶素配合物仍然存在，但浓度较低。这一方面可以通过比较两种提取物中质子化咖啡因的前体离子扫描来证明。在这些条件下获得的 GTE 和锡兰茶的光谱表明，咖啡因与表没食子儿茶素（EGC）、表儿茶素没食子酸酯（ECG）和表没食子儿茶素没食子酸酯（EGCG）的复合物在 GTE 中含量丰富（信号与化学噪声比在 50-100 范围内），而在锡兰茶中则可以忽略不计（信号与化学噪声比在 2-3 范围内）。马黛茶提取物显示形成涉及咖啡因但不涉及儿茶素的双分子配合物，绿原酸负责其他配合物的形成。在正离子和负离子条件下，精确质量测量允许鉴定马来醛、绿原酸、咖啡因、两种二咖啡酰奎宁酸异构体、芦丁和山奈酚-3-O-芸香糖苷。这些数据表明，天然提取物中配合物的形成是一种常见的行为，在描述天然提取物及其生物活性时必须考虑它们的存在。
