Evidence of noncovalent complexes in some natural extracts: Ceylon tea and mate extracts

• Published in: Journal of mass spectrometry. Vol. 55; no. 7; pp. e4459 - n/a
• Main Authors: Crotti, Sara, D'Aronco, Sara, Moracci, Laura, Tisato, Francesco, Porchia, Marina, Mattoli, Luisa, Burico, Michela, Bedont, Stella, Traldi, Pietro, Agostini, Marco
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 01-07-2020
• Subjects: 1H NMR; accurate mass measurements; Anions; Biflavonoids - analysis; bimolecular complexes; Biological activity; Caffeine; Caffeine - analysis; Camellia sinensis - chemistry; Catechin; Catechin - analogs & derivatives; Catechin - analysis; Ceylon tea; Chlorogenic acid; Chlorogenic Acid - analysis; Chromatography, Liquid; Complex formation; Complexity; Epicatechin; Epigallocatechin gallate; Green tea; Ilex paraguariensis - chemistry; Ions; Isomers; Kaempferol; Magnetic Resonance Spectroscopy; Mass Spectrometry - methods; Mate; natural products; Negative ions; NMR; Noise; Nuclear magnetic resonance; Organic chemistry; Plant Extracts - chemistry; Positive ions; precursor ion scans; Rutin; Spectrometry; Spectrometry, Mass, Electrospray Ionization; Tandem Mass Spectrometry - methods; Tea - chemistry; Mate; bimolecular complexes; natural products; precursor ion scans; 1H NMR; Ceylon tea; accurate mass measurements
• ISSN: 1076-5174; 1096-9888
• DOI: 10.1002/jms.4459

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 1H 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.