Evidence of non-covalent complexes in some natural extracts: Ceylon tea and Mate extracts

Considering the high complexity of natural extracts, due to the presence of organic molecules of different chemical nature, the possibility of formation of non-covalent 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 provenby 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 thatin the case of Ceylon tea extracts protonated theaflavin is detectable, together with theaflavin/caffein complexes, whilecaffeine/catechin complexes, already detected in green tea, are still present, but at lower concentration. This aspect is evidenced by the comparison of precursor ion scansperformed on protonated caffeine for the two extracts. The spectra obtained in these conditions for GTE and Ceylon teashow that the complexes of caffeine withepigallocatechin(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 behaviour and their presence must be considered in the description of natural extracts and, consequently, in their biological activity.