Position-Specific Isotope Analysis of Xanthines: A (13)C Nuclear Magnetic Resonance Method to Determine the (13)C Intramolecular Composition at Natural Abundance.

The natural xanthines caffeine, theobromine, and theophylline are of major commercial importance as flavor constituents in coffee, cocoa, tea, and a number of other beverages. However, their exploitation for authenticity, a requirement in these commodities that have a large origin-based price-range, by the standard method of isotope ratio monitoring by mass spectrometry (irm-MS) is limited. We have now developed a methodology that overcomes this deficit that exploits the power of isotopic quantitative (13)C nuclear magnetic resonance (NMR) spectrometry combined with chemical modification of the xanthines to enable the determination of positional intramolecular (13)C/(12)C ratios (δ(13)Ci) with high precision.

Occurrence of glycosidically conjugated 1-phenylethanol and its hydrolase β-primeverosidase in tea (Camellia sinensis) flowers.

A previous study found that 1-phenylethanol (1PE) was a major endogenous volatile compound in tea (Camellia sinensis) flowers and can be transformed to glycosically conjugated 1PE (1PE-Gly). However, occurrences of 1PE-Gly in plants remain unknown. In this study, four 1PE-Glys have been isolated from tea flowers.

Purification and gas chromatography-combustion-isotope ratio mass spectrometry of aroma compounds from green tea products and comparison to bulk analysis.

A method for carbon isotope ratio (δ(13)C) analysis was developed for compound-specific isotope analysis of tea volatiles, and the values were compared with the δ(13)C value from bulk isotope analyses. The δ(13)C value of 2-phenylethanol liberated via enzymatic hydrolysis of the 2-phenylethyl β-primeveroside standard was examined first. Isotope fractionations for 2-phenylethyl β-primeveroside from preparative high-performance liquid chromatography (HPLC) were also analyzed.

Isolation and identification of spermidine derivatives in tea (Camellia sinensis) flowers and their distribution in floral organs.

Background: Recently, tea (Camellia sinensis) flowers have attracted increasing interest because of their content of bioactive compounds such as catechins. The aim of this study was to investigate the occurrence of some characteristic compounds in tea flowers.

Results: A principal component analysis of metabolites using ultra-performance liquid chromatography/time-of-flight mass spectrometry showed differences in metabolite profile between flowers and leaves of C.