Untargeted Metabolomics Analysis for Studying Differences in High-Quality Colombian Cocoa Beans.

Colombia is a producer of fine cocoa, according to the International Cocoa Organization; however, most of its exports are in the ordinary cocoa category. To remedy this situation, several national organizations are working to create technological platforms for small producers to certify the quality of their beans. The objective of this study was to identify differential chemical markers in 36 cocoa bean samples from five Colombian departments and associate them with cocoa quality properties. For this purpose, a non-targeted metabolomics approach was performed using UHPLC-HRMS, along with sensory and physicochemical analyses. The 36 samples did not differ in sensory quality, polyphenol content, and theobromine/caffeine ratio. However, the multivariate statistical analysis allowed us to differentiate the samples into four clusters. In addition, a similar grouping of the samples was also observed in the physical analyses. The metabolites responsible for such clustering were investigated with univariate statistical analysis and presumptively identified by comparison of experimental mass spectra with those reported in databases. Alkaloids, flavonoids, terpenoids, peptides, quinolines, and sulfur compounds were identified as discriminants between sample groups. Here, it was presented the metabolic profiles as an important chemical feature for further studies in quality control and more specific characterization of fine cocoa.

Relationships between DFT/RRKM branching ratios of the complementary fragment ions [C5H5O]+ and [M - C5H5O]+ and relative abundances in the EI mass spectrum of N-(2-furylmethyl)aniline.

The energy-dependent branching ratios of the complementary fragment ions [C(5)H(5)O](+) and [HC(6)H(4)NH](+) ([M - C(5)H(5)O](+)), originating from the N-(2-furylmethyl)aniline molecular ion, [HC(6)H(4)NH-C(5)H(5)O](+•), were obtained from Rice-Ramsperger-Kassel-Marcus (RRKM) rate calculations based on density functional theory (DFT) energy profiles. The UB3LYP/6-311G+(3df,2p)//UB3LYP/6-31G(d) level of theory was used to model the competitive reaction mechanisms by which the molecular ion can be fragmented. Initially, eight pairs of products were taken into account, corresponding to the combination of two isomeric structures for each fragment ion and the concomitant radicals, which can be formed by direct dissociations or through some isomerization-fragmentation pathways. A great deal of the obtained pathways was discarded by looking over the kinetic barrier heights and the individual RRKM rate coefficients calculated for all the steps. This way, the potential energy profiles were simplified to only three reaction channels, two pathways to [C(5)H(5)O](+) and one to [M - C(5)H(5)O](+). The pre-equilibrium and steady-state approximations were then applied to different regions of the remaining potential energy profiles, allowing the branching ratios of the complementary fragment ions to be easily calculated and discriminated among the three rival processes. According to these results, the major fragment ion in the ion source is [C(5)H(5)O](+), which is produced as a mixture of two structures, the furfuryl and pyrylium cations, one formed by a direct C-N bond cleavage and the other through an isomerization-fragmentation channel. In turn, the direct fragmentation is the only mechanism to produce [M - C(5)H(5)O](+). To confront these results with the available experimental information, the model was broadened out to the 4-substituted analogues [4-R-C(6)H(4)NH-C(5)H(5)O](+•) in which R = F, Br, Cl, CH(3), and OCH(3), finding excellent correlations of the calculated branching ratios and the relative abundances in the electron ionization mass spectra.