Very recently, we described the formation of (+)-catechin- and (-)-epicatechin-derived polar chromophores by means of a cocoa alkalization process. In this study we focus on the generation of unpolar chromophores using model reactions via Dutching with softer alkaline conditions. UPLC-HR-ESI-TOF-MSe analysis and one-dimensional and two-dimensional NMR spectroscopy led to the unequivocal identification of dehydrodicatechin- and hydroxyxanthene-derived chromophores. The previously unknown 6- C-linked constitutional isomers of C-6'B/C-6D-(2 R,3 S)-dehydrodicatechin (3, 5) were first described, and furthermore, the dimers dehydrocatechin-C-6'B/C-8D-(2 S,3 S)-epicatechin (2) and dehydrocatechin-C-6'B/C-6D-(2 S,3 S)-epicatechin (4, 6) as well as the reddish-colored chromophores 8- C-xanthenocatechin (7), 8- C-xanthenoepicatechin (8), 6- C-xanthenocatechin (9), and 6- C-xanthenoepicatechin (10) were identified as new compounds. A LC-MS/MS method was developed to screen and quantify both classes of chromophores as well as their precursors in alkalized cocoa powders. The dehydrocatechin dimers showed degradation via the alkalization process; in contrast, the xanthenocatechins highlighted an increase in concentration with stronger alkalization, and, therefore, contribute to cocoa reddening. These results, together with those previously published, give a clear insight into the chemistry of polyphenol-derived chromophores generated by cocoa powder alkalization and enable a better understanding of chromophore formation mechanisms toward a more comprehensive color design of cocoa powders.

Very recently, we described highly antioxidative polyphenols isolated from the stem bark extract of the Garcinia buchananii tree. In this study, we describe additional antioxidants from Garcinia buchananii bark extract using hydrogen peroxide scavenging, oxygen radical absorbance capacity (ORAC), and trolox equivalent antioxidant capacity (TEAC) assays. UPLC-HR-ESI-TOF-MS(e) analysis, 1- and 2D-NMR, and circular dichroism (CD) spectroscopy led to the unequivocal identification of the antioxidative molecules as a series of five 3,8″-linked biflav(an)ones and two flavanone-C-glycosides. (2S,3R)-Taxifolin-6-C-β-d-glucopyranoside (2), (2R,3S,2″S,3″S)-manniflavanone (3), (2R,3S)-buchananiflavonol (4), and (2S,3R,2″R,3″R)-GB-1 (6) are new compounds, and (2S,3S)-taxifolin-6-C-β-d-glucopyranoside (1) was described so far only in one other plant. The structure of (2R,3S,2″R,3″R)-GB-1 (5) and (2R,3S,2″S)-GB2a (7) were confirmed. The H2O2 scavenging, TEAC, and the ORAC assays demonstrated that these natural products have an extraordinarily high antioxidative power, especially (2R,3S,2″S,3″S)-manniflavanone (3) with an EC50 value of 3.0 μM, 4.00 mmol TE/mmol, and 10.30 μmol TE/ μmol.