Chocolate melanoidins as a carrier for the delivery of phenolic compounds in the gut

Emerging evidence from in vitro and in vivo studies suggested that the gastro-intestinal tract may be the key site for the biological action of food melanoidins [1]. In this work, we tested high molecular weight melanoidins (HMWM) extracted from dark chocolate for their ability to release low molecular weight polyphenols following in vitro digestion. Water soluble HMWM were extracted by ultrafiltration (10 kDa) from three different types of dark chocolate (dark 70% cocoa (DC), dark 70% cocoa and 8% turmeric (TDC), dark 62% cocoa and 2% Sakura green tea (GTDC)). HMWM have been chemically characterized for their content in total polyphenols, protein, and polysaccharides [2]. HMWM were in vitro digested and separated from low molecular weight fractions (LMWF) by ultrafiltration. Digested HMWM were chemically characterized and LMWF were characterized for their total phenolic content. Individual phenolic compounds in the LMWF were identified and quantified by HPLC-ESI-QTOF-MS/MS. Results showed that melanoidins are carbohydrate-based structures with the phenolic content ranging from 8.62 ± 1.0 in TDC to 12.79 ± 0.4 g/100 g HMWM in GTDC. The in vitro digestion caused a general decrease in the polysaccharide, protein and phenolic content. Digestion resulted in the release of phenolic compounds from HMWM to LMWF. The highest amount was recovered in the LMWF of GTDC (436.2 ± 87.6 mg/L), whereas the lowest amount in the LMWF of TDC (242.1 ± 17.1 mg/L). The most representative classes of polyphenols released from HMWM were stilbenes (resveratrol and derivatives) and phenolic acids (hydroxybenzoic, benzoic, quinic, cinnamic, coumaric and ferulic acids). As expected, food matrices influenced the chemical composition of HMWM. Specific phenolic compounds were detected in the LMWF from GTDC (quercetin-3-rutinoside) and TDC (curcumin, cathecol and protocatechuic acid).