Identification and in vitro bioaccessibility of dark chocolate phenolic compounds

Polyphenols have become an intense focus of research interest because of their perceived health-beneficial effects such as anti-atherogenic, anti-inflammatory and anti-tumoral effects. Cocoa (Theobroma cacao) is a major economically important international crop and has been associated with several nutritional benefits [1]. The aim of the present study was to identify and quantify phenolic compounds from three different types of dark chocolate using HPLC-ESI-QTOF-MS/MS. Phenolic compounds were also identified and quantified after in vitro gastro-intestinal digestion. 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)) were in vitro digested with a simulated gastro-intestinal procedure [2]. Polyphenols were extracted from un-digested samples with methanol-water-formic acid solution (70:28:2 v/v) followed by a second extraction step with acetone. Total polyphenols were determined by Folin-Ciocalteau assay whereas antioxidant activity by FRAP methods. Individual phenolic compounds were identified and quantified using mass spectrometry. Total polyphenol concentration in the un-digested samples varied from 2.6 ± 0.1 in DC to 3.4 ± 0.2 g/100g of chocolate in GTDC. The antioxidant activity ranged between 6.3 ± 0.1 to 15.4 ± 0.7 mmol trolox/100g in DC and GTDC, respectively. As expected, monomeric and oligomeric flavan-3-ols were the most representative compounds in all the three samples, followed by resveratrol and derivative. In addition, some phenolic acids (caffeoylquinic, protocatechuic, vanillic acids) and ellagic acid derivative (ellagic acid, ellagic acid hexoside) were also identified. The addition of green tea and turmeric resulted in the presence of gallate flavan-3-ols (such as epigallocatechin-3-gallate, epigallocatechin and epicatechin gallate) and curcuminoids, respectively. In vitro digestion resulted in a decrease in total polyphenols and in the individual phenolic profile modification.