In Vitro Bioaccessibility and Antioxidant Activity of Coffee Silverskin Polyphenolic Extract and Characterization of Bioactive Compounds Using UHPLC-Q-Orbitrap HRMS

Abstract

Coffee silverskin (CS), the main by-product in the coffee industry, contains a vast number of human health-related compounds, which may justify its exploitation as a functional food ingredient. This study aimed to provide a comprehensive analysis of the polyphenolic and alkaloid profile through UHPLC-Q-Orbitrap HRMS analysis. The bioaccessibility of total phenolic compounds and changes in the antioxidant activity during an in vitro gastrointestinal digestion were also evaluated through spectrophotometric tests (TPC by Folin-Ciocalteu, ABTS, DPPH, and FRAP), to elucidate their efficacy for future applications in the nutraceutical industry. Caffeoylquinic and feruloylquinic acids were the most representative polyphenols, with a mean concentration of 5.93 and 4.25 mg/g, respectively. Results showed a high content of caffeine in the analyzed CS extracts, with a mean value of 31.2 mg/g, meaning a two-fold increase when compared to coffee brews. Our findings highlighted that both the bioaccessibility and antioxidant activity of CS polyphenols significantly increased in each in vitro gastrointestinal digestion stage. In addition, the colon stage might constitute the main biological site of action of these antioxidant compounds. These results suggest that in vivo, the dietary polyphenols from CS might be metabolized by human colonic microflora, generating metabolites with a greater antioxidant activity, increasing their well-known beneficial effects.

Colon Bioaccessibility under In Vitro Gastrointestinal Digestion of Different Coffee Brews Chemically Profiled through UHPLC-Q-Orbitrap HRMS

“…The untargeted analytes’ structural characterization relied on the MS/MS spectrum interpretation ( Figures S1 and S2 in Supplementary Material ), elemental composition assignment, and accurate mass measurement. The structural isomers CQA ( m / z 353.08780), diCQA ( m / z 515.11950), p -coumaroylquinic ( p CoQA; m / z 337.09289), caffeoyl-feruloylquinic and feruloyl-caffeoylquinic acids (CFQA and FCQA; m / z 529.13245) were identified by comparing their fragmentation pattern with information previously reported in the literature [ 25 ] and by comparing the retention times of standards with those of the peaks. The chromatographic separation of the analyzed compounds was performed in a total run time of 13 min.…”

“…High-molecular-weight melanoidins (HMWM) were quantified according to the previously described procedure [ 25 ]. Briefly, 4 mL of coffee brew properly diluted with demineralized water was subjected to ultrafiltration using an Amicon Ultra-4 (Millipore, Italy) at 7500× g for 70 min at 4 °C, equipped with a 10 kDa nominal molecular mass cutoff membrane.…”

Colon Bioaccessibility under In Vitro Gastrointestinal Digestion of a Red Cabbage Extract Chemically Profiled through UHPLC-Q-Orbitrap HRMS

“…The in vitro gastrointestinal digestion was evaluated according to the INFOGEST procedure until the duodenal stage. Subsequently, to reproduce the microbiota occurring in the colon phase, the combined action of Pronase E and Viscozyme L. was utilized [ 44 , 45 ].…”

Chemical Composition, In Vitro Bioaccessibility and Antioxidant Activity of Polyphenolic Compounds from Nutraceutical Fennel Waste Extract

“…The FRAP assay was carried out following the procedure described in a previous work et al [ 43 ] with some modifications. Briefly, the FRAP solution was prepared by mixing 1.25 mL of ferric chloride solution (20 mM, H 2 O), 1.25 mL of 2,3,5-triphenyltetrazolio chloride (TPTZ) solution (10 mM) in HCl (40 mM), and 12.5 mL of acetate buffer (0.3 M, pH 3.6).…”