UPLC—MS method for determination of phenolic compounds in chili as a coffee supplement and their impact of phytochemicals interactions on antioxidant activity in vitro

The use of polyphenols in food fortification is a common custom generally carried out to increase its nutritional value. In this paper, ground chili pepper was proposed as a potential functional coffee additive. Various phenolic compounds present in this spice were analyzed by a new, sensitive, and selective ultrahigh-performance liquid chromatography combined with mass spectrometry (UPLC–MS). Separation was done on a column filled with a modified silica gel RP-18, in gradient solvent systems A (1% H3PO4 in water) and B (40% CH3CN in solution A). The capsaicin was found as the main phenolic compound of ground chilli pepper, which concentration was 295.95 mg g−1. It was demonstrated that quercetin is present in this spice also in different forms: not only as dihydrocapsaicin but also as quercetin-3-O-deoxyhexoside-glucuronide and quercetin-3-O-deoxyhexoside, whereas luteolin in the form of three compounds: luteolin-7-O-dihexoside, luteolin-6-C-hexoside-8-C-pentoside, and luteolin-7-O-malonyl-dihexosyl-pent...