Coffee grounds are a valuable source of bioactive compounds. In Romania, most of the amount obtained is lost through non-recovery; the rest is occasionally used as organic fertilizer. The coffee grounds were selected according to the roasting degree: blonde roasted (BR), medium roasted (MR), and dark roasted (DR). The study aimed to evaluate three extracts, obtained with a mixture of ethanol/water/acetic acid (50/49.5/0.5), depending on the roasting degree. The majority phenolic component, the antioxidant, and anti-inflammatory effect, as well as the role that gastrointestinal transit had on the bioavailability of bioactive compounds were determined. Chlorogenic acid was inversely proportional to the roasting degree. BR showed the best correlation between antioxidant and anti-inflammatory activities in vitro/in vivo. The antiproliferative capacity of the extracts determined an inhibitory effect on the tumor cells. Antimicrobial activities, relevant in the control of type 2 diabetes, were exerted through the inhibition of microbial strains (Escherichia coli). Following gastric digestion, BR demonstrated a maximum loss of 20% in the stomach. The recovery of coffee grounds depended on the pattern of functional compounds and the bioavailability of the main component, chlorogenic acid.
Keywords: Escherichia coli; antioxidant activity; antiproliferative; chlorogenic acid; roasting degrees.