The main hydrophilic antioxidant compounds (3-, 4-and 5-monocaffeoylquinic and 3,4-, 3,5-and 4,5-dicaffeoylquinic acids, caffeine and browned compounds, including melanoidins) and the antioxidant capacity (Folin-Ciocalteau, ABTS, DPPH, Fremy´s salt and TEMPO) were evaluated in Arabica and Robusta spent coffee obtained from the preparation of coffee brews with the most common coffeemakers (filter, espresso, plunger and mocha). All spent coffee grounds, with the exception of those from mocha coffeemaker, had relevant amounts of total caffeoylquinic acids (6.22-13.24 mg/g of spent coffee), mainly dicaffeoyquinic acids (3.31-5.79 mg/g of spent coffee) which were 4-7 fold higher than in their respective coffee brews. Caffeine was ranged from 3.59 to 8.09 mg/g of spent coffee. The antioxidant capacity of the aqueous spent coffee extracts was 46.0-102.3% (filter), 59.2-85.6% (espresso), and less than 42% (plunger) in comparison to their respective coffee brews. This study allowed us to obtain spent coffee extracts with antioxidant properties that can be used as a good source of hydrophilic bioactive compounds.

Spent coffee that is produced in tons by restaurants and cafeterias, and consumers at domestic levels, could be a good opportunity to have an important source of natural antioxidants. The main aim of this work was to study the influence of several process factors on the antioxidant capacity extraction from spent coffee. Total phenolic compounds, radical scavenging activity (ABTS and DPPH) and browned compounds (Abs 420nm) of spent coffee extracts obtained with continuous (soxhlet 1h and 3h) and discontinuous methods (solid-liquid extraction and filter coffeemaker), several solvents (water, ethanol, methanol and their mixtures), successive extractions, and water with different pHs (4.5, 7.0 and 9.5) were carried out. Spent coffee extracts with the highest antioxidant capacity were obtained after one extraction with neutral water (pH 7.0) in a filter coffeemaker (24 g spent coffee per 400mL water). Furthermore, spent coffee defatting and extracts lyophilization allowed us to obtain spent coffee extracts powder with high antioxidant capacity that can be used as an ingredient or additive in food industry with potential preservation and functional properties.

21Spent coffee is the main by-product of the brewing process and a potential source of

23Coffee consumption decreases the risk of oxidative stress-related diseases. The by-24 product obtained after brewing process (spent coffee) has also shown antioxidant

21Spent coffee grounds are a potential commercial source of substantial amounts of chlorogenic 22 acids (CGAs). The aim of this study was to evaluate the stability of spent coffee CGAs using in 23 vitro simulated gastroduodenal digestion and to investigate their potential absorption using an in 24 vitro Caco-2 model of human small intestinal epithelium. During in vitro digestion, lactones 25 were partially degraded while caffeoylquinic and feruloylquinic acids were much more stable. 26Transport and metabolism studies showed that 1% of the total CGAs were absorbed and