The antioxidant properties of dried extracts from spent espresso coffee

Abstract

The importance of coffee waste utilization is based on the fact that it contains a large amount of biologically valuable components. Preparation of espresso coffee produces substantial quantities of polyphenolic acids that have a significant antioxidant activity. In this work, the contents of polyphenols and antioxidant activity of extracts obtained from spent espresso coffee were analyzed using different solvent systems. A 70% solution of methanol and a 70% solution of ethanol and distilled water were used as solvents. The total amounts of polyphenols were determined by the Folin-Ciocalteu method, while the antioxidant activities were determined by DPPH inhibition (2,2-diphenyl-1-picrylhydrazyl) and FRAP (Ferric Reducing Antioxidant Power). Both methods confirmed that the order of antioxidant activity of obtained dried extracts is as follows: water extract lt methanol extract lt ethanol extract, which was in accordance with their polyphenols content. Mild prooxidant activity was observed in the concentration of 200 μg/ml while investigating the DPPH inhibition. Prooxidant activity is a characteristic of some polypenolic acids that is considered to be one of the mechanisms of anticancer activity. The inhibition of DPPH radical, expressed by IC50 values, was compared with the results of the commercial antioxidants such are ascorbic acid and BHT (butylated hydroxytoluene). Comparing the IC50 values of ascorbic acid and BHT with the IC50 values of tested extracts it can be concluded that waste coffee extracts could be a good source of natural antioxidants.

U radu je određivan sadržaj polifenola i antioksidativna aktivnost osušenih ekstrakata otpadne espreso kafe dobijenih primenom različitih rastvarača. Kao rastvarači, u ekstrakcijama su korišćeni 70% rastvor metanola, 70% rastvor etanola i destilovana voda. Određen je ukupan sadržaj polifenola i antioksidativna aktivnost metodama inhibicije DPPH (2,2-difenil-1-pikrilhidrazil) radikala i FRAP (engl. ferric reducing antioxidant power). Inhibicija DPPH radikala je izražena preko IC50 vrednosti, a rezultati su poređeni sa rezultatima komercijalnih antioksidanata, askorbinskom kiselinom i BHT (butil-hidroksi-toluen). Obe metode su potvrdile da je redosled antioksidativne aktivnosti dobijenih suvih ekstrakta sledeći: vodeni ekstrakt lt metanolni ekstrakt lt etanolni ekstrakt. Poređenjem sa vrednostima IC50 za askorbinsku kiselinu i BHT može se zaključiti da ekstrakti otpadne kafe mogu biti dobar izvor prirodnih antioksidanata.