GC-MS Analysis, Phenolic Compounds Quantification, Antioxidant, and Antibacterial Activities of the Hydro-alcoholic Extract of Spent Coffee Grounds

Abstract

Coffee consumption has been positively linked with a decreased risk of different diseases. The spent coffee ground, the product obtained after the brewing process, can be reused for its beneficial abilities. This work contributes to the investigation of the chemical composition of the hydroalcoholic extract of spent coffee (Arabica and Robusta) grounds, its antioxidant and antibacterial activities. The GC-MS analysis of the extract obtained by Soxhlet revealed the presence of 14 components such as curlone, octadecane, and dillapiol. Also, the major compound found in our extract, namely curlone, was not previously reported in spent coffee grounds. These compounds are known for their important biological activities. The extract was found to be rich in polyphenolic compounds, with a value of 129.43 ± 6.05 mg GAE/g extract. The DPPH assay revealed an important antioxidant IC50 value (11.95 ± 0.96 μg/mL). Also, the antibacterial assay performed by the Agar Diffusion Method showed that all tested bacteria were sensitive against the hydroalcoholic spent coffee grounds extract (HECG), especially Escherichia coli. Minimal inhibitory concentrations (MIC) as low as 2.5 mg/mL (Luteibacter sp.) were recorded against different bacterial strains. These results suggest that “HECG” is a potential source of important bioactive compounds.