A Comparative Study of Phenolic Compounds, and the Antioxidant Properties of Arabica Coffee Beans (Coffea arabica) and Robusta Coffee Beans (Coffea canephora) and Their By-Products

Coffee, the second most consumed beverage in the world produces considerable quantities of coffee grounds, a brewing by-product that has a considerable impact on the environment. this study, the chemical composition and antioxidant properties of Arabica and Robusta coffee varieties and their coffee grounds were compared. Extracts were prepared by aqueous and hydroalcoholic maceration, and analyzed for total and reducing sugars, proteins, polyphenols, flavonoids, tannins, and antioxidant activity. the analysis revealed significant disparities between the samples. Robusta SCGs had the highest total sugar content (111.92 ± 0.95 mg Glu/g DW), while Arabica SCG contained higher levels of reducing sugars and proteins (24.65 ± 0.39 mg Glu/g DW and 85.81 ± 1.54 mg BSA/g DW, respectively). Robusta and its SCGs were particularly rich in polyphenols (CR-H = 342.73 ± 11.40; SCGR-H = 275.66 ± 0.54 mg GAE/g DW), flavonoids, and tannins. Antioxidant tests confirmed Robusta SCG’s superior activity with TAC (460.8 ± 8.5 mMAAE/g), FRAP (0.236 ± 0.01 mg/mL), and DPPH radical scavenging (IC50 = 0.115 ± 0.00 mg/mL). further HPLC-DAD analysis revealed distinct phenolic profiles, Robusta SCG being enriched in hydroxybenzoic acids and flavonol glycosides such as rutin and quercetin-3-O-glucoside. These results indicate the viability of spent coffee grounds, particularly Robusta coffee, as a sustainable source of valuable bioactive compounds that possess substantial antioxidant properties.