Functional Chewing Gum Enriched with Spent Coffee Grounds Extract: Chemical Characteristics and Antimicrobial Potential Against Oral Bacteria

Spent coffee grounds (SCGs), as a by-product, represent a sustainable source of bioactive components. Herein, the ethanol extract of SCGs was examined for its chemical characteristics and antimicrobial effect. The extract was incorporated into novel frankincense-based gums at concentrations of 0% (T0), 15% (T15), 20% (T20), and 25% (T25). The physicochemical properties and the antibacterial activity of the SCG-enriched gums against oral pathogens were assessed. SCG extract showed a total phenolic content of 999.38 ± 2.63 μg/g and demonstrated antioxidant activity with a 50% inhibitory concentration (IC50) of 107.28 ± 1.90 μL/mL. T25 showed the highest phenolic content (256.66 ± 2.93 μg/g) and enhanced scavenging activity IC50 = 211.05 ± 0.65 (DPPH) and 128.52 ± 4.05 μL/mL (ABTS). T25 demonstrated superior antimicrobial effects against Streptococcus mutans and Enterococcus faecalis at 400 µL/mL, with inhibition zones of 33.33 ± 2.89 and 20.33 ± 0.58 mm compared to T0. Both T25 and T0 inhibited Lactobacillus acidophilus similarly. Overall, incorporating SCG extract into natural frankincense-based gum presents a promising biodegradable functional gum with potential oral health benefits.