Antioxidant and antimicrobial activity of green and roasted coffee beans on human oral pathogens

This study aimed to determine the antioxidant content (total phenolics, chlorogenic acid (CGA), and caffeine), proximate composition, and antimicrobial activity of green and roasted coffee beans (coffee arabica and coffee canephora var Robusta) and evaluate their effect on three selected human oral pathogens (i.e., Porphyromonas gingivalis, Streptococcus mutans and Lactobacillus casei). Total phenolic content (TPC) was significantly higher in green C. robusta (5.48 mg/g) compared to green C. arabica (4.67 mg/g). However, there was significantly lower phenolic content in both roasted coffee types. Similarly, CGA content was higher in green C. robusta coffee (2.39 mg/g) compared to roasted C. robusta coffee (0.74 mg/g). Caffeine content was significantly higher in roasted C. robusta (1.36 mg/g) compared to green C. robusta (1.23 mg/g) and green C. arabica (1.04 mg/g). The extract of green C. robusta produced a larger mean diameter of inhibition zones at all concentrations against bacteria tested compared to C. arabica. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of all samples on L. casei were 50 mg/mL, while on S. mutans were 240 mg/mL. The MIC and MBC for green and roasted C. robusta and C. arabica tested on P. gingivalis were 100 mg/ml and 200 mg/mL, respectively. The results showed that green and roasted Robusta coffee had higher chlorogenic acid, total phenolic contents, and good antimicrobial activity compared to its counterparts. This study suggests the feasibility of using Robusta coffee in the food industry to increase the functionality of beverages.