es effets synergiques antimicrobiens et antioxydants du café (Coffea spp.) et du galanga (Alpinia galanga) : de l’usage traditionnel à la preuve scientifique

Abstract

This study aims to evaluate the antioxidant, antimicrobial, and synergistic effects of methanolic extracts from Coffea arabica and Alpinia galanga in order to scientifically validate their traditional use. The extracts were obtained by maceration in a methanol/water mixture (80:20) and subsequently characterized in terms of extraction yield, phenolic composition, and biological activities. Extraction yields were 5.90% for C. arabica and 1.16% for A. galanga. Phytochemical analysis revealed high levels of total polyphenols (233.07 mg GAE/g for C. arabica and 383.84 mg GAE/g for A. galanga) and flavonoids (16.36 ± 3.85 mg QE/g and 50.90 mg QE/g, respectively). Antioxidant activity assessed using the DPPH assay, demonstrated significant radical scavenging capacity, with IC₅₀ values of 372.54 µg/mL for C. arabica and 72.21 ± 1.78 µg/mL for A. galanga. Antimicrobial activity was evaluated using the agar well diffusion method and determination of minimum inhibitory concentration (MIC) against several pathogenic strains, including Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Bacillus cereus, and Candida albicans. The results showed notable inhibitory activity, with inhibition zones reaching up to 25 mm for A. galanga and MIC values varying depending on the strain. The synergistic effect, evaluated using the checkerboard method, revealed total synergy (FICI ≤ 0.5) against certain strains, particularly Klebsiella pneumoniae, as well as partial synergy or antagonism depending on the microorganism. The combination of extracts significantly reduced MIC values. In conclusion, these extracts exhibit promising biological properties and a significant synergistic potential for pharmaceutical, food, and cosmetic applications.