Synergistic antimicrobial effects of coffee green extract and oil microemulsions enhanced by photodynamic therapy: A strategy against antibiotic resistance

Abstract

Coffee is one of the main tropical crops, with Brazil accounting for more than a third of global production. It contains bioactive compounds such as chlorogenic acids that provide health benefits, such as antimicrobial activity, and is a natural alternative in combating antibiotic resistance, currently one of the major global threats to public health. Additionally, antimicrobial photodynamic therapy (aPDT) has also emerged as a way to overcome microbial resistance, using photosensitizers, light and oxygen to generate reactive species that eliminate microorganisms. Microemulsions were prepared by the spontaneous emulsification method, containing green coffee oil and extract, stabilized by surfactants. The dispersed systems obtained presented droplet size of approximately 25–60 nm, PDI of 0.088–0.290 and zeta potential of approximately −12 to −25 mV, at different temperatures and stability tests. In addition, they demonstrated Newtonian fluid behavior with a viscosity of approximately 30 cP. Furthermore, they were effective in treating microorganisms at lower doses than previously reported in the literature and were enhanced when associated with photodynamic therapy, acting at a minimum concentration of green coffee extract of 250 μg ml⁻¹ and when photoactivated, acting at 125 μg ml⁻¹, and they also exhibited activity in the absence of the incorporated extract. This study reveals a product that structures the use of plant-derived substances in the pharmaceutical industry, stimulating the bioeconomy and contributing to family farming, considering the economic importance of coffee in Brazil.