Antimicrobial and Antioxidant Effects of Aqueous, Methanolic, and a Deep Eutectic Solvent-Based Extracts of Althaea...

The increase in antimicrobial resistance has become a worldwide health emergency, rendering most conventional antibiotics ineffective and encouraging the research into alternative therapeutic methods.

The antioxidant and antimicrobial activity of Althaea officinalis flower extracts was investigated in this research with specific focus on the deep eutectic solvent-mediated extraction method. Deep eutectic solvent was synthesized using ammonium acetate and lactic acid in different molar ratios and utilized as a sustainable extraction solvent under ultrasound-assisted extraction conditions. Deep eutectic solvent-based extraction was optimized to produce high amounts of bioactive compounds, and extracts obtained were compared with aqueous and methanolic solvents. Total phenolic content, antimicrobial activity against standard bacterial and fungal strains, as well as azole-resistant and azole-sensitive clinical isolates of Candida albicans, were measured. Antioxidant capacity was calculated by 2,2-diphenyl-1-picrylhydrazyl radical scavenging assay.

Deep eutectic solvent-based extract was superior in extraction with greater total phenolic content (8.9 ± 0.4) and improved antimicrobial and antioxidant activity compared to the conventional extracts. Particularly, the deep eutectic solvent extract exhibited noteworthy inhibitory activity against Gram-positive and Gram-negative standard strains of bacteria, as well as standard and clinical yeast fungi. The biocompatibility of the deep eutectic solvent extract was assured by cytotoxicity analyses against 3T3 fibroblast cells.

These results demonstrate that DES-based extraction serves as a green and effective method for isolating bioactive compounds from Althaea officinalis. This procedure deserves its potential use in the synthesis of novel antimicrobial agents.