Green Extraction Strategies and Bioactivity of <i>Rheum cordatum</i> Losinsk: Antioxidant, Antimicrobial, and Molecular Docking Insights

This study aimed to compare the efficiency of different green extraction methods for obtaining bioactive compounds from the roots of <i>Rheum cordatum</i> Losinsk and to evaluate their antioxidant and antimicrobial properties. The presence of some important phytochemicals in the extracts obtained using ultrasound-assisted extraction (UAE), subcritical ethanol extraction (Sbc-EtOH), and supercritical CO₂ (ScCO₂) extraction was determined by LC-MS/MS, and their antioxidant and antimicrobial properties were examined against <i>Staphylococcus aureus</i>, <i>Enterococcus faecalis</i>, <i>Pseudomonas aeruginosa</i>, and <i>Escherichia coli</i>. The goal was to determine the optimal extraction conditions that maximize the yield of bioactive compounds while preserving their biological properties. Different pressures (100 bar and 400 bar) were tested in UAE extraction, different solvents and times were tested in Sbc-EtOH extraction, and different pressures were tested in ScCO₂ extraction. Most of the 53 important phenolic compounds have been extracted using the ScCO₂ extraction method, either exclusively or in the highest amounts. It has been observed that more and higher amounts of phenolic compounds were extracted at lower pressure. The highest antioxidant activity was exhibited by the ScCO₂ extracts. Additionally, the ScCO₂-100 extract obtained at 100 bar showed strong antimicrobial activity, with a minimum inhibitory concentration (MIC) ranging from 31.25 to 250 μg/mL. Gallic acid, epicatechin gallate, epigallocatechin gallate, and catechin were found in extracts. Additionally, molecular docking studies against the 1QWZ, 2ANQ, 3H77, and 6QXS proteins revealed that epicatechin exhibited docking scores of −6.127, −9.479, −5.836, and −7.067 kcal/mol, respectively.