Exploration on the Extraction of Phenolic Acid from Abutilon theophrasti and Antioxidant and Antibacterial Activities

This study selected Abutilon theophrasti Medicus as the research object and optimized the ultrasonic-assisted heat reflux extraction process using response surface methodology to achieve efficient extraction of phenolic acids from its leaves. The optimized conditions were as follows: methanol was used as the extraction solvent, with a liquid–solid ratio of 30:1 (mL/g), ultrasonic power of 200 W, ultrasonic time of 30 min, and reflux temperature of 70 °C. Under these conditions, the extraction yield of total phenolic acid reached 213.29 μg/g, which significantly higher than those obtained using traditional extraction methods. Subsequently, six phenolic acid compounds, gallic acid, protocatechuic acid, chlorogenic acid, vanillic acid, syringic acid, and p-hydroxybenzoic acid, were successfully separated and identified from the leaf extract. Meanwhile, the phenolic acid contents in the roots, stems, and leaves of A. theophrasti were analyzed by HPLC method. The results showed that the phenolic acid content in the leaves was significantly higher than in the roots and stems. Furthermore, the antioxidant and antibacterial activities of extracts obtained from different plant parts, and those of the six separated phenolic acids, were systematically evaluated. The results demonstrated that all the samples exhibited notable antioxidant and antibacterial activities. Among them, gallic acid, protocatechuic acid, syringic acid, and vanillic acid displayed strong antioxidant activity, while gallic acid and vanillic acid showed the highest antibacterial efficacy.