Optimization of processing parameters for ultrasound-assisted extraction of total phenolic content from Homalomena occulta rhizomes and characterization of their bioactivities

Abstract

Phenolic and flavonoid content extractions from Homalomena occulta are important ingredients in traditional Vietnamese medicine with bioactivities such as antiinflammatory, antibacterial, and antioxidant properties. In this study, the optimizing total phenolic content (TPC) extraction from H. occulta rhizomes using ultrasound-assisted extraction (UAE) and ethanol solvent is evaluated. Under the optimal conditions, the maximum TPC reached 206.75 mg GAE/g dw (mg of gallic acid equivalents per gram of dry weight of sample). The minimum inhibitory concentration (MIC) values of TPC extracts against Escherichia coli and Staphylococcus aureus were 400 and 600 µg/mL, respectively. The free radical scavenging activity of the TPC extracts from H. occulta rhizomes was assessed, yielding an IC50 value of 32.33 (μg/mL). The TPC presented high antioxidant activity at 84.54% compared to ascorbic acid. Thus, the UAE method and ethanol solvent can enhance the extraction of the TPC from H. occulta rhizomes and speed up the extraction process, and it can be considered a valuable source of antibacterial and antioxidant compounds.