Ultrasound-assisted ethanol extraction of mountainous Millettia dielsiana from Vietnam: Effects on flavonoid yield and anti-inflammatory potential

Abstract

This study evaluated the effects of temperature, ultrasound intensity, and extraction time on flavonoid yield and nitric oxide (NO) inhibitory activity of the extract from Millettia dielsiana (a rare mountainous medicinal plant of Vietnam) using 70% ethanol. Extractions were performed at 60-70 °C for a total duration of 60 min and 75 min, with and without ultrasound assistance at 30 W/cm² for 10-15 min. Flavonoid content was quantified, and NO production inhibition was assessed by determining IC₅₀ values. At 70°C without ultrasound, flavonoid yield was 68.5% with an IC₅₀ of 205.48 µg/mL. Application of ultrasound (30 W/cm²) for 10 or 15 min at the same temperature significantly increased yields to 74.9-75.1% and improved NO inhibition (IC₅₀: 176.15-169.28 µg/mL). At 60 °C with ultrasound for 15 min, the yield remained high (74.0%) with the strongest NO inhibition observed (IC₅₀: 150.89 µg/mL). Results indicate that moderate temperature combined with short ultrasound pre-treatment enhances both flavonoid extraction efficiency and bioactivity. These findings support the potential of ultrasound-assisted extraction as a green and effective method for producing bioactive flavonoid-rich extracts from Millettia dielsiana with implications for functional food and nutraceutical applications.