Ultrasound-Assisted Extraction for Simultaneous Quantitation of Potential Sweetening Compounds from Derris reticulata Aqueous Extracts: A Response Surface Methodology Approach

Background: Derris reticulata or Oi Sam Saun is a highly sweet Thai plant, rich in bioactive compounds, and widely used for its medicinal properties. In this study, sweet aqueous extracts from the stems of Oi Sam Saun were extracted using ultrasound-assisted extraction (UAE). Phenolic, flavonoid, and sugar compound extraction was optimized using the Box-Behnken design (BBD) and response surface methodology (RSM). Methods: Three independent variables—extraction temperature (40–80°C), sonication time (20–60 min), and extraction ratio (1:10–1:30 g/mL)—were investigated, and the optimal condition was used to determined phenolics, flavonoid and 18β-glycyrrhetinic acid by High performance liquid chromatography-diode array detector (HPLC-DAD). Sensory evaluation was also performed.Results: The values of 84°C, 64 min, and ratio 1:8 g/mL were found to be optimal. Under these conditions, experimental values were well correlated with predicted values, and phenolic, flavonoid, and sugar contents were determined as 0.4725 mgGAE/gDW, 0.1489 ± 0.033 mgCE/gDW, and 4.802 ± 0.651 mg/gDW, respectively. Gallic acid, p-coumaric acid, quercetin, and kaempferol was also found in optimal condition. Moreover, the extract contained 18β-glycyrrhetinic acid (0.529 ± 0.002 mg/100 mg) and was 166 times sweeter than sucrose.Conclusion: High level of phenolics, flavonoids and sugars was detected in optimal condition of the extract. Therefore, this Thai medicinal plant, which has several pharmacological benefits, is newly potentially and applicable as a sweetening agent or sugar substitute in foods.