Ultrasound-assisted extraction for simultaneous quantitation of potential sweetening compounds from Derris reticulata aqueous extracts: a response surface methodology approach

Derris reticulata or “Oi Sam Saun” is an extremely 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 prepared using ultrasound-assisted extraction (UAE). Phenolic, flavonoid, and sugar compound extraction was optimised using response surface methodology based on the Box–Behnken design (BBD). 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 values of 80 °C, 60 min, and a ratio 1:10 g/mL, respectively, were optimal. Under these conditions, experimental values were well correlated with predicted values, and phenolic, flavonoid, and sugar contents were 0.483 ± 0.032 mg GAE/g DW, 0.149 ± 0.033 mg CE/g DW, and 4.802 ± 0.651 mg/g DW, respectively. High performance liquid chromatography-diode array detector (HPLC–DAD) analysis showed that the “Oi Sam Saun” UAE extract contained gallic acid, p-coumaric acid, quercetin, and kaempferol. Moreover, the extract contained 18β-glycyrrhetinic acid (0.529 ± 0.002 mg/100 mg) and was 166 times sweeter than sucrose. Therefore, this Thai medicinal plant, which has several pharmacological benefits, is highly potent and can be utilised as a sweetening agent or sugar substitute in foods.