Optimization of Polyphenol Extraction Conditions from Rhizomes of Curcuma zedoaria with Antioxidant, Anti-Inflammatory and Anti-Diabetic Activities In Vitro

The recovery of polyphenol compounds is seen as an arduous task because polyphenol compounds are available as free aglycones, as sugar or ester conjugates, or as polymers with several monomeric components. The response surface method (RSM) as a tool to optimize the factors that affect extraction efficacy as well as to obtain maximum recovery of the compounds of interest. This study optimizes ultrasound-assisted polyphenol extraction from Curcuma zedoaria rhizomes using response surface methodology (RSM). Three variables were considered: Ethanol concentration (70 - 90 %, v/v), temperature (60 - 80 °C), and ultrasound time (15 - 25 min). Data were analyzed by ANOVA, yielding an R2 of 0.9993, a significant interaction effect (p < 0.0001), and an insignificant lack-of-fit test (p = 0.6684). Optimal conditions for maximum polyphenol content (TPC = 31.05 ± 0.53 mg GAE/g powder) were 80.02 % ethanol, 68 °C, 20.47 min ultrasound time, and 1/10 (w/v) raw material/solvent ratio. Experimental values matched RSM predictions, confirming successful extraction optimization from Curcuma zedoaria rhizomes. The polyphenol-rich optimum extract from Curcuma zedoaria rhizomes has been studied for its antioxidant, anti-inflammatory and anti-inflammatory properties in vitro. The results were found, the optimum extract of Curcuma zedoaria rhizomes could perform effective neutralization activities of free radicals performed in DPPH test (IC50 = 5.89 ± 0.23 µg/mL), NO· (IC50 = 5.89 ± 0.23 µg/mL) and ABTS·+ (IC50 = 8.28 ± 0.12 µg/mL). Besides, this optimum extract had the ability to protect red blood cell membranes and inhibit protein denaturation due to heat with IC50 times values ​​such as 29.06 ± 0.35 and 30.24 ± 0.32 µg/mL. In addition, it also significantly inhibited α-amylase, α-glucosidase enzyme activities with IC50 values ​​of 5.89 ± 0.23 and 9.62 ± 0.11 μg/mL, respectively. This investigation showed that the polyphenol-rich optimum extract from Curcuma zedoaria rhizomes was a promising antioxidant, anti-inflammatory and anti-diabetic agent. HIGHLIGHTS Using ultrasound and the Box-Behnken design to extract polyphenols from Curcuma zedoaria rhizomes can speed up and improve extraction efficiency. The goal of this study is to maximize the extraction parameters for polyphenols from the rhizomes of Curcuma zedoaria. There is strong agreement between the experimental data and the model that predicts the polyphenol content in the Box-Behnken design. In vitro biological activities such as anti-inflammatory, antidiabetic and antioxidant properties are significantly correlated with polyphenol concentration. The findings of our investigation show a noteworthy enhancement in the bioavailability of polyphenol compounds through increased extraction efficiency and bioactivity. GRAPHICAL ABSTRACT