Bioactivity Enhancement of Curcuma longa Extract via Optimized Enzyme-Assisted Ultrasonic Extraction

To enhance the levels of bioactive compounds in turmeric extract, we optimized the enzyme-assisted ultrasonication extraction conditions employing a Central Composite Design within Response Surface Methodology. By varying the α-amylase enzyme concentration (1.5%, 5%, or 8.5%) and ultrasonication time (10, 20, or 100 min), the conditions were optimized based on the levels of the response variables (total phenolic and flavonoid content, 2,2-diphenyl-1-picrylhydrazyl [DPPH] radical scavenging activity, and Trolox equivalent antioxidant capacity [TEAC]). The optimal conditions, comprising 8.14% enzyme concentration and 100 min of ultrasonication, achieved total phenolic content of 184.2 mg GAE/g, total flavonoid content of 197.1 mg QE/g, DPPH radical scavenging activity of 96.9 mM TE/g, and TEAC of 84.7 mM TE/g. Following treatment with the optimized extract, lipopolysaccharide-induced nitric oxide production as well as cell viability were evaluated. The results showed a NO inhibition rate over 90% at the optimized extract of 200 μg/mL, with minimal impact on cell survival. The optimized extract exhibited greater antidiabetic potential in the α-amylase and α-glucosidase inhibition assays and the greater inhibition of angiotensin-converting enzyme than the water- and solvent-derived extracts. These findings provide insight into the use of optimized extraction methods to extract higher levels of bioactive compounds from turmeric.