Abstract
In this study, the optimization and modeling of microwave-assisted extraction (MAE) of water-soluble curcuminoids prepared using novel steviol glycosides (SGs) was carried out using four independent process variables at varying levels—X1: microwave power (50–200 W), X2: stevioside concentration (50–200 mg/mL), X3: curcumin concentration (20–200 mg/mL), and X4: time (1–10 min)—in response surface methodology configuration. Moreover, the effects of stevioside, as the most cost-effective natural solubilizer, were also evaluated. The water solubility of curcuminoids increased from 11 to 1320 mg/L with the addition of stevioside as a natural solubilizer. Moreover, microwave heating synergistically with stevioside addition significantly (p < 0.05) increased the solubility up to 5400 mg/L. Based on the results, the optimum conditions providing the maximum solubilization of 16,700 mg/L were 189 W microwave power, 195 g/L stevioside concentration, 183 g/L curcuminoid concentration, and 9 min of incubation time. Moreover, MAE of curcuminoids using SGs might render a significant advantage for its wide-scale application to solubilizing the multitude of insoluble functional flavonoids in fruits, plants, and food materials.
Highlights
Turmeric (Curcuma longa L.), as the member of the Zingiberaceae family, is found globally in tropical and subtropical regions, including Southeast Asia
We demonstrated a novel solubilization method for poorly soluble curcuminoids using steviol glycosides
This result demonstrates that the bioactivity of curcuminoids can be completely maintained when they are solubilized in the presence of stevioside or rubusoside
Summary
Turmeric (Curcuma longa L.), as the member of the Zingiberaceae family, is found globally in tropical and subtropical regions, including Southeast Asia. Various published reports pertaining to animal and human studies have endorsed curcuminoids as safe, nontoxic, and tolerable at high doses (≤12 g/day); they are not yet approved as therapeutic agents due to limited aqueous solubility and absorption in the human gastrointestinal (GI) tract [1]. Their utility is limited because of poor water solubility (11 mg/L), relatively low in vivo bioavailability, slow dissolution, and instability in the GI tract under thermal and rapid hydrolysis in alkaline conditions (under pH range of 7.5–9.0) [4]. Even with an intake dose of 2 g in humans, curcuminoids exhibit undetectable or extremely low bioavailability
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