Preparation and characterization of iota carrageenan-cyclodextrin-curcumin fibers and the release nature of curcumin in simulated digestion conditions

Healthy foods, known as functional and medicinal foods, are gaining popularity as they contain reasonable amounts of bioactive compounds (BCs) that can boost immunity. However, the intrinsic water insolubility and instability of BCs limit the design and development of healthy foods. To this end, carriers are effective in overcoming these setbacks. Among the several carrier choices, herein, human-compatible hydrocolloid iota-carrageenan (IC), a food hydrocolloid with the ability to form thermos-reversible gels, is chosen due to its intrinsic non-toxic and inexpensive traits. The ordered network structures of iota-carrageenan have been created by complexing with α-, β-, and γ-cyclodextrin (CD); later, curcumin has been encapsulated. Curcumin release has been tested in aqueous, simulated gastrointestinal, and simulated intestinal conditions. The maximum curcumin release was obtained in the aqueous conditions, and the IC fibers containing 50 mM NaCl displayed the highest curcumin release of 1.55 mg/g, followed by IC50-0.1β-CD of 1.37 mg/g. On the other hand, in IC fibers with 100 mM NaCl, the best release obtained was from IC100-0.1γ-CD and IC100 of 0.84 and 0.83 mg/g, respectively, and the minimum release of 0.39 mg/g was from the IC100-0.5γ-CD fibers. In simulated gastric fluid (SGF) media (pH 1.2), the highest release detected was 0.26 mg/g from the fibers with 50 mM NaCl. However, in simulated intestinal fluid (SIF) conditions (pH 6.8), the maximum achieved release of 1.00 mg/g was from the IC50 fibers, followed by 0.93 mg/g from the IC50-0.1β-CD fibers. Overall, the IC-CD network thermally protects curcumin, and the type of CD impacts its sustained release nature. The outcome is important in designing value-added delivery systems of bioactive compounds required to develop novel functional foods and improve human health.