Chitosan-alginate microparticles loaded with hydrophobic mangostins present in the mangosteen rind extract have been formulated and optimized for colon-targeted bioactive drug delivery systems. The chitosan-mangostin microparticles were prepared using the ionotropic gelation method with sodium tripolyphosphate as the cross-linking agent of chitosan. The chitosan-mangostin microparticles were then encapsulated in alginate with calcium chloride as the linking agent. The mangostin release profile was optimized using the Box-Behnken design for response surface methodology with three independent variables: (A) chitosan-mangostin microparticle size, (B) alginate:chitosan mass ratio, and (C) concentration of calcium chloride. The following representative equation was obtained: percent cumulative release of mangostins (10 h) = 59.51 - 5.16A + 20.00B - 1.27C - 1.70AB - 5.43AC - 5.04BC + 0.0579A2 + 10.25B2 + 1.10C2. Cumulative release of 97% was obtained under the following optimum condition for microparticle preparation: chitosan-mangosteen particle size < 100 µm, alginate:chitosan mass ratio of 0.5, and calcium chloride concentration of 4% w/v. The alginate to chitosan mass ratio is the statistically significant variable in the optimization of sequential release profile of mangostins in simulated gastrointestinal fluids. Furthermore, a sufficient amount of alginate is necessary to modify the chitosan microparticles and to achieve a complete release of mangostins. The results of this work indicate that the complete release of mangostins to the colon area can be achieved using the chitosan-alginate microparticles as the bioactive delivery system.
Keywords: Box–Behnken optimization; alginate; chitosan; mangostin.