Preparation of a Delayed Releasing Device of Hydroxypropyl Methylcellulose Phthalate Macrocapsules Containing Peppermint Oil

In this study, pH-sensitive macrocapsules containing peppermint oil (PO) were prepared using a new emulsification/polymer precipitation technique. An aqueous alkaline solution of hydroxypropyl methylcellulose phthalate (HPMCP) was used to emulsify PO in water (O/W). This emulsion was then added dropwise to a solution of citric acid to result in a solid dispersion of macrocapsules. Screening studies showed that three different factors including the polymer and the acid concentrations, as well as the essential oil to water (O/W) ratio have considerable effects on the encapsulation process. Different formulations of macrocapsules were prepared and characterized in terms of PO loading, encapsulation efficiency, and release using GC-FID analysis. A 2- level factorial design with 4-centre points was then used to optimize PO loading and encapsulation efficiency against the above mentioned parameters. Optical microscopy showed a polydispersed O/W emulsion, whereas the macrocapsules were uniformly dispersed with mean diameter of 1 mm. The prepared macrocapsules could protect PO from acidic condition of stomach and release it in a simulated intestinal fluid.