Process optimization by response surface design and characterization study on geniposide pharmacosomes.

The objective of this study was to prepare and characterize geniposide-pharmcosomes (GP-PMS) and optimize the process and formulation variables using response surface methodology. Tetrahydrofuran was used as a reaction medium, GP and phospholipids were resolved into the medium, and GP-PMS was formed after the organic solvent was evaporated off under vacuum condition. The process and formulation variables were optimized by central composite design (CCD) of response surface methodology (RSM). The phospholipid-to-drug ratio (X(1)), reaction temperature (X(2)) and the drug concentration (X(3)) were selected as independent variables and the yield (%) of GP 'present as a complex' in the PMS was used as the dependent variable. The physico-chemical properties of the complex obtained by optimal parameters were investigated by means of Fourier transform infrared spectrophotometry (FT-IR), differential scanning calorimetry, n-octanol/water partition coefficient (P) and particle size analysis. Multiple linear regression analysis for optimization by CCD revealed that the higher the yield of GP 'present as a complex' in the GP-PMS was obtained wherein the optimal settings of X(1), X(2) and X(3) are 3, 50°C and 5.5 mg/mL, respectively. The DSC and IR studies of GP-PMS by the optimal settings demonstrated that GP and phospholipids in the GP-PMS were combined by non-covalent bond, not forming a new compound. GP-PMS could significantly increased the lipophilicify of GP, and P of GP-PMS in n-octanol and water was about 20 multiples more than that of GP material. Pharmacosomes could be an alternative approach to improve the absorption and permeation of biologically active constituents.