Development and DoE-Based Optimization of Dragon Fruit and Kiwi Fruit Herbal Syrup: Formulation, Physicochemical Characterization and Stability Evaluation

Background: Herbal syrups provide a convenient oral dosage form for incorporation of plant-derived constituents, but suspended herbal extracts may present challenges related to viscosity, sedimentation and physical stability. Objective: The study aimed to develop and optimize a herbal syrup containing dragon fruit and kiwi fruit peel extracts using a Design of Experiments approach and to characterize the optimized formulation for physicochemical properties and accelerated stability. Methods: Ethanolic and aqueous peel extracts of dragon fruit and kiwi fruit were incorporated into a sucrose-based syrup containing sodium carboxymethyl cellulose (Na-CMC). A two-factor, five-level Central Composite Design consisting of 13 experimental runs was used. Na-CMC concentration (0.16-0.44%) and sucrose concentration (34.4-72.6%) were independent variables, while viscosity and sedimentation were dependent responses. Quadratic models were evaluated by analysis of variance and numerical optimization. Results: The viscosity model was significant (F=29.59, p=0.0001, R²=0.9548) and the sedimentation model was significant (F=14.64, p=0.0014, R²=0.9127). Numerical optimization identified 0.318971% Na-CMC and 66.6245% sucrose, with desirability 1.000. Predicted viscosity and sedimentation were 364.22 cP and 0.0976969%, respectively. Experimental validation gave 368.45 cP viscosity and 0.10% sedimentation. Conclusion: The CCD-based approach identified an optimized herbal syrup containing approximately 0.32% Na-CMC and 66.62% sucrose with acceptable viscosity and minimal sedimentation. The formulation was selected for accelerated stability assessment at 40±2°C/75±5% RH for six months.