The Influence of Uncaria Gambir Extract and Tween 80/PEG-400 Ratio on the Physicochemical Properties and Physical Stability of Nanoemulsion-Based Moisturizer

Uncaria gambir is a plant-derived material containing bioactive compounds that have potential for use in cosmetic formulations. However, incorporating plant extracts into nanoemulsion-based moisturizers may affect their physical characteristics during storage. This study aimed to evaluate the effects of Uncaria gambir extract concentration and Tween 80/PEG-400 ratio on the homogeneity, organoleptic properties, and spreadability of nanoemulsion-based moisturizer formulations. A 4 × 2 factorial experimental design was employed using four concentrations of U. gambir extract (0, 0.3, 0.5, and 0.7 g/100 g formulation) and two Tween 80/PEG-400 ratios (25:15 and 30:10), resulting in eight formulations (F1–F8). The formulations were evaluated during four weeks of storage based on visual homogeneity, organoleptic characteristics, and spreadability. All formulations remained homogeneous throughout the four-week storage period, with no visible phase separation, clumping, or coarse particles. Incorporating U. gambir extract primarily affected the formulations' color, which changed from transparent in the extract-free formulations to brown in the extract-containing formulations, while no noticeable changes in odor or texture were observed during storage. Spreadability showed a slight increase over the storage period, while formulations containing the 25:15 Tween 80/PEG-400 ratio generally exhibited greater spreadability than those containing the 30:10 ratio. Variations in extract concentration did not cause visible deterioration in homogeneity or organoleptic characteristics. Overall, U. gambir extract can be incorporated into nanoemulsion-based moisturizer formulations while maintaining acceptable physical characteristics in terms of homogeneity, organoleptic properties, and spreadability over four weeks of storage. The Tween 80/PEG-400 ratio of 25:15 provided favorable overall physical performance, particularly with respect to spreadability.