Formulation Optimisation and Evaluation of a Turmeric Extract–Incorporated Emulgel Using a Simplex Lattice Approach

Turmeric (Curcuma longa L.) possesses well-established anti-inflammatory, antioxidant, antimicrobial, and wound-healing properties; however, its topical application is limited by poor solubility, instability, and inadequate skin penetration. The present study aimed to develop and optimise a turmeric extract–incorporated emulgel using a simplex lattice experimental design to overcome these limitations and achieve an effective topical delivery system. Preformulation studies, including FTIR and DSC analyses, were carried out to characterise the extract and assess compatibility with formulation excipients. Solubility screening was performed to select suitable oil, surfactant, and co-surfactant for nanoemulsion development. Nanoemulsions were prepared and incorporated into an HPMC-based gel to form Nanoemulgels, which were optimised using Design-Expert® software with particle size and viscosity as response variables. The optimised formulation (F6) exhibited a mean particle size of approximately 379 nm with acceptable polydispersity and zeta potential, indicating good physical stability. The nanoemulgel showed skin-compatible pH, desirable rheological behaviour, uniform drug content, good spreadability, and sustained in-vitro drug release. Accelerated stability studies confirmed formulation stability over the study period. Overall, the findings demonstrate that simplex lattice-based optimisation is an effective approach for developing a stable and efficient turmeric extract nanoemulgel suitable for topical therapeutic and cosmetic applications.