Optimization of Environmentally Sustainable UPLC-PDA Method Using Box–Behnken for Simultaneous Quantifying Curcumin and Candesartan Cilexetil in On-Demand Formulation for Treatment of Brain Ischemic Injury

Brain ischemic injury is characterized by reduced cerebral blood flow and neuronal cell damage. Curcumin and candesartan cilexetil were proposed to restore normal brain function. Therefore, a validated UPLC method is required to quantify drugs within the proposed formulation. The Box–Behnken design was used to optimize the ultra-performance liquid chromatography (UPLC) method. The impact of three critical parameters (aqueous phase percentage, flow rate, and column temperature) on the measured responses was studied. Additionally, the method's environmental impact was assessed using AGREE software. Finally, drug content, dispersed formulation stability, and antioxidant activity were investigated. The optimal conditions utilized a mobile phase (0.1% formic acid:acetonitrile; 44:56% v/v) with a flow rate of 0.2 mL/min through an Acquity UPLC BEH C18 1.8 μm (2.1 × 50 mm) column maintained at 40°C. This resulted in efficient curcumin and candesartan cilexetil separation peaks with retention times of 1.49 and 6.35 min, respectively. The method demonstrated excellent linearity. The calculated intraday and interday precision values were < 3.6% RSD with accuracy values (98.8%–105.1%). Moreover, the optimized UPLC method achieved a favorable eco-scale score of 0.77. The validated method successfully analyzed drug content within the SNEDDS formulation, which was able to solubilize both drugs and maintain the antioxidant activity of curcumin.