Development and Validation of Stability-Indicating RP-HPLC Method for the Estimation of Fisetin in Novel Cubosomal Nanoformulation: Application to the Marketed Formulation and Selected Plant Extracts

Background: Fisetin (FIS) is a bioactive flavonoid found in various plants, reported for many pharmacological activities, and presently marketed as a nutraceutical. To overcome less water solubility and bioavailability issues, FIS cubosomal nanoformulation has been prepared and characterized. Objective: To estimate FIS in prepared novel cubosomes, an RP-HPLC analytical method development with the most sensitivity, economical, robust, and wide applicability in marketed FIS formulations and plant extracts also. Methods: An RP-HPLC method was developed and validated as per ICH Q2R1 guidelines by using C-18 Phenomenex Luna 5μ, 100A0 column, LC-20 AD pump, and Shimadzu LC solution 1.25 software. The combination of acetonitrile and formic acid (0.1%v/v) in the ratio of 25:75 v/v was used as a mobile phase for chromatographic separation using a PDA detector at 360 nm and a flow rate of 1 ml/min. Results: The developed method was remarkably linear in the range of 0.1 to 16 μg/ml (R² #131; 0.999). This method was found to be accurate (recovery 98.24 to 100.65 %), precise, robust (% RSD #130; 2), and more sensitive than the earlier reported method with LOD and LOQ values of 17.26 and 52.31 ng/ml, respectively. The FIS estimation was also performed using the developed method in the marketed FIS formulation Doctor’s Best ® Fisetin, and different plant extracts such as strawberry, grapes, black tea, and green tea. The forced degradation study suggests that FIS was unstable in alkaline and oxidative stress conditions. Conclusion: For FIS estimation in cubosomal nanoformulation, a widely applicable, novel, robust, most sensitive, and economical RP-HPLC method was developed and validated and also applied to marketed formulations and plant extracts.