Validation of an UV spectrophotometric method for determining diffractaic acid from Usnea sp. in inclusion complexes with hydroxypropyl-β-cyclodextrin

Diffractaic acid (DA) presents several biological activities. The goal of this study was to develop and validate a UV spectrophotometric method for determining diffractaic acid in inclusion complexes with hydroxypropyl-β-cyclodextrin. Validation parameters were determined according to international guidelines for standardization. The linearity range of analytical curve was from 1 to 5 μg/mL and the regression equation: CDA = (Area - 0.0053)/0.1541 (r2 = 0.99998; n = 3). The intermediate precision indicated that the difference between the means was statistically insignificant (p < 0.05). Accuracy revealed a mean recovery percentage of diffractaic acid in inclusion complexes of 100.1 %. The method was robust and the formulation excipients did not interfere on diffractaic acid quantification. Limits of detection and quantification of diffractaic acid were 0.03 and 0.08 μg/mL, respectively. The proposed method proved to be accurate, precise and reproducible, thus being able to quantify diffractaic acid in raw material and inclusion complexes. Colegio de Farmacéuticos de la Provincia de Buenos Aires