Contour Plot-Based Interpretation of Factor Effects on Total Flavonoid Content in Morus alba var. shalun Using Box-Behnken Design

Abstract

Morus alba var. shalun is recognized as a potential source of flavonoids with important pharmacological properties. However, studies focusing on the statistical interpretation of extraction variables and contour plot analysis for flavonoid extraction from this plant remain limited. This study employed Response Surface Methodology (RSM) using a Box–Behnken design to evaluate the effects of ethanol concentration, extraction temperature, and extraction time on total flavonoid content (TFC). A quadratic regression model was analyzed using ANOVA, residual diagnostics, and contour plot visualization to examine the relationship between extraction variables and response behavior. The results showed that ethanol concentration had the strongest influence on TFC, followed by extraction time and temperature, whereas interaction effects among variables were relatively insignificant. The developed model demonstrated good statistical performance with an R² value of 0.9723. Residual and Box–Cox analyses confirmed the adequacy and reliability of the model for describing flavonoid extraction characteristics in Morus alba var. shalun.