Colorimetric Parameters Correlated with the Variation in the Marker Constituent Contents During the Stir-fry Processing of Schizonepetae Spica

Schizonepetae Spica (SS), the dried spike of Schizonepeta tenuifolia Briq., is often consumed in beverages, sauce, beneficial tea, or herbal medicine. Raw SS has the action of dispelling the common cold and fever. Schizonepetae Spica Carbonisata (SSC; raw SS processed by stir-frying until the surface becomes blackish brown and the interior turns dark yellow) has particularly strong efficacy in arresting bleeding from bloody stools and metrorrhagia. In this paper, a high-performance liquid chromatography diode array detector method and colorimetry were employed to determine 6 nonvolatile marker constituents, and the color parameters (L*, a*, and b*) of SS during stir-fry processing, respectively. According to Pearson correlation analysis, L*, a*, and b* showed significant correlations with the levels of luteolin-7-O-β-D-glucoside, apigenin-7-O-β-D-glucoside, hesperidin, and rosmarinic acid, while a* was significantly correlated with the amounts of luteolin and apigenin. The corresponding regression models were good fits for the color parameters as respective functions of the 6 marker constituents according to enter multiple linear regression and third-order polynomial curve fitting methods (adjusted R2 > 0.800). Surrogate prediction of marker compounds using color parameters provides a valuable and cost-saving tool for rapid or online monitoring of the processing degree of SS. Raw SS and SSC could be determined based on the color parameters and 6 marker constituent contents for a comprehensive quality evaluation for the first time. This paper provides scientific data to validate the relationship between color features and quality during the processing of SS.