Phenolic Indices and Antioxidant Properties of a Thermally Processed Model Matrix Containing Dried Cynanchum thesioides (Freyn) K. Schum Powder.

Phenolic compounds are valued for their antioxidant activity, but their measured response after heating can vary with the surrounding matrix. In this study, dried Cynanchum thesioides (Freyn) K. Schum powder (CTP) was added to a cookie matrix at 0%, 1%, 3%, and 5% (w/w) to examine phenolic indices, antioxidant activity, and physicochemical changes after baking. CTP affected moisture content, spread ratio, hardness, color, pH, and soluble solids in the baked matrix, whereas density was unchanged. Antioxidant activity increased with increasing CTP level. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activities increased from 8.04% to 46.33% and from 17.02% to 36.43%, respectively, while ferric reducing antioxidant power (FRAP) increased from 6.17 to 23.64 mM FeSO4 equivalents/g. Total polyphenol content (TPC) increased from 0.66 to 1.46 mg gallic acid equivalents/g, and total flavonoid content (TFC) increased from 0.20 to 0.85 mg catechin equivalents/g. These results show that increasing CTP raised the extractable phenolic indices, radical scavenging activity, and reducing capacity measured in the baked samples. The findings establish a formulation-dependent antioxidant response in the final baked products and provide a basis for future compound-specific studies of phenolic retention during processing.