The long historical use of herbs and spices for their medicinal benefits is fully acknowledged, and there is a growing amount of literature concerning the potential/purported benefits of these foods from a health perspective. These benefits include their possible role in conferring protection against cardiovascular and neurodegenerative diseases, cardiovascular disease, cancer and type 2 diabetes.

Polyphenols are found in numerous plant derived foods including herbs and spices, which, especially in their dried forms, generally contain relatively high levels of polyphenols compared to other polyphenol rich foods including broccoli, dark chocolate, red, blue and purple berries, grape and onion

Culinary herbs and spices are, in many instances, cooked prior to consumption, and then undergo digestion,  simmering and stewing increased the antioxidant capacity probably as a result of heat liberating the antioxidant compounds, in contrast, cooking techniques that involved dry heating, grilling and frying, resulted in a decrease in antioxidant capacity which was associated with browning and thus may be indicative of the Maillard reaction

References;

Culinary Herbs and Spices: Their Bioactive Properties, the Contribution of Polyphenols and the Challenges in Deducing Their True Health Benefits 

by Elizabeth I. Opara ^1,* and Magali Chohan ²¹School of Life Sciences, Kingston University. Int. J. Mol. Sci.2014, 15(10), 19183-19202; https://doi.org/10.3390/ijms151019183