Antioxidants play a crucial role in mitigating oxidative stress and preventing cellular damage caused by free radicals. This study aimed to compare the effectiveness of three antioxidant assays—DPPH, TEAC, and FRAP—in quantifying the antioxidant capacity of 15 plant-based spices, herbs, and food materials from five distinct plant families. The relationship between these assays and total polyphenol content (TPC) as well as total flavonoid content (TFC) was also investigated. The results showed that FRAP exhibited the strongest correlation with TPC (r = 0.913), followed by TEAC (r = 0.856) and DPPH (r = 0.772). Lamiaceae species, such as rosemary and thyme, consistently demonstrated high antioxidant activities across all assays. The study highlights the complementary nature of these assays in assessing antioxidant capacity and underscores their utility in profiling polyphenol- and flavonoid-rich plants for potential nutritional and therapeutic applications.