Background: Radix Sanguisorbae has long been used to treat diarrhea, enteritis, duodenal ulcers, and internal hemorrhage. Objective: We investigated the in vitro anti-inflammatory effects of Radix Sanguisorbae and performed quantitative analyses of three marker components, namely gallic acid, ellagic acid, and quercetin, using high-performance liquid chromatography coupled with a photodiode array detector. Materials and Methods: The three marker components were separated using a reversed-phase Gemini C18 analytical column maintained at 40°C by the gradient elution with two solvent systems. We examined the biological effects of the three marker compounds, gallic acid, ellagic acid, and quercetin, by determining their anti-inflammatory activities in the murine macrophage cell line RAW 264.7. Results: All of the marker compounds exhibited inhibitory effects on prostaglandin E2 production in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages, with no cytotoxicity. Particularly, ellagic acid significantly inhibited production of the proinflammatory cytokines tumor necrosis factor alpha and interleukin-6 in LPS-treated RAW 264.7 cells. Conclusion: Our results suggest that ellagic acid is the most potent bioactive phytochemical component of radix Sanguisorbae in the treatment of inflammatory diseases.