Constituents of Flavonoids from Tridax procumbens L. and Antioxidant Activity

Background: To study the chemical constituents and antioxidant activities of flavonoids in Tridax procumbens L. Materials and Methods: Diaion HP‑20, MCI‑Gel CHP‑20, Sephadex LH‑20, and silica gel column chromatography were used to isolate and purify the chemical components of T. procumbens L., and the structures of the compounds were identified by physical and chemical properties and spectral techniques (1H‑nuclear magnetic resonance [NMR] and 13C‑NMR). The antioxidant activities of five flavonoids were evaluated by 2,2‑diphenyl‑1‑picryl‑hydrazyl method. Results: Six compounds were isolated and identified as luteolin-7‑O‑β-D- glucoside (1), 5,7,3’‑trimethyl‑4’‑methoxyl‑3‑O‑β‑D‑flavonoid glucoside (2), 8,3’‑dihydroxyl‑3,7,4’‑trimethoxy‑6‑O‑β‑D‑flavonoid glucoside (3), 4,2’,4’‑trihydroxy‑6’‑methoxyl‑3’‑isopentenyl chalcone (4), quercetin-7‑O‑β- D‑glucopyranosyl‑(2→1)‑α‑L‑rhamnose (5), and nodakenin (6). Conclusions: All compounds except compound 3 were isolated from the plant for the first time. It was found that compounds 1–5 had significant antioxidant and free radical scavenging activities.