Activity-guided isolation of antioxidant xanthones from Swertia chirayita (Roxb.) H. Karsten (Gentianaceae).

An activity-guided isolation and purification process was used to identify the DPPH (l,l-diphenyl-2-picrylhydrazyl) radical-scavenging components of Swertia chirayita. A dry, whole plant of S. chirayita was extracted with different solvents and tested for its DPPH radical-scavenging activity. The acetone : water (8 : 2) extract showed the highest total phenolic content (TPC) and DPPH radical-scavenging activity, which was column chromatographed to obtain decussatin, swertianin, bellidifolin, isobellidifolin, amarogentin, swertianolin and mangiferin as active components. Good correlation was observed between TPC and DPPH scavenging activity among the extracts. The unique structure of xanthones, including the catecholic moiety and the completely conjugated system, enables them to be promising antioxidants.