Subcritical water extraction and antioxidant activity evaluation with on-line HPLC-ABTS•+ assay of phenolic compounds from marigold (Tagetes erecta L.) flower residues

Subcritical water extraction (SWE) of phenolics was investigated from marigold (Tagetes erecta L.) flower residues. The total phenolics content (TPC), total flavonoids content (TFC) and antioxidant capacities of extracts were determined, furthermore, antioxidant activities of individual compounds were evaluated with on-line HPLC-ABTS(center dot+) system. The optimum SWE time was 45 min, solid-to-liquid ratio was 1:50, and the highest TPC and TFC were obtained at 220 degrees C respectively. The effect of SWE temperature on TPC and TFC was significant (p<0.05), and TPC was ranged from 28.42 +/- 0.94 to 124.27 +/- 1.94 (mg GAE/g), and TFC ranged from 34.21 +/- 0.36 to 133.22 +/- 1.57 (mg GAE/g) between 80 and 220 degrees C. On-line HPLC-ABTS(center dot+) profiles revealed that quercetagetin from SWE at 200 degrees C had nearly twofold radical scavenging activities than that by leaching extraction.