title: Antioxidant activity and free radical-scavenging capacity of Gynura divaricata leaf extracts at different temperatures.
abstract: BACKGROUND
  Extraction temperature influences the total phenolic content (TPC), total flavonoid content (TFC) of medicinal plant extracts to a great extend. TPC and TFC are the principle activity constituents present in the plant. The effects of extraction temperature on TPC, TFC and free radical-scavenging capacity of Gynura divaricata leaf extracts are worth to study.
  
  
  METHODS
  Folin-Ciocalteu and aluminum chloride colorimetric assay were used to determine the TPC and TFC of Gynura divaricata leaf extracts at different temperatures. The antioxidant and free radical-scavenging activity were measured by 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid (ABTS) and phosphomolybdenum methods.
  
  
  RESULTS
  TPC and TFC were significantly elevated with increasing extraction temperature (from 40°C to 100°C). However, TPC and TFC were not significantly different (P > 0.05) at the extraction temperatures 90°C and 100°C. Also, the extracts obtained at a higher temperature exhibited a significant free radical-scavenging activity compared with extraction at lower temperatures (P < 0.05). The TPCs (13.95-36.68 mg gallic acid equivalent/g dry material) were highly correlated with DPPH (R(2) = 0.9229), ABTS (R(2) = 0.9951) free radical-scavenging capacity, and total antioxidant activity (R(2) = 0.9872) evaluated by phosphomolybdenum method.
  
  
  CONCLUSIONS
  The TPC and TFC of G. divaricata leaf was significantly influenced by the extraction temperatures, which were the main antioxidant constituents present in the G. divaricata plant.
authors.affiliation: State Key Laboratory of Food Science & Technology, Nanchang University, Nanchang - 330 047, Jiangxi,, China.
authors.forename: Chunpeng
authors.initials: C
authors.lastname: Wan
authors.forename: Yanying
authors.initials: Y
authors.lastname: Yu
authors.forename: Shouran
authors.initials: S
authors.lastname: Zhou
authors.forename: Wei
authors.initials: W
authors.lastname: Liu
authors.forename: Shuge
authors.initials: S
authors.lastname: Tian
authors.forename: Shuwen
authors.initials: S
authors.lastname: Cao