This study aimed to evaluate the antioxidant activity of Korean raspberry (Rubus coreanus Miq.) fruits, which are grown widely in the southwest area of Korea. Freeze-dried Rubus coreanus (RC) fruits and green tea (GT) were used to obtain water extracts (RCE and GTE, respectively). The total phenolic contents of the dried RC and GT were 126μmol CE (catechin equivalent)/g and 360μmol CE/g, respectively. The free radical scavenging activity of RCE and GTE was expressed as SC50 (50% scavenging capacity) and compared. The scavenging activity of RC toward DPPH, superoxide, and hydroxyl radicals was lower than that of GT. The inhibitory activity of RCE and GTE on AAPH-induced lipid peroxidation was also analyzed. In contrast with the free radical scavenging activities, the lipid peroxidation-inhibiting activity of RC was superior to that of GT. These results suggest that RCE contains effective scavengers of peroxyl radicals. In summary, RC contains less phenolics than does GT. Although RC has lower activity for scavenging DPPH, superoxide, and hydroxyl radicals than does GT, its activity to inhibit peroxyl radical-lipid peroxidation was higher. These results suggest that RC could be used as a valuable natural source of antioxidants. Materials and Methods
ChemicalsAAPH (3,2-azobis (2-amidinopropane) dihydrochloride), PMS (phenazine methosulfate), NBT (nitroblue tetrazolium), TBA (thiobarbituric acid), TCA (trichloroacetic acid), and MDA (malondialdehyde) were purchased from Sigma (St. Louis, MO, USA). CCA (coumarin-3-carboxylic acid) was purchased from Fluka (Buchs, Switzerland). High-grade GT was purchased at a store.
Preparation of water extracts from Rubus coreanusfruits and green tea RC fruits were collected from Gochang, Korea.Aqueous extracts of RC and GT were prepared by the following method. RC fruits were frozen overnight at −80 o C and then dried by using a lyophilizer (Hanil Science Industrial Co., Incheon, Korea). Dried fruits (5 g) and dried green tea (5 g, Hankook Tea Co., Gwangju, Korea) were homogenized in distilled water
Quantitation of phenol groupsThe phenol content of RCE and GTE was measured with FCR. 25 Aliquots of diluted RCE (200μL) and GTE (200μL) were mixed with 10% FCR (1 mL) in test tubes. The mixture was left to react for 3 min at room temperature, followed by the addition of 7.5% Na 2 CO 3 (0.8 mL) and incubation for 2 h in a shaking water bath.After incubation, the absorbance of the mixture was measured at 760 nm by use of a UV-spectrophotometer (model UV-1650PC, Shimadzu, Japan). The phenolic content was quantified from the standard curve plotted