Polyphenol contents and radical scavenging capacities of red maple (Acer rubrum L.) extracts

The crude ethanol and water extracts of different red maple (Acer rubrum L.) tissues: whole branches (WB), wood of branches (BW), bark of branches (BB), stem bark (SB) and whole twigs (T), were examined in order to determine their phenolic contents as well as their radical scavenging capacities. The total phenols (TP), total extractable tanins (TET) and non-precipitable phenols (NPP), were determined by combination of spectrophotometric and precipitation methods, while total flavonoids, hydroxy cinanmic acids and proanthocyanidins were determined spectrophotometrically. The radical scavenging activities of the extracts were determined against five reactive oxygen species (ROS): superoxide anion ( O 2 · - ), hydroxyl radical (HO), peroxyl radical (ROO), hypochlorite ion (ClO−), and hydrogen peroxide (H2O2) and one reactive nitrogen species (RNS): nitric oxide (NO). The extracts of stem bark were significantly more efficient (exhibiting the highest antioxidant efficiencies, AE) than the other studied extracts against all ROS (at p < 0.05, Duncan statistical tests), except against NO. The correlation coefficients determined between total phenolic (TP) content and antiradical efficiencies were R2 = 0.12 for O 2 · - ; R2 = 0.29 for HO; R2 = 0.40 for H2O2; R2 = 0.86 for ROO; R2 = 0.03 for NO and R2 = 0.73 for ClO−. Our results indicate potential utilisation of extracts as natural antioxidants.