ANTIOXIDANT CAPACITY AND PHENOLIC CONTENT OF FRAXINUS ORNUS L. AND FRAXINUS PENNSYLVANICA MARSCH. LEAVES AND BARK EXTRACTS

Abstract

UDK: 582.916.16:547.56
 547.56:543.42
 Total contents of phenols, flavonoids, phenolic acids and proanthocyanidins have been determined in methanolic extracts of Fraxinus ornus L. and Fraxinus pennsylvanica Marsch. leaves and branches bark. DPPH and FRAP assay were used in the determination of antioxidant capacity. F. ornus leaves had higher contents of flavonoids (13.08 mg RE g-1 DW) and proanthocyanidins (7.29 mg LCE g-1 DW) while the bark had higher contents of phenols (56.47 mg GAE g-1 DW), phenolic acids (14.32 mg CAE g-1 DW) and coumarins (94.81 mg CE g-1 DW). F. pennsylvanica leaves were richer in contents of phenols (25.73 mg GQE g-1 DW), flavonoids (2.87 mg CE g-1 DW and 5.13 mg RE g-1 DW), phenolic acids (14.60 mg CAE g-1 DW) and coumarins (20.01 mg CE g-1 DW) while the bark had more proanthocyanidins (6.88 mg CE g-1 DW). F. ornus leaves had lower contents of phenolic acids (11.09 mg CAE g-1 DW) than F. pennsylvanica leaves. Also, F. pennsylvanica bark had higher contents of flavonoids (1.25 mg RE g-1 DW) and proanthocyanidins (6.88 mg CE g-1 DW) than F. ornus bark. Antioxidant capacity for both species was higher for the leaves than the bark. Generally, F. ornus had better antioxidant capacity than F. pennsylvanica. Very high correlations were found between antioxidant capacity and phenols (r2= 0.9361-0.9805), flavonoids (r2= 0.9358-0.9876) and coumarins (r2= 0.9661-0.9938) in leaves. In bark, correlations were found for phenols (r2= 0.9744-0.9796) and coumarins (r2= 0.9757-0.9911).