Antioxidant, alpha-amylase inhibitory and brine-shrimp toxicity studies on Centaurea centaurium L. methanolic root extract.

Free radical scavenging activity of the methanolic extract of the roots of Centaurea centaurium L. (Asteraceae) and its phenolic, non-polar and water fractions was measured using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. The phenolic fraction showed high radical-scavenging activity with DPPH (IC(50) of 57 microg mL(-1)) and potent antioxidant properties both on lipid peroxidation and beta-carotene bleaching (IC(50) of 195 and 5 microg mL(-1), respectively). The n-hexane fraction of the extract showed the highest inhibitory activity against alpha-amylase with an IC(50) of 158 microg mL(-1). In this fraction, the most abundant constituents were the fatty acids: 11,14-eicosadienoic acid methyl ester, 9-octadecenoic acid methyl ester and 9-octadecenoic acid. Various terpenes, e.g. cypirene, alpha-zingiberene, beta-farnesene, beta-santalene, beta-bisabolene, beta-himachalene and azulene were also present. The LC(50) against the brine shrimp nauplii for the methanolic extract was found to be 44.05 microg mL(-1), whilst LC(50) values for the polyphenolic, lipophilic and water fractions were found to be 157.44, 25.98 and 152.81 microg mL(-1), respectively.