Radical scavenging and antioxidant activities of Centaurea centaurium L. (Asteraceae)

It is generally accepted that free radicals play an important role in the development of tissue damage and pathological events. Various species of Centaurea (Asteraceae) [1] are used as herbal remedies in Italy to treat fever and diabetes and are also used as diuretics [2-3]. Ethnopharmacognostic survey in Central-Eastern Italy showed that Centaurea species were used as emollient to whiten facial skin, to treat reddened and inflamed skin, to treat reddened eyes, to heal eye inflammations; to give a special gloss and blue nuance to grey and white hair (avoiding the yellowing of hair) [4]. Pharmacological studies on some Centaurea species have reported anti-inflammatory, antimicrobial, antipyretic, cytotoxic and immunological activities [5]. Phytochemical studies on Centaurea species have revealed the presence of methoxyflavones from the leaves of C. urvillei [6], flavonoids from C. cariensis, [7] sesquiterpenes and lignans from C. americana [8-10]. The presence of phytoecdysteroids in the seeds of C. americana was also reported [11]. However, no previous phytochemical studies and pharmacological tests on the bioactivities of C. centaurium have been performed. Free radical scavenging activity and antioxidant activities of methanolic extract and phenolic, non-polar and water fractions from C. centaurium L. (Asteraceae) roots was measured using DPPH assay, beta-carotene bleaching test and lipid peroxidation liposomes assay. The results were compared to the activities of antioxidant standard. A dose-response relationship was observed for all samples. The results of this study showed that phenolic fraction has potent antioxidant property with beta-carotene bleaching test and high radical scavenging activity on DPPH. Phenolic fraction showed high radical scavenging activity on DPPH (IC50 of 57 microg/ml) and potent antioxidant properties both on lipid peroxidation and beta-carotene bleaching (IC50 of 195 microg/ml and 5 microg/ml, respectively). On the contrary all the samples performed poorly in the lipid peroxidation liposomes assay, where its protective action to MDA formation was weak. These results showed different behaviour of the samples as oxidation inhibitor of linoleic acid and as oxidation inhibitor of liposomes. This discrepancy may be due to the different mechanisms involved in the different stages of oxidation.