Bioactivity of the extracts and isolation of lignans and a sesquiterpene from the aerial parts of Centaurea pamphylica (Asteraceae)

Centaurea pamphylica Boiss. & Heldr. (Family: Asteraceae), commonly known as 'pamphylia daisy', is a Turkish endemic species of the genus Centaurea that comprises ca. 500 species, many of which have been used as traditional medicines.
The n-hexane, dichloromethane (DCM) and methanol (MeOH) extracts of the aerial parts of C. pamphylica were assessed for antioxidant activity and general toxicity using, respectively, the 2,2-diphenyl-l-picrylhydrazy] (DPPH), and the brine shrimp lethality assays. The reversed-phase preparative HPLC and PTLC were used to isolate compounds from the extracts. The structures of these compounds [1-4] were elucidated by spectroscopic means, and also by direct comparison with the respective published data.
Both the DCM and the MeOH extract showed significant levels of antioxidant activities with the RC50 values of 72.6 x 10(-2) and 47.3 x 10-2 mg/mL, respectively. The MeOH extract exhibited low levels of toxicity towards brine shrimps (LD50 = 125.0 x 10(-2) mg/mL). Three major bioactive components of the MeOH extract were matairesinoside [1], arctim [21 and matairesinol [3]. An eudesmane-type sesquiterpene, pterodontriol [4], was also isolated from the DCM extract.
Since reactive oxygen species are important contributors to various ailments, the antioxidant properties of the extracts as well as the isolated compounds may be of medicinal significance. This is the first report on the occurrence of 1-4 in C. pamphylica, and 4 in the genus Centaurea.