Abstract

Antioxidant activity of the aerial parts of Leonurus cardiaca subsp. Persicus,Grammosciadium platycarpum and Onosma demawendicum were investigated employing six in vitro assay systems. IC₅₀ for 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical-scavenging activity was in the order: O. demawendicum (221 ± 11.7) > L. cardiaca (144 ± 12.1) > G. platycarpum (45 ± 2.1) gml^-1, respectively. The extracts showed very good nitric oxide-scavenging and Fe²⁺ chelating ability activity. The L. cardiaca subsp. Persicus showed Fe²⁺ chelating ability activity as ethylenediaminetetraacetic acid (EDTA) (IC₅₀ were 20 versus 18 gml^-1). None of the extracts exhibited good antioxidant activity in linoleic acid model. The extracts showed good reducing power that was better than vitamin C (p < 0.05). G. platycarpum and L. cardiaca subsp. Persicus had higher total phenolic and flavonoid contents than O. demawendicum. The total phenolic compounds in the extracts were determined as gallic acid equivalents, and total flavonoid contents were calculated as quercetin equivalents from a calibration curve.

Key words: Antioxidant activity, Fe²⁺ chelating, 1,1-diphenyl-2-picryl hydrazyl (DPPH), phenol, Leonurus cardiaca, Grammosciadium platycarpum, Onosma demawendicum.

Abbreviation

Abbreviations: DPPH, 1,1-Diphenyl-2-picryl hydrazyl radical; ROS, reactive oxygen species; TBARS, thiobarbituric acid reactive substances; TCA, trichloroacetic acid; BHA, butylated hydroxyanisole; FTC, ferric thiocyanate method; AD, Alzheimer's disease.