Comparative Study of Polyphenolic Content and Antioxidant Activity of Four Agastache Species (Lamiaceae)

Abstract

Agastache species (Lamiaceae) are aromatic plants that are used in traditional medicine for the treatment of gastrointestinal diseases and bacterial infections. Their phytochemical profile is characterized by the presence of essential oil, phenolic derivatives and terpenoid compounds. In the present study, the polyphenolic composition and antioxidant potential of four Agastache species (A. foeniculum, A. mexicana, A. scrophulariifolia, A. rugosa) and one cultivar (A. rugosa ‘After Eight’) were investigated. The total polyphenols content (TPC), caffeic acid derivatives content (TCADC) and flavonoids content (TFC) were evaluated spectrophotometrically. Also, the antioxidant capacity of Agastache extracts was measured using 2,2–diphenyl-picrylhydrazil (DPPH) and ferric-reducing antioxidant power (FRAP) methods. This study showed a TPC ranging from 1.92 to 3.64 mg GAE/g, TCADC ranging from 1.35 to 3.58 mg CAE/g, and TFC between 0.58 and 0.72 mg RE/g. The phenolic determinations are in accordance with the antioxidant activity. Thus, a higher TPC (3.64 mg GAE/g dried plant material) for A. mexicana methanolic extract is related to a higher DPPH radical scavenging activity (IC₅₀ = 109.08 µg/mL) and a higher ferric ion reducing antioxidant capacity (2346.88 µM TE/100 mL extract). The results open new directions in the pharmacognostic analysis of Agastache species and provide important preliminary information for further pharmacological research.