Stachys germanica subsp. heldreichii (Boiss.) Hayek: Phytochemical analysis, antioxidant and enzyme inhibitory activities

Abstract

Stachys species have traditionally been used by the people for thousands of years to treat various diseases. In this study, the chemical composition and enzyme inhibitory activities of the various extracts of Stachys germanica subsp. heldreichii (Boiss.) Hayek (Lamiaceae), which were isolated using solvents with different polarities, were investigated. Antioxidant activities of the extracts were analyzed by phosphomolybdenum, radical scavenging [on DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)], reducing power [CUPRAC (cupric-reducing antioxidant capacity) and FRAP (ferric reducing antioxidant power)] and ferrous ion chelating tests, while tyrosinase and α-amylase were used for enzyme inhibitory activity assays. RACI (relative antioxidant capacity index) analysis showed that the ranking of the extracts was MeOH (methanol) > Water > EtOAc (ethyl acetate). In ABTS radical scavenging (2.26 mg/mL), phosphomolybdenum (1.68 mg/mL), CUPRAC (1.35 mg/mL) and FRAP tests (0.75 mg/mL), the MeOH extract showed the highest activity. However, the water extract exhibited the highest activity in DPPH radical scavenging and ferrous ion chelating tests. Tyrosinase inhibition potential of the MeOH extract was significant (IC50: 2.90 mg/mL). On the other hand, in α-amylase inhibition assay, EtOAc extract showed the highest activity (2.24 mg/mL). Amount of phenolics was higher in all extracts than flavonoids. MeOH extract was the richest one in phenolics and flavonoids. The major compounds of the extracts were chlorogenic acid and verbascoside. Pearson correlation analysis showed that these compounds were responsible especially for radical scavenging activity. Correlation between chemical composition and activity findings showed that verbascoside and apigenin contributed to tyrosinase and α-amylase inhibition, respectively.