Enzyme inhibitory and antioxidant activities and HPLC quantification of chlorogenic acid in Helichrysum stoechas (L.) Moench and H. stoechas subsp. barrelieri (Ten) Nyman

Abstract

The inhibitory effects of ethanol (80%) and aqueous extracts of Helichrysum stoechas (L.) Moench and H. stoechas subsp. barrelieri (Ten) Nyman on acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), two sister enzymes associated with pathogenesis of Alzheimer's disease (AD), as well as on elastase and collagenase, linked to inflammation and skin aging, were investigated. Simultaneously, antioxidant activity of the extracts was assessed through DPPH radical scavenging activity, ferric reducing antioxidant power (FRAP), and metal-chelating activity assays, since oxidative damage plays a critical role in both AD pathophysiology and skin aging. Total phenol and flavonoid contents in the extracts were spectrophotometrically determined. The highest AChE inhibitory activity (44.60 ± 4.4% at 2000 µg/mL) was found in the ethanol extract of H. stoechas subsp. barrelieri collected from Hatay, and the uppermost BChE inhibitory activity at same concentration was found in the aqueous extract of H. stoechas subsp. barrelieri collected from Izmir (80.24 ± 2.63%, IC50: 38.52 ± 1.41 µg/mL). Both of them inhibited AChE and BChE in a concentration-dependent manner. Nevertheless, none of the extracts from the two plants inhibited the elastase and collagenase. Although both ethanolic and aqueous extracts had significant antioxidant activity in DPPH radical scavenging and FRAP assays, they demonstrated inadequate antioxidant activity in metal-chelating assay. Chlorogenic acid was quantified in the extracts using HPLC. The mentioned two extracts having strong cholinesterase (ChE) inhibition had also the highest chlorogenic acid content. The ethanol extract of H. stoechas (Hatay sample) and the aqueous extract of H. stoechas (Izmir sample) seem to contain promising ChE inhibitors, which deserve further investigation.