Antioxidant, α-amylase, and acetylcholinesterase inhibitory activities of Hertia cheirifolia essential oils: Influence of plant organs and seasonal variation

Abstract

Hertia cheirifolia is an endemic medicinal species of the Tunisian and Algerian flora. The species was found to be rich in monoterpene hydrocarbons and sesquiterpene lactones. Significant variation of essential oil composition was observed between the plant organs. Flower buds were characterized by the highest content of the drimane type (34.08%). Leaf essential oil showed the uppermost percentage of α-pinene (35.63%). Flowers and flower buds exhibited the highest amount of germacrene D (13.18 and 12.80%, respectively). The composition of leaf essential oil varied significantly depending on the harvesting time. The lowest amount of α-pinene (19.49%) and the uppermost contents of drimenin (36.16%) and the drimane type (29.14%) were observed in January (the beginning of the fruiting stage), while leaves collected in March (the full fruiting stage of plants) were marked by the most important accumulation of germacrene D (21.18%). All essential oils were found to possess antioxidant, acetylcholinesterase (AChE), and α-amylase inhibitory activities. The level of activity varied according to the oil composition. Leaf essential oils collected at the full flowering stage exhibited the important radical scavenging capacity (22.3 mg Eq trolox/g EO) and the uppermost inhibitory activities against AChE (2.91 mg Eq donepezil/g EO) and α-amylase (14.4 mg Eq acarbose/g EO). Flower buds essential oils were the most efficient inhibitors of AChE (1.86 mg Eq donepezil/g EO), while essential oils of leaves and fruits possess the highest activity against α-amylase (8.32 and 8.84 mg Eq acarbose/g EO, respectively).