Essential oils of hedgenettles (Stachys inflata, S. lavandulifolia, and S. byzantina) have antioxidant, anti-Alzheimer, antidiabetic, and anti-obesity potential: A comparative study

Stachys species (hedgenettle or woundwort) are important medicinal plants known for their flavor and fragrance. They are widely consumed in Europe and Asia as aromatic herbal teas. In this work, essential oils (EOs) of three popular Stachys herbs namely Stachys inflata Benth., S. lavandulifolia Vahl., and S. byzantina K. Koch were investigated for their chemical composition, antioxidant activity, and health benefits. The major volatile components of S. inflata were identified as germacrene D (21.6 %) and β-pinene (15.6 %). S. lavandulifolia contained mainly germacrene D (22.5 %) and α-pinene (15.5 %) whereas S. byzantina showed hexahydrofarnesyl acetone (25.7 %) and valeranone (17.1 %) as major volatile constituents. EOs exhibited promising reducing power in cupric reducing antioxidant capacity (58−204 mg Trolox equivalents/g EO) and ferric reducing antioxidant power (32−104 mg Trolox equivalents/g EO) assays. Moreover, the metal chelating activity of EOs was determined from 15 to 36 mg EDTA equivalents/g EO. S. inflata showed anti-Alzheimer’s disease effect through inhibition of cholinesterase enzymes (5.2–7.8 mg galantamine equivalents/g EO). All samples had a strong antidiabetic effect (α-glucosidase inhibition) with values ranging from 4.47 to 4.62 mmol acarbose equivalents/g EO. Also, remarkable anti-obesity (lipase inhibition with 88−159 mg orlistat equivalents/g EO) and anti-hyperpigmentation (tyrosinase inhibition with 24−35 mg kojic acid equivalents/g EO) potential were observed for Stachys EOs. These findings showed that EOs of hedgenettle (betony) plants could be employed in the preparation of formulations to be used in cosmetics, food, and pharmaceutical products due to their valuable antioxidant, neuroprotective, hypoglycemic, anti-obesity, and skin-care effects.