Ajuga chamaecistus subsp. scoparia (Boiss.) Rech.f.: A new source of phytochemicals for antidiabetic, skin-care, and neuroprotective uses

The genus Ajuga is used traditionally as food and medicine. The aim of this study was to investigate the antidiabetic, anti-Alzheimer's diseases, skin-protective, and antioxidant activities of essential oil and extracts of Ajuga chamaecistus subsp. scoparia (Boiss.) Rech.f., together with the identification of their chemical composition. The 1,1-diphenyl-2-picrylhydrazyl radical and 2,2-azino-bis (3-ethylbenzothiazloine-6-sulfonic acid) radical cation scavenging activity, metal chelating activity, reducing power, content of total bioactive compounds, general toxicity, and enzyme inhibitory potential of essential oil, ethanol extract, and water decoction of the plant were evaluated. Phenolics profile of the extracts was analyzed using the reverse-phase high-performance liquid chromatography with diode array detector and the chemical composition of the essential oil was determined using the gas chromatography and gas chromatography–mass spectroscopy techniques. The essential oil could significantly inhibit the activity of α-glucosidase (4.3 mmol Acarbose equivalents/g), α-amylase (2.8 mmol Acarbose equivalents/g), acetylcholinesterase (1.96 mg gallic acid equivalents/g), butyrylcholinesterase (2.2 mg gallic acid equivalents/g), and tyrosinase (36 mg kojic acid equivalents/g) while ethanol and water extracts showed moderate enzyme inhibitory activity. Furthermore, essential oil had the strongest antioxidant capacity in the 1,1-diphenyl-2-picrylhydrazyl scavenging, 2,2-azino-bis (3-ethylbenzothiazloine-6-sulfonic acid) scavenging, cupric reducing antioxidant capacity, ferric reducing antioxidant power, and metal chelating assays. Spathulenol (18.0%), thymol (15.1%), octen-3-ol (14.3%), and linalool oxide (11.2%) were identified as major constituents in the essential oil. Quantitative high-performance liquid chromatography analysis indicated that p-coumaric acid, gallic acid, and ferulic acid are the main phenolic compounds in this plant. The results suggested that Ajuga chamaecistus could be useful for several applications as functional foods, cosmetics, and pharmaceuticals.