Phenolic profiling and in vitro biological properties of two Lamiaceae species (Salvia modesta and Thymus argaeus): A comprehensive evaluation

The genus Salvia and Thymus have gained much popularity as an alternative therapy in Turkish folk medicine for abdominal pain, cold, nausea, among others. Nonetheless, some species are yet to be further explored for their bioactivities. We investigated the biological activities of 3 extracts (dichloromethane, methanol, and water (decoction)) of Salvia modesta Boiss. and Thymus argaeus (Fisch. & C.A.Mey.) Boiss. & Balansa. based on antioxidant and enzyme inhibition along with the determination of polyphenolic content. Antioxidant potential was assessed using six assays namely: 2,2-diphenyl-1-picrylhydrazyl, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid), cupric ion reducing antioxidant capacity, ferric reducing antioxidant power, phosphomolybdenum, and metal chelating. Moreover, enzyme inhibition activities of the extracts were studied against acetylcholinesterase, butyrylcholinesterase, tyrosinase, α-amylase, and α-glucosidase. Results revealed that the decoction of both plants was the strongest antioxidants. The methanol extracts displayed the highest tyrosinase inhibition while the dichloromethane extracts of both plants were the most effective butyrylcholinesterase and α-glucosidase inhibitors. In addition, the total phenolic and total flavonoid content was highest in the decoction and methanolic extract of Thymus argaeus, respectively. The most abundant phenolic compound was rosmarinic acid (6574 μg/g and 5390 μg/g in T. argaeus and S. modesta methanolic extracts, respectively). PASS prediction analysis revealed that chlorogenic acid showed the highest Pa value for antioxidant activity (0.809) including the mechanism of free radical scavenging (0.856), while rosmarinic acid showed the highest Pa value (0.798) for antidiabetic activity. To conclude, both Salvia modesta and Thymus argaeus can be regarded as new sources of antioxidants and enzyme inhibitors to manage oxidative stress and their complications.