Investigation of the Anticholinesterase and Antioxidant Activity of Several Iranian Thymus caramanicus Populations

Background: Thymus extracts have become attractive targets for screening bioactive compounds with potential applications in pharmaceuticals, food, and cosmetics industries. Objectives: This is the first report assessing the anticholinesterase and antioxidant activities, along with total phenolic and flavonoid contents (TPC and TFC), of hydroethanolic extracts from six populations of Thymus caramanicus Jalas at vegetative and flowering stages, collected from different regions in Kerman province, Iran. Methods: The anticholinesterase and antioxidant activity, as well as TPC and TFC of T. caramanicus hydroethanolic extracts, were evaluated using Ellman, DPPH, Folin-Ciocalteu, and aluminum chloride assays, respectively. Results: All extracts inhibited both acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) enzymes, with most showing a stronger effect on AChE. The extract T2-F exhibited the highest anti-AChE (IC50: 28.74 ± 0.21 µg/mL) and anti-BuChE (IC50: 65.49 ± 0.81 µg/mL) activities. The DPPH results indicated overall suitable antioxidant activity, with T4-F showing the highest antioxidant capacity (IC50: 16.22 ± 0.07 µg/mL), though about 4.2 times lower than ascorbic acid. The TPC (76.60 ± 0.98 - 211.73 ± 2.13 mg GAE/g extract) and TFC (19.15 ± 0.09 - 53.90 ± 0.13 mg QE/g extract) analyses revealed that T6-V and T5-F are rich sources of polyphenolic and flavonoid compounds. Pearson’s correlation analysis showed no direct correlation between TPC and TFC with their anticholinesterase and antioxidant activities. Conclusions: The hydroethanolic extracts of T. caramanicus demonstrated significant anticholinesterase and antioxidant activities, making them promising candidates for further studies aimed at developing therapeutic compounds with dual anticholinesterase and antioxidant properties, potentially for treating Alzheimer's disease (AD).