NMR metabolic profiling and biological activities of different extracts from a Turkish herbal tea-Clinopodium nepeta subsp. glandulosum

Clinopodium nepeta subsp. glandulosum (Req.) Govaerts (Lamiaceae), is traditionally used as antispasmodic, diaphoretic, stimulant, and tonic medicinal herbs and as mint-like spice used in various culinary recipes. Nonetheless, there is still a dearth of studies to validate its biological properties. The total phenolic and flavonoid contents, scavenging activity of DPPH and ABTS radicals, ferric reducing antioxidant power (FRAP), total antioxidant via phosphomolybdenum assay, metal ion chelating capacity of different extracts (n-hexane, dichloromethane, ethyl acetate, ethanol, ethanol/water and water) of C. nepeta were determined. The water extract contained the highest phenolic contents (51.47 ± 0.62 mg GAE/g) and ethanol/water extract yielded largest amount of flavonoid contents (43.86 ± 0.63 mg RE/g). The DPPH free radical scavenging activity of the extracts was in the order of ethanol/water > water > ethanol > ethyl acetate > dichloromethane > n-hexane. The enzyme inhibition of the different extracts was also investigated. Ethanol/Water extract demonstrated the highest AChE inhibitory capacity (2.66 mg GALAE/g) while ethyl acetate extract revealed high BChE inhibitory activity (3.29 mg GALAE/g). Exhaustive 2D-NMR investigation has revealed the presence of acacetin derivatives, ursolic acid along with and 2,4-di-t-butylphenol. These findings revealed that extracts of C. nepeta could be used as a promising therapeutic agent against free radicals, brain enzymes including AChE and BChE and in the treatment of hyperpigmentation as a skin whitening ingredient as well as in the treatment and management of diabetes. However, further studies are required to determine the safety profiles of these extracts.