A phytochemical study on two endemic nepeta species (Nepeta nuda L. subsp. glandulifera Hub.-Mor.& Davis and Nepeta cadmea Boiss.)

This study aimed to evaluate the chemical composition and in vitro antioxidant activities of the essential oils from two endemic Nepeta species (N. nuda subsp. glandulifera and N. cadmea). Chemical characterization of the essential oils was determined by GC and GC-MS. According to GC and GC-MS analysis, 22 and 10 compounds were identified representing 97.43% and 95.29% of the essential oils of N. nuda subsp. glandulifera and N. cadmea, respectively. The major constituents identified in the essential oil of N. nuda subsp. glandulifera were geijerene (61.02%), tricosane (12.64%), and neointermedeol (6.07%), whereas 4aβ,7α,7aβ-nepetalactone (70.94%), β-caryophyllene (6.29%), and linalool (5.87%) were identified as the major constituents of the essential oil from N. cadmea. The antioxidant potency of the oils was evaluated using different established methods, specifically ferrous ion chelating, free radical scavenging (DPPH or ABTS), reducing power (CUPRAC or FRAP), and total antioxidant (β-carotene bleaching and phosphomolybdenum tests) activities. N. nuda subsp. glandulifera oil showed higher activity in DPPH (2.02 mg TEs/g yağ) and ABTS (63.70 mg TEs/g yağ) radical scavenging, CUPRAC (52.63 mg TEs/g yağ) and FRAP (32.15 mg TEs/g yağ) reducing power, and phosphomolybdenum (13.40 mg TEs/g yağ) tests than those of N. cadmea oil. However, N. cadmea oil (25.81 mg EDTAEs/g yağ) exhibited strong chelating activity on ferrous ion, but no activity of N. nuda subsp. glandulifera oil was found. The data obtained from this study clearly indicates that these species have a significant potential to use as a source of natural agents for the management of oxidative process. Keywords: Nepeta nuda subsp. glandulifera, Nepeta cadmea, Essential oil, Antioxidant activity, Nepatalactone, Geijerene