Isoiridomyrmecin rich essential oil from Nepeta erecta Benth. and its antioxidant activity

Abstract

The essential oil composition of the aerial parts of Nepeta erecta Benth. (Family: Lamiaceae) from Uttarakhand, India was analysed by capillary gas chromatography (GC) and gas chromatography–mass spectrometry (GC–MS). A total of 34 constituents were identified representing 94.6% of the oil composition. Oxygenated monoterpenes (74.0%) constituted the major proportion of the oil, dominated by isoiridomyrmecin (70.6%) as a single major constituent. Other significant constituents were caryophyllene oxide (9.6%), β-Bourbonene (2.0%), humulene epoxide II (1.7%) and linalool (1.0%). The in vitro antioxidant activity (AOA) was assessed using β-Carotene bleaching assay, reducing power, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and inhibition of lipid peroxidation methods. The oil was found to exhibit AOA by inhibiting β-Carotene bleaching (54.6 ± 2.52%) and by scavenging DPPH free radical (IC₅₀ = 0.74 ± 0.12 mg mL⁻¹). The AOA of the essential oil of N. erecta and its major compound isoiridomyrmecin has not been reported so far.

Keywords:

• Nepeta
• Lamiaceae
• isoiridomyrmecin
• essential oil
• antioxidant activity

Acknowledgements

The authors thank the State Council of Science & Technology, Dehradun, for providing project grant, BSI for plant identification and IIT Roorkee for NMR work.