Antibacterial and Cytotoxic Activity ofNepeta CatariaL., N. Cataria Var. Citriodora (Beck.) Balb. andMelissa OfficinalisL. Essential Oils

Abstract

The aim of the present study was to investigate the susceptibility of bacteria that play a role in respiratory tract and skin infections to the essential oils of catnip (Nepeta cataria), lemon catnip (N. cataria var. citriodora) and lemon balm (Melissa officinalis) with regard to their chemical composition. In addition, we wanted to assess whether antibiotic-resistant and-sensitive strains differ in their susceptibility to the oils and if there are cross resistances between standard antibiotics and essential oils. To evaluate the safety of topical application, cytotoxicity of the oils was studied in human keratinocyte and bronchial epithelial cell lines and irritation threshold concentrations were determined in ovo using the HET-CAM-test. The composition of the essential oils was analyzed by GC and GC-MS. Their MICs and MBCs were determined by a broth microdilution method against both reference strains from culture collections and clinical isolates with different susceptibility to standard antibiotics. Cytotoxicity was assessed by the MTT assay. Except for P. aeruginosa (MIC ≥2 %), all reference strains tested were susceptible to catnip and lemon balm oils with MIC values ranging from 0.016 % to 0.25 % (v/v). The clinical isolates were as susceptible to the oils (± 1 serial dilution) as the corresponding reference strains, regardless of their origin and resistance to standard antibiotics. The oils were cytotoxic to both keratinocytes and bronchial epithelial cells at CC 50 values from 0.0012% to 0.015% (v/v). Lemon balm oil, whose main components were monoterpene aldehydes, exhibited the highest antibacterial and cytotoxic activity, followed by lemon catnip oil, which contained mainly monoterpene alcohols, and catnip oil, which was characterized by nepetalactones. Our results provide a rationale for the use of catnip, lemon catnip and lemon balm oils in the complementary topical treatment of respiratory tract infections, as the oils show a high antibacterial activity against respiratory tract pathogens, including clinical isolates with reduced susceptibility to standard antibiotics. However, cytotoxicity must be considered in topical therapy.

Volatile constituents analysis of Nepeta cataria from central Iran

“…It was found that nepetalactones were responsible for the feline attractant properties of Nepeta species. 4aα,7α,7aα-Nepetalactone, which was the main component of our oil, has been detected as the major one in four Nepeta species growing in Turkey [21] and also in N. cataria growing in Germany [22], while caryophyllene oxide, which was abundant in N. cataria from Lebanon [23] and Lithuania [24] (6.4%, 7.3% respectively), was not found in our work. β-Caryophyllene, which was the third major component of our oil, has been reported in the oil of some Nepeta species such as N. cataria [23], N. daenensis [25], and N. fissa from Iran [26], and in N. curviflora growing in Lebanon [23].…”

Constituents and antimicrobial activity of the essential oils of six Himalayan Nepeta species

“…9 The essential oil composition and antimicrobial activity of various Nepeta species were previously reported. [10][11][12][13][14][15][16][17][18][19][20][21][22][23] In earlier communications, some Himalayan Nepeta species were screened for their terpenoid constituents. 18-23 Iridodial β-monoenol acetate isolated from essential oil of N. leucophylla Benth.…”

Volatile Constituents of Melissa officinalis Leaves Determined by Plant Age

“…The oil extracted from lemon balm leaves and herb contains citral (responsible for the characteristic lemon scent of the leaves), linalool, citronellal, neral, and geranial [5][6][7][8][9][10][11]. Lemon balm oil has refreshing, sedative, antidepressant [12], antimicrobial [13,14], antidiabetic [15], antioxidant and antitumor properties [16,17]. The chemical composition of lemon balm oil shows high variability and depends, amongst others, on plant origin [6,9,18] and cultivation conditions [3,7,19,20].…”