Glechoma curviflora Volatile Oil from Palestine: Chemical Composition and Neuroprotective, Antimicrobial, and Cyclooxygenase Inhibitory Activities

Abstract

The rise of the emergence of microbial resistance of antibiotics, the dangerous side effects of nonsteroidal anti-inflammatory drugs, and noncompetent medications of Alzheimer's, Parkinson's, and other neurodegenerative diseases prompt scientists to search for phytochemicals that could be utilized in the remedy of lethal diseases. Glechoma curviflora (Boiss.) Kuntze (Nepeta curviflora) is a medicinal herb growing in the eastern parts of the Mediterranean Sea Basin and is widely consumed as a tea. The leaves of this plant have been traditionally used for the treatment of various infectious diseases. The current research was designed to identify the chemical composition of Glechoma curviflora (Boiss.) essential oil (EO) and to assess its antibacterial, antifungal, and cyclooxygenase inhibitory activities and the biophysical gating effect on AMPA receptors. Twenty phytochemicals were identified from G. curviflora leaves and flowers EO amounting to almost 100% of the total constituents using GC-MS technique, of which 1,6-dimethylspiro[4.5]decane (27.51%) 1, caryophyllene oxide (20.08%) 2, and β-caryophyllene (18.28%) 3 were the main constituents. The biophysical properties' effect from the plant extract on various AMPA-type receptors expressed in Human Embryonic Kidney (HEK293) cells was assessed by exploiting the whole-cell patch-clamp technique. Microdilution assay was adopted for assessing the antimicrobial property against eight virulent microbial strains whilst the cyclooxygenase inhibition effect was accomplished utilizing COX inhibitory screening colorimetric assay G. curviflora EO displayed potent activity against P. aeruginosa (MIC = 1.25 μg/mL), S. sonnei (MIC = 3.12 μg/mL), and E. coli (MIC = 1.25 μg/mL), compared with ciprofloxacin (positive control) and potent antibacterial activity against S. aureus, MRSA, S. sonnei, E. coli, and P. aeruginosa compared to Ampicillin (2nd positive control). It also showed anti-Candida (MIC = 6.25 μg/mL) and antimold (MIC = 3.125 μg/mL) activities compared with fluconazole (antifungal positive control). Likewise, our results showed an inhibition and biophysical impact of G. curviflora on all AMPARs subunits.

Figure 1

The structure of the major three components in G. curviflora EO.

Figure 2

G. curviflora EO GC-MS chromatogram.

Figure 3

Effect of G. curviflora EO on AMPARs. (a) Whole-cell current recording of AMPAR subtypes with and without G. curviflora EO treatment. The effect of 80 μM of G. curviflora EO (black) and 10 mM of glutamate alone (white) on the amplitude generated by different AMPARs. (b) The destination rate of various AMPARs before EO treatment (glutamate alone) vs. after treatment (glutamate + EO). Desensitization via the weighted time constant calculated by the pulses per 500 ms on the response of Glu alone and Glu + EO. (c) Pulses per 20 ms on the response of Glu alone and Glu + EO to calculate the deactivation. All trials performed on AMPAR expressing HEK293 cells, where the number of patch whole-cells, n = 5. One-way ANOVA with the following significance presented the data displayed in the figure: ^∗ < 0.05; ^∗∗ < 0.01; and ^∗∗∗ < 0.001; ns: not significant.