Assessment of Antimicrobial Activity, Mode of Action and Volatile Compounds of Etlingera pavieana Essential Oil

Etlingera pavieana (Pierre ex Gagnep.) R.M.S. is a rhizomatous plant in the Zingiberaceae family which could be freshly eaten, used as a condiment or as a traditional remedy. Our work investigated the chemical composition and antimicrobial activity of the E. pavieana essential oils extracted from the rhizome (EOEP). We extracted the EOEP from the rhizome by hydrodistillation and analyzed the chemical composition by headspace solid-phase microextraction coupled with gas chromatography/mass spectrometry (HS-SPME-GC/MS). A total of 22 volatile compounds were identified where trans-anethole (78.54%) and estragole (19.36%) were the major components in the EOEP. The antimicrobial activity of EOEP was evaluated based on the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) values using the broth dilution method and enumerating cell death overtime. Our work shows that the EOEP exhibits potent antibacterial activity against foodborne pathogenic Gram-positive bacteria, namely Bacillus cereus, Staphylococcus aureus and Listeria monocytogenes in the range of 0.1–0.3% (v/v). We further investigated the mechanism of EOEP inhibition using Synchrotron Fourier transformation infrared (FTIR) microspectroscopy. Here, we show significant differences in DNA/nucleic acid, proteins and cell membrane composition in the bacterial cell. To conclude, EOEP exhibited antimicrobial activity against foodborne pathogens, especially the Gram-positive bacteria associated with ready-to-eat (RTE) food and, thus, has the potential to serve as a natural preservative agent in RTE products.

Etlingera pavieana extract attenuates TNF-α induced vascular adhesion molecule expression in human endothelial cells through NF-κB and Akt/JNK pathways

The aim of this study was to determine whether ethanol extracts of Etlingera pavieana rhizomes (EPE) can inhibit the expression of ICAM-1 and VCAM-1 in TNF-α-stimulated human vascular endothelial cells. EPE significantly reduced ICAM-1 and VCAM-1 expression in a concentration-dependent manner. EPE also suppressed phospho-IκB level and nuclear translocation of NF-κB. EPE significantly inhibited phosphorylation of JNK and c-Jun, a major component of AP-1, but had no effects on ERK and p38 MAPK pathways. Akt phosphorylation was increased in the presence of EPE, and wortmannin and SP600125 reversed the inhibitory effects of EPE on ICAM-1 and VCAM-1 expression. Furthermore, the active EPE constituents 4-methoxycinnamyl p-coumarate and trans-4-methoxycinnamaldehyde attenuated TNF-α-induced expression of ICAM-1 and VCAM-1. Taken together, our data indicate that EPE protects against vascular inflammation in endothelial cells, in part via NF-κB and Akt/JNK signalings. In future studies, E. pavieana may be developed as a therapeutic agent or dietary supplement for treating and preventing inflammatory diseases.

Rhizomal Extract and Its Phenolic Compounds in Lipopolysaccharide-Stimulated Macrophages

BACKGROUND

In our continuing search for anti-inflammatory agents from Thai herbs, Etlingera pavieana (Pierre ex Gagnep.) R.M.Sm. showed potent inhibition on nitric oxide (NO) production in lipopolysaccharide (LPS)-induced macrophages. However, the mechanism behind its inhibitory effect has not been yet explored, and little is known regarding its bioactive compounds responsible for the anti-inflammatory effect.

OBJECTIVE

In the present study, anti-inflammatory effect of hexane, ethyl acetate, and water fractions of rhizomal ethanol extracts of E. pavieana was evaluated for their inhibition on NO production and mechanism in LPS-stimulated macrophages. Active compounds responsible for such anti-inflammatory activity were identified.

MATERIALS AND METHODS

Inhibitory activities on NO production were performed in LPS-stimulated RAW264.7 macrophage. Cytotoxicity of plant extracts was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, mRNA and protein expressions by reverse transcription-polymerase chain reaction and Western blotting analysis, respectively. Anti-inflammatory compounds were isolated by activity-guided isolation technique using column chromatography.

RESULTS

Ethyl acetate fraction of E. pavieana (EPE) showed the most potent inhibitory effect on NO production in macrophages. EPE significantly decreased NO production and inhibited inducible nitric oxide synthase (iNOS) protein and mRNA expression in a dose-dependent manner. Furthermore, the level of nuclear factor-kappa B p65 subunit was markedly reduced in activated cells treated with EPE. Four phenolic compounds, 4-methoxycinnamyl alcohol (1), trans-4-methoxycinnamaldehyde (2), 4-methoxycinnamyl p-coumarate (3), and p-coumaric acid (4), were obtained from bioactivity-guided isolation technique.

CONCLUSIONS

The anti-inflammatory property contained in E. pavieana rhizome extract and conferred through inhibition of iNOS expression, and NO formation provides scientific evidence and support for the development of new anti-inflammatory agents based on extracts from this plant.

SUMMARY

Ethyl acetate fraction (EPE) of Etlingera pavieana showed the most potent inhibitory effect on NO production in LPS-induced macrophagesFour phenolic compounds, 4-methoxycinnamyl alcohol (1), trans-4-methoxycinnamaldehyde (2), 4-methoxycinnamyl p-coumarate (3) and p-coumaric acid (4), responsible for the anti-inflammatory effect of EPE were isolated. Abbreviations used: EPE: Ethyl acetate fraction of Etlingera pavieana; EPH: Hexane fraction of Etlingera pavieana; EPW: Water fraction of Etlingera pavieana; NO: Nitric oxide (NO); LPS: Lipopolysaccharide; iNOS: Inducible nitric oxide synthase (iNOS); MTT: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; NF-κB: Nuclear factor-kappa B; DMSO: Dimethyl sulfoxide; EtOAc: Ethylacetate; MeOH: Methanol; AG: Aminoguanidine; DCM: Dichloromethane; MCA: 4-methoxycinnamyl alcohol; MCD: trans-4-methoxycinnamaldehyde; MCC: 4-methoxycinnamyl p-coumarate; CM: p-coumaric acid.

Uncommon secondary metabolites from Etlingera pavieana rhizomes

From the rhizomes of Etlingera pavieana (Pierre ex Gagnep.) R.M. Sm., four phenylpropens, (E)-3-(4-methoxyphenyl)prop-2-en-1-amine (1), (E)-4-methoxycinamaldehyde (2), (E)-4-methoxycinamic acid (3) and (E)-1-methoxy-4-(3-methoxyprop-1-enyl)benzene (4), together with two other compounds, (E)-((E)-3-(4-methoxyphenyl)allyl)3-(4-hydroxyphenyl)acrylate (5) and 4-methoxybenzoic acid (6) were isolated. This is the first report on the presence of all compounds in Etlingera. Compounds 1 and 5 have been previously synthesised, but this is the first report of their isolation from a natural source. Compound 5 exhibited weak activity against Mycobacterium tuberculosis with MIC 50.00 μg/mL and cytotoxic activity against the KB, MCF7 and NCI-H187 cells with IC50 values of 25.11, 20.16 and 34.83 μg/mL, respectively.