Essential oils of Zingiber officinale var. rubrum Theilade and their antibacterial activities

Chemical composition, antibacterial activity, and mechanism of action of the essential oil from Amomum kravanh

Amomum kravanh is widely cultivated and used as a culinary spice. In this work, the chemical composition of the essential oil obtained by hydrodistillation of A. kravanh fruits was analyzed by gas chromatography-mass spectrometry, and 34 components were identified. 1,8-Cineole (68.42%) was found to be the major component, followed by α-pinene (5.71%), α-terpinene (2.63%), and β-pinene (2.41%). The results of antibacterial tests showed that the sensitivities to the essential oil of different foodborne pathogens tested were different based on the Oxford cup method, MIC, and MBC assays, and the essential oil exhibited the best antibacterial activity against Bacillus subtilis, a gram-positive bacterium, and Escherichia coli, a gram-negative bacterium. Growth in the presence of Amomum kravanh at the MIC, as measured by monitoring optical density over time, demonstrated that the essential oil was bacteriostatic after 12 h to both B. subtilis and E. coli. Observations of cell membrane permeability, cell constituent release assay, and transmission electron microscopy indicated that this essential oil may disrupt the cell wall and cell membrane permeability, leading to leakage of intracellular constituents in both B. subtilis and E. coli.

Essential oil composition and antimicrobial activities of two closely related species, Alpinia mutica Roxb. and Alpinia latilabris Ridl., from Peninsular Malaysia

The essential oils obtained by hydrodistillation of the unripe and ripe fruits of Alpinia mutica Roxb. and Alpinia latilabris Ridl. were analysed by capillary GC and GC-MS. The oils were principally monoterpenic in nature. The unripe and ripe fruit oils of A. mutica were characterized by camphor (21.0% and 15.8%), camphene (16.6% and 10.2%), β-pinene (8.6% and 13.5%), and trans,trans-farnesol (8.0% and 11.2%), respectively. The oils of the unripe and ripe fruits were moderately active against Staphylococcus aureus, Bacillus subtilis, Trichophyton mentagrophytes, and Trichophyton rubrum. 1,8-Cineole (34.2% and 35.9%) and β-pinene (20.2% and 19.0%) were the two most abundant components in the unripe and ripe fruit oils of A. latilabris. The oil of the unripe fruits elicits moderate activity against Staphylococcus aureus and Trichophyton mentagrophytes while Candida glabrata was moderately sensitive to the oil of the ripe fruits.

Comparative evaluation of antioxidant and insecticidal properties of essential oils from five Moroccan aromatic herbs

This study describes the antioxidant and insecticidal activities of essential oils (EOs) of Mentha suaveolens subsp. timija, Thymus satureioides, Achillea ageratum, Cotula cinerea and Salvia officinalis widely used in Morocco as flavorings, food additives and preservatives. Sixty seven components were identified accounting for more than 95.0 % of the total oils. M. suaveolens subsp. timija oil had as main components menthone and pulegone. A. ageratum oil was particularly rich in artemisyl acetate and yomogi alcohol. The essential oil of T. satureioides was characterized by high contents of carvacrol and borneol. C. cinerea oil contained trans-thujone and cis-verbenyl acetate as major constituents, whereas S. officinalis oil was characterized by trans-thujone and camphor. Antioxidant activities were examined by means of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH), reducing power, β-carotene/linoleic acid bleaching and ABTS radical tests. In all assays, the highest antioxidant potency was observed in T. satureioides EO with IC50 values ranging from 0.15 ± 0.36 μg mL(-1) to 0.23 ± 0.67 μg mL(-1) across the four assays. The in vitro evaluation of the insecticidal activity showed that M. suaveolens subsp. timija EO present the highest insecticidal efficiency against adults of Tribolium castaneum with LD50 and LD90 values of 0.17 μL cm(-2) and 0.26 μL cm(-2), respectively and LT50, LT90 values ranged from 44.19 h to 2.98 h and 98.14 h to 6.02 h, respectively. Our data support the possible use of T. satureioides oil as potential antioxidant agent, while M. suaveolens subsp. timija oil can be developed as a new natural bio-insecticide.

In vivo evaluation of ethanolic extract of Zingiber officinale rhizomes for its protective effect against liver cirrhosis

Zingiber officinale is a traditional medicine against various disorders including liver diseases.The aim of this study was to assess the hepatoprotective activity of the ethanolic extract of rhizomes of Z. officinale (ERZO) against thioacetamide-induced hepatotoxicity in rats. Five groups of male Sprague Dawley have been used. In group 1 rats received intraperitoneal (i.p.) injection of normal saline while groups 2-5 received thioacetamide (TAA, 200 mg/kg; i.p.) for induction of liver cirrhosis, thrice weekly for eight weeks. Group 3 received 50 mg/kg of silymarin. The rats in groups 4 and 5 received 250 and 500 mg/kg of ERZO (dissolved in 10% Tween), respectively. Hepatic damage was assessed grossly and microscopically for all of the groups. Results confirmed the induction of liver cirrhosis in group 2 whilst administration of silymarin or ERZO significantly reduced the impact of thioacetamide toxicity. These groups decreased fibrosis of the liver tissues. Immunohistochemistry assessment against proliferating cell nuclear antigen did not show remarkable proliferation in the ERZO-treated rats when compared with group 2. Moreover, factions of the ERZO extract were tested on Hep-G2 cells and showed antiproliferative activity (IC50 38-60 μ g/mL). This study showed hepatoprotective effect of ERZO.

Chemical compositions, antioxidant and antimicrobial activities of essential oils of Piper caninum Blume

Chemical composition, antioxidant and antimicrobial activities of the fresh leaves and stems oils of Piper caninum were investigated. A total of forty eight constituents were identified in the leaves (77.9%) and stems (87.0%) oil which were characterized by high proportions of phenylpropanoid, safrole with 17.1% for leaves and 25.5% for stems oil. Antioxidant activities were evaluated by using β-carotene/linoleic acid bleaching, DPPH radical scavenging and total phenolic content. Stems oil showed the highest inhibitory activity towards lipid peroxidation (114.9 ± 0.9%), compared to BHT (95.5 ± 0.5%), while leaves oil showed significant total phenolic content (27.4 ± 0.5 mg GA/g) equivalent to gallic acid. However, the essential oils showed weak activity towards DPPH free-radical scavenging. Evaluation of antimicrobial activity revealed that both oils exhibited strong activity against all bacteria strains with MIC values in the range 62.5 to 250 μg/mL, but weak activity against fungal strains. These findings suggest that the essential oils can be used as antioxidant and antimicrobial agents for therapeutic, nutraceutical industries and food manufactures.

Essential oil composition of two unique ginger (Zingiber officinale Roscoe) cultivars from Sikkim

Volatile oils from two most popular cultivars from Sikkim namely, Bhaisa and Majulay, were isolated, characterised by analytical GC and GC-MS. Sixty constituents accounting for 94.9% and 92.6% of the Bhaisa and Majulay oils were identified. The major compounds of Bhaisa oil were geranyl acetate (18.8%), zingiberene (16.3%) and geranial (8.2%) and those of Majulay oil were zingiberene (19.8%) and geranial (16.5%). Compared to other ginger cultivar oils, the Bhaisa oil had higher content of oxygenated compounds (43.1%). This is the first report on the essential oils from Sikkim ginger cultivars.

Anti-quorum sensing activity of essential oils from Colombian plants

Essential oils from Colombian plants were characterised by GC-MS, and assayed for anti-quorum sensing activity in bacteria sensor strains. Two major chemotypes were found for Lippia alba, the limonene-carvone and the citral (geranial-neral). For other species, the main components included α-pinene (Ocotea sp.), β-pinene (Swinglea glutinosa), cineol (Elettaria cardamomun), α-zingiberene (Zingiber officinale) and pulegone (Minthostachys mollis). Several essential oils presented promising inhibitory properties for the short chain AHL quorum sensing (QS) system, in Escherichia coli containing the biosensor plasmid pJBA132, in particular Lippia alba. Moderate activity as anti-QS using the same plasmid, were also found for selected constituents of essential oils studied here, such as citral, carvone and α-pinene, although solely at the highest tested concentration (250 µg mL(-1)). Only citral presented some activity for the long chain AHL QS system, in Pseudomonas putida containing the plasmid pRK-C12. In short, essential oils from Colombian flora have promising properties as QS modulators.