Highly antibacterial electrospun cellulose acetate (CA) nanofiber mats with encapsulated lemon myrtle essential oil (LMEO) as a natural antibacterial agent were produced. The high antibacterial activity of LMEO was confirmed by minimum inhibitory concentration and the minimum bactericidal concentration analysis. Morphological, thermal, optical, chemical and antimicrobial properties of LMEO-loaded CA electrospun nanofibers were investigated. The morphology of the fiber mat was examined by SEM to study the effect of solvent type, solution viscosity, electrospinning voltage and incorporation of LMEO into the CA electrospun nanofibers. The average diameters of both CA and LMEO-loaded CA nanofibers were in the range of 440–515 nm. The electrospun nanofibers were of a white colour and low water activity. Thermogravimetric analysis indicated no change in degradation profile of CA, while differential scanning calorimetry indicated a lower degree of CA crystallinity upon incorporation of LMEO. The LMEO-loaded CA electrospun nanofibers eliminated Escherichia coli and Staphylococcus aureus by 100% even at the lowest loading concentration of LMEO of 2 wt%. The electrospun fiber mats, with moderate loading of LMEO, showed sustained release of LMEO over prolonged time and nanofibers retained their high antibacterial properties even after two months of storage. Therefore, these nanofibers could be promising candidates for active packaging or wound dressing applications with prolonged antimicrobial activity.

Cellulose acetate electrospun nanofibers encapsulating Lemon Myrtle essential oil as active agent with potent and sustainable antimicrobial activity

In this present study, we examined the anti-inflammatory and anti-oxidative properties of alcoholic lemon myrtle extract (LME). The total polyphenol and flavonoid content of LME were determined as 118.77 and 14.53 mg/g extract, respectively. LME showed anti-oxidative properties, such as 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) and 2,2′-azino-bis(3-ethylbenz-thiazoline-6-sulfonic acid) (ABTS) radical scavenging activity. The anti-inflammatory activities of LME were investigated using the lipopolysaccharide-stimulated murine macrophage RAW 264.7 cells. Pretreatment with LME was performed at non-cytotoxic concentrations of 10–100 μg/mL. LME inhibited the production of inflammatory mediators such as nitric oxide (NO). Enzyme-linked immunosorbent assay and reverse-transcriptase polymerase chain reaction (RT-PCR) revealed that pretreatment with LME suppressed the protein expression and mRNA levels of pro-inflammatory cytokines such as interleukin IL-6, and tumor necrosis factor (TNF)-α in a concentration-dependent manner, respectively. These results suggest that LME could be used as a potential therapeutic agent having potent anti-inflammatory effects that could be used to treat inflammatory bowel disease.

Anti-inflammatory and anti-oxidative activities of lemon myrtle (Backhousia citriodora) leaf extract

The essential oil of Backhousia citriodora, commonly known as lemon myrtle oil, possesses various beneficial properties due to its richness in bioactive compounds. This study aimed to characterize the chemical profile of the essential oil isolated from leaves of Backhousia citriodora (BCEO) and its biological properties, including antioxidant, antibacterial, and antibiofilm activities. Using gas chromatography–mass spectrometry, 21 compounds were identified in BCEO, representing 98.50% of the total oil content. The isomers of citral, geranial (52.13%), and neral (37.65%) were detected as the main constituents. The evaluation of DPPH radical scavenging activity and ferric reducing antioxidant power showed that BCEO exhibited strong antioxidant activity at IC50 of 42.57 μg/mL and EC50 of 20.03 μg/mL, respectively. The antibacterial activity results showed that BCEO exhibited stronger antibacterial activity against Gram-positive bacteria (Staphylococcus aureus and Staphylococcus epidermidis) than against Gram-negative bacteria (Escherichia coli and Klebsiella pneumoniae). For the agar disk diffusion method, S. epidermidis was the most sensitive to BCEO with an inhibition zone diameter of 50.17 mm, followed by S. aureus (31.13 mm), E. coli (20.33 mm), and K. pneumoniae (12.67 mm). The results from the microdilution method showed that BCEO exhibited the highest activity against S. epidermidis and S. aureus, with the minimal inhibitory concentration (MIC) value of 6.25 μL/mL. BCEO acts as a potent antibiofilm agent with dual actions, inhibiting (85.10% to 96.44%) and eradicating (70.92% to 90.73%) of the biofilms formed by the four tested bacteria strains, compared with streptomycin (biofilm inhibition, 67.65% to 94.29% and biofilm eradication, 49.97% to 89.73%). This study highlights that BCEO can potentially be a natural antioxidant agent, antibacterial agent, and antibiofilm agent that could be applied in the pharmaceutical and food industries. To the best of the authors’ knowledge, this is the first report, on the antibiofilm activity of BCEO against four common nosocomial pathogens.

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Chemical Composition, Antioxidant, Antibacterial, and Antibiofilm Activities of Backhousia citriodora Essential Oil

Anti-feedant and larvicidal activities of the essential oil, hexane, ethyl acetate and
methanol extracts of Backhousia citriodora (grown in Malaysia) were studied using
leaf disc no-choice and leaf dip methods respectively, against second instar larvae of S.
litura and C. binotalis. Backhousia citriodora, commonly known as lemon myrtle, is a
native Australian plant which belongs to the Myrtaceae family. Lemon myrtle steamdistilled
essential oil has been reported to exhibit effective repellent properties against
mosquitoes (domestic insects); making lemon myrtle a valuable exploratory source of
novel insecticides for the management of agricultural insects. Spodoptera litura and
Crocidolomia binotalis are dangerous agricultural insects. While S. litura is already
resistant to many classes of synthetic insecticides, insecticides used in controlling C.
binotalis are lethal to living organisms and also contaminate the environment.
Therefore this study was carried out to investigate the insecticidal potential of lemon
myrtle plant extracts against S. litura and C. binotalis.
Lemon myrtle hexane extract showed maximum larvicidal activity of 100% at 5.0%
(w/v) concentration with a lethal concentration (LC50) value of 1.8% (w/v), against C.
binotalis. At 5.0% (w/v) concentration, the hexane extract killed 80.0 ± 2.9% of second
instar S. litura larvae after 72 hours. The active hexane extract was subjected to
Vacuum Liquid Chromatography (VLC) which afforded four major fractions namely
LM1, LM4, LM5 and LM7. When tested against C. binotalis, fraction LM4 displayed
maximum larvicidal activity of 100%, at a concentration of 1.4% (w/v) with an LC50 of
0.8% (w/v). At the same concentration, the fraction LM4 also completely inhibited the
feeding activity of C. binotalis larvae, thus indicating good anti-feedant properties. Gas
Chromatography-Mass Spectrometry (GC-MS) and Orthogonal Partial Least Squares
(OPLS) were employed to investigate the chemical constituents of the different
fractions. The compounds responsible for the insecticidal activity of lemon myrtle
were identified as epoxy-linalool oxide, isopropyl 4-methyl-3-methylene-4-pentenoate, neric acid and citral. The results of this study indicated that lemon myrtle leaf extract,
particularly the hexane extract, possesses remarkable insecticidal properties and could
therefore, serve as a viable source for the development of a safer and efficient
insecticide for crop protection.

Identification of Malaysian Lemon Myrtle (Backhousia citriodora F. Muell) chemical constituents responsible for insecticidal activity using GC-MC-based metabolomics

Backhousia citriodora commonly known as lemon myrtle belongs to Myrtaceae family. This species is an evergreen tree which can grow up to 30 meters. Lemon myrtle is highly aromatic, having an exquisite flavour and aroma of a blend of lemongrass, lime and lemon. The leaf and flowers are used in tea blends and beverages, dairy, biscuits, breads, confectionery, pasta, syrups, liqueurs, flavoured oils, dipping and simmer sauces. In our study, the chemical composition and antioxidant properties of the lemon myrtle volatile oil obtained via hydro distillation were investigated. Examination by gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS) analysis showed that the volatile oil obtained from the leaves was made up predominantly neral (39.57%) and geranial (52.43%). Linalool (0.37%), citronellal (0.15%), E-isocitral (2.47%), geraniol (0.66%), ethyl geranate (0.13%), caryophyllene (0.08%) and spathulenol (0.09%) were the other component present in significant amounts. For the stem part, similarly the major components also are neral (36.76%) and geranial (56.30%). Other minor components found in stem oil were 6-methyl-5-hepten-2-one (0.13%), linolool (0.24%), citronellal (0.09%), trans-paramentha-2,8-dien-1-ol (0.39%), E-isocitral (0.92%), (3Z)-hexenyl-(3Z)-hexenoate (0.22%), 8-hydroxy-neo-menthol (1.17%), (E)-α-Damascene 0.70%), spathulenol (0.17%) and globulol (0.14%). The obtained volatile oils were screen for the antioxidant properties by using DPPH (1,2-diphenyl-2-picryl-hydrazyl) radical scavenging assay and xanthine/xanthine oxidase superoxide scavenging assay. Our study indicated both the lemon myrtle leaf and stem volatile oil showed high antioxidant properties. DPPH scavenging activity for both the leaf and stem parts are 83.72% and 84.46% respectively. As for the xanthine/ xanthine oxidase superoxide scavenging assay, both the lemon myrtle leaf and stem volatile oil showed high superoxide scavenging activity, which are 83.72% and 84.46% respectively.

Chemical Composition and Antioxidant Properties of Backhousia Citriodora Volatile Oil

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Sam Kar Yee

Papers

Chemical Composition and Antioxidant Properties of Backhousia Citriodora Volatile Oil

Chemical Composition and Antioxidant Properties of Volatile Oil

Magneto Dielectric Properties of