Antioxidant and anti-inflammatory activities of phenolic compounds extracted from lemon myrtle (Backhousia citriodora) leaves at various extraction conditions

Exploring the Anti-Inflammatory Potential of Australian Native Plants Based on their Ethnopharmacological Knowledge

Inflammation represents the inherent protective reaction of the human body to various harmful agents and noxious stimuli. Standard anti-inflammatory therapy including nonsteroidal anti-inflammatory drugs are associated with several side effects. In the past decades, people rely on medicinal plants for the treatment of inflammation. The traditional utilization of medicinal plants is regarded as a safe, cost-effective, and broadly accepted approach. In this study, anti-inflammatory activity of plants traditionally utilized by the D'harawal people in Australia has been assessed in vitro. Eighty Australian native plants were screened based on the Dharawal Pharmacopeia for their inhibitory effect on the nitric oxide (NO) production in lipopolysaccharides (LPS) and interferon (IFN)-γ stimulated RAW 264.7 murine macrophages for their anti-inflammatory activity. From the eighty ethanolic extracts screened, seventeen displayed potent NO inhibition with an IC50 recorded below 15 μg/mL. The aim of this review was to utilise the ethnopharmacological knowledge and to correlate the anti-inflammatory activity of the seventeen plants with either their known or unknown phytochemicals reported in the literature. In doing so, we have created a snapshot of Australian native plant candidates that warrant further chemical investigation associated with their anti-inflammatory activity.

Citral in lemon myrtle, lemongrass, litsea, and melissa essential oils suppress the growth and invasion of breast cancer cells

OBJECTIVE

Although cancer therapy suppresses recurrence and prolongs life, it may be accompanied by strong side effects; thus, there is a strong demand for the development effective treatments with fewer side effects. Cancer therapy using plant-derived essential oils is attracting attention as one promising method. This study investigated the antitumor effects of essential oil volatiles on breast cancer cells and identifies four essential oils that display antitumor activity.

METHODS

Breast cancer cells were cultured in a 96-well plate, then one of twenty essential oils was added dropwise to the central well. The plate was incubated at 37 °C for 48 h and the effect of the volatile components of each essential oil on the surrounding breast cancer cell growth ability was examined using an MTT assay. Gas chromatography was used to investigate the concentration of the transpiration components that may affect cancer cells.

RESULTS

Of the 20 essential oils, Lemongrass, Lemon myrtle, Litsea, and Melissa displayed strong anti-tumor effects. These essential oils inhibited the growth of nearby breast cancer cells, even when diluted more than 500-fold. The transpiration component of lemon Myrtle showed the strongest antitumor effect, but was the least cytotoxic to mononuclear cells in normal peripheral blood (PBMC). Each of these essential oils contained a very large amount of citral. The IC50 against breast cancer cells when citral was volatilized from each essential oil was 1.67 µL/mL for geranial and 1.31 µL/mL for neral. Volatilized citral alone showed strong anti-proliferation and infiltration-inhibiting effects.

CONCLUSION

The transpiration components of Lemongrass, Lemon myrtle, Litsea, and Melissa are thought to inhibit breast cancer cell proliferation due to their high levels of citral.

LC-ESI-QTOF-MS/MS Identification and Characterization of Phenolic Compounds from Leaves of Australian Myrtles and Their Antioxidant Activities

Phenolic compounds, present in plants, provide substantial health advantages, such as antioxidant and anti-inflammatory properties, which enhance cardiovascular and cognitive well-being. Australia is enriched with a wide range of plants with phytopharmacological potential, which needs to be fully elucidated. In this context, we analyzed leaves of aniseed myrtle (Syzygium anisatum), lemon myrtle (Backhousia citriodora), and cinnamon myrtle (Backhousia myrtifolia) for their complex phytochemical profile and antioxidant potential. LC-ESI-QTOF-MS/MS was applied for screening and characterizing these Australian myrtles' phenolic compounds and the structure-function relation of phenolic compounds. This study identified 145 and quantified/semi-quantified 27 phenolic compounds in these Australian myrtles. Furthermore, phenolic contents (total phenolic content (TPC), total condensed tannins (TCT), and total flavonoids (TFC)) and antioxidant potential of phenolic extracts from the leaves of Australian myrtles were quantified. Aniseed myrtle was quantified with the highest TPC (52.49 ± 3.55 mg GAE/g) and total antioxidant potential than other selected myrtles. Catechin, epicatechin, isovitexin, cinnamic acid, and quercetin were quantified as Australian myrtles' most abundant phenolic compounds. Moreover, chemometric analysis further validated the results. This study provides a new insight into the novel potent bioactive phenolic compounds from Australian myrtles that could be potentially useful for functional, nutraceutical, and therapeutic applications.

Essential oil of lemon myrtle (Backhousia citriodora) induces S-phase cell cycle arrest and apoptosis in HepG2 cells

ETHNOPHARMACOLOGICAL RELEVANCE

Lemon myrtle (Backhousia citriodora F.Muell.) leaves, whether fresh or dried, are used traditionally in folk medicine to treat wounds, cancers, skin infections, and other infectious conditions. However, the targets and mechanisms related to anti-cancer effect of lemon myrtle are unavailable. In our study, we found that the essential oil of lemon myrtle (LMEO) showed anti-cancer activity in vitro, and we initially explored its mechanism of action.

MATERIALS AND METHODS

We analyzed the chemical compositions of LMEO by GC-MS. We tested the cytotoxicity of LMEO on various cancer cell lines using the MTT assay. Network pharmacology was used also to analyze the targets of LMEO. Moreover, the mechanisms of LMEO were investigated through scratch assay, flow cytometry analysis, and western blot in the HepG2 liver cancer cell line.

RESULTS

LMEO showed cytotoxicity on various cancer cell lines with values of IC₅₀ 40.90 ± 2.23 (liver cancer HepG2 cell line), 58.60 ± 6.76 (human neuroblastoma SH-SY5Y cell line), 68.91 ± 4.62 (human colon cancer HT-29 cell line) and 57.57 ± 7.61 μg/mL (human non-small cell lung cancer A549 cell line), respectively. The major cytotoxic chemical constituent in LMEO was identified as citrals, which accounted for 74.9% of the content. Network pharmacological analysis suggested that apurinic/apyrimidinic endodeoxyribonuclease 1 (APEX1), androgen receptor (AR), cyclin-dependent kinases 1 (CDK1), nuclear factor erythroid 2-related factor 2 (Nrf-2), fatty acid synthase (FASN), epithelial growth factor receptor (EGFR), estrogen receptor 1 (ERα) and cyclin-dependent kinases 4 (CDK4) are potential cytotoxic targets of LMEO. These targets are closely related to cell migration, cycle and apoptosis. Notley, the p53 protein had the highest confidence to co-associate with the eight common targets, which was further confirmed by scratch assay, flow cytometry analysis, and western blot in the HepG2 liver cancer cell line. LMEO significantly inhibited the migration of HepG2 cells in time-dependent and dose-dependent manner. Moreover, LMEO caused a S-phase blocking on HepG2 cells and promoted apoptosis in the meanwhile. Western blot results indicated that p53 protein, Cyclin A2 and Bax proteins were up-regulated, while Cyclin E1 and Bcl-2 proteins were down-regulated.

CONCLUSION

LMEO showed cytotoxicity in various cancer cell lines in vitro. Pharmacological networks showed LMEO to have multi-component and multi-targeting effects that are related to inhibit migration of HepG2 cells, and affect cell cycle S-phase arrest and apoptosis through modulation of p53 protein.

Lemon Myrtle (Backhousia citriodora) Extract and Its Active Compound, Casuarinin, Activate Skeletal Muscle Satellite Cells In Vitro and In Vivo

Sarcopenia is an age-related skeletal muscle atrophy. Exercise is effective in improving sarcopenia via two mechanisms: activation of skeletal muscle satellite cells (SCs) and stimulation of muscle protein synthesis. In contrast, most nutritional approaches for improving sarcopenia focus mainly on muscle protein synthesis, and little is known about SC activation. Here, we investigated the effect of lemon myrtle extract (LM) on SC activation both in vitro and in vivo. Primary SCs or myoblast cell lines were treated with LM or its derived compounds, and incorporation of 5-bromo-2′-deoxyuridine, an indicator of cell cycle progression, was detected by immunocytochemistry. We found that LM significantly activated SCs (p < 0.05), but not myoblasts. We also identified casuarinin, an ellagitannin, as the active compound in LM involved in SC activation. The structure−activity relationship analysis showed that rather than the structure of each functional group of casuarinin, its overall structure is crucial for SC activation. Furthermore, SC activation by LM and casuarinin was associated with upregulation of interleukin-6 mRNA expression, which is essential for SC activation and proliferation. Finally, oral administration of LM or casuarinin to rats showed significant activation of SCs in skeletal muscle (p < 0.05), suggesting that LM and casuarinin may serve as novel nutritional interventions for improving sarcopenia through activating SCs.

Optimization of Microwave-Assisted Extraction of Polyphenols from Lemon Myrtle: Comparison of Modern and Conventional Extraction Techniques Based on Bioactivity and Total Polyphenols in Dry Extracts

The aromatic herb lemon myrtle is a good source of polyphenols, with high antioxidant and antimicrobial capacity. In this study, the green extraction technique microwave-assisted extraction (MAE) was applied and the extraction parameters were optimized using response surface methodology (RSM) to maximize the extraction yield of phenolic compound and antioxidant properties. Then, it was compared with other popular novel and conventional extraction techniques including ultrasound-assisted extraction (UAE) and shaking water bath (SWB) to identify the most effective technique for extraction of phenolic compounds from lemon myrtle. The results showed that the MAE parameters including radiation time, power, and sample to solvent ratio had a significant influence on the extraction yield of phenolic compounds and antioxidant capacity. The optimal MAE conditions were radiation time of 6 min, microwave power of 630 W, and sample to solvent ratio of 6 g/100 mL. Under optimal conditions, MAE dry extract had similar levels of total phenolic compounds (406.67 ± 8.57 mg GAE/g DW), flavonoids (384.57 ± 2.74 mg CE/g DW), proanthocyanidins (336.54 ± 7.09 mg CE/g DW), antioxidant properties, and antibacterial properties against (Staphylococcus lugdunensis and Bacillus cereus) with the other two methods. However, MAE is eight-times quicker and requires six-times less solvent volume as compared to UAE and SWB. Therefore, MAE is recommended for the extraction of polyphenols from lemon myrtle leaf.

Backhousia citriodora F. Muell. (Lemon Myrtle), an Unrivalled Source of Citral

Lemon oils are amongst the highest volume and most frequently traded of the flavor and fragrance essential oils. Citronellal and citral are considered the key components responsible for the lemon note with citral (neral + geranial) preferred. Of the myriad of sources of citral, the Australian myrtaceous tree, Lemon Myrtle, Backhousia citriodora F. Muell. (Myrtaceae), is considered superior. This review examines the history, the natural occurrence, the cultivation, the taxonomy, the chemistry, the biological activity, the toxicology, the standardisation and the commercialisation of Backhousia citriodora especially in relation to its essential oil.

Acai berry extract as a regulator of intestinal inflammation pathways in a Caco-2 and RAW 264.7 co-culture model

The aim of this study was to assess the anti-inflammatory effects of acai berries in a Caco-2 and RAW 264.7 macrophage co-culture model. The acai berry extract (ABE) was prepared using 70% ethanol, and total anthocyanin, polyphenol, and flavonoid contents in ABE were analyzed. To the antioxidant activity of ABE, we measured radical scavenging activity as well as ferric reducing antioxidant power values. Prior to inducing inflammation, Caco-2 cells were co-cultured with RAW 264.7. Inflammation was induced using lipopolysaccharides (LPS) in RAW 264.7 cells. The transepithelial electrical resistance value was significantly recovered and the mRNA level of tight junction proteins, including ZO-1, JAM-1, and claudin-4, tended to increase compared with that in the LPS group. LPS-induced interleukin (IL)-6, IL-8, and prostaglandin E2 levels reduced significantly following treatment with the highest ABE concentration. In the highest ABE concentration, the phosphorylation of p65, p38 mitogen-activated protein kinase, and c-Jun N-terminal kinase was downregulated compared with the LPS group. The phosphorylation of extracellular signal-regulated kinase showed a decreased tendency. These results suggest that acai berry may improve gastrointestinal health. PRACTICAL APPLICATIONS: Acai berry is known to have abundant anthocyanin, which has many biological activities, including anti-inflammatory, antioxidant, antihypertensive, and anticytotoxic/cytoprotective activities. This study demonstrated the anti-inflammatory effects of acai berry extracts via TEER value, expression of tight junction protein, and production of inflammatory mediators and cytokines in the Caco-2 and RAW 264.7 co-culture model. Therefore, acai berry has the potential to prevent intestinal inflammatory diseases.