Mānuka

Mānuka

 

Posted: November 2023

Author: Katie Donnelly, Adv Dip HSc Naturopathy

The NZ native – mānuka

 

The common properties of mānuka

Leptospermum scoparium (mānuka) is a renowned New Zealand native shrub, recognised internationally for potent antimicrobial actions.

Traditionally used in Rongoā rākau, plant medicine, for skin conditions and pain relief, mānuka was also inhaled to relieve colds. Further indications included urinary tract infections, digestion support, as a relaxant, and for gum disease. Some of the first travellers to New Zealand steeped mānuka leaves to drink as tea. More recent research has identified the use of this herb in bacterial and viral conditions.1

Arguably the most well-known form of mānuka is as a honey. The highly researched constituent methylglyoxal (MGO) is produced when dihydroxyacetone, found in the nectar of mānuka flowers, dehydrates. The measurement of these two factors contribute to the therapeutic effect of mānuka honey, and Unique Mānuka Factor honey ratings (UMF).

Commonly used in hospitals as a medical grade honey, mānuka demonstrated immunomodulatory actions during in vitro and in vivo studies. This included a reduction in interleukin-6 (Il-6), Il-1β, and tumour necrosis factor-alpha.2 For children, mānuka honey is an effective option to relieve upper respiratory infections and subsequent coughing spasms.3

Essential oil and hydroethanolic extracts have also grown in prevalence and popularity, utilising the herb leaf. Animal model studies on the essential oil support spasmolytic actions, particularly focused on smooth muscle contractions and potassium channel interactions. The active constituents, Alpha-terpineol, alpha-terpinene and terpinene-4-ol were highlighted as influencing the strength of contractions, while also supporting reduction of anxiety and stress.4 This links to early uses of the bark as a sedative. Hydroethanolic extracts have then shown high phenolic content and free radical scavenging actions in a separate analysis.5

Antimicrobial actions have also been attributed to the presence of β-triketones. This includes leptospermone and isoleptospermone present in the essential oils. These constituents provide antibacterial activity against Gram-positive and Gram-negative bacteria, via cell lysis, and prevent morphology of methicillin-resistant Staphylococcus aureus.4 Flavesones further provide antiviral activity against herpes simplex virus type 1 and 2, and Varicella-zoster, notably reducing the size of viral plaques.4,6

Recently, antifungal properties have been further explored. Mānuka oil prevented 90% of hyphae morphology development of Candida albicans, a critical factor in adhesion and biofilm development. Cell wall modifications were noted to be responsible for increased permeability of the membrane. This preventative action on proliferation makes mānuka a suitable option for C. albicans overgrowth.7

Triketones are particularly prevalent in East Coast mānuka varieties, determining the geographical significance of herbal material.5 This is further supported by higher monoterpene levels identified in Northland mānuka, including α-pinene and β- pinene, with Canterbury varieties higher in linalool. Sesquiterpenes were also noted to be more prevalent in younger plant material.4

Growing understanding of the actions of mānuka bark, leaves, and flowers lends to the extensive range of uses for this plant. This serves as an efficacious alternative treatment option to current medical concerns, including antibiotic resistance and high viral load.

References

  1. Noites A, Borges I, Araújo B, da Silva JCGE, de Oliveira NM, Machado J, Pinto E. Antimicrobial Activity of Some Medicinal Herbs to the Treatment of Cutaneous and Mucocutaneous Infections: Preliminary Research. Microorganisms. 2023 Jan 20;11(2):272. Available from: https://doi.org/10.3390/microorganisms11020272
  2. Masad RJ, Nasser RA, Bashir G, Mohamed YA, Al-Sbiei AA, Al-Saafeen BH, Fernandez-Cabzudo MJ, Al-Ramadi BK. Characterization of immunomodulatory responses induced by manuka honey. Frontiers in Immunology. 2022 Nov 2;13. Available from: https://doi.org/10.3389/fimmu.2021020574
  3. Mashat GD, Hazique M, Khan KI, Ramesh P, Kanagalingam S, Ul Haq Z, Victory Srinivasan N, Khan AI, Khan S. Comparing the Effectiveness of Honey Consumption With Anti-Cough Medication in Pediatric Patients: A Systematic Review. Cureus. 2022 Sep 20;14(9):e29346. Available from: https://doi.org/10.7759/cureus.29346
  4. Mathew C, Tesfaye W, Rasmussen P, Peterson GM, Bartholomaeus A, Sharma M, Thomas J. Mānuka Oil—A Review of Antimicrobial and Other Medicinal Properties. Pharmaceuticals. 2020; 13(11):343. Available from: https://doi.org/10.3390/ph13110343
  5. Alsaud N, Shahbaz K, Farid M. Antioxidant and antibacterial evaluation of Manuka leaves (Leptospermum scoparium) extracted by hydrophobic deep eutectic solvent. Chemical Engineering Research and Design. 2021;174:96-106. Available from: https://doi.org/10.1016/j.cherd.2021.08.004
  6. Shahzad A, Cohrs RJ. In vitro antiviral activity of honey against varicella zoster virus (VZV): A translational medicine study for potential remedy for shingles. Transl Biomed. 2012;3(2):2. Available from: https://doi.org/10.3823/434.
  7. Noites A, Araújo B, Machado J, Pinto E. Antifungal Potential of Some Herb Decoctions and Essential Oils on Candida Species. Healthcare 2022;10:1820. Available from: https://doi.org/10.3390/healthcare10101820.

 

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