Molecular diagnostics of Lemon Myrtle (Backhousia citriodora versus Leptospermum citratum)

Abstract

‘Lemon Myrtle’ is becoming increasingly popular in Europe both for use in cuisine and phytotherapy. However, this common name covers two completely different species, Backhousia citriodora F. Muell. and Leptospermum citratum Challinor, Cheel & A.R.Penfold. These species differ with respect to secondary compounds and even can cause, if mixed up and applied in high dose, toxic effects. We describe how the two species can be discriminated microscopically making use of differences in the morphology of leaf pavement cells and the relative size of palisade parenchyma. Based on the large subunit of ribulose-1,5-bisphosphate carboxylase oxygenase (rbcL) as molecular marker, the phylogenetic position of the two species within the Myrtaceae could be clarified. This sequence information was used to develop a simple assay to discriminate the two species even in dried and highly fragmented mixtures as typically occurring in commercial samples. This assay utilises the occurrence of single-nucleotide exchanges between those species that produce different fragments when the rbcL amplificates are restricted with Sac II.

This is a preview of subscription content, access via your institution.

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5

References

  1. 1.

    Ernst E (1998) Harmless herbs? A review of the recent literature. Am J Med 104:170–178

    Article  CAS  Google Scholar 

  2. 2.

    European Parliament and European Council (1997) Regulation on novel foods and novel food ingredients no. 258/97 of 27 January 1997. J Eur Comm L 43:1–5

    Google Scholar 

  3. 3.

    Green JM, Draper AK, Dowler EA (2003) Short cuts to safety: risk and `rules of thumb’ in accounts of food choice. Health Risk Soc 5:33–52

    Article  Google Scholar 

  4. 4.

    Hahn H, Michaelson I (1996) Mikroskopische Diagnostik pflanzlicher Nahrungs-, Genuss- und Futtermittel, einschliesslich Gewürze. Springer, Berlin

    Book  Google Scholar 

  5. 5.

    von Mueller FJH (1859) Fragmenta Phytographiae Australiae 1:78

    Google Scholar 

  6. 6.

    Thompson J (1989) A revision of the genus Leptospermum (Myrtaceae). Telopea 3:301–448

    Google Scholar 

  7. 7.

    Atkinson W, Brice H (1955) Antibacterial substances produced by flowering plants. Aust J Exp Biol 33:547–554

    Article  CAS  Google Scholar 

  8. 8.

    Greive KA, Staton JA, Miller PF, Peters BA, Oppenheim VMJ (2010) Development of Melaleuca oils as effective natural-based personal insect repellents. Aust J Entomol 49:40–48

    Article  Google Scholar 

  9. 9.

    Burke BE, Baillie JE, Olson RD (2004) Essential oil of Australian lemon myrtle (Backhousia citriodora) in the treatment of molluscum contagiosum in children. Biomed Pharmacother 58:245–247

    Article  CAS  Google Scholar 

  10. 10.

    Hood JR, Burton DM, Wilkinson JM, Cavanagh HMA (2010) The effect of Leptospermum petersonii essential oil on Candida albicans and Aspergillus fumigatus. Med Mycol 48:922–931

    Article  CAS  Google Scholar 

  11. 11.

    Lazar-Baker E, Hetherington S, Ku V, Newman S (2011) Evaluation of commercial essential oil samples on the growth of postharvest pathogen Monilinia fructicola (G. Winter) Honey. Lett Appl Microbiol 52:227–232

    Article  CAS  Google Scholar 

  12. 12.

    Doran JC, Brophy JJ, Lassak EV, House APN (2001) Backhousia citriodora F. Muell. Rediscovery and chemical characterization of the L-citronellal form and aspects of its breeding system. Flavour Fragr J 16:325–328

    Article  CAS  Google Scholar 

  13. 13.

    Hayes AJ, Markovic B (2002) Toxicity of Australian essential oil Backhousia citriodora (Lemon myrtle). Part 1. Antimicrobial activity and in vitro cytotoxicity. Food Chem Toxicol 40:535–543

    Article  CAS  Google Scholar 

  14. 14.

    Hayes AJ, Markovic B (2003) Toxicity of Australian essential oil Backhousia citriodora (Lemon myrtle). Part 2. Absorption and histopathology following application to human skin. Food Chem Toxicol 41:1409–1416

    Article  CAS  Google Scholar 

  15. 15.

    Consortium for the Barcode of Life (2009) A DNA barcode for land plants. Proc Natl Acad Sci USA 106:12794–12797

    Article  Google Scholar 

  16. 16.

    Walsh NG, Entwisle TJ (1996) Flora of Victoria, vol 3. Inkata Press, Melbourne

    Google Scholar 

  17. 17.

    Doyle JJ, Doyle JL (1987) A rapid DNA isolation procedure from small quantities of fresh leaf tissues. Phytochem Bull 19:11–15

    Google Scholar 

  18. 18.

    Tamura K, Dudley J, Nei M, Kumar S (2007) MEGA4: molecular evolutionary genetics analysis (MEGA) software version 4.0. Mol Biol Evol 24:1596–1599

    Article  CAS  Google Scholar 

  19. 19.

    Saitou N, Nei M (1987) The neighbor-joining method: a new method for reconstructing phylogenetic trees. Mol Biol Evol 4:406–425

    CAS  Google Scholar 

  20. 20.

    Felsenstein J (1985) Confidence limits on phylogenies: an approach using the bootstrap. Evolution 39:783–791

    Article  Google Scholar 

  21. 21.

    O’Brien TP, Feder N, McCully ME (1964) Polychromatic staining of plant cell walls by Toluidine Blue O. Protoplasma 59:367–373

    Google Scholar 

Download references

Acknowledgments

We acknowledge Angelika Piernitzki and Joachim Daumann, Botanical Garden of the University, for excellent horticultural support during the project and Olivia Huber for skillful technical support during DNA extraction and analysis.

Conflict of interest

The authors declare that they do not have any conflict of interest.

Author information

Affiliations

Authors

Corresponding author

Correspondence to Peter Nick.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Horn, T., Barth, A., Rühle, M. et al. Molecular diagnostics of Lemon Myrtle (Backhousia citriodora versus Leptospermum citratum). Eur Food Res Technol 234, 853–861 (2012). https://doi.org/10.1007/s00217-012-1688-9

Download citation

Keywords

  • Backhousia citriodora F.Muell
  • Lemon Myrtle
  • Leptospermum citratum Challinor, Cheel & A.R.Penfold
  • Molecular identification
  • Polymerase chain reaction (PCR)
  • Ribulose-bisphosphate carboxylase oxygenase large subunit (rbcL)