Planta Med 2005; 71(12): 1123-1127
DOI: 10.1055/s-2005-873175
Original Paper
© Georg Thieme Verlag KG Stuttgart · New York

Virucidal Activity of a β-Triketone-Rich Essential Oil of Leptospermum scoparium (Manuka Oil) Against HSV-1 and HSV-2 in Cell Culture

Jürgen Reichling1 , Christine Koch1 , Elisabeth Stahl-Biskup2 , Cornelia Sojka2 , Paul Schnitzler3
  • 1Institute of Pharmacy and Molecular Biotechnology, Department of Biology, University of Heidelberg, Heidelberg, Germany
  • 2Institute of Pharmacy, Department of Pharmaceutical Biology and Microbiology, University of Hamburg, Hamburg, Germany
  • 3Hygiene Institute, Department of Virology, University of Heidelberg, Heidelberg, Germany
Further Information

Publication History

Received: February 15, 2005

Accepted: June 10, 2005

Publication Date:
10 November 2005 (online)


The inhibitory activity of manuka oil against Herpes simplex virus type 1 (HSV-1) and Herpes simplex virus type 2 (HSV-2) was tested in vitro on RC-37 cells (monkey kidney cells) using a plaque reduction assay. In order to determine the mode of antiviral action of the essential oil, manuka oil was added at different times to the cells or viruses during the infection cycle. Both HSV types were significantly inhibited when the viruses were pretreated with manuka oil 1 h prior to cell infection. At non-cytotoxic concentrations of the essential oil, plaque formation was significantly reduced by 99.5 % and 98.9 % for HSV-1 and HSV-2, respectively. The 50 % inhibitory concentration (IC50) of manuka oil for virus plaque formation was determined at 0.0001 % v/v ( = 0.96 μg/mL) and 0.00006 % v/v ( = 0.58 μg/mL) for HSV-1 and HSV-2, respectively. On the other hand, pretreatment of host cells with the essential oil before viral infection did not affect plaque formation. After virus penetration into the host cells only replication of HSV-1 particle was significantly inhibited to about 41 % by manuka oil. Flavesone and leptospermone, two characteristic ß-triketones of manuka oil, inhibited the virulence of HSV-1 in the same manner as the essential oil itself. When added at non-cytotoxic concentrations to the virus 1 h prior to cell infection, plaque formation was reduced by 99.1 % and 79.7 % for flavesone and leptospermone, respectively.


Prof. Dr. Jürgen Reichling

Institute of Pharmacy and Molecular Biotechnology

Department of Biology

University of Heidelberg

Im Neuenheimer Feld 364

69120 Heidelberg