Also that year, Schnitzler et al. evaluated the antiviral effect of lemon balm oil on HSV-1 and HSV-2 in vitro on monkey kidney cells. They found that plaque formation was significantly lowered (by 98.8% for HSV-1 and 97.2% for HSV-2) by noncytotoxic lemon balm oil concentrations, with higher concentrations nearly eradicating infections. Using time-on-addition assays, the investigators determined that pretreatment with lemon balm oil significantly suppressed both viruses before infection of cells, suggesting that the oil impacted the virus prior to adsorption, but not after reaching the host cell. They concluded that this implies the capacity for direct antiviral activity. The authors added that the lipophilic nature of lemon balm oil allows for its penetration into the skin, further supporting its suitability as a topical treatment of herpes (Phytomedicine. 2008;15:734-40).
In a more recent in vitro experiment evaluating antiviral activity against HSV-1, Astani et al. compared an aqueous extract of M. officinalis and phenolic extract compounds (caffeic acid, p-coumaric acid, and rosmarinic acid). The lemon balm extract exhibited high virucidal activity against HSV-1, even at concentrations of 1.5 mcg/mL; phenolic compounds showed similar results only at concentrations 100 times greater. Further, lemon balm extract and rosmarinic acid dose-dependently suppressed HSV-1 attachment to host cells. The researchers concluded that rosmarinic acid was the primary constituent responsible for the antiviral activity displayed by lemon balm, but noted that M. officinalis extract, which imparted virucidal activity against HSV-1 in vitro with low toxicity, has a greater selectivity index against HSV than that of its constituents alone (Chemotherapy. 2012;58:70-7).
In 2008, Geuenich et al. investigated several species of the Lamiaceae family (including lemon balm) for their potency in suppressing HIV-1 infection. The aqueous extracts from the leaves of lemon balm (as well as peppermint and sage) dose-dependently displayed substantial activity against HIV-1 infection in T-cell lines, primary macrophages, and in ex vivo tonsil histocultures. The investigators also found that exposure of extracts to free virions strongly and quickly suppressed infections, though no antiviral effect was seen in exposure to surface-bound virions or target cells alone. Noting the antiherpetic activity of these Lamiaceae family extracts, the investigators suggested that the development of virucidal topical microbicides using such ingredients is warranted (Retrovirology. 2008;5:27).
Hypopigmentary Potential
A potential hypopigmentary application of lemon balm also may be emerging. In 2011, Fujita et al. isolated 16-hydroxy-9-oxo-10E,12E,14E-octadecatrienoic acid (also called Corchorifatty acid B [CFAB]) from the ethanol extracts of the aerial parts of M. officinalis, and found that it suppresses pigmentation in human melanocytes and murine melanoma B16 cells, probably by promoting accelerated degradation of tyrosinase in B16 cells. Further, they noted that the mechanism of action of CFAB is markedly different from those of many other hypopigmentary agents, which facilitate tyrosinase degradation in proteasomes or lysosomes. That is, the reductions in tyrosinase caused by CFAB are thought to take place in post–Golgi complex areas, not in proteasomal or lysosomal ones (Exp. Dermatol. 2011;20(5):420-4).
Conclusions
Like many botanical ingredients studied and harnessed in our modern pharmacopeia, lemon balm has a history of use in traditional medicine. Recent studies suggest antioxidant, anxiolytic, and, especially, antiviral properties, notably in the treatment of herpes viruses. More research is necessary, however, to establish a broader role for M. officinalis in the dermatologic armamentarium.
Dr. Baumann is in private practice in Miami Beach. She did not disclose any conflicts of interest. To respond to this column, or to suggest topics for future columns, write to Dr. Baumann at sknews@elsevier.com.