Used in foods, some traditional medicines, herbal tea, herbal toothpastes, and aromatherapy, Melissa officinalis (lemon balm) is a perennial herb in the Lamiaceae (mint) family found in southern Europe and the Mediterranean area. The medicinal use of lemon balm dates back at least 2,000 years (Ann. N. Y. Acad. Sci. 1965;130:474-82). Lower abdominal distress and nervous conditions are some of the ailments treated with lemon balm in folk medicine; herpes lesions are a modern indication (Nat. Prod. Res. 2008;22:1433-40). The essential oil and phenylpropanoid derivatives are thought to be the two primary groups of active constituents in lemon balm (Phytochemistry. 2011;72:572-8).
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Melissa officinalis (lemon balm)
The main individual components of M. officinalis essential oil have been identified as the monoterpenaldehydes citral a, citral b, and citronellal (Phytomedicine. 2008;15:734-40). The chief phenolic compounds are rosmarinic acid, which is an ester of caffeic acid and 3,4-dihydroxyphenyllactic acid, as well as caffeic acid, which is isolated from the fresh leaves and stems (J. Nat. Prod. 2009;72:1512-5Phytochemistry. 2011;72:572-8). Six flavonoids, including luteolin and apigenin, have also been isolated from the leaves of lemon balm (Acta. Pol. Pharm. 2002;59:139-43; J. Nat. Prod. 2007;70:1889-94). Given the presence of such ingredients known to exhibit antioxidant properties, it is not surprising that such a capacity is considered one of the main medicinal benefits of M. officinalis. Indeed, lemon balm is reputed to display significant antioxidant, anxiolytic (Med. J. Nutrition. Metab. 2011;4:211-8; Phytomedicine. 2010;17:397-403; Psychosom. Med. 2004;66:607-13), and antiviral (particularly antiherpetic) activity (Proc. Soc. Exp. Biol. Med. 1964;117:431-4; Virol. J. 2011;8:188). M. officinalis is also a component, with two other herbs, in a mixture (Ob-X) recently shown to lower body weight gain and adipose tissue mass in genetically obese mice (Pharm. Biol. 2011;49:614-9).
Antioxidant Activity
In a 2009 study, investigators examined the antioxidant potential of three plants (M. officinalis, Matricaria recutita (German chamomile), and Cymbopogon citrus [lemon grass]) used in Brazil to treat neurologic conditions. M. officinalis was found to deliver the greatest reduction in thiobarbituric acid reactive species (TBARS) and the most salient antioxidant effect as evaluated by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. The investigators concluded that M. officinalis warrants consideration as a treatment for oxidative stress–associated neurologic diseases (Neurochem. Res. 2009;34:973-83).
Additional evidence of its antioxidant activity is emerging. In early 2012, Martins et al. reported on their study in which an aqueous extract of M. officinalis significantly mitigated manganese-induced brain oxidative stress in mice. They found that the extract attenuated oxidative damage (TBARS) and reduced total thiol levels, and concluded that their findings show the potent antioxidant activity of M. officinalis (Brain. Res. Bull. 2012;87;74-9). In addition, a recent study found that lemon balm infusion in a tea, after 30 days of daily consumption, significantly lowered oxidative stress and DNA damage in radiology staff exposed to low doses of radiation at work (Toxicol. Ind. Health. 2011;27:205-12).
Antiviral Activity
In 2006, Gaby reported on various natural substances, used in the diet or topically, that exert activity against herpes simplex lesions and prevent recurrences, serving as effective alternatives to acyclovir and its attendant side effects. He cited lemon balm as having exhibited antiviral properties in two studies in the 1990s (Altern. Med. Rev. 2006;11:93-101).
In 1994, 116 patients with acute herpes simplex applied a standardized lemon balm cream (containing 1% Lo-701) or a placebo cream two to four times daily in a randomized, double-blind trial over a 5- to 10-day period within 72 hours of symptom onset. While only 19% of the placebo group reported satisfactory healing, 41% of the active treatment group was satisfied (Phytomedicine. 1994;1:25-31). In 1999, a double-blind, placebo-controlled trial randomized 66 patients with a minimum of four herpes simplex episodes per year to treatment (four times daily for 5 days) with the same standardized lemon balm cream or placebo. Symptom scores were significantly lower in the treatment group than the control group by the second day of the protocol, though the trend supporting active treatment over 5 days was not significant (Phytomedicine 1999;6:225-30).
In 2008, Mazzanti et al. evaluated the antiviral activity against herpes simplex virus type 2 (HSV-2) of a hydroalcoholic extract of lemon balm leaves using a cytopathic effect inhibition assay on Vero cells. They found that lemon balm diminished the cytopathic effect of HSV-2 on Vero cells, with a maximum suppression effect with 0.5 mg/mL. The extract, shown through NMR (nuclear magnetic resonance) and HPLC (high-performance liquid chromatography) analysis to contain rosmarinic acid (4.1% w/w), did not prevent the entry of HSV-2 into cells, indicating postpenetration activity by the botanical agent. The investigators concluded that their work supports the use of lemon balm for treating herpes lesions, and justifies its further study in clinical trials (Nat. Prod. Res. 2008;22:1433-40).