Asadi A et al (2019). Efficacy of Melissa officinalis L. (lemon balm) extract on glycemic control and cardiovascular risk factors in individuals with type 2 diabetes: A randomized, double-blind, clinical trial, 33:651-659. Phytother Res.

Summary: Findings from this study revealed that extract of M. officinalis improved the glycemic status, hyperlipidemia, and hypertension. It also reduced the inflammatory biomarker hs‐CRP with a slight increase in TAC levels in type 2 diabetic patients. Further investigation with a larger sample size and longer intervention time is needed to confirm the beneficial effects of M. officinalis the management of diabetes complications, inflammatory parameters, antioxidant indices in type 2 diabetic patients.

Abstract: Melissa officinalis is a plenteous source of antioxidant flavonols and flavonoids that contain health-promoting and antidiabetic properties, so this study was undertaken to provide the first assessment of the antidiabetic properties of hydroalcoholic extract of M. officinalis in type 2 diabetic patients. We did a randomized, placebo-controlled trial which included 62 patients, receiving either M. officinalis capsules (700 mg/d; n = 31) or the placebo (n = 31) twice daily for 12 weeks. There were significant differences in serum FBS (P = 0.007), HbA1c (P = 0.002), β-cell activity (P = 0.05), TG (P = 0.04), HDL-c (P = 0.05), hs-CRP (P = 0.001), and systolic blood pressure (P = 0.04) between the two groups at the end of the study; but total cholesterol, LDL-c, insulin, and HOMA-IR showed no significant changes between the groups. In M. officinalis group, there was a significant change in HDL-c (P = 0.009) and QUICKI (P = 0.005) compared with baseline values. No adverse effects were observed. It seems that M. officinalis is safe and effective in improvement of lipid profile, glycemic control, and reduction of inflammation.

Watson K et al (2019). A randomized controlled trial of Lavender (Lavandula Angustifolia) and Lemon Balm (Melissa Officinalis) essential oils for the treatment of agitated behavior in older people with and without dementia, 42: 366-373. Complement There Med.

Summary: This study’s post hoc results indicate Lavender may be more effective in reducing agitation and physical nonaggressive behavior in people with dementia. Lemon balm was indicated to be more effective in reducing agitation in people without dementia. This study is important as it adds weight to the conversation that essential oils may be effective in reducing agitation in older people with and without dementia. The findings are of benefit to future researchers to consider large-scale placebo-controlled studies that monitor participant compliance with treatment in their design.

Abstract: Objective: Lavender and Lemon Balm essential oils are popular in the management of older person agitation due to their ease of application, minimal side effects and low interaction with concurrent medications. This study addressed limitations in the literature to evaluate and compare effectiveness of Lavender and Lemon Balm essential oils on the agitated behaviour of older people with and without dementia living in residential aged care facilities [RACFs].

Methods: Forty-nine nursing home residents with dementia (n=39) and without dementia (n=10) exhibiting agitation participated in this study. Participants were randomised to a counterbalanced, repeated measures design experiment that tests the treatments Lavender, Lemon Balm, and Placebo (Sunflower oil). Treatments were administered once daily for two-weeks followed by a two-week washout period before commencing the subsequent treatment. All participants trialed all three treatments over a 10-week period. Data were collected on the Neuropsychiatric Inventory (NPI) and Cohen-Mansfield Agitation Inventory (CMAI).

Results: A significant difference was shown when essential oils effect were compared between the cognitive groups. Post hoc analysis reports Lemon Balm more effective in reducing NPI agitation (p = .04) and CMAI physical non-aggressive behaviour (PNAB) (p = .02) in residents without dementia. Lemon Balm less effective in reducing NPI irritability (p = 0.01) and Lavender more effective in reducing CMAI PNAB (p = 0.04) in dementia.

Conclusion: The findings support an opposing effect of Lemon Balm and Lavender in reducing agitated behaviour between the participant cognitive groups. There was no reduction in agitation with treatments when compared to placebo independent of cognitive groups.

Asadi A et al (2018). Safety and efficacy of Melissa officinalis (lemon balm) on ApoA-I, Apo B, lipid ratio and ICAM-1 in type 2 diabetes patients: A randomized, double-blinded clinical trial, 40: 83-88. Complement Ther Med.

Summary: The study showed that parts of M. officinalis caused significant improvement on serum Apo AI, TC/ HDL-c, and LDL-c/ HDL-c, key factors promoting cardiovascular disease, although it had no significant effects on other lipids ratios, liver enzymes, ICAM-1 and anthropometric indices in type 2 diabetic patients. M. officinalis extract may act as a safe complementary medicine in regulating blood lipids and atherogenic markers in patients. Additional research with a larger sample size and higher doses of M. officinalis are needed to confirm its beneficial effects in the management of type 2 diabetes complications.

Abstract: Background: The purpose of this study was to investigate the safety and effects of Melissa officinalis, a good source of bioactive components, on apolipoprotein (Apo)B, Apo A-I, and their ratio, lipids ratios and intercellular adhesion molecule-1(ICAM-1) in patients with type 2 diabetes.

Methods: For the present randomized, double-blinded, placebo-controlled clinical trial, 70 type 2 diabetic patients aged 20-65 years old were randomly assigned to receive hydroalcoholic extract of M. officinalis (HEMO) (700 mg/d) or placebo twice-daily for 12 weeks.

Results: There were significant differences in serum Apo A-I, TC/ HDL-c and LDL-c/ HDL-c between the two groups at the end of the study (p < 0.05), but we did not show significant differences in the values for Apo B, Apo B/Apo A-I, TG/HDL-c, ICAM-1 and liver enzymes include AST, ALT, and ALP between the study groups. Although both groups showed a significant reduction in ICAM-1, AST and, ALP (p < 0.05), no significant differences in ICAM-1, AST and, ALP were observed. At end, in M. officinalis group, there was a significant increase in Apo A-I (p = 0.003) and significant reduction in TG/HDL-c (p = 0.05) compared with initial values, as well as in placebo group, there was a significant rising in Apo B/Apo A-I (p = 0.02) and significant reduction in Apo A-I (p = 0.001) compared with baseline values.

Conclusion: M. officinalis is safe and effective in improvement of Apo A-I, Apo B/Apo A-I, and lipids ratios as key factors promoting cardiovascular disease (CVD) in type II diabetic patients.

Chizzola R et al (2018). Biodiversity within Melissa officinalis: Variability of Bioactive Compounds in a Cultivated Collection, 23: 294+. Molecules.

Summary: Both lemon balm subspecies can clearly be differentiated by the composition of their essential oils. This plasticity might be the base for the selection of lines and optimization of cultivation to obtain highly valuable plants high in rosmarinic acid and citrus-like aroma aldehydes.

Abstract: Phytochemical characters were evaluated in a five-year-old lemon balm collection consisting of 15 and 13 subspecies officinalis and altissima accessions, respectively. Stems were lower in essential oil than leaves. First cut leaves (June) gave more oil than those of the second cut (August). Subspecies officinalis plants had leaf oils rich in geranial, neral and citronellal in various proportions in the first cut. However, in the second cut the oils from all accessions appeared very similar with 80-90% geranial plus neral. Leaf oils of subsp. altissima contained sesquiterpenes (β-caryophyllene, caryophyllene oxide, germacrene D) and also further monoterpenes in the second cut. Leaves had higher rosmarinic acid (RA) contents than stems. More RA was in subsp. officinalis than subsp. altissima leaves. First cut leaves were richer in RA than those from second cut. Total phenolics and antioxidant parameters showed that lemon balm is a valuable source of plant antioxidants.

Haybar H et al (2018). The effects of Melissa officinalis supplementation on depression, anxiety, stress, and sleep disorder in patients with chronic stable angina, 26: 47-52. Clin Nutr ESPEN.

Summary: In the present study Melissa officinalis supplementation had beneficial effects on depression, anxiety, stress, and sleep disorder in patients with chronic stable angina. However, further investigations are required to confirm these results.

Abstract:  Background: Despite advances in the treatment of cardiovascular diseases in recent decades, patients experience high levels of depression, anxiety, stress, and insomnia. Since the calming effect of Melissa officinalis (MO) has been known, this study aimed to determine the effects of MO supplementation on depression, anxiety, stress, and sleep disturbances in patients with chronic stable angina (CSA).

Methods: In this double-blind placebo-controlled clinical trial, 80 patients with CSA were divided randomly into two groups (taking 3g MO supplement or placebo daily for 8 weeks). The shortened 21-item version of the depression, anxiety and stress scale (DASS-21) test and Pittsburgh sleep quality index were done before and after the intervention.

Results: At the end of the study, the intervention group receiving MO capsules had a significant reduction in scores of depression, anxiety, stress, and total sleep disturbance, compared with the placebo group (P < 0.05).

Conclusions: The results showed that 8-week supplementation with 3g MO can decrease depression, anxiety, stress, and sleep disorder in patients with CSA.

Javid AZ et al (2018). The effects of Melissa officinalis (lemon balm) in chronic stable angina on serum biomarkers of oxidative stress, inflammation and lipid profile, 27: 785-791. Asia Pac J Clin Nutr.

Summary: The present study showed that Melissa officinalis supplementation has beneficial effects on MDA, PON1, hs-CRP and lipid profiles in patients with chronic stable angina. However, further investigations are required to confirm these results.

Abstract: Background and objectives: Coronary artery disease (CAD) is a major cause of death worldwide. Chronic stable angina (CSA) is the primary sign of CAD. Oxidative stress and inflammation play a substantial role in pathogenesis and progression of CAD. The aim of this study was to investigate the effects of oral administration of powdered Melissa officinalis (MO) on biomarkers of oxidative stress, inflammation, and lipid profile in patients with CSA.

Methods and study design: A randomized, double-blind, placebo-controlled clinical trial was performed in 80 patients with CSA. The subjects were randomly assigned to obtaineither oral MO 3 g/d (n=40) or placebo (n=40) for eight weeks. Anthropometric indices, biomarkers of oxidative stress, inflammation, and lipid profile were evaluated at baseline and post-intervention.

Results: CThe mean serum concentrations of triglycerides, total-cholesterol, LDL-cholesterol, and malondialdehyde (MDA), and high sensitive C-Reactive Protein (hs-CRP) were lower in the intervention group compared with placebo (p<0.01) data-preserve-html-node="true" post intervention. Moreover, the mean serum concentration of paraxonase 1 (PNO1) and HDL-c were higher (p<0.001) data-preserve-html-node="true" in the intervention group compared with the control group.

Conclusions: Oral MO supplementation improves the lipid profile, MDA, hs-CRP, and PNO1 in patients with CSA.

Serra E et al (2018). Antifungal Activity of Commercial Essential Oils and Biocides against Candida Albicans, 7: 15. Pathogens.

Summary: This study showed that all the twelve commercial essential oils, two terpenes and triclosan and CHX had antifungal activity against planktonic C. albicans. Six of these compounds (CHX, cinnamon, E-cinnamaldehyde, linalool, geranium and melissa) were also active against C. albicans biofilms, which are usually challenging to effectively inhibit. Cytotoxicity screening revealed that the commercial essential oils halved fibroblast proliferation at concentrations lower than those required to inhibit C. albicans growth. Further investigation on the effect of these agents is warranted. The antifungal potential of these essential oils could be a future therapeutic for topical candidosis to overcome emerging antifungal drug resistance.

Abstract: Management of oral candidosis, most frequently caused by Candida albicans, is limited due to the relatively low number of antifungal drugs and the emergence of antifungal tolerance. In this study, the antifungal activity of a range of commercial essential oils, two terpenes, chlorhexidine and triclosan was evaluated against C. albicans in planktonic and biofilm form. In addition, cytotoxicity of the most promising compounds was assessed using murine fibroblasts and expressed as half maximal inhibitory concentrations (IC50). Antifungal activity was determined using a broth microdilution assay. The minimum inhibitory concentration (MIC) was established against planktonic cells cultured in a range of concentrations of the test agents. The minimal biofilm eradication concentration (MBEC) was determined by measuring re-growth of cells after pre-formed biofilm was treated for 24 h with the test agents. All tested commercial essential oils demonstrated anticandidal activity (MICs from 0.06% (v/v) to 0.4% (v/v)) against planktonic cultures, with a noticeable increase in resistance exhibited by biofilms (MBECs > 1.5% (v/v)). The IC50s of the commercial essential oils were lower than the MICs, while a one hour application of chlorhexidine was not cytotoxic at concentrations lower than the MIC. In conclusion, the tested commercial essential oils exhibit potential as therapeutic agents against C. albicans, although host cell cytotoxicity is a consideration when developing these new treatments.

Miraj S et al (2017). Melissa officinalis L: A Review Study With an Antioxidant Prospective, 22: 385-394. J Evidence-based Complement & Altern Med.

Summary: In this review regarding its traditional usage, antimicrobial activity (antiparasitic, antibacterial, antiviral, etc.), antispasmodic, insomnia properties were reported. Many studies confirmed the antioxidative effects of Melissa officinalis. Thus, its effect in preventing and treating oxidative stress-related diseases appear reliable. The results of numerous studies on antioxidant or radical scavenging effects may be a basis for future detailed in vivo research on its anti-inflammatory activities. Results showed that more complementary studies in different therapeutic effects are required in clinical trial studies. In addition, more studies are needed to diagnose new chemical compounds in a safe dose that cause its antioxidant activity.

Abstract: Melissa officinalis is a plant cultivated in some parts of Iran. The leaves of lemon balm, Melissa officinalis L (Lamiaceae), are used in Iranian folk medicine for their digestive, carminative, antispasmodic, sedative, analgesic, tonic, and diuretic properties, as well as for functional gastrointestinal disorders. This review article was aimed not only to introduce Melissa officinalis (its growth condition, its chemical compounds, and its traditional usages) but also to overview its antioxidant properties in detail. This review was carried out by searching studies in PubMed, Medline, Web of Science, and IranMedex databases up to 2016. The search terms used were “Melissa officinalis L,” “antioxidant properties,” oxidative stress,” “oxidative damage”, “ROS.” Articles whose full texts were not available were excluded from the study. In this study, firstly, traditional usage of this herb was reviewed, including antimicrobial activity (antiparasitic, antibacterial, antiviral, etc.), antispasmodic, and insomnia properties. Then, its antioxidant properties were overviewed. Various studies have shown that Melissa officinalis L possesses high amount of antioxidant activity through its chemical compounds including high amount of flavonoids, rosmaric acid, gallic acid, phenolic contents. Many studies confirmed the antioxidative effects of Melissa officinalis; thus, its effect in preventing and treating oxidative stress-related diseases might be reliable.

Perez-Sanchez A et al (2016). Lemon balm extract (Melissa officinalis, L.) promotes melanogenesis and prevents UVB-induced oxidative stress and DNA damage in a skin cell model, 84: 169-177. J Dermatol Sci.

Summary: Lemon balm extract (LBE) protects skin cells against UVB-induced cytotoxicity and ROS generation while it decreases UVB-induced DNA damage and the DNA damage response in keratinocytes. LBE promotes melanogenesis in melanoma cells and has the potential to protect human skin against UV-induced damage.

Abstract: Background: Solar ultraviolet (UV) radiation is one of the main causes of a variety of cutaneous disorders, including photoaging and skin cancer. Its UVB component (280-315nm) leads to oxidative stress and causes inflammation, DNA damage, p53 induction and lipid and protein oxidation. Recently, an increase in the use of plant polyphenols with antioxidant and anti-inflammatory properties has emerged to protect human skin against the deleterious effects of sunlight.

Objective: This study evaluates the protective effects of lemon balm extract (LBE) (Melissa Officinalis, L) and its main phenolic compound rosmarinic acid (RA) against UVB-induced damage in human keratinocytes.

Methods: The LBE composition was determined by HPLC analysis coupled to photodiode array detector and ion trap mass spectrometry with electrospray ionization (HPLC-DAD-ESI-IT-MS/MS). Cell survival, ROS generation and DNA damage were determined upon UVB irradiation in the presence of LBE. The melanogenic capacity of LBE was also determined.

Results: RA and salvianolic acid derivatives were the major compounds, but caffeic acid and luteolin glucuronide were also found in LBE. LBE and RA significantly increased the survival of human keratinocytes upon UVB radiation, but LBE showed a stronger effect. LBE significantly decreased UVB-induced intracellular ROS production. Moreover, LBE reduced UV-induced DNA damage and the DNA damage response (DDR), which were measured as DNA strand breaks in the comet assay and histone H2AX activation, respectively. Finally, LBE promoted melanogenesis in the cell model.

Conclusion: These results suggest that LBE may be considered as a candidate for the development of oral/topical photoprotective ingredients against UVB-induced skin damage.

Pourghanbari G et al (2016). Antiviral activity of the oseltamivir and Melissa officinalis L. essential oil against avian influenza A virus (H9N2), 27: 170-178. VirusDis..

Summary: Lemon balm (MOEO) seems to act as natural and novel antiviral substance through the different stages of influenza virus (H9N2) replication. Avian influenza A (AIV) was, also, suppressed with MOEO before cell infection with the direct drug–virus interaction, but not through hemagglutination assay inhibition. Moreover, in accordance to the results, different mechanisms of action seem to be present. Also, a synergistic activity was observed between oseltamivir and MOEO. However, the mechanisms underlying the antiviral efficacy of MOEO against influenza viruses have not been determined completely and it supports the need for further studies.

Abstract: Lemon balm derivatives are going to acquire a novelty as natural and potent remedy for treatment of viral infections since the influenza viruses are developing resistance to the current antivirals widely. Oseltamivir, Melissa officinalis essential oil (MOEO) and their synergistic efficacy against avian influenza virus (AIV) subtype H9N2 were evaluated in vitro in MDCK cells at different time exposure by using TCID50, HA, Real Time PCR and HI assay. The results showed that MOEO could inhibit replication of AVI through the different virus replication phase (P ≤ 0.05). Also, the highest antiviral activity of MOEO was seen when AIV incubated with MOEO before cell infection. The TCID50/ml was reduced 1.3–2.1, 2.3–2.8, 3.7–4.5 log 10 than control group (5.6 log 10), HAU/50 µl was decreased 85–94, 71.4–94, 71.4–94 % and viral genome copy number/µl was brought down 68–95, 90–100, 89.6–99.9 % at pre-infection, post-infection and simultaneous stage, respectively. Hemagglutination inhibition result showed the MOEO was not able to inhibit agglutination of the chicken red blood cell (cRBC). Replication of the AVI was suppressed by the different concentration of oseltamivir completely or near 100 %. Also, oseltamivir showed a synergistic activity with MOEO especially when oseltamivir concentration reduced under 0.005 mg/ml. The chemical composition was examined by GC–MS analysis and Its main constituents were identified as monoterpenaldehydes citral a, citral b. In conclusion, the findings of the study showed that lemon balm essential oil could inhibit influenza virus replication through different replication cycle steps especially throughout the direct interaction with the virus particles.

Rabbani M et al (2016). Assessment of the antimicrobial activity of Melissa officinalis and Lawsonia inermis extracts against some bacterial pathogens, 25: 59-65. Comp Clin Pathol.

Summary: This study established there is a synergism for the combination of M. officinalis extract and alcoholic extract of L. inermis powder on S. aureus. Overall, the results suggest that both extracts were capable of inhibiting the growth of antibiotic-resistant microorganisms involved in causing burn wound infections although clinical evaluation must be considered for realizing the possibility of using these extracts in skin infection.

Abstract: The postburn infections especially antibiotic-resistant bacterial infections have been recognized as a significant and major public health problem. Staphylococcus aureus, Escherichia coli, Acinetobacter, Klebsiella pneumoniae, and Pseudomonas aeruginosa are among very important bacterial pathogens isolated from postburn infections. The present study has evaluated the antimicrobial activity of some plant extracts (Melissa officinalis and Lawsonia inermis) against some bacterial pathogens causing burn wound infection. The minimal inhibitory concentration (MIC) and the minimal bactericidal concentration (MBC) of the extracts were determined using the microdilution method. Aqueous and alcoholic extracts of L. inermis leaves or powder and hydro-alcoholic extract of M. officinalis were studied. All extracts had the highest antibacterial activity against S. aureus. Although there was no significant difference between antibacterial activity of L. inermis leaves and powder extracts, significant difference was observed between alcoholic and aqueous extracts of this plant. In addition, the results showed that alcoholic extract of L. inermis powder and M. officinalis extracts showed synergistic effect. Overall, these findings support the potential benefits of M. officinalis and L. inermis extracts in the treatment of burn infections.

Astani A et al (2014). Attachment and penetration of acyclovir-resistant herpes simplex virus are inhibited by Melissa officinalis extract, 28: 1547-1552. Phytother Res.

Summary: The Melissa extract and rosmarinic acid inhibited HSV-1 attachment to host cells in a dose-dependent manner for acyclovir-sensitive and acyclovir-resistant strains. Penetration of herpes viruses into cells was inhibited by Melissa extract at 80% and 96% for drug-sensitive and drug-resistant viruses, respectively. Melissa extract exhibits low toxicity and affects attachment and penetration of acyclovir-sensitive and acyclovir-resistant HSVs in vitro.

Abstract: Medicinal plants are increasingly of interest as novel source of drugs for antiherpetic agents, because herpes simplex virus (HSV) might develop resistance to commonly used antiviral drugs. An aqueous extract of Melissa officinalis and the phenolic compounds caffeic acid, p‐coumaric acid and rosmarinic acid were examined for their antiviral activity against herpes simplex virus type 1 (HSV‐1) acyclovir‐sensitive and clinical isolates of acyclovir‐resistant strains in vitro. When drugs were added during the intracellular replication of HSV‐1 infected cells, no antiviral effect was observed by plaque reduction assay. However, Melissa extract interacted directly with free viral particles of two acyclovir‐resistant HSV strains at low IC50 values of 0.13 and 0.23 µg/mL and high selectivity indices of 2692 and 1522, respectively. The Melissa extract and rosmarinic acid inhibited HSV‐1 attachment to host cells in a dose‐dependent manner for acyclovir‐sensitive and acyclovir‐resistant strains. These results indicate that mainly rosmarinic acid contributed to the antiviral activity of Melissa extract. Penetration of herpes viruses into cells was inhibited by Melissa extract at 80% and 96% for drug‐sensitive and drug‐resistant viruses, respectively. Melissa extract exhibits low toxicity and affects attachment and penetration of acyclovir‐sensitive and acyclovir‐resistant HSVs in vitro

de Sousa AC et al (2010). Melissa officinalis L. essential oil: antitumoral and antioxidant activities, 56: 677-681. J Pharm Pharmacol.

Summary: In addition to establishing the best conditions to obtain oil from Melissa officinalis, the results demonstrated this oil has antioxidant and tumoricidal activity indicative of its potential use for cancer treatment and/or prevention. Experiments are necessary to identify which of the oil components are responsible for these activities.

Abstract: Melissa officinalis L (lemon balm) is a traditional herbal medicine used widely as a mild sedative, spasmolytic and antibacterial agent. This paper focuses on the analysis of the chemical composition and the biological activities of M. officinalis essential oil obtained under controlled harvesting and drying conditions. An in‐vitro cytotoxicity assay using MTT indicated that this oil was very effective against a series of human cancer cell lines (A549, MCF‐7, Caco‐2, HL‐60, K562) and a mouse cell line (B16F10). This oil possessed antioxidant activity, as evidenced by reduction of 1,1‐diphenyl‐2‐picryl‐hydrazyl (DPPH). These results pointed to the potential use of M. officinalis essential oil as an antitumoral agent.

Schnitzler P et al (2008). Melissa officinalis oil affects infectivity of enveloped herpesviruses, 15: 734-740, Phytomedicine.

Summary: The study’s results indicate that lemon balm oil affected viruses before adsorption and in a different manner than acyclovir. It remains to be determined whether the inhibitory effect of the oil is due to binding to viral proteins involved in host cell adsorption and penetration or is due to damage to the virions, possibly their envelopes, thereby impairing their ability to infect host cells. Lemon balm oil possess antiviral activity against herpes simplex virus in vitro. The topical use of balm for the treatment of HSV infections seems promising, especially for those patients who experience frequent recurrences.

Abstract: Extracts and essential oils of medicinal plants are increasingly of interest as novel drugs of antimicrobial and antiviral agents, since herpes simplex virus (HSV) might develop resistance to commonly used antiviral agents. Melissa officinalis essential oil was phytochemically examined by GC-MS analysis, its main constituents were identified as monoterpenaldehydes citral a, citral b and citronellal. The antiviral effect of lemon balm oil, the essential oil of Melissa officinalis, on herpes simplex virus was examined. The inhibitory activity against herpes simplex virus type 1 (HSV-1) and herpes simplex virus type 2 (HSV-2) was tested in vitro on monkey kidney cells using a plaque reduction assay. The 50% inhibitory concentration (IC50) of balm oil for herpes simplex virus plaque formation was determined at high dilutions of 0.0004% and 0.00008% for HSV-1 and HSV-2, respectively. At noncytotoxic concentrations of balm oil, plaque formation was significantly reduced by 98.8% for HSV-1 and 97.2% for HSV-2, higher concentrations of lemon balm oil abolished viral infectivity nearly completely. In order to determine the mode of antiviral action of this essential oil, time-on-addition assays were performed. Both herpesviruses were significantly inhibited by pretreatment with balm oil prior to infection of cells. These results indicate that Melissa oil affected the virus before adsorption, but not after penetration into the host cell, thus lemon balm oil is capable of exerting a direct antiviral effect on herpesviruses. Considering the lipophilic nature of lemon balm essential oil, which enables it to penetrate the skin, and a high selectivity index, Melissa officinalis oil might be suitable for topical treatment of herpetic infections.

Mimica-Dukic N et al (2004). Antimicrobial and Antioxidant Activities of Melissa officinalis L. (Lamiaceae) Essential Oil, 52: 2485-2489. J Agric Food Chem.

Summary: The study concluded that significant antimicrobial, particularly antibacterial, activity was found in the investigated lemon oil. The oil exhibited high radical scavenging capacity, which was found to be in correlation to the content of mainly monoterpene ketones and aldehydes. Also, a very strong protective activity of the oil in lipid peroxidation processes, especially against hydroxyl radicals formed in the Fenton reaction, was recorded. These results indicate the oil could serve as safe antioxidant and antiseptic supplements in preventing deterioration of foodstuff and beverage products and pharmaceuticals.

Abstract: The present study describes antimicrobial and free radical scavenging capacity (RSC) together with the effects on lipid peroxidation (LP) of Melissa officinalis essential oil. The chemical profile of essential oil was evaluated by the means of gas chromatography−mass spectrometry (GC-MS) and thin-layer chromatography (TLC). RSC was assessed measuring the scavenging activity of essential oil on the 2,2-diphenyl-1-picrylhydrazyl (DPPH•) and OH• radicals. The effect on LP was evaluated following the activities on Fe2+/ascorbate and Fe2+/H2O2 systems of induction. The antimicrobial activity was tested against 13 bacterial strains and six fungi. The examined essential oil exhibited very strong RSC, reducing the DPPH radical formation (IC50 = 7.58 μg/mL) and OH radical generation (IC50 = 1.74 μg/mL) in a dose-dependent manner. According to the GC-MS and TLC (dot-blot techniques), the most powerful scavenging compounds were monoterpene aldehydes and ketones (neral/geranial, citronellal, isomenthone, and menthone) and mono- and sesquiterpene hydrocarbons (E-caryophyllene). Very strong inhibition of LP, particularly in the Fe2+/H2O2 system of induction (94.59% for 2.13 μg/mL), was observed in both cases, also in a dose-dependent manner. The most effective antibacterial activity was expressed on a multiresistant strain of Shigella sonei. A significant rate of antifungal activity was exhibited on Trichophyton species.