Melissa officinalis L. (Lamiaceae) (lemon balm) is used in folk medicine for nervous complaints, lower abdominal disorders and, more recently, for treating Herpes simplex lesions. In this work the antiviral activity of a hydroalcoholic extract of lemon balm leaves against the Herpes simplex virus type 2 (HSV-2) was assessed by the cytopathic effect inhibition assay on Vero cells (ATCC CCL-81), in comparison with acyclovir. The cytotoxicity of the extract on Vero cells was previously tested by evaluating the cellular death and was confirmed by the Trypan blue test. Lemon balm showed to reduce the cytopathic effect of HSV-2 on Vero cells, in the range of non-toxic concentrations of 0.025-1 mg mL(-1) (with reference to the starting crude herbal material). The maximum inhibiting effect (60%) was obtained with 0.5 mg mL(-1). The viral binding assay showed that the extract does not prevent the entry of HSV-2 in the cells, thus suggesting a mechanism of action subsequent to the penetration of the virus in the cell. The extract was also chemically characterised by NMR and HPLC analysis; it showed to contain cinnamic acid-like compounds, mainly rosmarinic acid (4.1% w/w). Our experiments support the use of lemon balm for treating Herpes simplex lesions and encourage clinical trials on this medicinal plant.

Nigella sativa seeds have wide therapeutic effects and have been reported to have significant effects against many ailments such as skin diseases, jaundice, gastrointestinal problems, anorexia, conjunctivitis, dyspepsia, rheumatism, diabetes, hypertension, intrinsic hemorrhage, paralysis, amenorrhea, anorexia, asthma, cough, bronchitis, headache, fever, influenza and eczema. Thymoquinone (TQ) is one of the most active constituent and has different beneficial properties. Focus on antimicrobial effects, different extracts of N. sativa as well as TQ, have a broad antimicrobial spectrum including Gram-negative, Gram-positive bacteria, viruses, parasites, schistosoma and fungi. The effectiveness of N. sativa seeds and TQ is variable and depends on species of target microorganisms. The present review paper tries to describe all antimicrobial activities that have been carried out by various researchers.