Page 17 Introduction Melissa officinalis Labiatae is an edible herb native to the Mediterranean and Eastern Europe. It is one of the oldest and still most popular medicinal plants. Lemon Balm is the common name of Melissa officinalis. This plant naturalizes easily, reproduces by underground stems and grows up to 45 cm in height. The herbal tea can be used therapeutically for soothing stomach cramps, indigestion and nausea. It is also lightly stimulating and a good tea to drink when studying. Melissa should be distilled before it flowers. The entire above ground plant is taken, the heavier stems discarded and steam-distilled to obtain the hydrosols. The major components of lemon balm are cafeic acid, the flavonoids: luteolin-7-O-glucoside, isoquercitrin, apigenin-7-O-glucoside, ahe essential oil (0.19%) from the flowers contains various aldehydes including citronellal (22-36%), citral (11-26%), β-caryophyllene (10-15%), and germacrene D (10-20%).(Mulkens & Kapetanidis, 1987) The essential oil is hypotensive, a calming sedative and anti-inflammatory. It is used for insomnia, hysteria and irritability by inhalation and will relieve a cold sore if applied externally.(Wu, Hong, Klauck, Lin, & Eferth, 2015) Rosmarinic acid has been known as ‘’Labiatengerbstof’’ even before its chemical structure was elucidated. It is a tannin-like compound, described as a depside of cafeic acid. Originally identified in rosemary (Rosmarinus officinalis L.), the structure was elucidated as an ester of cafeic acid and 3-(3,4-dihydroxyphenyl)lactic acid. (Sanbongi et al., 2003; Youn et al., 2003) The compound has been reported to occur in several taxonomically non-related families of the plant kingdom. It has attracted much attention since it was identified to be the main compound responsible for the antiviral activity of lemon balm in treating Herpes simplex.(Sanchez-Medina et al., 2007) Rosmarinic acid is defined as a phenolic acid or an ester of cafeic acid. It has antioxidant, anti-inflammatory and antimicrobial activities.(Zhou et al., 2016) Its antioxidant activity is stronger than that of vitamin E and helps to prevent cell damage caused by free radicals; thereby reducing the risk for cancer and arthrosclerosis. It is also used for its anti-allergic activity, and unlike antihistamines, rosmarinic acid prevents the activation of immune responder cells, which cause swelling and fluid formation. Moreover, rosmarinic acid is used to treat peptic ulcers, arthritis, cataract, cancer, rheumatoid arthritis and bronchial asthma.(Ferreira Jde et al., 2015; Kantar Gok et al., 2015; Mushtaq et al., 2015) Also, it sustains normal basophile, cytokine and eosinophile American Research Journals of Chemistry Volume 1, Issue 1, pp: 17-23 Research Article Open Access www.arjonline.org Isolation and Structural Elucidation of Rosmarinic Acid by Nuclear Magnetic Resonance Spectroscopy Elias Akoury Faculty of Chemistry and Pharmacy Ludwig-Maximilians-University Munich, Munich, Germany eliasakoury@icloud.com Abstract: Lemon balm is a herbal tea known for its therapeutic practice in soothing stomach cramps, indigestion and nausea. One of its chemical components is rosmarinic acid, known for its anti-inflammatory and antiviral activities in treating Herpes simplex. Despite the eforts, recovery and purification of rosmarinic acid from Lemon balm in high yields has not been entirely successful. Here, we report the aqueous extraction of rosmarinic acid from dried leaves of Lemon balm using Soxhlet distillation after optimizing the conditions with various organic solvents. We have isolated rosmarinic acid under optimum process conditions and high yield (96%) and elucidated its structure by NMR spectroscopy. Keywords:Rosmarinic acid, Lemon Balm, Natural Product Isolation, NMR spectroscopy