Lemon balm (Melissa officinalis, Lamiaceae) is a plant native to the eastern Mediterranean and western Asia that has been used traditionally as a spice, tea, and medicine. Modern pharmacological studies have reported lemon balm to possess antioxidant and antimicrobial properties. The purpose of this study was to investigate how essential oil composition, especially rosmarinic acid content and antioxidant activity, changes between lemon balm subspecies, plant parts, and harvests.

Central European climate conditions allow for permanent lemon balm fields with multiple yearly harvests. The 28 lemon balm accessions analyzed in this study comprised two subspecies, officinalis (MOFF) and altissima (MALT). They were planted in March 2008 at the Leibniz Institute of Plant Genetics and Crop Plant Research (IPK) in Gatersleben, Germany, and then harvested in June and August 2013. To procure samples, the plants were dried, separated into leaves and stems, and then hydrodistilled. Gas chromatography/mass spectrometry (GC/MS) and…