Chemical composition, biological activities, and surface tension properties of Melissa officinalis L. essential oil

: Lemon balm ( Melissa officinalis L.) is a plant of the family Lamiaceae. The present study aimed to determine the chemical composition of the lemon balm essential oil grown in Northeastern Bulgaria, to perform a comparative analysis of its antimicrobial activity with that of citral, and to determine its surface tension properties. The main compounds of the essential oil (concentration above 3%) were: β-caryophyllene (20.45%), geranial (19.74%), neral (15.81%), germacrene D (11.50%), (R)-(+)-citronellal (3.07%), and geranyl acetate (3.04%). The antibacterial activity of the essential oil was weak against the tested gram-negative and gram-positive bacteria. Exceptions were observed for Listeria monocytogenes and Salmonella enterica subsp. Enterica serovar Abony. Citral exhibited higher antimicrobial activity against investigated gram-positive bacteria compared to gram-negative. The surface tension of the essential oil was determined at six different temperatures (6, 10, 15, 20, 25, and 3 ℃ ). The energy presented minimal differences from 124.52 to 125.57 mN/m at different temperatures. Surface heat capacity was between 10492.11 and 11394.17 N/(m.K).