Abstract
The ever-growing demand for new and safe antimicrobials for the prevention and treatment of clinical and foodborne pathogens has stimulated considerable research interest into Lamiaceae plants as natural antimicrobial agents and food preservatives. Among them, lemon balm (Melissa officinalis L.) has been recently emerged as a promising food additive owing to its outstanding antimicrobial and food preserving capacities, particularly of its polar extracts and aqueous decoctions. Consequently, in this work, investigation of the polar/hydrophilic antimicrobial constituents of the medicinally and culinary used aerial parts of lemon balm has resulted in the isolation and identification of three new ursene triterpene glycosides; melissiosides A-C (1-3), along with the known triterpenoidal glycoside 23-sulfate ester of niga-ichigoside F1 (4). Compounds 1-4 demonstrated varied antimicrobial activities in comparison with the tested antimicrobial standards using the agar diffusion assay, especially against Gram-negative bacteria and yeast. These results highlight the potential of lemon balm as a promising source of natural antimicrobials and alternative food preservatives, which largely contribute to its nutritherapeutic, pharmaceutical, and food-related applications in the future. (C) 2019 SAAB. Published by Elsevier B.V. All rights reserved.