Antibacterial and Antibiofilm Effects of Allelopathic Compounds Identified in Medicago sativa L. Seedling Exudate against Escherichia coli

• Published in: Molecules (Basel, Switzerland) Vol. 28; no. 6; p. 2645
• Main Authors: Abouzeid, Sara, Beutling, Ulrike, Elekhnawy, Engy, Selmar, Dirk
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 14.03.2023; MDPI
• Subjects: Alfalfa; alfalfa seed exudates; allelopathic; Allelopathy; Antibacterial activity; Antimicrobial activity; Barley; Biofilms; Canavanine; Canavanine - analysis; Canavanine - pharmacology; dipeptides; E coli; Escherichia coli; Exudates; Exudates and Transudates; Exudation; Flavonoids; Flowers & plants; Food contamination & poisoning; Gene expression; Germination; hyperoside; Ionic mobility; Liquid chromatography; Mass spectrometry; Mass spectroscopy; Medicago sativa; Medicago sativa - chemistry; Minimum inhibitory concentration; Pathogens; Plant species; Scientific imaging; Seedlings; Seeds; Seeds - chemistry; dipeptides; allelopathic; hyperoside; flavonoids; canavanine; alfalfa seed exudates
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules28062645

In this study, the allelopathic properties of L. (alfalfa) seedling exudates on the germination of seeds of various species were investigated. The compounds responsible for the allelopathic effects of alfalfa were identified and characterized by employing liquid chromatography ion mobility high-resolution mass spectrometry. Crude exudates inhibited the germination of seeds of all various plant species tested. Overall, nine compounds in alfalfa were identified and quantified. The most predominant compounds were a hyperoside representing a flavonoid glucoside, the non-proteinogenic amino acid canavanine, and two dipeptides, identified as H-Glu-Tyr-OH and H-Phe-Glu-OH. The latter corresponds to the first finding that dipeptides are exuded from alfalfa seedlings. In addition, the antibacterial and antibiofilm activities of alfalfa exudate and its identified compounds were elucidated. Both hyperoside and canavanine revealed the best antibacterial activity with minimum inhibitory concentration (MIC) values that ranged from 8 to 32 and 32 to 256 µg/mL, respectively. Regarding the antibiofilm action, hyperoside and canavanine caused a decline in the percentage of isolates that possessed a strong and moderate biofilm-forming potential from 68.42% to 21.05% and 31.58%, respectively. Studies on their inhibiting effects exhibit that these major substances are predominantly responsible for the allelopathic and antimicrobial effects of the crude exudates.