CONICET | Buscador de Institutos y Recursos Humanos

Aims: To study the antimicrobial activityof naringin, a flavonoidextracted fromcitrus industrywaste, andnaringin derivatives (naringenin, prunin and alkyl pruninesters) againstpathogenic bacteria such as L. monocytogenes, E. coli O157:H7 and S.aureus. Therelationship betweenthe structureof the chemical compoundsand theirantagonistic effectwas also analyzed. Methods and Results: The agar dilution technique and direct contact assaying were applied. Naringenin, prunin and naringin showed no antimicrobialactivity at a concentration of 0.25 mM. Similarly, fattyacids with a chain length betweenC2 and C18 showed no antimicrobialactivity atthe same concentration. However, prunin-6´´-O-acyl esters presented high antibacterial activity, mainlyagainst Gram-positive strains. This activityincreased withincreasing chainlength (up to10-12 carbonatoms). Alkyl prunin esters with 10-12 carbon atoms diminished viability of L. monocytogenes by about 3 log orders and S. aureus 6 log orders after 2 h of contact at 37 ºC and at a concentration of 0.25 mM. The compounds examined were not effective against any of the Gram-negative strains assayed, even at the highest concentration. Conclusions: Addition of sugars to the aglycone did notenhance itsantimicrobial activity. Attachment of a saturated aliphatic chain with 10-12 carbon atoms to the A ring of the flavonoid (or to sugars attached to this ring), seems to be the most promising modification. In conclusion, alkylprunin esterswith a chain length of C10-C12 have promising features as antimicrobial agentsdue to their high anti-listerial and anti-staphylococcal activity. Significance and impact of the study: This study shows that it is possible to obtain naringin derivatives with important antimicrobial activity, especially against Gram-positive pathogenic bacteria. It also provides guidelines on the structural modifications in similar molecules to enhance antimicrobial activity.