Plants are considered a wealthy resource of novel natural drugs effective in the treatment of multidrug-resistant infections. Here, a bioguided purification of Ephedra foeminea extracts was performed to identify bioactive compounds. The determination of antimicrobial properties was achieved by broth microdilution assays to evaluate minimal inhibitory concentration (MIC) values and by crystal violet staining and confocal laser scanning microscopy analyses (CLSM) to investigate the antibiofilm capacity of the isolated compounds. Assays were performed on a panel of three gram-positive and three gram-negative bacterial strains. Six compounds were isolated from E. foeminea extracts for the first time. They were identified by nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS) analyses as the well-known monoterpenoid phenols carvacrol and thymol and as four acylated kaempferol glycosides. Among them, the compound kaempferol-3-O-α-L-(2″,4″-di-E-p-coumaroyl)-rhamnopyranoside was found to be endowed with strong antibacterial properties and significant antibiofilm activity against S. aureus bacterial strains. Moreover, molecular docking studies on this compound suggested that the antibacterial activity of the tested ligand against S. aureus strains might be correlated to the inhibition of Sortase A and/or of tyrosyl tRNA synthase. Collectively, the results achieved open interesting perspectives to kaempferol-3-O-α-L-(2″,4″-di-E-p-coumaroyl)-rhamnopyranoside applicability in different fields, such as biomedical applications and biotechnological purposes such as food preservation and active packaging.

The employment of chemical agents in the food industry is raising several concerns by consumers and is leading to an increasing interest in natural food preservatives. Among alternatives, host defense peptides (HDPs) have attracted great interest for their ability to preserve food samples from contamination without altering their quality, taste, and organoleptic properties. Recently, we evaluated the applicability of ApoB‐derived peptides as novel food bio‐preservatives and demonstrated their ability to prevent chicken meat sample contamination when immobilized on chitosan films. To perform a further step towards the applicability of these peptides in the food field, here we evaluated peptides biosafety and digestibility. To do this, we used a multidisciplinary approach including the evaluation of the peptides' toxicity and antimicrobial activity, the analysis of resistance phenotype development, an in silico prediction of the peptides' susceptibility to proteases and the evaluation of the peptides' stability in simulated gastric and intestinal fluids. ApoB‐derived peptides were found to be nontoxic when tested on human gastric carcinoma cells SNU‐1 and on human colon‐rectal adenocarcinoma cells HT‐29, and not to induce resistance phenotype in Salmonella strains. Bioinformatic analyses showed that the peptides are susceptible to several proteases, as also confirmed by experiments in simulated gastric and intestinal fluids. Altogether these findings open interesting perspectives to the future applicability of ApoB‐derived peptides as novel food biopreservatives.