Synergistic effects of essential oils and phenolic extracts on antimicrobial activities using blends of Artemisia campestris, Artemisia herba alba, and Citrus aurantium.

This study explores the synergistic antibacterial effects of essential oils (EOs) and phenolic extracts from three plants against foodborne pathogenic bacteria. The present work aimed to investigate the synergistic effects of the binary and the ternary combinations of extracts using different blend proportions of the following plant extracts: Artemisia campestris (AC), Artemisia herba alba (AHA), and Citrus aurantium (CA). The antimicrobial activities of EOs and phenolic extracts were determined and evaluated against five strains. For the EOs, the results of the DIZ showed the existence of synergism for different combinations of binary blends, such as AC/AHA or AHA/CA against Escherichia coli, and AC/CA against Enterobacter faecalis. In addition, ternary blends of AC:AHA:CA at a ratio of 1/6:2/3:1/6 exhibited a synergy effect, as measured by the CI, against E. coli. On the other hand, for the phenolic extracts, synergistic effects were noticed for binary blends of AC/CA at different ratios against E. coli, E. faecalis, and Pseudomonas aeruginosa strains. Similarly, ternary blends of phenolic extracts presented synergy against E. coli, E. faecalis, P. aeruginosa strains, and even C. albicans. In this case, the blending ratios were crucial determining factors for maximizing the synergy effect. The study established that the proportion of a single drug could play an essential role in determining the bioefficacy of a drug combination treatment. Therefore, the results showed the importance of studying the modulation of antibacterial activities based on the proportions of extracts in the mixture and finding the range of proportions (as determined by SLMD) that have a synergistic/additive/antagonistic effect with no or low side effects, which can be used in a food preservation system.

In vitro study of the antioxidant, sun factor protection, antimicrobial, and antifungal activities with molecular docking of methanolic extracts from leaves and fruit of Phillyrea angustifolia L.

This study aimed to evaluate the potential therapeutic effects of Phillyrea angustifolia L leaves and fruits from Algeria. The total phenolic and flavonoid contents, sun protection factor, antimicrobial, antifungal, and antioxidant activities such as DPPH, ABTS, FRAP, CUPRAC, and o-phenanthroline reduction were determined. The findings of the comparative analysis revealed that the leaves contained higher levels of total phenolic content (TPC) and flavonoid content (TFC) compared to the fruit, indicating their maximum antioxidant potential. TPC values for leaves ranged from 528.411 ± 9.94 to 816.352 ± 5.09 µg EAG/mg of dry extract, while for fruits, it ranged from 378.215 ± 5.26 to 579.392 ± 14.2 µg EAG/mg extract/ml. Similarly, TFC values for leaves varied from 65.833 ± 9.42 to 147.986 ± 5.59 µg EAG/mg of dry extract, and for fruits, it ranged from 45.486 ± 5.00 to 90.208 ± 6.77 µg EAG/mg extract/ml. Moreover, both leaves and fruit extracts showed significant growth inhibition against Staphylococcus aureus and Enterococcus faecalis, with the highest activity against Staphylococcus aureus, followed by Escherichia coli. The sun protection factor (SPF) values of both leaves and fruits extracts are close to the values of standard sunscreen VICHY. In addition, molecular docking studies identified promising compounds, including Demethyloleuropein, Luteolin-7-O-glucoside, Apigenin 7-Glucoside, Oleuropein, Pinoresinol, and Syringaresinol monoglucopyranoside of leaves from P. angustifolia L, these compounds are showing a better binding affinity than native ligands against Rhomboid protease GlpG from E. coli, the same thing about luteolin-7-O-glucoside and apigenin 7-glucoside exhibited similar binding free energy values to the target protein S. aureus sortase A. The study suggests that leaves and fruits of Phillyrea angustifolia L could be valuable sources for developing drugs against pathogenic oral yeasts, Gram-negative and Gram-positive bacteria. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-023-03877-5.