Effect of Red Onion (Allium cepa var ascalonicum) Skin Ethanolic Extract on the Motility and the Adhesion Index of Pseudomonas aeruginosa and Macrophage Phagocytosis Index

Abstract

Red onion skin (Allium cepa var ascalonicum) contains various ingredients that may function as antibacterial agents against microorganisms, as well as anti-inflammatory and immunomodulator agents for host cells, such as macrophages. Pseudomonas aeruginosa found in the oral cavity is commensal bacteria that may turn into opportunistic pathogen by utilizing its virulence factors such as motility and adhesion to the host cell. The purpose of this study was to investigate the effect of red-onion-skin ethanolic extract towards P. aeruginosa ATCC 9027 on the motility and adhesion ability, furthermore, to know its effect on the macrophage phagocytosis. The research was conducted into three parts of experiment using red-onionskin ethanolic extract. Extract-induced bacterial motility test was carried out on semi-solid media, stained using 0.1% crystal violet, then the radial length of the bacterial movement was measured. The bacterial adhesion index to buccal cells was calculated after incubated for two hours and stained with Gram stain. Phagocytic activity of the host cells on P. aeruginosa was done by exposing the extract to the mouse peritoneal macrophages, then the phagocytosed bacteria were counted after Giemsa staining. Statistical test results from the three experiments showed significant differences between the test groups compared to the control groups (p <0.05). It was concluded that the red onion-skin ethanolic extract not only affects P. aeruginosa by reducing swarming motility and preventing bacterial adhesion to buccal epithelial cells, but also induces the host cells by increasing the ability of macrophage phagocytosis to these bacteria.

Antimicrobial Properties of Newly Developed Silver-Enriched Red Onion–Polymer Composites

“…It is to point out that red onion peel extract itself (the main bioactive agents are phenolic compounds) or in combination with silver nanoparticles provides inhibition properties against different bacteria as was shown by several authors: Streptococcus agalactiae (Gram-positive), Pseudomonas aeruginosa (Gram-negative), Salmonella typhimurium (Gram-negative), and Staphylococcus aureus (Gram-positive) [63]. The antimicrobial compounds made of red onion peel have various mechanisms to inhibit bacteria: inhibition of phagocytosis in macrophages; increasing the production of Interleukin-12 (IL-12) by quercetin and thus increasing the phagocytic ability of macrophages; altering the membrane potential of bacterial cells and disrupting their performance; and binding to bacteria pili and inhibiting bacterial adhesion [64]. The red onion skin extract also indicates antifungal properties against some fungi, however to a lesser extent and with lower effectiveness as compared with bacteria [9,65,66].…”