Antibacterial Activity of Red Onion and White Ginger Extract Combinations Against Staphylococcus aureus In Vitro

Abstract

Rhinosinusitis is an inflammatory disease of the nose and paranasal sinuses in which Staphylococcus aureus is a frequent causative pathogen. Rising antibacterial resistance has prompted interest in plant-derived agents such as red onion and white ginger, which contain flavonoids, alkaloids, saponins, terpenoids, and essential oils with reported antimicrobial activity. This study evaluated the in vitro antibacterial activity of combined red onion (Allium cepa L.) and white ginger (Zingiber officinale Roscoe) ethanol extracts against S. aureus. Extracts were prepared in 96% ethanol by maceration and combined at ratios of 25%:75%, 50%:50%, and 75%:25% (red onion:white ginger); 100% single extracts were also tested. Antibacterial activity was assessed using the agar well diffusion method on Mueller–Hinton agar seeded with S. aureus (0.5 McFarland). Ciprofloxacin 50 µg/mL and dimethyl sulfoxide (DMSO) served as positive and negative controls, respectively. Inhibition zones were measured in millimetres and analysed using one-way ANOVA followed by the Games–Howell test. The extract combinations produced mean inhibition zones ranging from 2.98 to 7.80 mm. The 75%:25% combination yielded the largest inhibition zone (7.80 ± 0.26 mm), whereas the 25%:75% combination produced the smallest (2.98 ± 1.71 mm). Ciprofloxacin generated a markedly larger inhibition zone (29.50 ± 1.32 mm), while DMSO showed no inhibition. Statistical analysis showed significant differences between most extract combinations and the controls (p < 0.05), except for the 25%:75% combination versus the negative control. In conclusion, combined red onion and white ginger ethanol extracts exhibit modest in vitro antibacterial activity against S. aureus, with the 75%:25% ratio being the most active, although still far weaker than ciprofloxacin.