Inhibition of Staphylococcus aureus and methicillin-resistant S. aureus by Terminalia arjuna fruit extract and its synergistic interaction with ampicillin

Terminalia arjuna is in the Combretaceae family. Its fruit is a plant ingredient in Thai traditional formulas for treating phlegm and gastrointestinal tract diseases. A prior investigation demonstrated that T. arjuna bark extracts exhibit strong inhibitory effects against Staphylococcus aureus [ 1 ]. This research aimed to examine the antibacterial efficacy of T. arjuna fruit extract against S. aureus and methicillin-resistant S. aureus (MRSA). Furthermore, a study examines the interaction between T. arjuna extract and ampicillin in inhibiting S. aureus and MRSA. The findings indicated that the ethanolic extract of T. arjuna fruit inhibited S. aureus and MRSA, exhibiting a minimum inhibitory concentration (MIC) of 0.625 mg/mL. Ampicillin demonstrated an inhibitory action against S. aureus and MRSA, with MIC values of 0.078 and 200 μg/mL, respectively. Additionally, the co-incubation of T. arjuna fruit extract with ampicillin had a synergistic effect in vitro against MRSA, providing a FIC index of 0.375 [ 2 ]. Conversely, they exhibited indifference to inhibiting S. aureus , indicated by a FIC value exceeding 0.5. The plant extract examined in this study may contain components that inhibit the resistance mechanism of ampicillin. The chemical components of T. arjuna fruit extract were studied. It comprised two hydrolyzable tannins, namely chebulagic acid and gallic acid, with respective contents of 18.65 and 1.48% w/w. Hydrolyzable tannin has been documented to block efflux pumps and demonstrate a synergistic impact with β-lactams against MRSA isolates [ 3 ]. T. arjuna may be used together with β-lactam antibiotics to combat antibiotic-resistant microorganisms. Publication History Article published online: 05 March 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany