Saponins and their synergistic antibacterial activity with traditional antibiotics against Staphylococcus aureus and Escherichia coli: Review

Abstract

The rapidly increasing rate of antimicrobial drug resistance requires novel ways of treating infections. Harnessing the synergistic effect of the combined use of conventional antibiotics with naturally occurring antimicrobial substances is an emerging frontier in the fight against the spread of antimicrobial resistance. Synergy is measured by using the fractional inhibitory concentration index (FICI). Saponins are secondary metabolites produced by plants and they help defend the plant against natural stressors. This article aims to review the synergistic activity of saponins with traditional antibiotics. Thirteen plants were included in the final review, out of which eight species showed a FICI score below 0.5 (synergistic). These were _Jatropha curcas_, _Melanthera elliptica_, _Glycine max, Tribulus terrestris, Salvia officinialis, Spergulara marginata, Paromychia argenetea_, and _Syzigium aromaticum_. The highest degree of synergy was observed against S. aureus with the combined use of J_atropha curcas_ and rifampicin (FICI 0.04), _Melanthera elliptica_ and tetracycline (0.05), and _Glycine max_ and benzylpenicillin (0.22). In addition, a high degree of synergy against E. coli was observed with the combined use of _Melanthera elliptica_ and tetracycline (0.07), _Jatropha curcas_ and rifampicin (0.08), _Salvia officinialis_ and amoxicillin (0.38).