Essential oils from 9 exotic and endemic medicinal plants from Mauritius shows in vitro antibacterial and antibiotic potentiating activities

Abstract

Essential oils (EOs) extracted from botanical resources have greatly been appraised as antimicrobials against a broad spectrum of microorganisms. A panoply of experimental studies have pointed out the immense potency of EOs as natural antimicrobial agents at relatively low doses; largely attributed to the synergistic interactions of various bioactive components. In the present study, 10 EOs prepared from two endemic (Pittosporum senacia Putterl. subsp. Senacia and Syzygium coriaceum J. Bosser & J. Guého) and seven exotic (Cinnamomum camphora (L.) Nees & Eberm, Citrus aurantium L., Curcuma longa L, Morinda citrifolia L., Petroselinum crispum (Mill.) Fuss, Plectranthus amboinicus (Lour.) Sprengel and Syzygium samarangense (Blume) Merr. & L. M. Perry) aromatic medicinal plants from Mauritius, were screened for their growth inhibitory activities against eight bacteria (ATCC strains and clinical isolates) using broth microdilution techniques. The EOs were found to possess varying degree of antibacterial potency. The most active EOs were found to have minimum inhibitory concentration (MIC) of 0.25–4 mg/mL and minimum bactericidal concentration (MBC) of 0.25–16 mg/mL. In particular, at its MIC values, P. amboinicus EO showed bactericidal effects against four strains. However, all tested bacteria were insensitive to P. senecia and C. aurantium fruit peel EOs. Bacillus spizizenii was found to be the most susceptible strain to the active EOs. Additionally, P. amboinicus and the two Syzygium spp. EOs showed antibiotic potentiating activities. Mostly synergistic and partial synergistic actions of the EOs in combination with the conventional antibiotics (streptomycin, chloramphenicol and ciprofloxacin) at a ratio of 1:1 were obtained against the tested bacteria. Thus, results from this study highlighted the antibacterial potential and the efficacy of the most active EOs as antibiotic potentiating agents that could potentially be used in combinational therapies along with conventional antibiotics for a synergistic approach in the treatment/management of clinically relevant bacterial infections.