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Background: Recent declines in new antibiotic discovery and the increase in antibiotic resistance have resulted in failing against bacterial pathogens. To develop novel antibiotic therapies, medical researchers have begun to focus on traditional therapies. Combinational therapies consisting of medicinal plants and conventional antibiotics may reactivate current drugs that are otherwise ineffective against antibioticresistant bacteria. Terminalia sericea Burch. Ex DC, Terminalia prunioides Laws. and Terminalia gazensis Bak. f. are native South African plants with antimicrobial properties. However, combinations of Terminalia sericea, Terminalia prunioides and Terminalia gazensis with conventional antibiotics are yet to be evaluated for growth inhibitory activity against gastrointestinal pathogens. Methods: Terminalia spp. leaves were extracted with solvents of varying polarity. Antimicrobial screening was performed using disc diffusion and broth microdilution assays. Toxicity was measured using Artemia franciscana nauplii lethality assays. Results: All extracts (except the T. sericea extracts) showed low to moderate inhibitory activity against B. cereus and E. faecalis, A. faecalis, A. hydrophilia, S. sonnei and S. newport in both the disc diffusion and liquid dilution assay. Twenty-three extract/antibiotic combinations produced synergy, 26 were additive, 24 were non-interactive and seven were antagonistic. Most of the antagonist interactions occurred in combinations containing gentamicin. All extracts were either non-toxic or of low toxicity in the Artemia bioassay. Conclusion: Terminalia spp. extracts may mimic the actions of a resistance modifying agents, enhancing the activity of several antibiotics that are relatively ineffective alone. Further studies are required to identify the bioactive and potentiating components and their mechanisms of action. [ABSTRACT FROM AUTHOR]

Background: Terminalia ferdinandiana (Kakadu plum) is an endemic Australian plant with an extremely high antioxidant capacity. The fruit has long been used by the first Australians as a nutritional food and as a medicine and recent studies have reported its potent growth inhibitory activity against a broad panel of bacteria. Despite this, T. ferdinandiana extracts are yet to be tested for the ability to inhibit the growth of Bacillus anthracis. Materials and Methods: Solvent extracts were prepared using both the fruit and leaf of Kakadu plum. The ability to inhibit the growth of B. anthracis was investigated using a disc diffusion assay. Their MIC values were determined to quantify and compare their efficacies. Toxicity was determined using the Artemia franciscana nauplii bioassay. The most potent extracts were investigated using non-targeted GC-MS head space analysis (with screening against a compound database) for the identification and characterisation of individual components in the crude plant extracts. Results: Solvent extractions of T. ferdinandiana fruit and leaf displayed good growth inhibitory activity in the disc diffusion assay against B. anthracis. Fruit ethyl acetate and methanolic leaf extracts were particularly potent growth inhibitors, with MIC values of 451 and 377 µg/mL respectively. The fruit methanolic and chloroform extracts, as well as the aqueous leaf extracts also were good inhibitors of B. anthracis growth, albeit with lower efficacy (MIC values of 1800 and 1414 µg/mL respectively). The aqueous fruit extract and leaf chloroform extracts had only low inhibitory activity. All other extracts were completely devoid of growth inhibitory activity. Furthermore, all of the extracts with growth inhibitory activity were nontoxic in the Artemia fransiscana bioassay, with LC50 values >1000 µg/mL. Non-biased GC-MS phytochemical analysis of the most active extracts (fruit ethyl acetate and methanolic leaf) putatively identified and highlighted several compounds that may contribute to the ability of these extracts to inhibit the growth of B. anthracis. Conclusions: The low toxicity of the T. ferdinandiana fruit ethyl acetate and methanolic leaf extracts, as well as their potent growth inhibitory bioactivity against B. anthracis, indicates their potential as medicinal agents in the treatment and prevention of anthrax. [ABSTRACT FROM AUTHOR]