ANTIBACTERIAL ACTIVITY AND TOXICITY OF Tasmannia lanceolata (Tasmanian pepper) BERRY EXTRACT.

Abstract

Introduction. Tasmannia lanceolata (TL) is an endemic Australian plant, long used as a food and a medicine by Indigenous Australians. The medicinal bioactivities of this plant are poorly studied. Methods. TL extracts were prepared with various solvents, dried and then re-suspended in water. Antibacterial activity of these preparations was determined by growth inhibition against a panel of pathogenic bacteria and fungi. Toxicity (LC50) was assessed by the Artemia franciscanna (brine shrimp) nauplii bioassay. Results. All extracts inhibited the growth of 50% of the bacteria tested and 100% of the fungi via disc diffusion assay. The ethyl acetate and hexane extracts proved to have the greater antibacterial activity with lower Minimum Inhibition Concentration (MIC) values. In comparison to the other extracts, the chloroform extract had a lower bacterial inhibitory activity with higher MIC’s. All TL extracts were equally effective against Gram-positive (50 %) and Gram-negative bacteria (50 %), suggesting the phytochemical components are effective in penetrating the Gram-negative outer membrane lipopolysaccharide layer. The water, hexane and ethyl acetate extracts were non toxic, with no significant increase in mortality induction. The methanol extract toxicity was unable to be determined, at the concentration tested. The chloroform extract displayed low toxicity in the Artemia fransiscana bioassay (LC50 >1500 µg/ml). Conclusions. The low toxicity of the TL extracts and their inhibitory bioactivity against a range of bacteria validate traditional Aboriginal usage of the Tasmannia lanceolata and indicates its medicinal potential.