Mirbelia oxylobioides F. Muell. Leaf Extracts Lack Antibacterial Activity and are Non-toxic in vitro

Introduction: The development of bacterial strains that are resistant to multiple antibiotics has made the discovery of new antibiotics a priority for medical research. Examination of plants for new antimicrobial agents is an attractive prospect and numerous recent studies have screened plants for antibacterial activity. Despite this, Australian native plants have been relatively neglected. Mirbelia oxylobioides F.Muell. is a native Australian shrub of the family Fabaceae. Very few studies have yet examined species for antibacterial properties against human pathogens. Methods: The ability of M. oxyloboides leaf extracts to inhibit the growth of a panel of bacterial pathogens was investigated by disc diffusion assay. Toxicity was examined using the Artemia franciscana nauplii bioassay. Results: M. oxyloboides methanolic and aqueous extracts were ineffective at inhibiting the growth of gram-positive and gram-negative panels of bacteria. The extracts were nontoxic or of low toxicity following 24 h exposure. Conclusion: The M. oxyloboides leaf extracts lacked growth inhibitory bioactivity against a panel of pathogenic bacteria and were nontoxic in the Artemia nauplii assay. However, these extracts may have other therapeutic properties and testing against protozoa, fungi, virus and tumour cells is required.