An Examination of the Medicinal Potential of Pittosporum phylliraeoides: Toxicity, Antibacterial and Antifungal Activities

Abstract

Introduction: Pittosporum phylliraeoides is an endemic Australian plant historically used as a medicinal agent by indigenous Australians. P. phylliraeoides solvent extracts were tested for antibacterial and antifungal activities and toxicity in vitro. Results: All extracts displayed antibacterial activity in the disc diffusion assay. The methanol and hexane extracts demonstrated the broadest specificity, inhibiting the growth of 4 of the 14 bacteria tested (28.6%). The water, ethyl acetate, and chloroform extracts inhibited the growth of 2 (14.3%), 3 (21.4%), and 3 (21.4%) of the 14 bacteria tested respectively. P. phylliraeoides methanolic extract was also effective as an antifungal agent, inhibiting the growth of a nystatin resistant strain of Aspergillus niger. It did not affect the growth of Candida albicans. All extracts were more effective at inhibiting the growth of Gram-negative bacteria than Gram-positive bacteria. Indeed, only the methanol and hexane extracts were capable of inhibiting the growth of any of the Gram- positive bacteria, inhibiting the growth of only 1 of the 4 (25%) Gram-positive bacteria tested each. All P. phylliraeoides extracts displayed low toxicity in the Artemia franciscana bioassay. The only significant increase in mortality above that of the control was seen for the ethyl acetate, chloroform and hexane extracts, although even these extracts displayed low toxicity, inducing less than 50% mortality at 72 h. Conclusions: The low toxicity of the P. phylliraeoides extracts and their inhibitory bioactivity against bacteria and fungi validate Australian Aboriginal usage of P. phylliraeoides and indicates its medicinal potential.