Bioactivity in Australian native willow: comparative analysis of leaf extracts on cell viability

Australian native willow, (Pittosporum angustifolium Lodd.), known also as gumby gumby, has been traditionally used as a medicinal plant in Australian Aboriginal communities, anecdotally, to treat various skin conditions including cancer (1). A small number of in vitro studies have examined the cytotoxicity of P. angustifolium Lodd. leaf extracts on breast, lung, and glioblastoma cancer cells. The aim of the present study was to examine the cytotoxic effects of a series of extracts from P. angustifolium Lodd. leaves collected from three geographically different locations (GG1, GG2, and GG3). Extraction was accomplished either by decoction (GGD) or mechanical juicing (GGJ). The cell viability was assessed using the MTT (3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay on squamous cell carcinoma (SCC25) and non-cancerous human keratinocyte (HaCaT) cell lines. SCC25 and HaCaT (6000 and 3000 cells/well, respectively) cells were treated with sterile filtered decoction (GGD1, GGD2, and GGD3) or juice (GGJ1, GGJ2, and GGJ3) extracts over a range of concentrations (5 – 100 µg extract/mL). The dose-response curve of all the extracts significantly showed decreases in cell viabilities for both SCC25 and HaCaT cells (p < 0.0001). In conclusion, a comparative analysis of extracts is useful to examine the bioactivities, their cancer cell selectivity and the phytochemical variation(s) of plant extracts.

The contribution and assistance of Dale Chapman (First Foods) are gratefully acknowledged.

[1] Cayzer LW, Crisp MD, Telford IRH. Revision of Pittosporum (Pittosporaceae) in Australia. Australian Systematic Botany. 2000;13:845 – 902.