Background paper. Andrew Pengelly PhD. 2018.

Introduction

Persoonia is an endemic Australian genus of shrubs and small trees in the family Proteaceae, the family of Proteas, Banksias and Grevilleas – though appearance-wise it doesn’t closely resemble any of these.

Traditional uses

Persoonia’s are most commonly referred to as “geebung” – an Aboriginal name for the succulent fruit, a traditional source of food across much of the Australian continent. The fruit pulp is basically chewed off the hard stone as a snack, described as tasting like sweet cotton wool (Cribb & Cribb, 1974). In the Kimberley region fruit of local species are reportedly roasted, crushed and stored in paperbark (Low, 1989).

The tropical species P. falcata known as milky plum, is a revered medicinal plant in parts of Queensland and Northern Territory. A tea made from the leaves is used for diarrhoea and chest infections, while phytochemical screening revealed the presence of saponins and tannins (Aboriginal Communities of the Northern Territory of Australia, 1988).

Although medicinal uses for New South Wales Persoonia are not widely reported in the literature, geebung fruit (most likely from P. linearis) is highly revered by the Wiradjuri Language people of the Hunter Valley, NSW. One of its’ reported uses is by the application of the juice derived from the fruit, for local treatment of skin infections due to infection by Staphylococcus bacteria, and for other skin disorders including psoriasis.

Scientific research

In a massive screening program for antibiotics from Australian plants and fungi conducted during the 1940s, the most potent agents against both Staphylococcus aureus and Salmonella typhi (gram positive and gram negative pathogenic bacteria respectively) from the 1200 plants screened, were from three Persoonia species (Atkinson, 1949). In volume 4 of her Medicinal Plants in Australia series, Williams provides further details of Atkinson’s investigations, observing that fruits from P. juniperina inhibited the typhoid causing bacteria, and that P. pinifolia exerted antibacterial effects also, but only when the fruit was partly ripe ie between the green and purple stage, the very young and very old berries exerting minimal activity (Williams, 2013).

During a more recent screening of indigenous species at the National Botanical Gardens, extracts prepared from the ripening fruit of a hybrid of Persoonia linearis and P. pinifolia was found to inhibit the growth of pathogenic bacteria (gram positive and negative) and a fungus (Phytophthora cinnamomi). Further investigations revealed the presence of a single antimicrobial compound, a previously unknown phenolic glycoside ester (MacLeod, Rasmussen & Willis, 1997). By coincidence, researchers from New Zealand had simultaneously isolated the same compound from the leaves of a close relative of Persoonia, known as Toronia toru (Perry & Brennan, 1997), which demonstrated antimicrobial and cytotoxic effects against human leukemia cells.

Proposed Research Project

In order for geebung fruit to be developed as a topical product for treatment of skin infections, the following steps are proposed.

1. Gather further anecdotal reports of the use of Persoonia as a folk medicine by Aboriginal and other residents of the Hunter Valley.
2. Harvest ripening geebung fruit during the summer, keeping them frozen until ready for extraction.
3. Perform extraction using freeze-drying or other appropriate method
4. Subject extract to chemical analysis using chromatography and mass spectrometry.
5. Confirm the presence of the previously described antimicrobial compound, and gain an overall chemical analysis.
6. Replicate previous experiments to confirm the antimicrobial properties of Persoonia fruit from wild sources of linearis harvested in the Hunter Valley.
7. Perform antioxidant studies
8. Test the composition of the leaf, since there is evidence suggesting it may also have the antimicrobial component, and it is more readily available.
9. Test for variables:
   1. different species eg pinifolia and the hybrid if available
   2. different stages of fruit ripeness
   3. different drying methods
10. Generate safety data

There is a growing interest and research base into the properties of Australian native herbs and fruits, and most of the data gathered to date indicates our native fruits are higher in nutrients and antioxidant performance compared to most non-Australian fruit and herbs (Konczak, 2017). As the seminal text by Sultanbawa and Sultanbawa (eds) informs us, the nutritional and bioactive characteristics, processing and extraction technologies for Australian species are now well advanced, much of this based on extensive laboratory analysis by CSIRO researcher Dr. Konczak.

We are fortunate to have a research centre at the University of Newcastle who are well equipped to perform the above procedures. At the School of Life and Environment Studies research labs situated on Ourimbah Campus, Dr. Quan Vuong and his group are actively studying the chemical composition and therapeutic activities of numerous native Australian species, including Eucalyptus leaf and another plant with edible fruit – the lilly pilly (Syzygium paniculatum) (Vuong et al., 2014). The present author also performed his doctoral research in these labs, on the native hop bush (Dodonaea viscosa).

Conclusion

There is no doubt that anecdotal reports and some scientific investigations have indicated the likelihood of the Hunter Valley species of Persoonia fruit having potent antimicrobial properties, which may suitable for conversion into a product for topical application.

Creation of such a product in conjunction with the local community, particularly the Aboriginal Land Council and Land Care group, could provide economic and cultural benefits.

In order to embark on this project some research funding is required. This could occur in stages eg. a pilot study could be conducted to perform an initial chemical analysis for a reasonable cost. Positive findings from the pilot study would provide leverage for a subsequent grant application of a scale necessary to complete the proposed project. Meanwhile research into the propagation and cultivation of the plant would be ongoing.

Obtaining some initial funding could ensure that potential short- and long-term benefits of the proposed research would be shared within the Hunter community.

• Short term outcomes: awareness of the plant in community and through land care groups have an impact on indiscriminate land clearing that may reduce the population size
• Long term outcomes:
  • Confirmation of the antimicrobial properties
  • commercialisation of medication spawning a new industry in the propagation, harvesting and processing of the plant.

This in turn would bring employment and revenue for the Aboriginal and non-Aboriginal Hunter Valley community.

References

Aboriginal Communities of the Northern Territory of Australia (1988). Traditional Bush Medicines. An Aboriginal Pharmacopoeia. Greenhouse Publications.

Atkinson, N.  1949. Antibiotics from Australian plants and fungi. Medical Journal 1, 605-610.

Cribb, AB & JW. (1974). Wild Food in Australia. Fontana Collins.

Emery, N. Catelotti, K. & Offord, C. (2016). Research on eastern Australian Persoonia. Australian Plants 28, 210-217.

Konczak, I. (2017). Health attributes of indigenous Australian plants. In Cherikoff, V. Wild Foods. New Holland Publishers.

Low, T. (1989). Wild Food Plants of Australia. Angus & Robertson.

MacLeod, JK. Rasmussen, HB. & Willis, AC. (1997). A new glycoside antimicrobial agent from Persoonia linearia x pinifolia. Journal of Natural Products 60, 620-622.

Perry, NP. & Brennan, NJ. (1997).  Antimicrobial and Cytotoxic Phenolic Glycoside Esters from the New Zealand Tree Toronia toru. Journal of Natural Products 60, 623-626.

Sultanbawa, Y. & Sultanbawa, F. (eds.) 2016. Australian Native Plants. Cultivation and uses in the health and food industries. CRC Press.

Vuong, QV. Hirun, S. et al. (2014). Physicochemical composition, antioxidant and anti-proliferative capacity of a lilly pilly (Syzygium paniculatum) extract. J. Herbal Med. 4, 134-140.

Williams, C. (2013). Medicinal Plants in Australia vol.4. Rosenberg.