(Davidsonia Pruriens & Davidsonia Jerseyana)
Davidson’s plum is an ancient species and it is native to the Australian Tropical rainforest. Although the colour and shape of Davidson’s plum are similar to the European plum, they are not closely related. The European plum has smooth peel and firm flesh, but Davidson’s plum has rough and hairy peel and juicy flesh. Actually, the Davidson’s plum has golden hair grown on both stem and peel. Davidson’s plum is a traditionally “bush tucker” for the Queensland indigenous people. They have been eating it for tens of thousands of years. Local women also use plum pulp to treat wounds.
There are two species of Davidson plum used primarily for commercial production. The predominant species is D. jerseyana. The tree’s natural range is
sub-tropical rainforest areas from around Ballina to the Tweed Valley in far northern New South Wales, and around 30 kilometres inland from the
coast. This suggests the optimum growing area. The fruit of the D. jerseyana has trunk-bearing characteristics, which lends well to hand-harvesting from ground level.
The other species, D. pruriens, has a natural range in the coastal and upland rainforests of far north-east Queensland; however, the species is also
grown commercially in mid-north coastal areas of New South Wales and on the Atherton Tableland in north Queensland. Its fruit is larger, firmer and generally grows on the upper branches of the fruit tree, rather than along the trunk as in D. jerseyana. Both D. jerseyana and D. pruriens fruit contain two flat fibrous seeds, which need to be removed for production of products from the fruit or its pulp.
Rainforest Heart has over 1,000 Davidson’s Plum trees in our rainforest orchard in Far North Queensland, the native home of the pruriens variety.
With vivid red flesh colour and intense flavour, this native tropical Australian plum is widely used in yoghurt and other dairy foods, jams, sauces, fruit wines and other products. It is very high in antioxidants and can be supplied as frozen puree (skin and flesh only, no seed), fresh whole (in season) or as a dried powder.
Extensive research has been undertaken on Australian native rainforest fruits and many have been shown to have high potential as functional food ingredients, in particular the Davidson’s plum due to its high antioxidants values, which are three times higher than Blueberries (which are considered the benchmark fresh fruit for high levels of antioxidant capacity.
Davidson’s Plum contains high levels of anthocyanins, natural pigments that are strong antioxidants. It also contains lutein, vitamin E and folate, Zn, Mg, Ca and Mo, as well as a high potassium:sodium (K:Na) ratio which is good for people with high blood pressure.
This information is the result of a systematic evaluation of commercially grown native Australian herbs and fruits with respect to:
- i) cell-protective and genome-protective capacity; Extracts of Davidson’s plum and lemon myrtle exhibited superior total reducing capacities, higher than reference samples of blueberry and bay leaf, respectively. Tasmannia pepper leaf extract displayed an oxygen radical absorbance capacity that was superior to all plants studied.
- ii) anti-proliferative activities against human cancer cells and
equivalent normal cells; All extracts evaluated within this study exhibited differential killing ability, or an ability to reduce the proliferation of cancer cells without a damaging effect on normal cells with the extract from anise myrtle displaying superior activity. All extracts displayed cytoprotective activities, as demonstrated, respectively, by effective protection of HepG2 cells from H2O2-induced cell death and cellular antioxidant activities.
iii) bioavailability of plant components to human cells; The activity of plant extracts in the cellular antioxidant activity (CAA) assay indicates their uptake and metabolism by a live cell. The study with Caco-2 cell monolayer model confirms that compounds originating from the native herbs and fruits evaluated in this study were bioavailable to human cells.
- iv) inhibitory activities towards two key enzymes relevant to
metabolic syndrome: α-glucosidase, responsible for the digestion of sugars; and pancreatic lipase, responsible for the digestion of fats; All extracts actively inhibited the activity of isolated α-glucosidase, with extracts from anise myrtle, lemon myrtle and Davidson’s plum being the strongest inhibitors. Extracts from Tasmania pepper leaf and quandong were the most efficient inhibitors of pancreatic lipase. The inhibitory activities against isolated enzymes: α-glucosidase and pancreatic lipase, suggest potential benefit in health issues such as diabetes and obesity from these plants.
The results obtained within the study suggest a number of potential health-enhancing properties of the evaluated native Australian herbs and fruits. These results have been generated in an array of cell culture based assays. Further nutritional/clinical studies with humans are required to confirm the identified potential health benefits.
Research projects have identified potential for significant nutritional and medicinal benefits from the fruits, some of which are already used in nutraceutical and functional food products. Published reports are available from the RIRDC website http://www.rirdc.gov.au/publications