Abstract
Despite the growing national and international interest for Australian traditional plant foods, information on nutritional and functional properties of many endemic species is limited. This restricts their incorporation in food, beverage and nutraceutical applications. This pilot study explored the phytochemical profiles and antimicrobial activity of two Australian endemic fruits: Diploglottis bracteata and Syzigium aqueum, to explore their marketability. Profiling of major bioactive phytochemicals showed the presence of 3 anthocyanins in S. aqueum (delphinidin-3-glucoside, cyanidin-3-glucoside and peonidin-3-glucoside) and four carotenoids in D. bracteata (lutein, zeaxanthin, β-cryptoxanthin and β-carotene). The total carotenoid content was comparable to that of orange coloured carrots, an important dietary source of carotenoids. Elemental analysis revealed that, compared to blueberry (a popular dietary source), D. bracteata had 4.5 times higher potassium, and 3.7 times higher magnesium content. Calcium levels of S. aqueum was 4.9 times higher than blueberry. Methanol, acetone and water extracts of both fruits were analysed for total phenolic content (TPC) and antimicrobial activity. TPC of D. bracteata and S. aqueum methanolic extracts were 2.9 and 1.4 mg gallic acid equivalents/g FW which is in the same range as blueberry, a popular dietary source of bioactive phenolic compounds. Antimicrobial analysis showed methanol, acetone and water extracts of both fruits have strong inhibitory effects against both Gram positive (Staphylococcus aureus) and Gram negative (Escherichia coli) bacteria, but no effects against fungi (Candida albicans). These promising initial results, diverse phytochemical profiles and strong antibacterial activity, warrant further investigation.
Author Contributions
M.C.: designed the experiments, carried out analysis and interpretation, and prepared the draft; A.D.T.P.P. and H.T.H.: carried out instrumental analysis; G.M.: provided plant materials and contributed to study design; M.E.N. and Y.S.: secured the funding for the study and contributed to study design. All authors have read and agreed to the published version of the manuscript.
Funding
This research was funded by Innovation Connections, grant number ICG000612.
Acknowledgments
We acknowledge the Traditional Owners of the lands on which the botanicals we study are harvested, and respect the knowledge and experience the Traditional Owners hold regarding the care, harvest and use of these plants.
Conflicts of Interest
The authors declare no conflict of interest.
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