Oral Presentation Royal Australian Chemical Institute National Congress 2026

The composition of indigenous Australian Citrus fruit: polyphenols and volatile profiles (134206)

Joel B Johnson 1 , Natasha L Hungerford 2 , Yasmina Sultanbawa 3 , Michael E Netzel 1
  1. Centre for Nutrition and Food Sciences, QAAFI, The University of Queensland, Coopers Plains, Qld, Australia
  2. Centre for Animal Science, QAAFI, The University of Queensland, Coopers Plains, Qld, Australia
  3. ARC Industrial Transformation Training Centre for Uniquely Australian Foods, The University of Queensland, Indooroopilly, Qld, Australia

Indigenous Australian plants are a valuable source of phytochemicals which may provide nutritional value and bioactive properties. However, many native plants have not been adequately investigated from a phytochemical and nutritional perspective1. This study investigated the chemical composition of fruit from five indigenous Australian Citrus species (Citrus australis, C. australasica, C. garrawayi, C. glauca and C. inodora); the first time this has been conducted for several of these species. Flavonoids and other phytochemicals were profiled using liquid chromatography-high resolution accurate mass (LC-HRAM) spectrometry. Dozens of flavonoid compounds were identified, including various glycosides of quercetin, myricetin, luteolin, isorhamnetin and kaempferol. The common citrus flavanone hesperetin was also identified in its aglycone and glycosylated forms (hesperidin, neohesperidin, hesperetin 7-O-glucoside), as well as several bitter limonoid species (limonin and nomilinic acid). Hesperetin and its derivatives tended to be slightly more abundant in the pulp compared to the peel.

Volatilome profiling using headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) revealed the characteristic volatile profiles of native Australian Citrus – in both their pulp and peel. The number of volatile compounds detected for each species ranged from 51 (for C. inodora) to 141 (for C. australasica). The monoterpene d-limonene was the most abundant volatile compound for most species, constituting 70% of the total volatiles (by peak area) in C. australasica pulp, 66% in C. inodora, and 15% in C. garrawayi; but only 6% in C. australis and 5% in C. glauca. α-Pinene was the dominant volatile in C. australis pulp (55% of the total volatiles) and C. glauca pulp (20%). Results were similar for the peel volatile profiles of these species. In general, the volatilomes of C. garrawayi and C. glauca were dominated by sesquiterpenoids, while those of C. australis and C. australasica were predominantly monoterpenoids. This information may facilitate the commercialisation of these species, which offer valuable opportunities for innovative applications in the food and nutrition sector.

  1. Johnson, J.B., Hungerford, N.L., Sultanbawa, Y. and Netzel, M.E., 2025. Unlocking the sublime: A review of native Australian citrus species. Foods, 14(14), 2425. DOI: 10.3390/foods14142425