Native Australian Citrus as a valuable source of vitamins and antioxidants

Australia has six endemic species of Citrus: Citrus australasica (finger lime), C. australis (Gympie lime), C. garrawayi (Mount White lime), C. glauca (desert lime), C. gracilis (Humpty Doo lime) and C. inodora (Russell River lime). However, the nutritional and chemical composition of the fruit from many species remains largely unknown. An analysis of five of the native Australian Citrus species by HPLC-UV revealed that the vitamin C content of C. inodora flesh was 4× higher than that of commercial Tahitian lime (C. × latifolia), while C. glauca had almost 7× higher vitamin C. Two species (C. australasica and C. glauca) contained quantifiable levels of pro-vitamin A (β-carotene; 7-18 mg/kg DW) in their pulp, compared to no detectable β-carotene in Tahitian lime, while the peel of C. australis contained 3× more β-carotene than Tahitian lime peel. C. australasica and C. glauca pulp contained comparable vitamin E (α-tocopherol) content to Tahitian lime, while the α-tocopherol of C. inodora was 3× higher. Furthermore, the peel of four C. australasica varieties contained 18-33× higher α-tocopherol content compared to Tahitian lime. Finally, the antioxidant capacity (DPPH assay) of C. glauca pulp was double that of Tahitian lime. These results show the promising nutritional composition of native Australian Citrus, with potential uses for fresh consumption, food processing, or in cosmetic products.