Exogenous 2-Keto-L-Gulonic Acid Supplementation Promotes L-Ascorbic Acid Biosynthesis in Drosophila melanogaster

L-ascorbic acid (ASA) is an essential micronutrient critical for antioxidant defense and metabolic regulation in animals. Unlike many vertebrates, Drosophila melanogaster possesses the ability to synthesize ASA endogenously, yet the regulatory mechanisms governing this biosynthesis remain unclear. 2-keto-L-gulonic acid (2KGA), a key precursor in industrial vitamin C production, has been shown to enhance ASA accumulation in plants, but its role in invertebrates is unknown. This study systematically investigated the effect of exogenous 2KGA supplementation on ASA biosynthesis in Drosophila. Fruit flies were reared on media with or without 2KGA (1.6 g/L; n = 30 per group) for 12 days, followed by ASA quantification via high-performance liquid chromatography (HPLC). Results showed that 2KGA treatment increased mean ASA content from 0.00853 ± 0.0012 to 0.01064 ± 0.0015 μg/fly (24.74% increase; p = 0.0194, r² = 0.558) compared to the control group, indicating that 2KGA acts as a metabolic regulator to promote ASA biosynthesis. Sex-separated analyses further revealed that this effect was primarily driven by male flies (p = 0.0057, r² = 0.879), whereas females showed no significant response (p = 0.1783), pointing to a sex-dependent regulation of 2KGA-mediated ASA biosynthesis. These findings provide the first evidence that 2KGA modulates ASA levels in an invertebrate disease model and suggest that fruit flies can serve as a useful platform to explore conserved redox-regulatory mechanisms relevant to human health and disease.