Metabolomic and biofunctional insights into lemon-ginger mixture protection against heated oil hepatotoxicity

Reuse of cooking oils at high temperatures is a widespread culinary practice that alters their composition and compromises food safety. This study examined the chemical and biological consequences of thermal oil degradation and evaluated the hepatoprotective potential of a natural lemon-ginger blend. Gas chromatography-mass spectrometry (GC-MS) profiling of fresh and re-heated corn and safflower oils revealed a marked decline in phytosterols, tocopherols, and unsaturated fatty acids, along with the accumulation of harmful byproducts such as amides, monoacylglycerols, fatty acyl nitriles, and aldehydes. Oxidized corn oil exhibited the highest degree of degradation, indicating its poor suitability for reuse. Phytochemical profiling of lemon and ginger extracts by SPME/GC-MS and ¹H NMR identified hepatoprotective metabolites, including choline, zingiberene, α-curcumene, and dehydrogingerdione, which were retained in the combined extract. The lemon-ginger blend demonstrated improved chemical stability and a preserved metabolic profile compared with individual extracts. In vivo results revealed that rats fed oxidized oil exhibited significant hepatotoxicity, with elevated ALT (45.0 ± 0.6 U/L), AST (64.3 ± 0.6 U/L), and ALP (143.2 ± 1.6 U/L) levels compared with controls (28.3, 41.5, and 105.3 U/L, respectively), along with increased MDA (18.7 ± 0.5 nmol/g) and decreased SOD (2.8 ± 0.1 U/g). Co-administration of the lemon-ginger blend normalized these biomarkers (ALT 31.2 ± 0.6 U/L and SOD 5.1 ± 0.1 U/g) and restored hepatic architecture, as confirmed histologically. These findings provide integrative metabolomic and biofunctional evidence supporting this blend as a natural dietary intervention against re-heated oil-induced hepatotoxicity, bridging food chemistry and functional nutrition.