Abstract
Abstract This study investigates the seasonal variation in the phytochemical composition of rowan (Sorbus aucuparia L.) fruit extracts collected during the summer and autumn vegetation periods. Gas chromatography–mass spectrometry (GC–MS) was employed to characterize qualitative and quantitative changes in individual compounds and compound classes associated with fruit ripening and metabolic adaptation. The summer extracts were dominated by secondary metabolites, primarily lactones and furan derivatives, with dihydro-3-methylene-5-methyl-2-furanone and 5-hydroxymethylfurfural representing the major constituents. Their elevated levels indicate intensive carbohydrate transformation and active metabolic processes during early fruit development. In contrast, the autumn samples exhibited a pronounced accumulation of primary metabolites, particularly polyols (sorbitol, 1,4-anhydro-D-galactitol, mannitol) and fatty acids, including n-hexadecanoic (palmitic) and unsaturated fatty acids. This metabolic shift reflects physiological maturation and preparation for overwintering, accompanied by enhanced energy storage and osmoprotective mechanisms. Comparative analysis revealed a significant decrease in lactones and furans alongside a substantial increase in sugar alcohols and lipid components in autumn fruits. Visualization techniques, including dumbbell, lollipop, grouped bar, and sunburst charts, highlighted a fundamental restructuring of the metabolome from volatile and reactive compounds toward more stable constituents. Overall, the results demonstrate that harvest season plays a critical role in determining the chemical profile and functional properties of Sorbus aucuparia fruits, which is essential for their targeted use in food, pharmaceutical, and nutraceutical applications.