Does vegetable colour matter? A comparative assessment of bioactive composition and biological properties

This study evaluated the physicochemical composition, bioactive compounds, antioxidant capacity, and inhibitory activity against α-amylase and α-glucosidase in vegetables of different colours and species. Significant variation was observed across all parameters, with species and edible organ type (R² = 0.529; 52.9%) of total multivariate variance exerting a stronger influence than colour alone (R² = 0.468; 46.8%). Violet vegetables (cabbage, cauliflower, and carrot varieties) generally showed the highest polyphenol content and antioxidant activity (particularly in ABTS, ORAC assays), which were strongly correlated with anthocyanin and total phenolic content (r ≈ 0.80-0.90). Green vegetables were characterised by elevated levels of chlorophylls, carotenoids, glucosinolates, free amino acids, and minerals. In contrast, beetroot was distinguished by its high sugar content, dry matter, and energy value. Enzyme inhibition varied among the samples and was associated mainly with phenolic composition rather than colour. Multivariate analyses (PCA, HCA) identified four compositional patterns: phenolic-rich violet vegetables, pigment- and glucosinolate-rich green vegetables, carbohydrate-rich beetroot storage organs, and white or pale-coloured intermediate samples. These findings highlight the importance of species diversity in determining the nutritional and functional value of vegetables.