Phytochemical composition and cultivar-dependent variation in colored lettuce (Lactuca sativa) and their α-amylase inhibitory activity.

BACKGROUND: This study investigated cultivar-dependent variation in the phytochemical composition of lettuce (Lactuca sativa) using liquid chromatography-tandem mass spectrometry (LC-MS/MS) profiling and high-performance liquid chromatography (HPLC) quantification, with a focus on enzyme inhibitory activity. RESULTS: Significant differences were observed among six colored cultivars, with red cultivars exhibiting higher levels of phenolic compounds, particularly miquelianin (2), chicoric acid (4), and quercetin 3-O-malonylglucoside (3). Quantitative analysis revealed that these metabolites were markedly enriched in red-pigmented cultivars. Multivariate analysis further confirmed a clear compositional separation between red and green cultivars. α-Amylase inhibitory activity was also evaluated, and the red leaf crude extract yielded the highest efficacy among the matrices (IC50 = 1.24 mg mL⁻¹). Among the pure constituents, quercetin 3-O-malonylglucoside (3) demonstrated the strongest enzymatic inhibition (IC50 = 18.57 μg mL⁻¹). Molecular docking analysis supported these findings, revealing that compound 3 possessed the highest binding affinity (-9.8 kcal mol⁻¹) toward the α-amylase catalytic site by interacting with key active residues. CONCLUSION: These findings demonstrate that phytochemical composition and enzyme inhibitory activity in L. sativa are strongly influenced by cultivar type. Particularly, red-pigmented cultivars represent promising sources of bioactive compounds with potential applications in nutritional and functional food development. © 2026 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.