Relationships between betalains, phenolic compounds and bioactivity in selected plant matrices

Betalain-rich fruits and vegetables are recognised as important sources of bioactive compounds; however, the relative contributions of betalains and co-occurring polyphenols to antiglycation and enzyme inhibitory activities remain insufficiently understood. This study comparatively evaluated six betalain-rich plant matrices (yellow and pink pitaya, yellow and red prickly pear, red Swiss chard, and red beetroot) to characterise their phytochemical compositions and associated biological activities. UHPLC-DAD-MS analysis identified forty-two betalains and thirteen polyphenols, alongside the total phenolic and flavonoid contents. Antioxidant capacity, α-amylase and α-glucosidase inhibition, and suppression of advanced glycation end-products (AGEs) were assessed using glucose- and methylglyoxal-based model systems. Red prickly pear showed the highest betalain content (33.30 mg/g dm), whereas pink pitaya exhibited the highest phenolic content. Red Swiss chard exibited the strongest antiglycation activity (84.70% and 30.17% in the BSA-GLU and BSA-MGO models, respectively), whereas pink pitaya showed the highest inhibition of α-amylase (39.27%) and α-glucosidase (17.51%). Red beetroot and Swiss chard exhibited the highest antioxidant capacities. The results indicate that betalains are more strongly associated with the inhibition of glucose-derived glycation, whereas polyphenols contribute predominantly to methylglyoxal-derived glycation and enzyme inhibition. These findings highlight the importance of phytochemical composition in determining the functional properties of selected plant matrices.