Natural extract rich in betalains and polyphenols from Bougainvillea glabra bracts as natural pigments with antioxidant and antiproliferative activities

Abstract

Betalains are a group of nitrogenous compounds produced by plants of the Caryophyllales order, as secondary metabolites derived from betalamic acid, characterized by their vibrant coloration in fruits, bracts, and leaves (red-violet, yellow). Their technological importance relies on their role as natural pigments, and high bioactivity potential (free-radical scavenging, anti-inflammatory, anti-cancer, gene regulators, and anti-diabetic properties), however, betalain sources have been limited to widely studied Beta vulgaris (beetroot). Polyphenols are the most abundant secondary metabolites and are characterized by a phenolic ring linked to a hydroxyl group in a complex structure, they can be found in fruits, vegetables, and beverages. They are widely recognized as pigments with antioxidant activity, anti-inflammatory and immunomodulation activity, and a strong association with the gut microbiome. Bougainvillea glabra is an ornamental species of the family Nyctaginaceae, widely cultivated in Latin America, characterized for its intense bract coloration, still, its application as a functional ingredient and bioactive compound source remains understudied. The primary objective of the investigation was to evaluate the biological and technological potential of an extract rich in betalains and phenolic compounds from the industrially underexploited bracts of Bougainvillea glabra. B. glabra extract (BGE) was obtained using solid-liquid ultrasound-assisted extraction. The total betalain content in BGE was 0.118 mg total betalain content (TBC) per mg of bract powder, while the total polyphenol content was determined as 0.002 mg of TPC per meg of bract powder. The identification of phytochemicals was performed by UPLC chromatography linked to mass spectrometry in both targeted and untargeted metabolomic analysis. BGE scavenged ABTS radical with inhibition (p < 0.05) values ranging from 149-180 μM Trolox equivalents, an α-amylase test inhibition revealed a 27.9 % inhibition (p < 0.05) by BGE at 5 mg/mL. BGE had selective cytotoxicity effects of 30% GIE (growth inhibitory effect) on the Caco-2 cell line. BGE showed synergistic in vitro effects with cisplatin on Caco-2 cells, inducing apoptosis and autophagy processes.