Analysis of Red Amaranth (Amaranthus cruentus L.) Betalains by LC-MS

Abstract

Abstract. Betalains are natural pigments responsible for the colour of flowers, bracts, stems, and leaves of genus Amaranthus, and they are bioactive compounds. Due to their great chemical diversity, the determination and confident identification of betalains are still challenges and of great interest as they are natural colourants for health benefit. By high-performance liquid chromatography (LC) coupled to tandem mass spectrometry (MS), the catalog of betalains in red amaranth (Amaranthus cruentus L.) was defined. In total, 30 betacyanins and 13 betaxanthins were found. Mass measurements for the parent ion and for its fragments with errors of less than 5 parts per million (ppm) achieved the recommended criteria for identification of compounds. This work defines the main betalains in red amaranth (A. cruentus) and valorizes the leaves and inflorescence of red amaranth as betalain pigments sources. Resumen. Las betalaínas son pigmentos naturales responsables del color en las flores, brácteas, tallos y hojas del género Amaranthus y también son compuestos bioactivos. Debido a su amplia diversidad química, la identificación y determinación confiable de betalaínas siguen siendo desafíos y son de gran interés puesto que son colorantes naturales beneficiosos para la salud. Por medio de cromatografía de líquidos de alta eficiencia acoplada a espectrometría de masas en tándem se definió el catálogo de betalaínas en “amaranto rojo” (Amaranthus cruentus L.). En total se encontraron 30 betacianinas y 13 betaxantinas. Las mediciones de las masas del ion molecular y sus fragmentos con errores menores a 5 partes por millón (ppm) garantizaron los criterios recomendados para la identificación de compuestos. Este trabajo define las principales betalaínas del amaranto rojo (A. cruentus) y valora las hojas e inflorescencias del amaranto rojo como fuente de pigmentos betalaínicos.

HPLC-Based Metabolomic Analysis and Characterization of Amaranthus cruentus Leaf and Inflorescence Extracts for Their Antidiabetic and Antihypertensive Potential

“…A key group of metabolites contributing to the antioxidant effects of A. cruentus is its rich betalain composition. In our previous studies on this A. cruentus accession, among the 43 betalains, amaranthin, isoamaranthin, gomphrenin-I, and betanin are the most abundant [32]. Betalains, amino acid derivatives of betalamic acid, possess an amino aromatic chemical structure capable of stabilizing free radicals, for instance, DPPH, through electron donation [55].…”

“…Amaranthus cruentus is distinguished by its high concentration of phenolic compounds and flavonoids. Additionally, its leaves and inflorescences are rich in betalains, such as amaranthin and its epimer isoamaranthin, which are the most abundant [32]. These findings underscore that amaranth is a promising source for natural antioxidant therapies.…”

“…Due to the presence of large amounts of betalains in plants, which are classified into two large classes, betacyanins and betaxanthins, we decided to quantify these natural colorants using the spectrophotometry method proposed by Cai et al, (1998) [31]. The method utilizes the molar extinction coefficient of amaranthin 5.66 × 10 4 cm −1 mol −1 L to determine betacyanin content and betaxanthins content with indicaxanthin 4.81 × 10 4 cm −1 mol −1 L. As previously found, A. cruentus produces amaranthin and isoamaranthin as its primary betacyanins [32]. In the lyophilized samples of A. cruentus, the concentration of these compounds was found to differ significantly (p < 0.05) between the inflorescences and the leaves.…”

“…Phytochemicals, including betalains, were extracted via the matrix solid-phase dispersion (MSPD) method published by Araujo-León et al (2023) [32]. A uniform powder was obtained by grinding 100 mg of lyophilized tissue at room temperature in a mortar with 400 mg of C18 stationary phase (BondElut-C18).…”