Identification of bioactive compounds in quinoa grains following a chemometrics-assisted metabolomics approach

Abstract

Quinoa (Chenopodium Quinoa Willd.) is an Andean grain renowned for its diverse array of bioactive compounds, harbouring considerable potential for various biological activities. This food has been the subject of study in recent years due to its high-quality protein content, as well as an excellent balance of essential amino acids. In addition, the bioactive compounds present in quinoa, mainly polyphenols, present relevant medicinal attributes such as potent antioxidant and anticarcinogenic properties, alongside a remarkable ability to mitigate cardiovascular diseases. This work has been focused on the identification of polyphenols within four different commercially available quinoa grains: black (B, from Peru), red (R, from Peru), white (W, from Peru) and royal (RO, white quinoa from Bolivia). The identification process employed a non-targeted metabolomics strategy based on liquid chromatography coupled to mass spectrometry (LC-MS). The obtained chromatograms were cross-referenced with a database of polyphenols created from an exhaustive review of literature on low molecular mass bioactive compounds. The investigation unveiled a total of 25 polyphenols distributed among the four quinoa grains, predominantly from the quercetin and kaempferol families. To assess the polyphenolic composition variance among the quinoa grains, a multivariate chemometric analysis was conducted utilizing principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA). The results exhibited distinct clustering of the grains into three primary groups: B, R, and W-RO. Surprisingly, minimal differentiation was observed between the white quinoas (W and RO), indicating that the origin of the white quinoa had negligible impact on its polyphenol content. Among the identified polyphenols, quercetins emerged as the most significant compounds for discriminating between the quinoa grain classes. These flavonols are renowned for their potent bioactive properties, as extensively documented in the literature.