Legumes have long been the subject of health-related research based on their nutritional value and many reported health benefits across the lifespan. Cowpea (Vigna unguiculata) is one of the most important crops for global food and nutritional security, providing the main source of dietary protein, fiber, minerals, and vitamins for millions of people in sub-Saharan Africa. Understanding the metabolomic makeup of cowpeas and other important legumes (e.g. beans, pigeon pea) is key for performing nutrition studies in undernourished populations. In this study, the cooked food powders of three different local varieties of cowpeas commonly cultivated and consumed in Ghana, along with a pigeon pea (Cajanus cajan) and a navy bean (Phaseolus vulgaris), were analyzed using an untargeted, global metabolomics approach on a reverse phase ultra-performance liquid-chromatography time of flight mass spectrometry (UPLC-MS) platform. 50 mg of each cooked legume food powder was extracted with absolute ethanol prior to LC-MS. Legumes were compared both by common type (cowpea, pigeon pea (adua), navy bean) as well as cowpea variety (namely dagbantuya, sangyi, tukara). Principal components analysis revealed a 52.7% separation in Component 1 between the 5 foods tested. A total of 775 metabolites were detected, with 551 of those metabolites significantly differentiating between legume groups, and 320 significantly differentiating between cowpea varieties in ANOVA analyses. Metabolite profiles showed that cowpea varieties were clearly more similar to each other than the other two legumes, and that the navy bean was more similar to the cowpeas when compared to the pigeon pea. These metabolite profiles have parallels to their phylogenetic relationships. Using fold change analyses, we found log2(fold change) differences of -12.07, 12.77, and 9.22 for proline betaine, integristerone A 25-acetate, and corchorusoside A when compared between cowpeas and pigeon pea. The cowpea varieties showed metabolomes that were heavily composed of diverse lipids and lipid-like molecules as well as unclassified groups of metabolites and phytochemicals. These legume metabolite profile findings will further support an integrated analysis for identification of nutritional biomarkers using blood and urine collected from individuals consuming the cowpeas.

Non-targeted metabolomics of cooked cowpeas and pigeon pea from Ghana

ACS Fall 2021

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