A review of the nutrient and ethnomedicinal value of cowpea (Vigna unguiculata (L.) Walp.)

Background Cowpea ( Vigna unguiculata L.) is a key legume in sub-Saharan Africa and an affordable source of protein for humans and livestock, yet up to 50% of leaves are discarded post-harvest, limiting its contribution to food and nutrition security. Objective This review aims to summarize current evidence on the nutritional, anti-nutritional, ethnomedicinal and phytochemical properties of cowpea leaves, seeds and pods, and to assess how common processing methods influence their nutritional quality and bioactive potential. Methods A narrative literature review was conducted using peer-reviewed articles retrieved from PubMed, ScienceDirect, Google scholar and Web of Science databases. Studies reporting proximate composition, micronutrients, anti-nutritional factors, phytochemicals, ethnomedicinal uses, biological activities, and the effects of processing methods (boiling, cooking, autoclaving and other thermal treatments) on cowpea parts were screened and qualitatively synthesized. Results Cowpea leaves, seeds and pods contain substantial macronutrients (carbohydrates, proteins, fats), micronutrients (vitamins and minerals), anti-nutrients (trypsin inhibitors, phytates, tannins) and diverse bioactive phytochemicals. Mineral levels are generally highest in leaves, followed by seeds and pods. Thermal processing markedly reduces anti-nutritional factors but also causes variable nutrient losses. Reported bioactivities of cowpea-derived compounds include antioxidant, antidiabetic, anticancer, antimicrobial, analgesic, thrombolytic, hepatoprotective and anti-aging effects. Conclusion Cowpea is a nutrient-dense, multifunctional crop whose different parts have complementary nutritional and health-promoting properties. Leaves show particular promise for pharmaceutical or nutraceutical applications, whereas seeds and pods are suitable for protein enrichment in animal feed and flour-based foods. Improved utilization of all cowpea components, alongside strategies to reduce post-harvest losses, could strengthen food and nutrition security in resource-limited settings.