Monkey orange (Strychnos spinosa lam): a review of phytonutrients, bio-accessibility, value-added products, and potential as a functional food

Introduction Strychnos spinosa Lam. (monkey orange) is a drought-tolerant indigenous fruit tree distributed across sub-Saharan Africa, valued traditionally for nutrition and medicine but remaining underutilised in formal economies. This review synthesises literature on the fruit’s physicochemical properties, phytonutrient profile, value-added products, and bio-accessibility to evaluate its potential as a functional food. Methods A systematic literature search was conducted following PRISMA guidelines across database using different keyword strings. Of 387 initial records identified, 75 studies met inclusion criteria and were included in the qualitative synthesis. Results The pulp is characterised by high acidity (pH 2.5–4.0), soluble solids (12–22 °Brix), and pulp yield (30–60%). Nutritionally, it is rich in carbohydrates, dietary fibre, and minerals including potassium, magnesium, calcium, iron, and zinc. Phytochemical profiling revealed bioactive compounds such as chlorogenic acid, caffeic acid, rutin, and carotenoids, underpinning antioxidant, antimicrobial, and anti-inflammatory activities. Value-added products including juices, jams, fermented beverages, and dried rolls have demonstrated feasibility. However, a critical knowledge gap persists: while compositional analyses confirm high phytonutrient content, their bio-accessibility remains poorly characterised. Discussion Factors including carotenoid lipophilicity, phenolic compound stability during digestion, and processing impacts on nutrient release have not been systematically quantified. Without integrating standardised bio-accessibility studies, the physiological relevance of S. spinosa’s phytonutrients cannot be validated, and commercialisation as a functional food remains speculative. Fermentation emerges as a promising traditional and scalable method to enhance nutrient bioavailability through phenolic modification, cell wall disruption, and reduction of anti-nutritional factors. Conclusion This review recommends prioritising bio-accessibility investigations alongside fermentation optimisation to transform S. spinosa into a validated, climate-smart functional food for sub-Saharan Africa, supporting evidence-based product development, nutrition security, and rural economic opportunities.