An update on functional, nutraceutical and industrial applications of watermelon by-products: A comprehensive review

Agro-waste is of rising concern since they present social, economic and environmental challenges. Conversion of food waste is receiving an increasing attention towards the fact that these materials represent possible utilization sources for conversion into useful products and increasing the demand for natural bioactive compounds. Watermelon (Citrullus lanatus) is consumed all over the world that contains a large number of seeds and rind, which is discarded and used as animal feed. These by-products contain phytochemical compounds with great nutritional and functional potential.This review article describes the scientific studies from the last five years regarding the nutritional and bioactive compounds present in the watermelon rind (WMR) and watermelon seeds (WMSs). This review also focused on their nutraceutical worth fully justified by the presence of functional active compounds, as well as their potential industrial application for future research concerning novel or functional, nutraceutical, pharmaceutical and cosmeceutical product development.Key findings and conclusion: WMR is a rich source of fatty acids, minerals, and phenolic compounds and dietary fibers. It also contains soluble carbohydrates (45–65%), carotenoids, alkaloids, saponin, and phytates. WMSs are an excellent source of protein (15–50%) such as albumin, globulin, prolamin, and glutelin. WMSs are also a good source of vitamin B-complex (B₁, B₂, B₃, B₆ B12), polyunsaturated fatty acids, essential and non-essential amino acids as well as phenolic compounds. Moreover. Watermelon by-products also present therapeutic properties including anti-diabetic, antioxidant, antihypertensive, anti-inflammatory, antiulcer, antitumor, hypocholesterolemic, hepato-, nephron- and neuro-protective effects and antibacterial properties fully evidenced from recently published literature. Therefore, the use of these byproducts to design and develop innovative functional food products with added value is important for sustainability across the food chain. Nevertheless, further research is needed on the clinical studies of WMR and WMSs to fully support the development of functional food products, nutraceutical and pharmaceutical applications.