Phytochemical Composition, Bioactive Compounds, and Antidiabetic Potential of Four Medicinal Plants Native to the UAE: Capparis spinosa, Citrullus colocynthis, Morus alba, and Rhazya stricta

This review highlights the significant therapeutic properties of four indigenous plants in the United Arab Emirates. These include Capparis spinosa L. (family: Capparaceae), commonly known as caper and locally referred to as Kabir; Citrullus colocynthis (L) Schrad. (family: Cucurbitaceae), known in English as bitter apple and locally as Alhanzal; Morus alba L. (family: Moraceae), referred to as white mulberry and locally named Firsad; and Rhazya stricta Decne. (family: Apocynaceae), commonly called harmal-e-shami and known locally as Alhi-rimi. These species are traditionally used for various ethnobotanical purposes and are important components of the region’s flora, such as managing diabetes and associated metabolic disorders. These plants contain diverse bioactive compounds with notable pharmacological activities. For example, caper exhibits antidiabetic effects through flavonoids such as quercetin and kaempferol, which enhance insulin sensitivity and lower blood glucose levels. Bitter apple is rich in cucurbitacins and alkaloids that lower glycated hemoglobin and support pancreatic β-cell function. White mulberry contains chlorogenic acid, rutin, and 1-deoxynojirimycin, which improve glucose uptake, inhibit α-glucosidase, and reduce oxidative stress. Harmal-e-shami exhibits variable antidiabetic activity, including dipeptidyl peptidase-IV inhibition and enhancement of glucagon-like peptide-1 secretion, which is influenced by the type and dosage of the extract. Despite these promising effects, challenges remain in standardization, phytochemical variability, and clinical validation. This review underscores the therapeutic potential of these plants and recommends further research for their integration into sustainable, plant-based diabetes management strategies.