Proximate composition, minerals, phytochemicals, and functional activities of jujube fruits grown in Bangladesh

Different varieties of jujube fruits are being grown and consumed in Bangladesh for their nutritional and biological functions. The functional properties of jujube fruits are credited to the abundance of phytochemical compounds. Unfortunately, the quantification and functional characterization of phytochemicals in jujube fruits grown in Bangladesh have not been investigated. To address this, four cultivars of jujube (Ziziphus mauritiana) fruits grown in Bangladesh were characterized with respect to proximate composition, mineral and phytochemical contents with their antioxidant and antidiabetic activities. Investigations showed that all cultivars of jujube fruits contained a significant amount (% DM) of carbohydrate (76.10–77.3), protein (4.23–5.00), fat (1.35–2.33), ash (3.08–3.28), and fiber (5.66–7.35). Calcium, potassium, sodium, and iron were the major minerals in four cultivars of jujube fruits. Apple Kul showed considerably (p < 0.05) highest contents of total phenolic (17.4 mg GAE/g DM), total flavonoid (4.75 mg QE/g DM), and anthocyanin (17.18 mg cyanidin 3-glucoside/g DM) followed by Kolmi Kul, Deshi Kul, and BAU Kul. The vitamin C content followed the order (p < 0.05): BAU Kul > Deshi Kul > Komli Kul > Apple Kul. The carotenoid content was highest in Kolmi Kul. The antioxidant activity was highest in Apple Kul while BAU Kul and Kolmi Kul represented the highest antidiabetic activity. Correlation analysis showed that vitamin C, total phenolic, and total flavonoid content were the main phytochemicals for antioxidant and antidiabetic functions in jujube fruits. Jujube fruits were also found to have maximum contents of phytochemicals and antioxidant activity at the “mature” stage than “ripening start”, “full ripe” and “overripe” stages. Therefore, the results demonstrated that the jujube fruits in Bangladesh have promising potential to be used as functional foods or natural antioxidants with beneficial effects on human health.