Maturity stage at harvest influences antioxidant phytochemicals and antibacterial activity of jujube fruit (Ziziphus mauritiana Lamk. and Ziziphus spina-christi L.)

Fruits of the genus Ziziphus are known for their medicinal and nutritional value. Thus, this study aimed to investigate the influence of different maturity stages (unripe, half-ripe, and ripe fruit) at harvest on the physicochemical characteristics, phytochemical composition, antioxidants, and antibacterial activities of Ziziphus mauritiana and Ziziphus spina-christi fruits. In both plant species, the unripe fruits had significantly higher (P < 0.05) phenolic and flavonoid content and antioxidant and antibacterial activity compared with ripe fruits. At all maturity stages, these features were significantly higher (P < 0.05) in Z. spina-christi fruits than in Z. mauritiana fruits. Regardless of the species, 13 phenolic compounds were identified and quantified in the fruit extracts. For both species, the concentration of individual phenolic compounds changed with fruit maturity. Among the phenolic compounds, the gallic acid, 4-hydroxybenzoic acid, salicylic acid, catechin, and rutin levels were significantly higher (P < 0.05) in Z. spina-christi fruits than those for Z. mauritiana fruits, whereas vanillic acid and quercetin showed the opposite trend. Additionally, trans-cinnamic acid was only detected in Z. spina-christi fruits. In conclusion, the mature unripe jujube fruit, especially in Z. spina-christi, was shown to be a promising source of various naturally occurring compounds of significant interest owing to its pharmacological and therapeutic properties as an antioxidant, anti-inflammatory, and analgesic.