Phytochemical Constituents and In Vitro Anti-Diabetic Properties of Ziziphus jujubа (Rhamnaceae) Fruits

In the current study the phytochemical profile of 70% ethanol extract of Ziziphus jujubа (Rhamnaceae), cultivated in Bulgaria has been investigated. The fruit extract contained numerous phytochemicals, such as triterpenes, phenolic acids and flavonoids. Five triterpenes, 11 phenolic acids and 5 flavonoids have been identified. The fruit extract had a total phenolic content of 21.62 ± 0.0265 mg/g and total flavonoid content 1.34 ± 0.017 mg/g dried extract. Among the triterpenes with the highest concentration was the betulinic acid 20943.17±527.06 µg/g dried extract, rosmarinic acid (1174.26±29.55 µg/g) among the phenolic acids, followed by myricetin (214.61±5.40 µg/g) as a representative of flavonoids and rutin 3 046.89±76.68 among the quercetin glycosides. The inhibitory effect of Z. jujubа fruit extract has been investigated on the key enzymes linked to diabetes – α-glucosidase and α-amylase. In order to evaluate the type of inhibition a Lineweaver-Burk plot was produced. The results obtained from the enzyme kinetic studies exhibited a mixed noncompetitive-uncompetitive type of inhibition on α-glucosidase and mixed competitive-non-competitive type of inhibition on α-amylase. Besides that the obtained results proved high inhibition of α-glucosidase (79.46% at 1.33 mg.ml-1 extract) and moderate inhibition of α-amylase (39.10% at 0.666 mg.ml-1 extract concentration). These results suggest the possible use of fruits of Z. jujubа in the management of diabetes mellitus.