Multiple biological effects of secondary metabolites of Ziziphus jujuba: isolation and mechanistic insights through in vitro and in silico studies

In this study, we tested tyrosinase and α-glucosidase effects of different extracts of Ziziphus jujuba fruits. The n-BuOH subextract inhibited both tyrosinase and α-glucosidase (IC(50) = 18.82 ± 1.13 and 25.03 ± 0.77 µg/mL, respectively) better than the positive controls kojic acid and acarbose (IC(50) = 58.26 ± 0.25 and 46.10 ± 2.3 µg/mL, respectively). Thus, the n-BuOH extract was selected for further phytochemical studies. Indole-3-lactic acid methylester, catechin, magnoflorine, kaempferol 3-O-α-rhamnopyranosyl-(1 → 6)-β-galactopyranoside, quercetin 3-O-α-rhamnopyranosyl-(1 → 6)-β-galactopyranoside, and procyanidin B4 were isolated from the extract. We tested α-glucosidase and tyrosinase inhibitory effects, as well as DNA nuclease effects of the isolated compounds. Procyanidin B4 exhibited the best activity against both tyrosinase and α-glucosidase (IC(50) = 60.25 ± 0.88 and 170.18 ± 5.60 µg/mL, respectively). The isolates did not show any nuclease effect at increasing concentrations. Molecular docking studies provided insights into inhibition mechanisms of the isolates against tyrosinase and α-glucosidase at the molecular level. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00217-021-03946-0.