Antioxidant and Antidiabetic Activities of Manalagi Apple (Malus sylvestris Mill) Juice and Water Kefir: An In Vitro and In Silico Study

Diabetes mellitus is associated with oxidative stress, which is linked to an increased production of reactive oxygen species, potentially resulting in cellular damage. Antioxidant compounds have been shown to effectively reduce this damage in individuals with diabetes mellitus. Among the prominent sources of these antioxidants are apple juice and water kefir. The aim of this research was to asses the antioxidant and antidiabetic activities of Manalagi apple juice (MAJ) and Manalagi apple water kefir (MAWK) using in vitro and in silico methods. Antioxidant and antidiabetic activities were determined using 2,2-diphenyl-1-picrilhydrazyl (DPPH) assay and α-glucosidase inhibition. The interactions of the active compounds were analyzed in silico using molecular docking techniques. MAJ and MAWK contain flavonoids, saponins, and tannins. MAWK showed a higher potential with a pH of 4.7, total flavonoid content of  0.014 – 0.025 mg QE/g, total phenolic content of 224.270 – 413.973 mg GAE/g, vitamin C content of 56.320–166.613 mg/100 mL, antioxidant activity with an IC50 value of 6.48% (w/v), and α-glucosidase inhibition activity with an IC50 value of 23.82% (w/v). Chlorogenic acid, as a phytoconstituent of plants, is reported to exhibit both antioxidant and antidiabetic properties. This assertion is substantiated by molecular docking studies, which reveal Gibbs free energy values of -6.9 kcal/mol for its antioxidant activity and -6.7 kcal/mol for its antidiabetic activity.  Consequently, MAWK has potential as a functional food that serves as an antioxidant and aids in the regulation of blood glucose levels in diabetes mellitus.