Antioxidant and Antihyperglycemic Effects of Bay Leaf (Syzygium polyanthum [Wight.] Walp) Kombucha in Alloxan-Induced Diabetic Mice

Kombucha is a popular functional beverage known for its health benefits, and recent research has focused on using alternative substrates for its production. Syzygium polyanthum (bay leaf) is a medicinal plant with various pharmacological properties, yet its potential as a kombucha fermentation substrate remains unexplored. This study aimed to evaluate the polyphenol content, antioxidant capacity, and antihyperglycemic effects of kombucha made from S. polyanthum extract. The research followed four main stages: S. polyanthum extraction, fermentation, product standardization, and pharmacological testing. Chemical analysis quantified the total phenolic and flavonoid content, while biological evaluations included an in vitro antioxidant assessment using the DPPH assay and an in vivo antihyperglycemic study in alloxan-induced diabetic mice. Data were analyzed using independent T-tests and ANOVA with a 95% confidence interval. A non-significant increase was observed in the total phenolic content of S. polyanthum kombucha (8.01±0.69 mg GAE/g) compared to the non-fermented infusion (7.71±0.37 mg GAE/g, p = 0.547), along with a slight increase in flavonoid content (5.04±0.25 mg QE/g vs. 4.74±0.23 mg QE/g, p = 0.196). The kombucha also exhibited significantly stronger antioxidant activity than its non-fermented infusion (IC₅₀: 449.31±38.9 µg/mL vs. 578.93±20.67 µg/mL; p <0.05), although both were considerably less potent than the standard gallic acid (IC₅₀: 25.68±3.26 µg/mL). Furthermore, after 14 days of treatment, S. polyanthum kombucha significantly reduced blood glucose levels in diabetic mice by 61.45±11.63%, surpassing both metformin (50.47±4.28%) and the non-fermented S. polyanthum infusion (53.34±5.71%) (p=0.001; p<0.05). These findings indicate that the kombucha is a promising functional beverage with potential applications in diabetes management.