Application of the Kombucha 'tea fungus' for the enhancement of antioxidant and starch hydrolase inhibitory properties of ten herbal teas

Ten herbal teas (Acacia arabica, Aegle marmelos flower, A. marmelos root bark, Aerva lanata, Asteracantha longifolia, Cassia auriculata, Hemidesmus indicus, Hordeum vulgare, Phyllanthus emblica, Tinospora cordifolia) were fermented with the Kombucha 'tea fungus'. The pH values of the fermented beverages ranged from 4.0 to 6.0 by day 7, while the titratable acidity ranged from 2.5 to 5.0 g/mL (P < 0.05). Gallic acid had statistically significantly increased (P < 0.05) in almost all the samples by day 7. The Oxygen radical absorbance capacity assay indicated 5 of the Kombucha beverages to have statistically significant increases (P < 0.05) by day 7. The α-amylase inhibitory activities ranged from 52.5 to 67.2 μg/mL in terms of IC₅₀ values following fermentation, while the α-glucosidase inhibitory activities ranged from 95.2 to 196.1 μg/mL. In conclusion, an enhancement of the antioxidant and starch hydrolase inhibitory potential of the herbal teas was observed by adding the tea fungus.