Characterization of Kombucha Tea as an Inhibitor of α‐Amylase

Kombucha tea (KT) is a fermented beverage gaining mainstream popularity due to purported and demonstrated health benefits. KT has previously demonstrated a hypoglycemic effect in an induced diabetes rat model which indicates bioactive compounds within KT may act as effective anti‐diabetic agents. One method by which KT may induce hypoglycemia in a biological model is via inhibition of α‐amylase. Indeed, KT inhibits α‐amylase with an IC50 of 0.16±0.06% (v/v) in vitro. Two potential mechanisms to explain this phenomenon were explored, including acid‐based inhibition and inhibition by phenolic molecules present in the pre‐fermentation substrate. Initial results indicate that KT‐dependent inhibition of α‐amylase is not completely dependent on pH, as neutralized KT retains partial inhibitory properties (IC50=1.2±0.23% (v/v)), however complete inhibition is not observed (Activity minimum = 49.8±5.1%). However, pre‐fermentation black tea substrate fails to demonstrate any inhibition of α‐amylase activity which indicates that KT fermentation may either biotransform inactive substrate molecules or synthesize new inhibitory molecules de novo . Further experimentation with Kombucha fermented in the absence of tea (MT) resulted in retention of partial acid‐dependent inhibition (IC50=6.3±5.4%(v/v)) but loss of pH‐independent inhibition. Corresponding analysis of the phenolic profile of MT and KT support the hypothesis that tea phenolics undergo fermentative biotransformation resulting in increased α‐amylase inhibition and provides evidence that KT fermentation may result in synthesis of a novel hypoglycemic agent.