Characterization of the Role of Phenolic Compounds in the Inhibition of α-Amylase by Kombucha Tea
Samantha Renee Armando, Rebecca Anne Schneider, Francis M Mann
Kombucha is a tea blend that is fermented by a symbiotic culture of bacteria and yeast (SCOBY) and is of high interest in the United States for its health benefits. Research indicates that Kombucha can improve resistance against cancer, prevent cardiovascular disease, promote digestive functions, reduce inflammatory problems, and lower blood glucose levels. The hypoglycemic activity is the primary focus of this study. Kombucha brewed in black tea contains phenolics, and this class of molecules has previously demonstrated inhibitory effects on α-amylase. Previous research indicated that unfermented black tea is not appreciably inhibitory, and thus it was hypothesized that the black tea phenolics undergo biotransformation during fermentation. In order to discriminate the specific inhibitory molecules found in Kombucha, Mock Tea (MT) replicates were made containing no tea polyphenols and compared to fermented Black Tea (BT) replicates. After fermentation, the replicates were treated to remove glycosides and separated over C18 resin. Three fractions were collected and measured for α-amylase inhibition and polyphenolic content. Prior to the evaluation of the data, the pH of the tea was neutralized to negate the effect of inhibition due to acidity. The results demonstrate an acid-independent inhibition of α-amylase by BT but not MT (−30% activity at 2.5% (v/v) analyte in most inhibitory fractions). This does not correlate to black tea phenolic content, as the phenolic content of the BT was or lower than that of the MT in most inhibitory fractions (BT=4.7ug/mL vs. MT= 37.6 ug/mL). However, this may be correlated to oxidative biotransformation of the black tea phenolics as polar fractions resulted in BT dependent inhibition and increased phenolic content (−50% activity at 2.5% (v/v) analyte with phenolic concentrations of BT= 106.3 ug/mL vs. MT= 62.8 ug/mL). While this indicates that the mechanism of α-amylase inhibition is indeed dependent on black tea components, it is likely there are multiple inhibitory molecules with diverse chemical properties. Furthermore, it appears that the SCOBY synthesizes hydrophobic phenolic compounds, but the molecules are not inhibitors of α-amylase.
Keywords: acidity, black tea, cancer, glucose, ph, polyphenols
Citation: The FASEB JournalISSN (print): 0892-6638 | ISSN (online): 1530-6860
Date Updated: March 28, 2020