Determination of phenolic composition, antioxidant activity, and cytotoxicity characteristics of kombucha beverage containing Echium amoenum

Echium amoenum is a valuable green medicinal plant with beneficial health effects. This study aimed to determine the phenolic composition, flavonoid, and anthocyanin content, antioxidant activity, and cytotoxicity characteristics of kombucha beverages containing Echium amoenum as a fermentation substrate for a replacement of black tea (80:0, 50:30, 40:40, 30:50, and 0:80). The physicochemical properties of formulated beverages were evaluated during a 15-day fermentation period and statistical analysis was performed based on one-way analysis of variance. As a result, the reduction of pH and formation of the cellulosic pellicle layer verified the suitability of E. amoenum for kombucha consortium activation. The total phenol, anthocyanin, and flavonoid content along with the antioxidant activity of samples were significantly increased by the addition of E. amoenum and the increase of fermentation time. HPLC analysis revealed that the highest phenolic compound in the traditional kombucha and the prepared samples with E. amoenum were gallic and coumaric acid, respectively. The cell cytotoxicity study results demonstrated that the kombucha beverages prepared from the highest amount of E. amoenum infusion without containing black tea infusion had higher cancer cell cytotoxicity than the traditional ones. Furthermore, the sample contained 30% black tea infusion, and 50% E. amoenum infusion could be promoted as a novel product with high health benefits as well as better sensorial acceptability due to a milder taste and a tempting pleasant color which can be a suitable choice for consumers, especially who subjected to the oxidative stress.