SUMMARYResearch backgroundKombucha is consumed worldwide for its beneficial health effects. Kombucha teas fermented with various herbal infusions have become very important nowadays. Although black tea is used for kombucha fermentation, kombucha teas fermented with different herbal infusions have gained great importance. In this study, three different traditional medicinal plants, namely hop (Humulus lupulusL.), madimak (Polygonum cognatum) and hawthorn (Crataegus monogyna) were used for the fermentation of kombucha beverages, and the bioactivity of these beverages was investigated extensively.Experimental approachThe microbiological profile, bacterial cellulose formation, antibacterial, antiproliferative and antioxidant activities, sensory properties, total phenolic content and flavonoid content of kombucha beverages were investigated. Liquid chromatography-coupled mass spectrometry analysis was used to identify and quantify specific polyphenolic compounds in the samples.Results and conclusionsAccording to the results, the hawthorn-flavoured kombucha, which has lower free radical scavenging activity than the other samples, came into prominence in terms of sensory properties. All examined kombucha beverages showed a strong cytotoxic effect on Mahlavu and HCT116 cell lines, but only the madimak-flavoured kombucha sample, which had a higher total phenolic/flavonoid content, had antibacterial activity against all microorganisms used in the study.Novelty and scientific contributionConsidering the results of this study, madimak could be an effective herb for the development of new kombucha beverages, although its sensory properties still need to be improved. This study contributes to science in terms of producing new fermented beverages with improved beneficial health effects.