Bioactive properties of Kombucha beverages produced with Anatolian hawthorn (Crataegus orientalis) and nettle (Urtica dioica) leaves

The aim of the present study was to evaluate the bioactive properties of plant tea and Kombucha samples produced using Anatolian hawthorn (KH), nettle leaves (KN) and black tea (KC, as control) during storage at 4 °C for 120 days. The total phenolic and flavonoid contents of Kombucha samples were found in the range of 995.33 mg GAE/L-2456.83 mg GAE/L and 75.21 mg CE/L-193.68 mg CE/L, respectively, where the values were higher than plant tea samples. During storage period, total phenolic contents of KC were generally higher than other samples, while higher total flavonoid content, total acidity and ash contents were found in KN. When antioxidant activity was detected by ABTS method, no significant differences was observed between Kombucha samples (89.68%–94.84%), while DPPH method gave higher results in KC than KH and KN. Although antioxidant activity of the samples showed a fluctuation during storage period, higher levels (80.48%–90.36% by ABTS method and 65.60%–70.76% by DPPH method) were observed in KC at the end of the storage (P < 0.05), which is compatible with the total phenolic content results. Antimicrobial activities of the samples were examined by detecting minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). MIC values were in the range of 15.63 ?g/mL-125.00 ?g/mL. Besides, antimicrobial effect of KN was found higher than KH and KC. However, inhibition effects of Kombucha samples were decreased at the end of the storage time. The results make Anatolian hawthorn and nettle leaves interesting for the production of Kombucha beverages, which have distinct bioactive properties. © 2023 Elsevier Ltd