Contents and functions of catechins and free amino acids in microorganism-fermented teas

Background and objectives: Microorganism-fermented tea is a rare type of tea that is fermented by microorganisms, such as lactic acid bacteria. We have previously shown that Sichuan dark tea, a microorganism-fermented tea, had a suppressive effect on lipid metabolism and the development of atherosclerosis in a rat model of diet-induced atherosclerosis, compared with green tea. The purpose of the present study was to determine the biochemical properties of Japanese and Chinese microorganism-fermented teas in vitro. Methods: Six types of microorganism-fermented tea were investigated, and green tea was used as a control. The antioxidant capacity (The 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity), enzyme inhibitory activity (against a-glucosidase, lipase, and hyaluronidase), and anti-allergic activity of the teas were evaluated in in vitro tests. The anti-allergic activity was assessed via degranulation inhibition tests conducted using the rat basophil-like cell line RBL-2H3 as an indicator of b-hexosaminidase release activity. The catechin and free amino acid contents were determined by HPLC. Results: The antioxidant activity was more than 50% at 1 mg/mL in Awa-bancha, green tea, Go-ishi tea, and Ishizuchi dark tea. a-Glucosidase inhibitory activity was generally low, but Awa-bancha, Goishi tea, and green tea showed 30%-40% activity. In lipase inhibitory activity, all the microorganism-fermented teas, except Bataba tea, showed more than 50% activity at 1 mg/mL, and green tea and Awa-bancha showed more than 90% activity, followed by Sichuan dark tea and Goishi tea. The hyaluronidase inhibitory activity was different from the results for the other enzyme inhibitory activities, with Bataba tea and green tea showing more than 50% activity at 1 mg/mL, followed by Puer tea. b-Hexosaminidase release activity showed a decrease in the order green tea, Sichuan dark tea, Awa-bancha, and Ishizuchi dark tea at 100 μg/mL. Conclusions: We determined the functionality of six types of Japanese and Chinesemicroorganism-fermented teas in vitro. In the future, we plan to investigate the relationship between the functional properties and the catechin and free amino acid content of the teas.