Physicochemical properties and biological activities of a high-theabrownins instant Pu-erh tea produced using Aspergillus tubingensis

High-theabrownins (TB) instant Pu-erh tea was produced via a novel submerged fermentation (SF) by Aspergillus tubingensis and compared with samples produced commercially via the conventional solid-state fermentation (SSF). All tea samples were assessed for physicochemical properties and biological activities (cytotoxicity toward cancer cells; antioxidant capacity). TB content of SF tea was nearly 4-fold compared to SSF teas. SF instant Pu-erh tea had significantly higher levels of theabrownins, total polyphenols, total flavonoids, caffeine and theobromine compared to the SSF ripe tea, but had significantly lower levels of gallic acid, total catechins, epicatechin, epicatechin gallate, theaflavins, thearubigins, amino acids, total carbohydrate and polysaccharides. The free radical scavenging ability of SF-produced tea was lower than of the teas made via SSF. At suitable combinations of concentration and contact time, the instant Pu-erh tea had anticancer and antioxidative effects in vitro. The cytotoxic effect and the intracellular reactive oxygen species scavenging capacity of SF tea was mainly associated with theabrownins.