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Tannase (E.C. 3.1.1.20) is hypothesized to be involved in the metabolism of gallates and gallic acid (GA) in pu-erh tea fermentation. In this work, we measured tannase in Aspergillus niger fermented tea leaves and confirmed the production of fungal tannase during pu-erh tea fermentation. A decrease in catechin and theaflavin gallates and a significant increase in GA content and the relative peak areas of ethyl gallate, procyanidin A2, procyanidin B2, procyanidin B3, catechin-catechin-catechin, epiafzelechin, and epicatechin-epiafzelechin [variable importance in the projection (VIP) > 1.0, p 1.5] were observed using high performance liquid chromatography (HPLC) and metabolomics analysis of tea leaves fermented or hydrolyzed by tannase. In vitro assays showed that hydrolysis by tannase or polymerization of catechins increased the antioxidant activity of tea leaves. In summary, we identified a metabolic pathway for gallates and their derivatives in tea leaves hydrolyzed by tannase as well as associated changes in gallate and GA concentrations caused by fungal tannase during pu-erh tea fermentation.

Previously, we found that phospholipids derived from large yellow croaker (Pseudosciaena crocea) roe had a higher level of docosahexaenoic acid (DHA-PL), which had beneficial effects on lipid metabolism. However, the mechanism by which DHA-PL from P. crocea roe exerts these effects has not yet been illuminated. Herein, we investigated the underlying molecular action of DHA-PL by examining changes in liver protein expression in control, hyperlipidemic, and DHA-PL-treated mice. A total of 16 proteins, 9 up-regulated and 7 down-regulated, were identified and classified into several metabolic pathways, such as fat digestion and absorption, peroxisome proliferator activated receptor (PPAR) signaling, and antigen processing and presentation; the largest functional class found was that of fat digestion and absorption. We revealed Apoa1 to be a biomarker of DHA-PL effects on hyperlipidemic mice by DHA-PL diet. These results not only improve our current understanding of hyperlipidemic regulation by DHA-PL, but also suggest that DHA-PL should be applied as a beneficial food additive.