Heavy fermentation impacts NO-suppressing activity of tea in LPS-activated RAW 264.7 macrophages

The effect of fermentation on the nitric oxide (NO)-suppressing activity of tea was investigated using an lipopolysaccharide (LPS)-activated RAW 264.7 cell model. Two species of tea, Taiwan tea No. 12 and Chinsin Oolong, commonly cultivated and consumed in Taiwan, were selected and manufactured with three degrees of fermentation. All of the teas including non-fermented green, partially fermented paochong and fully fermented black teas, were prepared from a single batch of fresh tea leaves. Additionally, the freeze-dried solids of tea infusions were used to treat cells and their NO-suppressing activities were compared. The results showed that the two species of black tea inhibited the NO production, inducible nitric oxide synthase (iNOS) catalytic activity and iNOS protein expression in LPS-activated cells, more weakly than did green and paochong teas. Meanwhile, the NO-suppressing activity was highly correlated with the total phenolics content. Clearly, heavy fermentation strongly affects the NO-suppressing activity of tea, and the decline of the NO-suppressing activity is attributed to the elimination of the phenolics.