Tea is the most popular functional beverage in the world and has been gaining more and more attention for its health beneficial properties. Among common teas, black tea is consumed more than green tea and oolong tea worldwide. Numerous studies have shown the biological activities of black tea and its polyphenols that include anti-oxidant, anti-tumor, anti-inflammation and metabolic regulation. Tea polyphenols such as theaflavins and catechins are considered to be multifunctional compounds that could be effective in the prevention or treatment of various cancers, cardiovascular disease, chronic inflammation, obesity, metabolic syndrome, and neurodegenerative diseases. In this review, we summarized the up-to-date research and underlying molecular mechanisms of black tea and its polyphenols.

The inhibitory effects of a formulated product from citrus peel extract, Gold Lotion (GL), on 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in mouse skin was reported in this study. It is found that in the TPA-induced skin inflammation model, the topical application of GL effectively inhibited the transcriptional activation of iNOS and its mRNA and protein in mouse skin. It is also discovered that GL significantly inhibited TPA-induced mouse skin inflammation by decreasing inflammatory gene parameters. Furthermore, GL dramatically inhibited 7,12-dimethylbenez[a]anthracene (DMBA)/TPA-induced skin tumor formation and reduced tumor incidence, tumor weight and tumor multiplicity of papillomas at 20 weeks. In essence, these in vivo data have revealed that GL is an effective anti-tumor agent that functions by down-regulating the protein levels of COX-2, ornithine decarboxylase (ODC), and vascular endothelial growth factor (VEGF) in mouse skin, suggesting that GL is a novel functional natural product capable of preventing inflammation-associated tumorigenesis.