Recent Progress in Natural Anticancer Agents Discovery from Tea (Camellia sinensis): A Review

Tea, as the bud from the plant Camellia sinensis, is the most consumed popular beverage just next to water; especially green tea has gained much attention because of its health effects. The anticancer effects of tea components including tea polyphenols, in particular epigallocatechin gallate and tea polysaccharides, are widely investigated in recent years. Based on the articles and patents published in the last 10 years, this review focuses on the structural activities and molecular mechanisms of the anticancer effects of tea components (mainly tea polyphenols and tea polysaccharides) to provide references for future anticancer studies of tea. In the database, a literature search was conducted with "tea polyphenols", "tea polysaccharides", "theanine" and "anticancer" as the keywords, and the limited time range was "2010-2021". After sorting out and analyzing the retrieval results, the structure, activity and molecular mechanism, as well as the research progress on the structural modification, drug delivery system and toxicology of natural agents in tea in recent years, were summarized. We found that the natural anticancer agents in tea mainly include tea polyphenols, tea polysaccharides, theanine, caffeine and other components by summarizing the literature. The anticancer mechanisms can be divided into the induction of cell apoptosis, inhibition of cell proliferation, metastasis and invasion, and inhibition of angiogenesis. In the past 10 years, there was little literature on the structural modification, drug delivery system and toxicological evaluation of natural anticancer agents in tea, and there were reports of novel research on nano preparations. The studies showed that nano preparation technology could effectively improve the bioavailability and targeting treatment of anticancer tea components. In addition, in the past decade, patents on tea and natural anticancer agents in tea were relatively rich, among which pharmaceutic preparation patents were the majority, and tea polyphenols were the main ones. This paper concluded that there are many kinds of natural anticancer agents in tea, and the anticancer mechanism is complex. Further research on the structural modification, drug delivery system and toxicological evaluation of relevant anticancer active components can be carried out. In general, tea components as new anticancer substances have a certain potential for development. In addition, future research can be focused on the comprehensive study of the structure-activity relationship, the in-depth study of the molecular mechanism, the in-depth understanding of the anticancer effects in vivo, and the verification of large-scale production.