Tea Catechins 18 Alessandra Baldi, Helena Abramovič, Nataša Poklar Ulrih, and Maria Daglia
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Tea Catechins 18 Alessandra Baldi, Helena Abramovič, Nataša Poklar Ulrih, and Maria Daglia Contents 18.1 Introduction ............................................................................. 931 18.1.1 Botanical Description ......................................................... 931 18.1.2 History ......................................................................... 931 18.1.3 Traditional Medical Application .............................................. 932 18.1.4 Tea Classification and Production Processes ................................. 932 18.2 Bioactive Constituents .................................................................. 934 18.2.1 Tea Catechins .................................................................. 934 18.2.2 Factors Determining a Modification of Tea Catechin Profile................ 936 18.2.3 Catechins Distribution in Tea Products ....................................... 941 18.3 Bioavailability and Metabolism ........................................................ 941 18.3.1 Absorption ..................................................................... 941 18.3.2 Metabolism .................................................................... 942 18.3.3 Factors Influencing Tea Catechins Bioavailability ........................... 943 18.4 Bioactivities ............................................................................. 943 18.4.1 Neuroprotective Activity ...................................................... 944 18.4.2 Anticancer Activity ............................................................ 945 A. Baldi Consortium Tefarco Innova, National Inter-University Consortium of Innovative Pharmaceutical Technologies, Parma, Italy e-mail: [email protected] H. Abramovič · N. Poklar Ulrih Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia e-mail: [email protected]; [email protected] M. Daglia (*) Department of Pharmacy, University of Naple Federico II, Naples, Italy International Research Center for Food Nutrition and Safety, Jiangsu University, Zhenjiang, China e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2021 929 J. Xiao et al. (eds.), Handbook of Dietary Phytochemicals, https://doi.org/10.1007/978-981-15-4148-3_19 930 A. Baldi et al. 18.4.3 Activity Against Cardiovascular Diseases .................................... 947 18.4.4 Antidiabetic Activity .......................................................... 949 18.4.5 Anti-obesity Activity .......................................................... 950 18.4.6 Other Activities ............................................................... 951 18.5 Benefits................................................................................. 952 18.5.1 Neurodegenerative Diseases .................................................. 953 18.5.2 Cancers ........................................................................ 953 18.5.3 Cardiovascular Diseases ...................................................... 954 18.5.4 Diabetes ....................................................................... 955 18.5.5 Obesity ......................................................................... 956 18.5.6 Osteoporosis ................................................................... 957 18.6 Applications in Food ................................................................... 958 18.6.1 Tea Catechins Isolation ....................................................... 959 18.6.2 Tea Catechins as Food Additives ............................................. 960 18.6.3 Tea Catechins Regulatory Status .... ......................................... 962 18.7 Safety: Toxicity and Side Effects ...................................................... 963 18.8 Marketed Products ...................................................................... 964 18.9 Patents ................................................................................... 966 18.10 Perspectives ............................................................................. 967 References ....................................................................................... 968 Abstract Tea, a water infusion of leaves from Camellia sinensis (L.) Kuntze, is the oldest, most consumed beverage worldwide. Archeologists have recently discovered traces of tea drinking dating to around 206 B.C. There are five major types of tea, differing in production processes and, therefore, in chemical composition: green tea, white and yellow teas, oolong tea, black tea, and dark tea. Compounds identified in green tea are involved in several biological activities and can have various health-promoting functions, which can include antioxidant, anti-inflam- matory, antiviral, anticancer, antidiabetic, and anti-obesity activities, as well as activities against CVD and neurodegenerative diseases, and many others. These beneficial effects are mainly ascribed to tea catechins, bioactive constituents belonging to the flavonoid family (flavan-3-ols subclass), which represent approx- imately 70% of all polyphenols in tea. However, the maximal concentrations of the catechins detected in blood in human subjects or animals after oral ingestion are in submicromolar or low micromolar levels, which indicate that only small amounts are absorbed and passed into the blood. Chapter “Tea Catechins” describes the chemical composition of C. sinensis leaves and the beneficial effects on human health upon tea consumption, focusing on tea catechin bioactive constituents. This chapter also takes into account their bioavailability, toxicological aspects, and safety profiles. Furthermore, recent applications of tea catechins in the food market are presented. Keywords Camellia sinensis · Tea catechins · Phytochemistry · Bioactive compounds · Health properties · Bioavailability 18 Tea Catechins 931 18.1 Introduction Tea is the most consumed beverage worldwide, and tea plant from which it is derived, Camellia sinensis (L.) Kuntze, is currently grown in over 50 countries of the world. The main producers of tea are China and India, with 2,473,443 t and 1,325,050 t harvested, respectively, in 2017 alone, followed by Indonesia, Iran, Turkey, Vietnam, Kenya, and Sri Lanka (FAOSTAT 2019). 18.1.1 Botanical Description According to its botanical classification, C. sinensis belongs to the Theaceae family which are woody plants with simple leaves, which may be more or less leathery and have smooth or toothed edges, widespread in temperate regions. C. sinensis is a small, highly branched tree, standing at 5–10 m tall, characterized by spaded oval evergreen leaves with toothed edges, which are soft and velvety when young and coriaceous when they are ripe. The shape and size of the leaves are distinctive characteristics in establishing the variety of the plant. The flowers have six to nine petals, are creamy white, and are solitary or grouped in twos or threes, while the fruit consists of a small woody capsule with a few dark, flattened seeds. The oil pressed from these seeds is used in cooking, due to its sweet taste. The plants are cultivated to the height of 1 m to facilitate harvesting, which occurs almost exclusively by hand in order to obtain the finest products and provides for the collection of unopened terminal buds, called pekoe, and the first leaves, young and soft, which produce one of the highest quality tea infusions. Shortly preceding the first harvest, which takes place between April and May, it is traditional practice to obscure the plant to encourage an increase in the content of flavonoids, sugars, and other molecules, which are representative of the quality of the tea, creating the necessary conditions for obtaining a sweeter and more precious product. The products of the first harvest differ from later harvests as they may include both the first leaves of the new season and the remaining leaves of the previous season. The varieties of tea plant with commercial value are C. sinensis var. sinensis (called China type) and C. sinensis var. assamica (called Assam type, deriving from the Northeast state of India). Recent publications on the genetic profiling of tea have clarified that other tea varieties, e.g., C. assamica subsp. lasiocalyx Planch (called Cambod type), which have been considered to be synonyms of China and Assam tea types, are actually hybrids. Indeed, as breeding techniques have evolved, artificial pollination and hybridization are also steadily growing in importance. 18.1.2 History A Chinese legend states that tea was discovered accidentally by Emperor Shen Nong in 2700 B.C., when camping under a tree after a long trip, some tea leaves fell in his pot of boiling water. However, tea as a beverage was first mentioned in Erh Ya, 932 A. Baldi et al. a Chinese book dating from 350 B.C. Archeologists have recently discovered evidence of tea drinking in the excavation of “Han Yang Ling Mausoleum” in the Shaanxi province of China, revealing the diffusion of tea in the Han dynasty (206 B.C.). Tea drinking spread to Japan around the sixth century, as a privilege of high society, and became more widely popular about 700 years ago. The occidental consumption of tea arose from the tea trade between China and Holland, from which the English first gained an appreciation for drinking tea. In the seventeenth century, England was the first player in tea commerce imported from India, imposing restrictive trade conditions and strict taxation on the colonies. That is why, following the approval of the Tea Act in 1773, American colonials threw the tea cargo of British