Abstract
Tea polysaccharides (TPSs) are one of the main bioactive constituents of tea with various biological activities such as hypoglycemic effect, antioxidant, antitumor, and immunomodulatory. The bioactivities of TPSs are directly associated with their structures such as chemical composition, molecular weight, glycosidic linkages, and conformation among others. To study the relationship between the structures of TPSs and their bioactivities, it is essential to elucidate the structure of TPSs, particularly the fine structures. Due to the vast variation nature of monosaccharide units and their connections, the structure of TPSs is extremely complex, which is also affected by several major factors including tea species, processing technologies of tea and isolation methods of TPSs. As a result of the complexity, there are few studies on their fine structures and chain conformation. In the present review, we aim to provide a detailed summary of the multiple factors influencing the characteristics of TPS chemical structures such as variations of tea species, degree of fermentation, and preparation methods among others as well as their applications. The main aspects of understanding the structural difference of TPSs and influencing factors are to assist the study of the structure and bioactivity relationship and ultimately, to control the production of the targeted TPSs with the most desired biological activity.
Highlights
Tea, an important agricultural product made from the fresh leaves and buds of plant Camellia sinensis, is the most consumed functional beverage in the world [1]
It can be seen that the molecular weight (Mw) of polysaccharides using enzyme extraction were decreased, indicating that enzyme catalyzed cleavage of Tea polysaccharides (TPSs) bonds occurred in the extraction process
The investigation of the chemical structures of water soluble fractions (GTPS and BTPS) and insoluble fractions (GTPI and BTPI) from green and black teas found that soluble fractions GTPS and BTPS were consisted of a main chain of (1→3)-β-Galp with side chains of α-Araf and terminal units of α-Araf, α-Fucp and α-Rhap substituted at O-6 by (1→6)-linked-β-Galp, whereas water insoluble fractions, GTPI and BTPI were composed of a main chain of (1→4)-β-Xylp, substituted at O-3 by α-Araf, β-Galp, and α-Glcp units [54]
Summary
An important agricultural product made from the fresh leaves and buds of plant Camellia sinensis, is the most consumed functional beverage in the world [1]. It has a long history of dietary and medicinal application, especially in Asian countries—such as China, Japan, India, and Thailand—for more than five thousand years [2]. Tea possesses multiple biological functions, including antioxidant, hypoglycemic effect, anti-microbial, lowering blood lipids, and anticancer [1,4,5]. These biological activities have been attributed to the variety of chemical ingredients of tea, mostly to tea polyphenols such as catechins, theaflavins, thearubigins, theasinensins and other flavonoids, and polysaccharides, alkaloids (caffeine, theobromine and theophylline), proteins, lipids, and inorganic elements (selenium, iron, manganese, etc.) among others [1,4,5,6]
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