Tea Chemistry

Critical Reviews in Plant Sciences (Impact Factor: 5.29). 01/1997; 16:415-480. DOI: 10.1080/07352689709701956

ABSTRACT The chemistry of tea as a beverage is reviewed in depth, covering both historical and current chemical perspectives. Special attention is given to the polyphenols in tea, although the general composition and properties are also treated. Current trends in tea science, particularly in the area of polyphenol complexation and antioxidant properties, are also covered. The need for a chemically based understanding, rather than one hypothesized from generalized and indirect observation, is stressed.

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    ABSTRACT: Insect prophenoloxidase (PPO) is an important innate immunity protein due to its involvement in cellular and humoral defense. It belongs to a group of type-3 copper-containing proteins that occurs in almost all organisms. Insect PPO has been studied for over a century, and the PPO activation cascade is becoming clearer. The insect PPO activation pathway incorporates several important proteins, including pattern-recognition receptors (PGRP, β GRP, and C-type lectins), serine proteases, and serine protease inhibitors (serpins). Due to their complexity, PPO activation mechanisms vary among insect species. Activated phenoloxidase (PO) oxidizes phenolic molecules to produce melanin around invading pathogens and wounds. The crystal structure of Manduca sexta PPO shows that a conserved amino acid, phenylalanine (F), can block the active site pocket. During activation, this blocker must be dislodged or even cleaved at the N-terminal sequence to expose the active site pockets and allow substrates to enter. Thanks to the crystal structure of M. sexta PPO, some domains and specific amino acids that affect PPO activities have been identified. Further studies of the relationship between PPO structure and enzyme activities will provide an opportunity to examine other type-3 copper proteins, and trace when and why their various physiological functions evolved. Recent researches show that insect PPO has a relationship with neuron activity, longevity, feces melanization (phytophagous insects) and development, which suggests that it is time for us to look back on insect PPO beyond the view of immunity in this review.
    Frontiers in Physiology 07/2014; 5:252. DOI:10.3389/fphys.2014.00252
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    ABSTRACT: ABSTRACT Tea and coffee are rich in polyphenols with a variety ofbiological activities. Polyphenols found in tea are predominantlyflavonoids, of which up to 15% are present as free or esterified gallic acid. Coffee polyphenols are almost wholly comprised of chlorogenic acids. Many of the demonstrated,activities of polyphenols are consistent with favourable effects on the riskof chronic diseases. In investigatingthe relationships between intake and exposure to such
  • Bone 05/2011; 48. DOI:10.1016/j.bone.2011.03.612 · 4.46 Impact Factor


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May 26, 2014