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Figure 4.1
Structures of caffeine and tea catechins. Major catechins in green tea are
mainly classified into two categories by the existence of a galloyl group on
the oxygen atom at the C3 position, non-galloylated and galloylated
catechins.
the stereochemical structure of complexes of caffeine and CA and EC of non-
galloylated catechins were investigated. Crystals of the complexes of caffeine
and two non-galloylated catechins, CA and EC, were prepared, and the
stereochemical structure and intermolecular interactions were investigated and
compared with those of the complexes of caffeine and CA, and caffeine
and EC.
Next, we focused on CA of non-galloylated catechins and Cg of galloylated
catechins. The structural difference between CA and Cg is the presence or
absence of a galloyl group on the oxygen atom at the C3 position, and all
others are the same. X-Ray crystallographic analysis of complexes of caffeine
and CA, Cg were performed to determine the stereochemical structures and to
elucidate the detailed non-covalent interaction between caffeine and CA, Cg
moieties. Furthermore, we investigated the difference of non-covalent bonds in
the stereochemical structures having a galloyl group or not.
4.2
Stereochemical Structures of Complexes of Caffeine
and Catechins
4.2.1 Complex of Caffeine and CA
A solution containing equimolecular amounts of caffeine and CA in water was
lyophilized to give a pale orange powder, which was recrystallized from
methanol to afford colorless needles. The crystal structure was determined to
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