Effect of solution pH on complex formation between epi-type catechin and b-cyclodextrin
with (-)-epigallocatechin gallate, a major active constituent of
A-ring of EGCg and 5-H situated in a deep position of the
0
0
green tea. J Inorg Biochem. 2002;88:7–13.
b-CD cavity and between H-2 (H-6 ) on the B-ring and
-H in a shallow position of the cavity were observed in
3
. Okumura H, Ichitani M, Takihara T, Kunimoto K. Facile quan-
titative analysis of gallated catechins in tea beverage by UV
absorption spectra. Jpn J Food Chem. 2007;14:128–33.
3
both of the ROESY spectra at pH 3.0 and pH 8.5 (Fig. 3).
The large negative values of DH and DS would reflect
4. Ohata T, Ikeda H, Inenaga M, Mizobe T, Yukawa M, Fujisawa
M, Aki H. Drug-tea polyphenol interaction (II) complexation of
piperazine derivatives with green tea polyphenol. Thermochim
Acta. 2017;653:1–7.
5. Ikeda H, Tsuji E, Matsubara T, Yukawa M, Fujisawa M, Yukawa
E, Aki H. Incompatibility between propericiazine oral solution
and tea-based drink. Chem Pharm Bull. 2012;60:1207–11.
1
1
hydrogen bonding between an OH group on the A-ring of
EGCg and an internal O atom of b-CD. On the other hand,
the formation of the second type depended on the solution
0
pH, because the B -ring of EGCg was shallowly inserted in
the b-CD cavity (right in Fig. 4). The cross-peak between
6
. Yokozawa T, Cho EJ, Hara Y, Kitani K. Antioxidative activity of
0
0
0
00
0
H-2 (H-6 ) on the B -ring of EGCg and 3-H of b-CD was
confirmed in the ROESY spectrum only at pH 3.0.
Decreases in n and K with the increase in pH indicated
green tea treated with radical initiator 2,2 -azobis (2-amidino-
propane) dihydrochloride. J Agric Food Chem. 2000;48:5068–73.
7. Lee LS, Kim SH, Kim YB, Kim YC. Quantitative analysis of
major constituents in green tea with different plucking periods
and their antioxidant activity. Molecules. 2014;19:9173–86.
2
2
that complexation at a 1:1 molar ratio became difficult due
0
00
to the ionization of the 4 -OH group on the B -ring.
8
. Kobayashi M, Nishizawa M, Inoue N, Hosoya T, Yoshida M,
Ukawa Y, Sagesaka YM, Doi T, Nakayama T, Kumazawa S,
Ikeda I. Epigallocatechin gallate decreases the micellar solubility
of cholesterol via specific interaction with phosphatidylcholine.
J Agric Food Chem. 2014;62:2881–90.
Decreases in the negative values of DH and DS would
2
2
indicate that the hydrogen bonding between an OH group
0
on the B -ring of EGCg and an internal O atom of b-CD
disappeared as pH increased.
9
. Asahi Y, Noiri Y, Miura J, Maezono H, Yamaguchi M, Yama-
moto R, Azakami H, Hayashi M, Ebisu S. Effects of the tea
catechin epigallocatechin gallate on Porphyromonas gingivalis
biofilms. J Appl Microbiol. 2014;116:1164–71.
In this study, it was found that EGCg with some
insertable sites formed two types of inclusion complexes
with b-CD. The stoichiometry (n), association constant
1
0. Tamura M, Saito H, Kikuchi K, Ishigami T, Toyama Y, Takami
M, Ochiai K. Antimicrobial activity of gel-entrapped catechins
toward oral microorganisms. Biol Pharm Bull. 2011;34:638–43.
11. Khan N, Mukhtar H. Tea and health: studies in humans. Curr
Pharm Des. 2013;19:6141–7.
2. Yukawa M, Moriwaki H, Murakami T, Ikeda H, Iwase Y, Aki H.
Effect of pH on the conformation of inclusion complexes between
b-lactam antibiotics and b-cyclodextrins in aqueous solution.
Kobunshi Ronbunshu. 2010;67:192–7.
(
K) and thermodynamic parameters (DG, DH and DS)
could be calculated from the calorimetric titration curves.
ITC might be indispensable to discuss the inclusion
mechanism between cyclodextrin and compounds such as
EGCg.
1
1
3. Wszelaka-Rylik M. Thermodynamics of b-cyclodextrin–ephe-
drine inclusion complex formation and covering of nanometric
Conclusions
calcite with these substances.
2017;127:1825–34.
14. Ikeda H, Fukushige Y, Matsubara T, Inenaga M, Kawahara M,
Yukawa M, Fujisawa M, Yukawa E, Aki H. Improving water
solubility of nateglinide by complexation of b-cyclodextrin.
J Therm Anal Calorim. 2016;123:1847–50.
15. Sb aˆ rcea L, Udrescu L, Lede ¸t i I, Szabadai Z, Fulia s¸ A, Sb aˆ rcea C.
b-Cyclodextrin inclusion complexes of lisinopril and zofenopril.
J Therm Anal Calorim. 2016;123:2377–90.
6. Semalty A, Tanwar YS, Semalty M. Preparation and characteri-
zation of cyclodextrin inclusion complex of naringenin and crit-
ical comparison with phospholipid complexation for improving
J Therm Anal Calorim.
In the complexation of EGCg-b-CD, the AC-ring was
easily inserted into the cavity of b-CD independently of pH
0
to form the first type of the complex. The B -ring of EGCg
would be included by b-CD in the acid and neutral solu-
tions to form the second type, but the formation of the
complex in the basic solutions (C pH 8.0) would be diffi-
0
cult due to the ionization of the B -ring.
1
solubility and dissolution.
2014;115:2471–8.
7. Ishizu T, Hirata C, Yamamoto H, Harano K. Structure and
intramolecular flexibility of b-cyclodextrin complex with (-)-
epigallocatechin gallate in aqueous solvent. Magn Reson Chem.
J
Therm Anal Calorim.
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