Y. Ochiai, K. Ogawa, Y. Sawada et al.
Tetrahedron Letters 73 (2021) 153140
OH
OH
GO
OG
O
HO
OH
O
O
OH
HO
HO
O
MeOH
O
O
Acetone
O
OH
HO
O
OH
OH
H
2O
OH
OG
OG
OH
OH
1a
1b
Fig. 4. Equilibrated structures of 1.
[3] Blumberg, J. Introduction to the proceedings of the third international
scientific symposium on tea and human health: role of flavonoids in the
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[4] A.B. Sharangi, Medicinal and therapeutic potentialities of tea (Camellia
Sinensis L.) – a review, Food Res. Int. 42 (5-6) (2009) 529–535, https://doi.
[5] M. Grzesik, K. Naparło, G. Bartosz, I. Sadowska-Bartosz, Antioxidant properties
of catechins: comparison with other antioxidants, Food Chem. 241 (2018)
Three types of solvents were used: 100% H2O, 50% dioxane aq., and
100% dioxane. The ratios of 1a and 1b in each solvent were 1: 7,
1:19, and 1:25, respectively (Figs. S2, S3). Compounds 2–4 were
not produced in 50% dioxane aq. and 100% dioxane. In contrast, 5
formed under all conditions and tended to increase as the propor-
tion of water increased. This result suggests that compounds 2–4
may be produced from 1a, and 5 may be produced from either
1a or 1b.
Conclusion
[7] L. Zhang, C.-T. Ho, J. Zhou, J.S. Santos, L. Armstrong, D. Granato, Chemistry and
We investigated the stability of oolongtheanin 30-O-gallate (1)
in an aqueous solution under heating conditions and isolated four
compounds. We observed that 1 undergoes an oxidative degrada-
tion reaction under heating conditions. Compound 1 exists as an
equilibrium mixture depending on the solvent conditions. On the
basis of the yield of compounds 2–5 under different solvent condi-
tions, 2–4 were presumed to be produced from 1a, and 5 from 1a
or 1b. Hence, it can be suggested that compounds 2–5 may be pre-
sent in oolong tea because they were generated under mild condi-
tions in aqueous solution.
biological activities of processed camellia sinensis teas:
a comprehensive
review, Compr. Rev. Food Sci. Food Saf. 18 (5) (2019) 1474–1495, https://doi.
[8] Y. Matsuo, F. Tadakuma, T. Shii, Y. Saito, T. Tanaka, Selective oxidation of
pyrogallol-type catechins with unripe fruit homogenate of citrus unshiu and
structural revision of oolongtheanins, Tetrahedron 71 (17) (2015) 2540–2548,
Along with several catechin dimers, complicated polymers such
as major polyphenols have also been reported as the components
of fermented tea such as oolong tea. Compound 1 is a minor com-
ponent of oolong tea leaves and is produced from catechins during
fermentation. The oxidative degradation of 1 may also occur. It is
possible that compounds 2–5 produced from 1 are intermediates
of catechin polymerization during fermentation. We believe that
clarifying the degradative reaction of catechin dimers such as
oolongtheanin holds the key to understanding the chemical struc-
ture of polymeric polyphenols. Further studies are now in progress.
[10] K. Ogawa, S. Hirose, H. Yamamoto, M. Shimada, S. Nagaoka, E. Yanase,
Synthesis of oolongtheanins and their inhibitory activity on micellar
cholesterol solubility in vitro, Bioorg. Med. Chem. Lett. 25 (4) (2015) 749–
[11] S. Hirose, K. Tomatsu, E. Yanase, Isolation of key intermediates during
formation of oolongtheanins, Tetrahedron Lett. 54 (51) (2013) 7040–7043,
[12] S. Hirose, Y.O. Kamatari, E. Yanase, Mechanism of oolongtheanin formation via
[13] Q.Y. Zhu, R.M. Hackman, J.L. Ensunsa, R.R. Holt, C.L. Keen, Antioxidative
activities of oolong tea, J. Agric. Food Chem. 50 (23) (2002) 6929–6934, https://
[14] L.-K. Han, T. Takaku, J. Li, Y. Kimura, H. Okuda, Anti-obesity action of oolong
[15] Y. Toyoda-Ono, M. Yoshimura, M. Nakai, Y. Fukui, S. Asami, H. Shibata, Y. Kiso,
I. Ikeda, Suppression of postprandial hypertriglyceridemia in rats and mice by
oolong tea polymerized polyphenols, Biosci. Biotechnol. Biochem. 71 (4)
[16] I. Ikeda, T. Yamahira, M. Kato, A. Ishikawa, Black-tea polyphenols decrease
micellar solubility of cholesterol in vitro and intestinal absorption of
cholesterol in rats, J. Agric. Food Chem. 58 (15) (2010) 8591–8595, https://
Declaration of Competing Interest
The authors declare that they have no known competing finan-
cial interests or personal relationships that could have appeared
to influence the work reported in this paper.
Appendix A. Supplementary data
[17] M. Weerawatanakorn, W.-L. Hung, M.-H. Pan, S. Li, D. Li, X. Wan, C.-T. Ho,
Chemistry and health beneficial effects of oolong tea and theasinensins, Food
Sci. Hum. Wellness
Supplementary data to this article can be found online at
[18] H.-S. Wang, H.-J. Li, J.-L. Wang, Y.-C. Wu, Protecting-group-free synthesis of
haterumadienone- and puupehenone-type marine natural products, Green
[19] S. Hirose, K. Ogawa, E. Yanase, Equilibrated structures of oolongtheanins,
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